View source for Nuclear winter

{{Short description|Hypothetical climatic effect of nuclear war}}
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[[File:Firestorm cloud over Hiroshima.jpg|thumb|[[Pyrocumulonimbus]] cloud formed by the firestorm following the [[atomic bombing of Hiroshima]], 1945. Nuclear winter effects are triggered by at least a hundred such city firestorms.<ref name="pnas.0710058105" />]]
{{nuclear weapons}}
{{Pollution sidebar|War}}

'''Nuclear winter''' is a severe and prolonged [[anti-greenhouse effect|global climatic cooling]] effect that is hypothesized{{sfn|Goure|1985}}<ref name=autogenerated4>{{cite book |title=Human Impacts on Weather and Climate |url=https://books.google.com/books?id=hq7_TAFD4osC&q=nuclear+winter |first1=William R. |last1=Cotton | first2=Roger A. Sr. | last2=Pielke |date=1 February 2007 |publisher=Cambridge University Press |isbn=978-1-139-46180-1}}</ref> to occur after widespread urban [[firestorm]]s following a large-scale [[Nuclear warfare|nuclear war]].<ref name="2008physicstoday">{{Cite journal |last1=Toon |first1=Owen B. |last2=Robock |first2=Alan |last3=Turco |first3=Richard P. |date=December 2008 |title=Environmental consequences of nuclear war |url=http://climate.envsci.rutgers.edu/pdf/ToonRobockTurcoPhysicsToday.pdf |journal=Physics Today |volume=61 |issue=12 |pages=37–42 |bibcode=2008PhT....61l..37T |doi=10.1063/1.3047679 |archive-url=https://web.archive.org/web/20120312010114/http://climate.envsci.rutgers.edu/pdf/ToonRobockTurcoPhysicsToday.pdf |archive-date=2012-03-12 |quote=environmental changes triggered by smoke from firestorms. |doi-access=free}}</ref> The hypothesis is based on the fact that such fires can inject [[soot]] into the [[stratosphere]], where it can block some [[Diffuse sky radiation|direct sunlight]] from reaching the surface of the Earth. It is speculated that the resulting cooling, typically lasting a decade, would lead to widespread [[crop failure]], a global [[nuclear famine]], and an [[animal]] [[Mass extinction events|mass extinction event]].<ref>{{cite web|last1=Diep|first1=Francie |title=Computer Models Show What Exactly Would Happen To Earth After A Nuclear War|url=https://www.popsci.com/article/science/computer-models-show-what-exactly-would-happen-earth-after-nuclear-war|website=Popular Science|date=July 19, 2014 |access-date=4 February 2018|archive-url=https://web.archive.org/web/20171114114449/https://www.popsci.com/article/science/computer-models-show-what-exactly-would-happen-earth-after-nuclear-war|archive-date=14 November 2017|url-status=live}}</ref><ref name=":1">{{Cite journal|last1=Toon|first1=Owen B.|last2=Bardeen|first2=Charles G.|last3=Robock|first3=Alan |last4=Xia|first4=Lili|last5=Kristensen|first5=Hans|last6=McKinzie|first6=Matthew|last7=Peterson |first7=R. J.|last8=Harrison|first8=Cheryl S.|last9=Lovenduski|first9=Nicole S.|last10=Turco|first10=Richard P. |date=2019-10-01|title=Rapidly expanding nuclear arsenals in Pakistan and India portend regional and global catastrophe |journal=Science Advances|volume=5|issue=10|article-number=eaay5478|doi=10.1126/sciadv.aay5478 |pmid=31616796|pmc=6774726|bibcode=2019SciA....5.5478T|issn=2375-2548}}</ref>

[[Climatology|Climate researchers]] study nuclear winter via computer models and scenarios. Results are highly dependent on [[Nuclear weapon yield|nuclear yields]], whether and how many [[Countervalue|cities are targeted]], their [[flammable material]] content, and the firestorms' atmospheric environments, [[convection]]s, and durations. Firestorm case studies include the [[World War II]] bombings of [[Atomic bombings of Hiroshima and Nagasaki|Hiroshima]], [[Bombing of Tokyo|Tokyo]], [[bombing of Hamburg|Hamburg]], [[Bombing of Dresden|Dresden]], and [[Second Great Fire of London|London]],{{sfn|Toon|Turco|Robock|Bardeen|2007}} and modern observations from large-area [[wildfire]]s as the [[2021 British Columbia wildfires]].<ref name="2008physicstoday" /><ref name="agu.org">{{cite journal|last1=Fromm |first1=M. |last2=Stocks |first2=B. |last3=Servranckx |first3=R. |last4=Lindsey |first4=D. |year=2006 |title=Smoke in the Stratosphere: What Wildfires have Taught Us About Nuclear Winter |journal=[[Eos (journal)|Eos, Transactions, American Geophysical Union]] |volume=87 |issue=52 Fall Meet. Suppl |at=Abstract U14A–04 |url=http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm06&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm06%2Ffm06&maxhits=200&=%22U14A-04%22 |bibcode=2006AGUFM.U14A..04F  |archive-url=https://web.archive.org/web/20080124034041/http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm06&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm06%2Ffm06&maxhits=200&=%22U14A-04%22 |archive-date=2008-01-24}}</ref><ref>{{harvnb|Toon|Turco|Robock|Bardeen|2007}}. "the injection height of the smoke is controlled by the energy release from the burning fuel not from the nuclear explosion"., "...smoke plumes deep within the stratosphere over Florida that had originated a few days earlier in Canadian fires, implying that the smoke particles had not been significantly depleted during injection into the stratosphere (or subsequent transport over thousands of kilometers in the stratosphere)."</ref>

Studies suggest that a [[Nuclear holocaust|full-scale nuclear war]], expending thousands of weapons in the largest arsenals in [[Russia and nuclear weapons|Russia]] and the [[Nuclear weapons of the United States|United States]], could cool global temperatures by more than 5&nbsp;°C, exceeding the [[last ice age]]. According to these models, five billion people would die from famine within two years, and 40–50% of animal species would go [[Extinction|extinct]].<ref name="s421">{{cite journal |last=Xia |first=Lili |last2=Robock |first2=Alan |last3=Scherrer |first3=Kim |last4=Harrison |first4=Cheryl S. |last5=Bodirsky |first5=Benjamin Leon |last6=Weindl |first6=Isabelle |last7=Jägermeyr |first7=Jonas |last8=Bardeen |first8=Charles G. |last9=Toon |first9=Owen B. |last10=Heneghan |first10=Ryan |date=2022-08-15 |title=Global food insecurity and famine from reduced crop, marine fishery and livestock production due to climate disruption from nuclear war soot injection |url=https://www.nature.com/articles/s43016-022-00573-0.pdf |journal=Nature Food |publisher=Springer Science and Business Media LLC |volume=3 |issue=8 |pages=586–596 |doi=10.1038/s43016-022-00573-0 |issn=2662-1355 |access-date=2025-07-22 |doi-access=free}}</ref> Studies of a regional nuclear war involving hundreds of weapons, such as between [[India and nuclear weapons|India]] and [[Pakistan and Nuclear Weapons|Pakistan]], could also cause cooling of a few degrees, threatening up to two billion people and making 10–20% of animal species extinct.<ref name=":1" /><ref name="e551">{{cite journal |last=Hess |first=G. D. |date=2021-03-05 |title=The Impact of a Regional Nuclear Conflict between India and Pakistan: Two Views |url=https://www.tandfonline.com/doi/pdf/10.1080/25751654.2021.1882772?needAccess=true |journal=Journal for Peace and Nuclear Disarmament |volume=4 |issue=sup1 |pages=163–175 |doi=10.1080/25751654.2021.1882772 |access-date=2025-07-22 |doi-access=free}}</ref><ref name="x903">{{cite journal |last=Robock |first=Alan |last2=Xia |first2=Lili |last3=Harrison |first3=Cheryl S. |last4=Coupe |first4=Joshua |last5=Toon |first5=Owen B. |last6=Bardeen |first6=Charles G. |date=2023-06-19 |title=Opinion: How fear of nuclear winter has helped save the world, so far |journal=Atmospheric Chemistry and Physics |publisher=Copernicus GmbH |volume=23 |issue=12 |pages=6691–6701 |doi=10.5194/acp-23-6691-2023 |issn=1680-7324 |doi-access=free}}</ref> However, many gaps remain in the understanding and modeling the effects of nuclear war.<ref>[https://www.nationalacademies.org/news/2025/06/potential-environmental-effects-of-nuclear-war-new-report Potential Environmental Effects of Nuclear War], National Academy of Sciences, June 2025.</ref>

==General==
"Nuclear winter", or as it was initially termed, "nuclear twilight", began to be considered as a scientific concept in the 1980s after it became clear that an earlier hypothesis predicting that [[#Early work|fireball generated NOx]] emissions would devastate the [[ozone layer]] was losing credibility.<ref name=":2" /> It was within this context that the climatic effects of soot from fires became the new focus of the climatic effects of nuclear war.<ref name="Nuclear Winter Documentary 1984" /><ref name="bmartin.cc1">{{cite web |author=Martin |first=Brian |date=1988 |title=John Hampson's warnings of disaster |url=http://www.bmartin.cc/pubs/88Hampson.html |url-status=live |archive-url=https://web.archive.org/web/20141130145905/http://www.bmartin.cc/pubs/88Hampson.html |archive-date=2014-11-30 |access-date=2014-10-03 |website=www.bmartin.cc}}</ref> In these model scenarios, various soot clouds containing uncertain quantities of soot were assumed to form over cities, [[Kuwait oil fires|oil refineries]], and more rural [[missile silo]]s. Once the quantity of soot is decided upon by the researchers, the climate effects of these soot clouds are then modeled.<ref name="babel.hathitrust.org">{{cite report |title=An assessment of global atmospheric effects of a major nuclear conflict |last1=Muench |first1=H. S. |last2=Banta |first2=R. M. |date=10 May 1988 |publisher=Air Force Geophysics Laboratory |last3=Brenner |first3=S. |last4=Chisholm |first4=D. A. |place=Hanscom Air Force Base, Massachusetts |hdl=2027/uc1.31822020694212}}</ref> The term "nuclear winter" was a [[neologism]] coined in 1983 by [[Richard P. Turco]] in reference to a one-dimensional computer model created to examine the "nuclear twilight" idea. This model projected that massive quantities of soot and [[smoke]] would remain aloft in the air for on the order of years, causing a severe planet-wide drop in temperature.

After the failure of the predictions on the effects of the 1991 [[Kuwait oil fires]] that were made by the primary team of climatologists that advocate the hypothesis, over a decade passed without new published papers on the topic. More recently, the same team of prominent modellers from the 1980s have begun again to publish the outputs of computer models. These newer models produce the same general findings as their old ones, namely that the ignition of 100 firestorms, each comparable in intensity to that observed in [[Hiroshima]] in 1945, could produce a "small" nuclear winter.{{sfn|Toon|Turco|Robock|Bardeen|2007}}<ref>{{cite journal |author=Robock |first1=Alan |last2=Oman |first2=Luke |last3=Stenchikov |first3=Georgiy L. |last4=Toon |first4=Owen B. |last5=Bardeen |first5=Charles |last6=Turco |first6=Richard P. |name-list-style=amp |date=2007 |title=Climatic consequences of regional nuclear conflicts |url=http://climate.envsci.rutgers.edu/pdf/acp-7-2003-2007.pdf |url-status=live |journal=Atmos. Chem. Phys. |volume=7 |issue=8 |pages=2003–12 |bibcode=2007ACP.....7.2003R |doi=10.5194/acp-7-2003-2007 |archive-url=https://web.archive.org/web/20130629153655/http://climate.envsci.rutgers.edu/pdf/acp-7-2003-2007.pdf |archive-date=2013-06-29 |access-date=2007-12-05 |doi-access=free}}</ref> These firestorms would result in the injection of soot (specifically [[black carbon]]) into the Earth's stratosphere, producing an [[anti-greenhouse effect]] that would lower the [[Temperature record|Earth's surface temperature]]. The severity of this cooling in [[Alan Robock]]'s model suggests that the cumulative products of 100 of these firestorms could cool the [[global climate]] by approximately 1&nbsp;°C (1.8&nbsp;°F), largely eliminating the magnitude of [[anthropogenic global warming]] for the next roughly two or three years.<ref name="news.nationalgeographic.com">{{cite web |author=Choi |first=Charles Q. |date=2011-02-23 |title=Small Nuclear War Could Reverse Global Warming for Years |url=http://news.nationalgeographic.com/news/2011/02/110223-nuclear-war-winter-global-warming-environment-science-climate-change/ |archive-url=https://web.archive.org/web/20140916215816/http://news.nationalgeographic.com/news/2011/02/110223-nuclear-war-winter-global-warming-environment-science-climate-change/ |archive-date=2014-09-16 |access-date=2014-09-20 |work=National Geopraphic}}</ref> Robock and his collaborators have modeled the effect on global food production, and project that the injection of more than 5 Tg of soot into the stratosphere would lead to mass food shortages persisting for several years. According to their model, livestock and aquatic food production would be unable to compensate for reduced crop output in almost all countries, and adaptation measures such as food waste reduction would have limited impact on increasing available calories.<ref name=Xia2022>{{Cite journal |last1=Xia |first1=Lili |last2=Robock |first2=Alan |last3=Scherrer |first3=Kim |last4=Harrison |first4=Cheryl S. |last5=Bodirsky |first5=Benjamin Leon |last6=Weindl |first6=Isabelle |last7=Jägermeyr |first7=Jonas |last8=Bardeen |first8=Charles G. |last9=Toon |first9=Owen B. |last10=Heneghan |first10=Ryan |date=2022-08-15 |title=Global food insecurity and famine from reduced crop, marine fishery and livestock production due to climate disruption from nuclear war soot injection |journal=Nature Food |language=en |volume=3 |issue=8 |pages=586–596 |doi=10.1038/s43016-022-00573-0 |pmid=37118594 |s2cid=251601831 |issn=2662-1355|doi-access=free |bibcode=2022NatFd...3..586X |hdl=11250/3039288 |hdl-access=free }}</ref><ref>{{cite journal | last1=Jägermeyr | first1=Jonas | last2=Robock | first2=Alan | last3=Elliott | first3=Joshua | last4=Müller | first4=Christoph | last5=Xia | first5=Lili | last6=Khabarov | first6=Nikolay | last7=Folberth | first7=Christian | last8=Schmid | first8=Erwin | last9=Liu | first9=Wenfeng | last10=Zabel | first10=Florian | last11=Rabin | first11=Sam S. | last12=Puma | first12=Michael J. | last13=Heslin | first13=Alison | last14=Franke | first14=James | last15=Foster | first15=Ian | last16=Asseng | first16=Senthold | last17=Bardeen | first17=Charles G. | last18=Toon | first18=Owen B. | last19=Rosenzweig | first19=Cynthia | title=A regional nuclear conflict would compromise global food security | journal=Proceedings of the National Academy of Sciences | volume=117 | issue=13 | date=2020-03-16 | issn=0027-8424 | doi=10.1073/pnas.1919049117 | pages=7071–7081 | pmid=32179678 | pmc=7132296 | doi-access=free | bibcode=2020PNAS..117.7071J }}</ref>

[[File:How would a nuclear war between Russia and the US affect you personally? - Future of Life Institute.webm|thumb|Simulation of a nuclear war between Russia and the US based on Xia et al.<ref name="Xia2022" /> and others: Over 80% of the global population would starve to death unless they succumbed to other causes sooner. The death toll in the US, Russia, Europe, and China would be approximately 99%, with over 90% of fatalities occurring in countries not directly involved in the nuclear exchange.]]

As nuclear devices need not be detonated to ignite a firestorm, the term "nuclear winter" is something of a misnomer.{{Sfn | Badash |2009 | pp = 242–244}} The majority of papers published on the subject state that without qualitative justification, nuclear explosions are the cause of the modeled firestorm effects. The only phenomenon that is modeled by computer in the nuclear winter papers is the [[climate forcing]] agent of firestorm-soot, a product which can be ignited and formed by myriad means.{{Sfn | Badash |2009 | pp = 242–244}} Although rarely discussed, the proponents of the hypothesis state that the same "nuclear winter" effect would occur if 100 large scale conventional firestorms were ignited.<ref name="ReferenceC">{{harvnb|Toon|Turco|Robock|Bardeen|2007|p=1998}}. "...fires occurred within a few months of each other in 1945, the Hamburg mass fire occurred in 1943. These five fires potentially placed 5% as much smoke into the stratosphere as our hypothetical nuclear fires. The optical depth resulting from placing 5 Tg of soot into the global stratosphere is about 0.07, which would be easily observable even with techniques available in WWII."</ref>

A much larger number of firestorms, in the thousands,{{failed verification|date=December 2016}} was the initial assumption of the computer modelers who coined the term in the 1980s. These were speculated to be a possible result of any large scale employment of counter-value [[air burst|airbursting]] [[nuclear weapon]] use during an American-Soviet [[total war]]. This larger number of firestorms, which are not in themselves modeled,<ref name="babel.hathitrust.org" /> are presented as causing nuclear winter conditions as a result of the smoke inputted into various climate models, with the depths of severe cooling lasting for as long as a decade. During this period, summer drops in average temperature could be up to 20&nbsp;°C (36&nbsp;°F) in core agricultural regions of the US, Europe, and China, and as much as 35&nbsp;°C (63&nbsp;°F) in Russia.<ref name="Robock">{{cite journal |last1=Robock |first1=Alan |last2=Oman|first2=Luke |last3=Stenchikov |first3=Georgiy L. |date=6 July 2007 |title=Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences |journal=[[Journal of Geophysical Research]] |volume=112 |issue=D13 |at=D13107 |doi=10.1029/2006JD008235 |doi-access=free |bibcode=2007JGRD..11213107R |url=http://climate.envsci.rutgers.edu/pdf/RobockNW2006JD008235.pdf |access-date=2007-12-05 |archive-url= https://web.archive.org/web/20110928005224/http://climate.envsci.rutgers.edu/pdf/RobockNW2006JD008235.pdf |archive-date=2011-09-28 |url-status=live  |issn=2156-2202}}</ref> This cooling would be produced due to a 99% reduction in the natural [[insolation|solar radiation]] reaching the surface of the planet in the first few years, gradually clearing over the course of several decades.<ref name=autogenerated3/>

Since the advent of photography that captured evidence of tall clouds,<ref>London 1906, San Francisco Fire and others.</ref> it has been known that firestorms could inject soot smoke and [[aerosol]]s into the stratosphere, but the longevity of this slew of aerosols was a major unknown. Independent of the team that continue to publish theoretical models on nuclear winter, in 2006, [[Mike Fromm]] of the [[Naval Research Laboratory]], experimentally found that each natural occurrence of a massive wildfire firestorm, much larger than that observed at Hiroshima, can produce minor "nuclear winter" effects, with short-lived, approximately one month of a nearly immeasurable drop in surface temperatures, confined to the [[Hemisphere of the Earth|hemisphere]] that they burned in.<ref name="Fire-Breathing Storm Systems">{{cite web |author=Finneran |first=Michael |date=2010-10-19 |title=Fire-Breathing Storm Systems |url=http://www.nasa.gov/topics/earth/features/pyrocb.html |url-status=live |archive-url=https://web.archive.org/web/20140824082109/http://www.nasa.gov/topics/earth/features/pyrocb.html |archive-date=24 August 2014 |publisher=NASA}}</ref><ref>{{cite journal |last1=Fromm |first1=M. |last2=Tupper |first2=A. |last3=Rosenfeld |first3=D. |last4=Servranckx |first4=R. |last5=McRae |first5=R. |title=Violent pyro-convective storm devastates Australia's capital and pollutes the stratosphere |doi=10.1029/2005GL025161 |journal=Geophysical Research Letters |volume=33 |issue=5 |pages=L05815 |year=2006 |bibcode=2006GeoRL..33.5815F|s2cid=128709657 |doi-access=free }}</ref><ref>{{cite web |url=http://earthobservatory.nasa.gov/Features/PyroClouds/|title=Russian Firestorm: Finding a Fire Cloud from Space|date=31 August 2010|website=earthobservatory.nasa.gov|access-date=12 February 2015|archive-url=https://web.archive.org/web/20150212163237/http://earthobservatory.nasa.gov/Features/PyroClouds/ |archive-date=12 February 2015|url-status=live}}</ref> This is somewhat analogous to the frequent [[Volcanic explosivity index#Classification|volcanic eruptions that inject sulfates into the stratosphere]] and thereby produce minor, even negligible, [[volcanic winter]] effects.

A suite of satellite and aircraft-based firestorm-soot-monitoring instruments are at the forefront of attempts to accurately determine the lifespan, quantity, injection height, and [[optical extinction|optical properties]] of this smoke.<ref>{{cite web|title=NASA to study how pollution, storms and climate mix |url=https://www.sciencedaily.com/releases/2013/06/130606133058.htm|access-date=2018-02-28|archive-url= https://web.archive.org/web/20180612140237/https://www.sciencedaily.com/releases/2013/06/130606133058.htm |archive-date=2018-06-12|url-status=live}}</ref><ref>{{cite web|title=Wildfires Smoke Crosses the Atlantic |date=2 July 2013 |website=earthobservatory.nasa.gov |url=http://earthobservatory.nasa.gov/IOTD/view.php?id=81500|access-date=3 October 2014|archive-url=https://web.archive.org/web/20141006110758/http://earthobservatory.nasa.gov/IOTD/view.php?id=81500|archive-date=6 October 2014|url-status=live}}</ref><ref name="journals.ametsoc.org">{{cite journal |title=The untold story of pyrocumulonimbus, 2010 |doi=10.1175/2010BAMS3004.1 |volume=91 |issue=9 |journal=Bulletin of the American Meteorological Society |pages=1193–1209 |year=2010 |last1=Fromm |first1=Michael |bibcode=2010BAMS...91.1193F |doi-access=free}}</ref><ref>{{cite journal |last1=Jacob |first1=D. J. |display-authors=etal |year=2010 |title=The Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission: design, execution, and first results |journal=Atmos. Chem. Phys. |volume=10 |issue=11 |pages=5191–5212 |bibcode=2010ACP....10.5191J |doi=10.5194/acp-10-5191-2010 |doi-access=free}}</ref><ref>{{cite journal|title=Canadian and Siberian Boreal Fire Activity during ARCTAS Spring and Summer Phases |last1=Stocks |first1=B. J. |last2=Fromm |first2=M. D. |last3=Soja |first3=A. J. |last4=Servranckx |first4=R. |last5=Lindsey |first5=D. |last6=Hyer |first6=E. |date=December 2009|journal=AGU Fall Meeting Abstracts|volume=2009|at=A41E–01 |bibcode=2009AGUFM.A41E..01S}}</ref> Information regarding all of these properties is necessary to truly ascertain the length and severity of the cooling effect of firestorms, independent of the nuclear winter computer model projections.{{citation needed|date=January 2024}}

Currently, from satellite tracking data, it appears that stratospheric smoke aerosols dissipate in a time span under approximately two months.<ref name="journals.ametsoc.org" /> The existence of a [[Tipping point (climatology)|tipping point]] into a new stratospheric condition where the aerosols would not be removed within this time frame remains to be determined.<ref name="journals.ametsoc.org" />

== Mechanism ==
{{Main|Pyrocumulonimbus cloud}}
[[File:Picture of a pyro-cumulonimbus taken from a commercial airliner.jpg|thumb|Picture of a [[pyrocumulonimbus cloud]] taken from a commercial airliner cruising at about 10 km. In 2002, various sensing instruments detected 17 distinct pyrocumulonimbus cloud events in [[North America]] alone.<ref name="Fire-Breathing Storm Systems" />]]
The nuclear winter scenario assumes that 100 or more city firestorms<ref name=pnas.0710058105>{{cite journal |title=Massive global ozone loss predicted following regional nuclear conflict |last1=Mills |first1=Michael J. |last2=Toon|first2=Owen B. |last3=Turco|first3=Richard P. |last4=Kinnison |first4=Douglas E. |last5=Garcia|first5=Rolando R. |date=April 8, 2008 |journal=PNAS |volume=105 |issue=14 |pages=5307–5312 |doi=10.1073/pnas.0710058105|pmid=18391218 |pmc=2291128 |bibcode=2008PNAS..105.5307M |doi-access=free }} "50 Hiroshima-size (15 kt) bombs could generate 1–5 Tg of black carbon aerosol particles in the upper troposphere, after an initial 20% removal in "black rains" induced by firestorms..." & "the 1 to 5 Tg soot source term derives from a thorough study of the smoke produced by firestorms..."</ref><ref name="climate.envsci.rutgers.edu">{{harvnb|Toon|Turco|Robock|Bardeen|2007|p=1994}}. "the injection height of the smoke is controlled by the energy release from the burning fuel not from the nuclear explosion".</ref> are ignited by [[nuclear explosion]]s,<ref name="Robock Toon 2012"/> and that the firestorms lift large amounts of sooty smoke into the upper [[troposphere]] and lower stratosphere by the movement offered by the pyrocumulonimbus clouds that form during a firestorm. At {{convert|10|-|15|km|mi|abbr=off|0}} above the Earth's surface, the absorption of sunlight could further heat the soot in the smoke, lifting some or all of it into the [[stratosphere]], where the smoke could persist for years if there is no rain to wash it out. This aerosol of particles could heat the stratosphere and prevent a portion of the sun's light from reaching the surface, causing surface temperatures to drop drastically. In this scenario it is predicted{{By whom|date=July 2017}} that surface air temperatures would be the same as, or colder than, a given region's winter for months to years on end.

The modeled stable [[inversion (meteorology)|inversion layer]] of hot soot between the troposphere and high stratosphere that produces the anti-greenhouse effect was dubbed the "Smokeosphere" by [[Stephen Schneider (scientist)|Stephen Schneider]] et al. in their 1988 paper.<ref name=autogenerated4/>{{Sfn | Badash |2009 | p = 184}}<ref name="assets.cambridge.org">{{Cite book |last1=Cotton |first1=William R. |url=http://assets.cambridge.org/97805218/40866/frontmatter/9780521840866_frontmatter.pdf |title=Human Impacts on Weather and Climate |last2=Pielke |first2=Roger A. |date=February 2007 |publisher=Cambridge University Press |isbn=978-0-521-84086-6 |edition=2nd |language=en |access-date=2014-09-22 |archive-url=https://web.archive.org/web/20140924042009/http://assets.cambridge.org/97805218/40866/frontmatter/9780521840866_frontmatter.pdf |archive-date=2014-09-24 |url-status=live}}</ref>

Although it is common in the climate models to consider city firestorms, these need not be ignited by nuclear devices;{{Sfn | Badash |2009 | pp = 242–244}} more conventional ignition sources can instead be the spark of the firestorms. Prior to the previously mentioned solar heating effect, the soot's injection height is controlled by the [[power (physics)|rate of energy release]] from the firestorm's fuel, not the size of an initial nuclear explosion.<ref name="climate.envsci.rutgers.edu" /> For example, the [[mushroom cloud]] from the [[Little Boy|bomb dropped on Hiroshima]] reached a height of six kilometers (middle troposphere) within a few minutes and then dissipated due to winds, while the individual fires within the city took almost three hours to form into a firestorm and produce a [[pyrocumulus]] cloud, a cloud that is assumed to have reached upper tropospheric heights, as over its multiple hours of burning, the firestorm released an estimated 1000 times the energy of the bomb.{{sfn|Toon|Turco|Robock|Bardeen|2007|p=1994 |loc="Altitudes of smoke columns"}}

As the incendiary effects of a [[nuclear explosion]] do not present any especially characteristic features,<ref name="The Effects of Nuclear Weapons">{{Citation |editor-last=Glasstone |editor-first=Samuel |editor2-last=Dolan |editor2-first=Philip J. |year=1977 |chapter="Chapter VII – Thermal Radiation and Its Effects |title=The Effects of Nuclear Weapons |edition=Third |publisher=United States Department of Defense and the Energy Research and Development Administration |url=http://www.fourmilab.ch/etexts/www/effects/ |chapter-url=http://www.fourmilab.ch/etexts/www/effects/eonw_7.pdf#zoom=100 |access-date=2014-09-22 |archive-url=https://web.archive.org/web/20141031024929/http://www.fourmilab.ch/etexts/www/effects/ |archive-date=2014-10-31  |pages=300, § "Mass Fires" ¶ 7.61}}</ref> it is estimated by those with [[strategic bombing]] experience that as the city was a firestorm hazard, the same fire ferocity and building damage produced at Hiroshima by one [[Little Boy|16-kiloton nuclear bomb]] from a single [[Boeing B-29 Superfortress|B-29 bomber]] could have been produced instead by the conventional use of about 1.2 [[kilotons]] of [[incendiary bomb]]s from 220 B-29s distributed over the city.<ref name="The Effects of Nuclear Weapons"/><ref name="here">{{cite book |editor-last=D'Olier |editor-first=Franklin |editor-link=Franklin D'Olier |year=1946 |title=United States Strategic Bombing Survey, Summary Report (Pacific War) |location=Washington |publisher=United States Government Printing Office |url=http://www.anesi.com/ussbs01.htm |access-date=November 6, 2013 |url-status=live |archive-url=https://web.archive.org/web/20080516014539/http://www.anesi.com/ussbs01.htm |archive-date=May 16, 2008}}</ref><ref>{{cite web| url=http://marshall.csu.edu.au/Marshalls/html/WWII/USSBS_Summary.html |title=United States Strategic Bombing Survey, Summary Report|quotation=+would have required 220 B-29s carrying 1,200 tons of incendiary bombs, 400 tons of high-explosive bombs, and 500 tons of anti-personnel fragmentation bombs, if conventional weapons, rather than an atomic bomb, had been used. One hundred and twenty-five B-29s carrying 1,200 tons of bombs (Page 25 ) would have been required to approximate the damage and casualties at Nagasaki. This estimate pre-supposed bombing under conditions similar to those existing when the atomic bombs were dropped and bombing accuracy equal to the average attained by the Twentieth Air Force during the last 3 months of the war|website=Marshall.csu.edu.au|date=October 9, 2005 |access-date=2016-05-11|archive-url= https://web.archive.org/web/20160314161528/http://marshall.csu.edu.au/Marshalls/html/WWII/USSBS_Summary.html |archive-date=2016-03-14|url-status=live}}</ref>

While the [[bombing of Dresden|firestorms of Dresden]] and Hiroshima and the [[Operation Meetinghouse|mass fires of Tokyo]] and [[bombing of Nagasaki|Nagasaki]] occurred within mere months in 1945, the more intense and [[bombing of Hamburg|conventionally lit Hamburg firestorm]] occurred in 1943. Despite the separation in time, ferocity and area burned, leading modelers of the hypothesis state that these five fires potentially placed five percent as much smoke into the stratosphere as the hypothetical 100 nuclear-ignited fires discussed in modern models.<ref name="ReferenceC"/> While it is believed that the modeled climate-cooling-effects from the mass of soot injected into the stratosphere by 100 firestorms (one to five million [[Tonne|metric tons]]) would have been detectable with technical instruments in WWII, five percent of that would not have been possible to observe at that time.<ref name="ReferenceC"/>

=== Aerosol removal timescale ===
[[File:SmokeCeilingInLochcarron.jpg|thumb|Smoke rising in [[Lochcarron]], [[Scotland]], is stopped by an overlying natural low-level inversion layer of warmer air (2006).]]
The exact timescale for how long this smoke remains, and thus how severely this smoke affects the climate once it reaches the stratosphere, is dependent on both chemical and physical removal processes.<ref name="babel.hathitrust.org" />

The most important physical removal mechanism is "[[Rainout (radioactivity)|rainout]]", both during the "fire-driven [[convection|convective]] column" phase, which produces "[[firestorm|black rain]]" near the fire site, and rainout after the [[Plume (hydrodynamics)|convective plume]]'s dispersal, where the smoke is no longer concentrated and thus "wet removal" is believed to be very efficient.{{sfn|Toon|Turco|Robock|Bardeen|2007|p=1994}} However, these efficient removal mechanisms in the troposphere are avoided in the [[Robock]] 2007 study, where solar heating is modeled to quickly loft the soot into the stratosphere, "detraining" or separating the darker soot particles from the fire clouds' whiter [[water condensation]].{{sfn|Toon|Turco|Robock|Bardeen|2007|pp=1994–1996}}

Once in the stratosphere, the [[Physics|physical]] removal mechanisms affecting the timescale of the soot particles' residence are how quickly the aerosol of soot collides and [[aerosol#coagulate|coagulates]] with other particles via [[Brownian motion]],<ref name="babel.hathitrust.org" />{{sfn|Toon|Turco|Robock|Bardeen|2007|pp=1997–1998}}<ref name="a.mpg.de">[http://www.atmosphere.mpg.de/enid/906c8d956939bb335e9b051e10f45223,0/2__Particles/-_Transformation_and_removal_296.html Transformation and removal] {{webarchive| url=https://web.archive.org/web/20110727031911/http://www.atmosphere.mpg.de/enid/906c8d956939bb335e9b051e10f45223,0/2__Particles/-_Transformation_and_removal_296.html |date=2011-07-27 }} J. Gourdeau, LaMP Clermont-Ferrand, France, March 12, 2003</ref> and falls out of the atmosphere via gravity-driven [[dry deposition]],<ref name="a.mpg.de" /> and the time it takes for the "[[Phoresis|phoretic effect]]" to move coagulated particles to a lower level in the atmosphere.<ref name="babel.hathitrust.org"/> Whether by coagulation or the phoretic effect, once the aerosol of smoke particles are at this lower atmospheric level, [[cloud seeding]] can begin, permitting [[precipitation (meteorology)|precipitation]] to wash the smoke aerosol out of the atmosphere by the [[wet deposition]] mechanism.

The [[Chemistry|chemical]] processes that affect the removal are dependent on the ability of [[atmospheric chemistry]] to [[oxidize]] the [[carbonaceous]] component of the smoke, via reactions with oxidative species such as [[ozone]] and [[nitrogen oxides]], both of which are found at all levels of the atmosphere,<ref>[http://www.atmosphere.mpg.de/enid/906c8d956939bb335e9b051e10f45223,0/4__Gases_in_the_atmosphere/-_Distribution___concentration__2__3tg.html Distribution & concentration (2)] {{webarchive| url=https://web.archive.org/web/20110727031921/http://www.atmosphere.mpg.de/enid/906c8d956939bb335e9b051e10f45223,0/4__Gases_in_the_atmosphere/-_Distribution___concentration__2__3tg.html |date=2011-07-27 }} Dr. Elmar Uherek – Max Planck Institute for Chemistry Mainz, April 6, 2004</ref><ref>{{harvnb|Toon|Turco|Robock|Bardeen|2007|p=1999}}. "At one time it was thought that carbonaceous aerosol might be consumed by reactions with ozone (Stephens et al., 1989) and other oxidants, reducing the lifetime of soot at stratospheric altitudes. However recent data shows that the reaction probability for such loss of soot is about 10^-11 so it is not an important process on times scales of several years (Kamm et al., 2004). A full simulation of stratospheric chemistry, along with additional laboratory studies, would be needed to evaluate the importance of these processes. Rate constants for a number of potentially important reactions are lacking."</ref> and which also occur at greater concentrations when air is heated to high temperatures.

Historical data on residence times of aerosols, albeit a [[atmospheric particulate matter|different mixture of aerosols]], in this case [[stratospheric sulfur aerosols]] and [[volcanic ash]] from [[megavolcano]] eruptions, appear to be in the one-to-two-year time scale,<ref>{{cite web |website=How Volcanoes Work |url=http://www.geology.sdsu.edu/how_volcanoes_work/climate_effects.html |access-date=2011-04-15 |archive-url=https://web.archive.org/web/20110423214804/http://www.geology.sdsu.edu/how_volcanoes_work/climate_effects.html| archive-date=2011-04-23|url-status=live|title=Climate Effect of Volcanic Eruptions}}</ref> however aerosol–atmosphere interactions are still poorly understood.<ref>{{cite web |author=Geerts |first=B. |title=Aerosols and climate |url=http://www-das.uwyo.edu/~geerts/cwx/notes/chap02/aerosol&climate.html |url-status=live |archive-url=https://web.archive.org/web/20190121203256/http://www-das.uwyo.edu/~geerts/cwx/notes/chap02/aerosol%26climate.html |archive-date=2019-01-21}}</ref><ref>{{cite web| url=http://gacp.giss.nasa.gov/|title=Global Aerosol Climatology Project| website=gacp.giss.nasa.gov |publisher=NASA |access-date=2011-04-15|url-status=live |archive-url=https://web.archive.org/web/20080523102619/http://gacp.giss.nasa.gov/|archive-date=2008-05-23}}</ref>

=== Soot properties ===
{{see also|Tihomir Novakov|Aethalometer}}
Sooty aerosols can have a wide range of properties, as well as complex shapes, making it difficult to determine their evolving atmospheric [[Optical depth#Atmospheric sciences|optical depth]] value. The conditions present during the creation of the soot are believed to be considerably important as to their final properties, with soot generated on the more efficient spectrum of [[stoichiometry|burning efficiency]] considered almost "elemental [[carbon black]]," while on the more inefficient end of the burning spectrum, greater quantities of [[Pyrolysis|partially burnt]]/oxidized fuel are present. These partially burnt "organics" as they are known, often form tar balls and [[brown carbon]] during common lower-intensity wildfires, and can also coat the purer black carbon particles.<ref>{{cite web| url=http://www.mtu.edu/news/stories/2013/august/new-insights-wildfire-smoke-could-improve-climate-change-models.html|title=New Insights on Wildfire Smoke Could Improve Climate Change Models|access-date=2014-11-03| archive-url=https://web.archive.org/web/20141104015918/http://www.mtu.edu/news/stories/2013/august/new-insights-wildfire-smoke-could-improve-climate-change-models.html|archive-date=2014-11-04|url-status=live|date=2013-08-27}}</ref><ref>{{cite web|url=http://www.abqjournal.com/440827/news/lanl-study-wildfire-smokes-effect-on-climate-underestimated.html|title=LANL study: Wildfire smoke's effect on climate underestimated|first=Olivier|last=Uyttebrouck|website=www.abqjournal.com|access-date=2014-11-03|archive-url=https://web.archive.org/web/20150627114118/http://www.abqjournal.com/440827/news/lanl-study-wildfire-smokes-effect-on-climate-underestimated.html|archive-date=2015-06-27|url-status=live}}</ref><ref>{{cite web |url=http://wildfiretoday.com/2013/07/17/research-wildland-fire-smoke-contributes-to-climate-change-more-than-previously-thought/|title=Research: wildland fire smoke, including tar balls, contribute to climate change more than previously thought - Wildfire Today|date=17 July 2013|access-date=3 November 2014|archive-url=https://web.archive.org/web/20140724224709/http://wildfiretoday.com/2013/07/17/research-wildland-fire-smoke-contributes-to-climate-change-more-than-previously-thought/|archive-date=24 July 2014|url-status=live}}</ref> However, as the soot of greatest importance is that which is injected to the highest altitudes by the pyroconvection of the firestorm – a fire being fed with storm-force winds of air – it is estimated that the majority of the soot under these conditions is the more oxidized black carbon.<ref>{{harvnb|Toon|Turco|Robock|Bardeen|2007|pp=1996–1997|loc="Optical properties of soot particles"}}. "mass fires are likely to completely oxidize the fuels that are readily available".</ref>

== Consequences ==
[[File:Global temperature changes after nuclear winter.jpg|thumbnail|left|upright=1.8|Diagram obtained by the [[CIA]] from the ''International Seminar on Nuclear War'' in Italy 1984. It depicts the findings of Soviet 3-D computer model research on nuclear winter from 1983, and although containing similar errors as earlier Western models, it was the first 3-D model of nuclear winter. (The three dimensions in the model are longitude, latitude and altitude.){{sfn|Goure|1986|pp=2–7}} The diagram shows the models predictions of global temperature changes after a global nuclear exchange. The top image shows effects after 40 days, the bottom after 243 days. A co-author was nuclear winter modelling pioneer [[Vladimir Alexandrov]].{{sfn|Interagency Intelligence Assessment|1984|pp=10–11}}<ref name="Alexandrov, V. V 1983">Alexandrov, Vladimir V. and Stenchikov, G. I. (1983): "On the modeling of the climatic consequences of the nuclear war" ''The Proceeding of Appl. Mathematics'', The Computing Center of the USSR Academy of Sciences, Moscow, USSR.</ref> Alexandrov disappeared in 1985. As of 2016, there remains ongoing speculation by friend, [[Andrew Revkin]], of foul play relating to his work.<ref>{{cite web |title=Scientific thaw during the cold war |url=http://www.pulitzercenter.org/reporting/scientific-thaw-during-cold-war |website=Pulitzer Center |archive-url=https://web.archive.org/web/20161202101346/http://pulitzercenter.org/reporting/scientific-thaw-during-cold-war |archive-date=2016-12-02 |url-status=live |date=May 2, 2016 |author=Kit R. Roane}}</ref>]]

=== Climatic effects ===
A study presented at the annual meeting of the [[American Geophysical Union]] in December 2006 found that even a small-scale, regional nuclear war could disrupt the global climate for a decade or more. In a regional nuclear conflict scenario where two opposing nations in the [[subtropics]] would each use 50 [[Atomic bombings of Hiroshima and Nagasaki|Hiroshima]]-sized nuclear weapons (about 15 kilotons each) on major population centers, the researchers estimated as much as five million tons of soot would be released, which would produce a cooling of several degrees over large areas of North America and Eurasia, including most of the grain-growing regions. The cooling would last for years, and, according to the research, could be "catastrophic",<ref name=autogenerated3/><ref>{{cite web |title=Regional Nuclear War Could Devastate Global Climate |url=https://www.sciencedaily.com/releases/2006/12/061211090729.htm |archive-url= https://web.archive.org/web/20180516230926/https://www.sciencedaily.com/releases/2006/12/061211090729.htm |archive-date=2018-05-16 |url-status=live |work=Science Daily |date=December 11, 2006}}</ref> disrupting agricultural production and food gathering in particular in higher latitude countries.<ref>{{Cite web |date=2022-03-30 |title=How would a nuclear winter impact food production? |url=https://www.sciencedaily.com/releases/2022/03/220330164525.htm |access-date=2022-04-04 |website=ScienceDaily |language=en}}</ref><ref name=Xia2022/>

=== Ozone depletion ===
Nuclear detonations produce large amounts of [[NOx|nitrogen oxides]] by combining elements in the surrounding air. These are then lifted upwards by thermal convection. As they reach the stratosphere, these nitrogen oxides are capable of catalytically breaking down the [[ozone]] present in this part of the atmosphere. [[Ozone depletion]] would allow a much greater intensity of harmful [[ultraviolet radiation]] from the sun to reach the ground.<ref>{{cite journal |last1=Kao |first1=Chih-Yue Jim |last2=Glatzmaier |first2=Gary A. |last3=Malone |first3=Robert C. |last4=Turco |first4=Richard P. |title=Global three-dimensional simulations of ozone depletion under postwar conditions |journal=Journal of Geophysical Research |date=1990 |volume=95 |issue=D13 |article-number=22495 |doi=10.1029/JD095iD13p22495|bibcode=1990JGR....9522495K }}</ref>

A 2008 study by Michael J. Mills et al., published in the [[Proceedings of the National Academy of Sciences]], found that a nuclear weapons exchange between Pakistan and India using their current arsenals could create a near-global [[ozone hole]], triggering human health problems and causing environmental damage for at least a decade.<ref>{{cite Q|Q24657259}}</ref> The computer-modeled study looked at a nuclear war between the two countries involving 50 Hiroshima-sized nuclear devices on each side, producing massive urban fires and lofting as much as five million metric tons of soot about {{convert|50|mi|km}} into the [[stratosphere]]. The soot would absorb enough solar radiation to heat surrounding gases, increasing the breakdown of the stratospheric [[ozone layer]] protecting Earth from harmful ultraviolet radiation, with up to 70% ozone loss at northern high latitudes.<ref>{{Cite journal |last1=Bardeen |first1=Charles G. |last2=Kinnison |first2=Douglas E. |last3=Toon |first3=Owen B. |last4=Mills |first4=Michael J. |last5=Vitt |first5=Francis |last6=Xia |first6=Lili |last7=Jägermeyr |first7=Jonas |last8=Lovenduski |first8=Nicole S. |last9=Scherrer |first9=Kim J. N. |last10=Clyne |first10=Margot |last11=Robock |first11=Alan |date=2021-09-27 |title=Extreme Ozone Loss Following Nuclear War Results in Enhanced Surface Ultraviolet Radiation |url=https://onlinelibrary.wiley.com/doi/10.1029/2021JD035079 |journal=Journal of Geophysical Research: Atmospheres |language=en |volume=126 |issue=18 |doi=10.1029/2021JD035079 |bibcode=2021JGRD..12635079B |s2cid=238213347 |issn=2169-897X}}</ref>

=== Nuclear summer ===
A "nuclear summer" is a hypothesized scenario in which, after a nuclear winter caused by [[aerosol]]s inserted into the atmosphere that would prevent sunlight from reaching lower levels or the surface,<ref name="New Scientist">{{cite journal|journal=[[New Scientist]]|date=February 26, 1987|title=Researchers Blow Hot and Cold Over Armageddon|page=28}}</ref> has abated, a [[greenhouse effect]] then occurs due to carbon dioxide released by combustion and [[methane]] released from the [[marsh gas|decay of the organic matter]] such as corpses that froze during the nuclear winter.<ref name="New Scientist"/><ref name="Irregular Warfare">{{cite web |author=Gates |first=John M. |title=The U.S. Army and Irregular Warfare, Chapter Eleven The Continuing Problem of Conceptual Confusion |url=http://www3.wooster.edu/history/jgates/book-ch11.html |archive-url=https://web.archive.org/web/20110814051805/http://www3.wooster.edu/history/jgates/book-ch11.html |archive-date=2011-08-14 |access-date=2011-11-27}}</ref>

Another more sequential hypothetical scenario, following the settling out of most of the aerosols in 1–3 years, the cooling effect would be overcome by a heating effect from [[greenhouse warming]], which would raise surface temperatures rapidly by many degrees, enough to cause the death of much if not most of the life that had survived the cooling, much of which is more vulnerable to higher-than-normal temperatures than to lower-than-normal temperatures. The nuclear detonations would release CO<sub>2</sub> and other greenhouse gases from burning, followed by more released from the decay of dead organic matter. The detonations would also insert [[nitrogen oxide]]s into the stratosphere that would then deplete the [[ozone layer]] around the Earth.<ref name="New Scientist"/>

Other more straightforward hypothetical versions exist of the hypothesis that nuclear winter might give way to a nuclear summer. The high temperatures of the nuclear fireballs could destroy the ozone gas of the middle stratosphere.<ref name="Irregular Warfare"/>

== History ==
=== Early work ===
[[File:Nukecloud.png|thumb|upright=2|The mushroom cloud height as a function of [[TNT equivalent|explosive yield]] detonated as [[surface burst]]s.<ref name="Figure 1">{{cite magazine |author=Martin |first=Brian |date=December 1982 |title=The global health effects of nuclear war |url=http://www.bmartin.cc/pubs/82cab/ |url-status=live |magazine=Current Affairs Bulletin |volume=59 |issue=7 |pages=14–26 |archive-url=https://web.archive.org/web/20141006093303/http://www.bmartin.cc/pubs/82cab/ |archive-date=2014-10-06 |access-date=2014-10-03 |via=www.bmartin.cc}}</ref>{{sfn|Committee on the Atmospheric Effects of Nuclear Explosions|1985 |loc="Chapter: 4 Dust" pp. 20–21, figure 4.2 & 4.3}} As charted, yields at least in the megaton range are required to lift dust/[[fallout]] into the stratosphere. Ozone reaches its maximum concentration at about 25 km (c. 82,000 ft) in altitude.<ref name="Figure 1"/> Another means of stratospheric entry is from [[High-altitude nuclear explosion|high altitude nuclear detonations]], one example of which includes the 10.5 kiloton Soviet ''test [[1961 Soviet nuclear tests|no.#88]]'' of 1961, detonated at 22.7 km.<ref>{{cite web |url=http://www.futurescience.com/emp/test184.html|title=Electromagnetic Pulse - Soviet Test 184 - EMP |website=www.futurescience.com|access-date=2015-07-20|url-status=live|archive-url=https://web.archive.org/web/20150718124742/http://www.futurescience.com/emp/test184.html|archive-date=2015-07-18}}</ref><ref>{{cite web |url=http://www.iss-atom.ru/sssr2/1_9.htm|archive-url=https://web.archive.org/web/20140406175913/http://www.iss-atom.ru/sssr2/1_9.htm|archive-date=6 April 2014|title=ЯДЕРНЫЕ ИСПЫТАНИЯ В СССР, ТОМ II, глава 1|date=6 April 2014}}</ref> US high-yield upper atmospheric tests, ''Teak'' and ''Orange'' were also assessed for their ozone destruction potential.<ref>{{cite web |url=https://www.fas.org/sgp/othergov/doe/lanl/docs1/00322994.pdf|title=United States High-Altitude Test Experiences – A Review Emphasizing the Impact on the Environment 1976. Herman Hoerlin. LASL |access-date=2016-10-28|archive-url=https://web.archive.org/web/20161006125252/https://fas.org/sgp/othergov/doe/lanl/docs1/00322994.pdf |archive-date=2016-10-06|url-status=live}}</ref><ref>{{cite journal|title=Review of Nuclear Weapons Effects |journal=[[Annual Review of Nuclear Science]] |volume=18 |pages=153–202 |year=1968 |last1=Brode |first1=H. L. |bibcode=1968ARNPS..18..153B|doi=10.1146/annurev.ns.18.120168.001101}}</ref><br /> 0 = Approx altitude commercial aircraft operate<br />1 = [[Fat Man]]<br />2 = [[Castle Bravo]]]]

In 1952, a few weeks prior to the [[Ivy Mike]] (10.4 [[Megatons|megaton]]) bomb test on [[Elugelab]] Island, there were concerns that the aerosols lifted by the explosion might cool the Earth. Major Norair Lulejian, [[USAF]], and astronomer Natarajan Visvanathan studied this possibility, reporting their findings in ''Effects of Superweapons Upon the Climate of the World'', the distribution of which was tightly controlled. This report is described in a 2013 report by the [[Defense Threat Reduction Agency]] as the initial study of the "nuclear winter" concept. It indicated no appreciable chance of explosion-induced climate change.<ref>{{cite Q|Q63070323}}</ref>

The implications for civil defense of numerous surface bursts of high yield [[hydrogen bomb]] explosions on [[Pacific Proving Ground]] islands such as those of Ivy Mike in 1952 and Castle Bravo (15 Mt) in 1954 were described in a 1957 report on ''The Effects of Nuclear Weapons'', edited by [[Samuel Glasstone]]. A section in that book entitled "Nuclear Bombs and the Weather" states: "The dust raised in severe [[volcanic eruptions]], such as that at [[1883 eruption of Krakatoa|Krakatoa]] in 1883, is known to cause a noticeable reduction in the sunlight reaching the earth ... The amount of [soil or other surface] debris remaining in the atmosphere after the explosion of even the largest nuclear weapons is probably not more than about one percent or so of that raised by the Krakatoa eruption. Further, solar radiation records reveal that none of the nuclear explosions to date has resulted in any detectable change in the direct sunlight recorded on the ground."<ref>[http://babel.hathitrust.org/cgi/pt?seq=9&view=image&size=100&id=mdp.39015010999814&u=1&num=69 The Effects of Nuclear Weapons] {{Webarchive|url=https://web.archive.org/web/20140824081908/http://babel.hathitrust.org/cgi/pt?seq=9&view=image&size=100&id=mdp.39015010999814&u=1&num=69|date=2014-08-24}} Samuel Glasstone, Washington DC, Government Printing Office, 1956, p. 69071. A similar report had been issued in 1950 under a slightly different title: {{cite Q|Q63133275}}. This earlier version seems not to have discussed Krakatoa nor other climate change possibilities.</ref> The US [[Weather Bureau]] in 1956 regarded it as conceivable that a large enough nuclear war with megaton-range surface detonations could lift enough soil to cause a new [[ice age]].<ref>{{cite journal | doi = 10.1086/661272 | pmid=21936194 | volume=26 | title=The Politics of Atmospheric Sciences: "Nuclear Winter" and Global Climate Change | journal=Osiris | pages=198–223 | year=2011 | last1 = Dörries | first1 = Matthias| s2cid=23719340 | url=https://univoak.eu/islandora/object/islandora%3A62598 }}</ref>

The 1966 [[RAND corporation]] memorandum ''The Effects of Nuclear War on the Weather and Climate'' by E. S. Batten, while primarily analysing potential dust effects from surface bursts,{{sfn|Committee on the Atmospheric Effects of Nuclear Explosions|1985|p=185}} notes that "in addition to the effects of the debris, extensive fires ignited by nuclear detonations might change the surface characteristics of the area and modify local weather patterns ... however, a more thorough knowledge of the atmosphere is necessary to determine their exact nature, extent, and magnitude."<ref>{{Cite web |author=Batten |first=E. S. |date=August 1966 |title=The Effects of Nuclear War on the Weather and Climate |url=https://www.rand.org/content/dam/rand/pubs/research_memoranda/2008/RM4989.pdf |url-status=live |archive-url=https://web.archive.org/web/20160304061417/http://www.rand.org/content/dam/rand/pubs/research_memoranda/2008/RM4989.pdf |archive-date=2016-03-04 |access-date=2016-06-04}}</ref>

In the [[United States National Research Council]] (NRC) book ''Long-Term Worldwide Effects of Multiple Nuclear-Weapons Detonations'' published in 1975, it states that a nuclear war involving 4,000 Mt from ''present arsenals'' would probably deposit much less dust in the stratosphere than the Krakatoa eruption, judging that the effect of dust and oxides of nitrogen would probably be slight climatic cooling which "would probably lie within normal global climatic variability, but the possibility of climatic changes of a more dramatic nature cannot be ruled out".<ref name="Figure 1"/>{{sfn|Committee on the Atmospheric Effects of Nuclear Explosions |1985|p={{page needed|date=September 2021}}}}<ref>{{Cite book |author=National Research Council |title=Long-term worldwide effects of multiple nuclear weapons detonations |place=Washington DC |publisher=National Academy of Sciences |page=38 |isbn=978-0-309-02418-1 |year=1975 |access-date=2016-06-04 |url=https://books.google.com/books?id=JVArAAAAYAAJ&q=%22Long-term%20worldwide%20effects%20of%20multiple%20nuclear%20weapons%20detonations%22&pg=PA25}}</ref>

In the 1985 report, ''The Effects on the Atmosphere of a Major Nuclear Exchange'', the Committee on the Atmospheric Effects of Nuclear Explosions argues that a "plausible" estimate on the amount of stratospheric dust injected following a surface burst of 1 Mt is 0.3 teragrams, of which 8 percent would be in the [[Micrometre|micrometer]] range.{{sfn|Committee on the Atmospheric Effects of Nuclear Explosions|1985 |loc="Chapter: 4 Dust" pp. 17–25}} The potential cooling from soil dust was again looked at in 1992, in a US [[National Academy of Sciences]] (NAS)<ref name="Sciences 1992, pp. 433">{{cite book |author=National Academy of Sciences |title=Policy implications of greenhouse warming: Mitigation, adaptation and the science base |publisher=National Academy Press |place=Washington DC |year=1992 |pages=433–464}}</ref> report on [[climate engineering|geoengineering]], which estimated that about 10<sup>10</sup> kg (10 teragrams) of stratospheric injected soil dust with [[particulate matter|particulate grain]] dimensions of 0.1 to 1 micrometer would be required to mitigate the warming from a [[climate sensitivity|doubling of atmospheric]] carbon dioxide, that is, to produce ~2&nbsp;°C of cooling.<ref>{{cite journal |author=Bala |first=G. |date=10 January 2009 |title=Problems with geoengineering schemes to combat climate change |journal=Current Science |volume=96 |issue=1}}</ref>

In 1969, [[Paul Crutzen]] discovered that [[NOx|oxides of nitrogen]] (NOx) could be an efficient catalyst for the destruction of the ozone layer/[[stratospheric ozone]]. Following studies on the potential effects of NOx generated by engine heat in stratosphere flying [[Supersonic Transport]] (SST) airplanes in the 1970s, in 1974, John Hampson suggested in the journal ''[[Nature (journal)|Nature]]'' that due to the creation of atmospheric NOx by [[nuclear fireball]]s, a full-scale nuclear exchange could result in depletion of the ozone shield, possibly subjecting the earth to ultraviolet radiation for a year or more.{{sfn|Committee on the Atmospheric Effects of Nuclear Explosions |1985|p={{page needed|date=September 2021}}}}<ref>{{cite journal |author=Hampson |first=John |date=1974 |title=Photochemical war on the atmosphere |journal=Nature |volume=250 |issue=5463 |pages=189–191 |bibcode=1974Natur.250..189H |doi=10.1038/250189a0 |s2cid=4167666}}</ref> In 1975, Hampson's hypothesis "led directly"<ref name="bmartin.cc1" /> to the [[United States National Research Council]] (NRC) reporting on the models of ozone depletion following nuclear war in the book ''Long-Term Worldwide Effects of Multiple Nuclear-Weapons Detonations''.{{sfn|Committee on the Atmospheric Effects of Nuclear Explosions |1985|p={{page needed|date=September 2021}}}}

In the section of this 1975 NRC book pertaining to the issue of fireball generated NOx and ozone layer loss therefrom, the NRC presented model calculations from the early-to-mid 1970s on the effects of a nuclear war with the use of large numbers of multi-megaton yield detonations, which returned conclusions that this could reduce ozone levels by 50 percent or more in the northern hemisphere.<ref name="Figure 1"/>{{sfn|Committee on the Atmospheric Effects of Nuclear Explosions|1985|p=186}}

However, independent of the computer models presented in the 1975 NRC works, a paper in 1973 in the journal ''[[Nature (journal)|Nature]]'' depicts the stratospheric ozone levels worldwide overlaid upon the number of nuclear detonations during the era of atmospheric testing. The authors conclude that neither the data nor their models show any correlation between the approximate 500 Mt in historical atmospheric testing and an increase or decrease of ozone concentration.<ref name="Goldsmith 1973">{{cite journal |last1=Goldsmith |first1=P. |last2=Tuck|first2=A. F. |last3=Foot|first3=J. S. |last4=Simmons|first4=E. L. |last5=Newson |first5=R. L. |year=1973 |title=Nitrogen Oxides, Nuclear Weapon Testing, Concorde and Stratospheric Ozone |journal=Nature |volume=244 |issue=5418 |pages=545–551 |doi=10.1038/244545a0 |bibcode=1973Natur.244..545G |s2cid=4222122 |url=http://www.uow.edu.au/~bmartin/pubs/79bias/Goldsmith.pdf|access-date=2016-10-26|archive-url=https://web.archive.org/web/20161208052639/http://www.uow.edu.au/~bmartin/pubs/79bias/Goldsmith.pdf |archive-date=2016-12-08 }}</ref> In 1976, a study on the experimental measurements of an earlier atmospheric nuclear test as it affected the ozone layer also found that nuclear detonations are exonerated of depleting ozone, after the at first alarming model calculations of the time.<ref>{{cite journal |last=Christie |first=J. D. |date=1976-05-20 |title=Atmospheric ozone depletion by nuclear weapons testing |journal=Journal of Geophysical Research |volume=81 |issue=15 |pages=2583–2594 |bibcode=1976JGR....81.2583C |doi=10.1029/JC081i015p02583}}</ref> Similarly, a 1981 paper found that the models on ozone destruction from one test and the physical measurements taken were in disagreement, as no destruction was observed.<ref name=":2">{{cite journal |doi=10.1029/JC086iC02p01167 |bibcode=1981JGR....86.1167M |volume=86 |issue=C2 |title=Measurements of nitric oxide after a nuclear burst |journal=Journal of Geophysical Research |page=1167 |year=1981 |last1=McGhan |first1=M.}}</ref>

In total, about 500 Mt were atmospherically detonated between 1945 and 1971,<ref>{{cite book |title=Atmospheric Nuclear Tests|first=O. A.|last=Pavlovski|date=13 September 1998|publisher=Springer Berlin Heidelberg |pages=219–260 |doi=10.1007/978-3-662-03610-5_17|chapter = Radiological Consequences of Nuclear Testing for the Population of the Former USSR (Input Information, Models, Dose, and Risk Estimates) |isbn=978-3-642-08359-4}}</ref> peaking in 1961–1962, when 340 Mt were detonated in the atmosphere by the United States and Soviet Union.<ref>{{cite web|title=Worldwide Effects of Nuclear War – Radioactive Fallout |website=www.atomicarchive.com |url=http://www.atomicarchive.com/Docs/Effects/wenw_chp2.shtml |access-date=2014-10-03|archive-url=https://web.archive.org/web/20141006131515/http://www.atomicarchive.com/Docs/Effects/wenw_chp2.shtml |archive-date=2014-10-06|url-status=live}}</ref> During this peak, with the multi-megaton range detonations of the two nations nuclear test series, in exclusive examination, a total yield estimated at 300 Mt of energy was released. Due to this, 3 × 10<sup>34</sup> additional molecules of [[nitric oxide]] (about 5,000 [[Tonne|tons]] per Mt, 5 × 10<sup>9</sup> grams per megaton)<ref name="Goldsmith 1973"/><ref>[http://nuclearweaponarchive.org/Nwfaq/Nfaq5.html Nuclear weapons archive, Carey Mark Sublette 5.2.2.1] {{Webarchive|url=https://web.archive.org/web/20140428174041/http://nuclearweaponarchive.org/Nwfaq/Nfaq5.html |date=2014-04-28 }} "The high temperatures of the nuclear fireball, followed by rapid expansion and cooling, cause large amounts of nitrogen oxides to form from the oxygen and nitrogen in the atmosphere (very similar to what happens in combustion engines). Each megaton of yield will produce some 5000 tons of nitrogen oxides."</ref> are believed to have entered the stratosphere, and while ozone depletion of 2.2 percent was noted in 1963, the decline had started prior to 1961 and is believed to have been [[Ozone depletion|caused by other meteorological effects]].<ref name="Goldsmith 1973"/>

In 1982 journalist [[Jonathan Schell]] in his popular and influential book ''[[The Fate of the Earth]]'', introduced the public to the belief that fireball generated NOx would destroy the ozone layer to such an extent that crops would fail from solar UV radiation and then similarly painted the fate of the Earth, as plant and aquatic life going extinct. In the same year, 1982, Australian physicist [[Brian Martin (social scientist)|Brian Martin]], who frequently corresponded with John Hampson who had been greatly responsible for much of the examination of NOx generation,<ref name="bmartin.cc1" /> penned a short historical synopsis on the history of interest in the effects of the direct NOx generated by nuclear fireballs, and in doing so, also outlined Hampson's other non-mainstream viewpoints, particularly those relating to greater ozone destruction from upper-atmospheric detonations as a result of any widely used [[anti-ballistic missile]] ([[ABM-1 Galosh]]) system.<ref>{{Cite web |author=Martin |first=Brian |date=1988 |title=John Hampson's warnings of disaster |url=http://www.bmartin.cc/pubs/88Hampson.html |url-status=live |archive-url=https://web.archive.org/web/20141130145905/http://www.bmartin.cc/pubs/88Hampson.html |archive-date=2014-11-30 |access-date=2014-10-03 |quote=Crutzen of course knew of Hampson's work, and also had received correspondence from Hampson around 1980. His own impression was that nuclear explosions above the stratosphere probably wouldn't lead to nitrogen oxides at a low enough altitude to destroy a lot of ozone.}}</ref> However, Martin ultimately concludes that it is "unlikely that in the context of a major nuclear war" ozone degradation would be of serious concern. Martin describes views about potential ozone loss and therefore increases in [[Ultraviolet|ultraviolet light]] leading to the widespread destruction of crops, as advocated by Jonathan Schell in ''[[The Fate of the Earth]]'', as highly unlikely.<ref name="Figure 1" />

More recent accounts on the specific ozone layer destruction potential of NOx species are much less than earlier assumed from simplistic calculations, as "about 1.2 million tons" of natural and [[wikt:anthropogenic|anthropogenic]] generated stratospheric NOx is believed to be formed each year according to Robert P. Parson in the 1990s.<ref>{{cite web|url=http://stason.org/TULARC/science-engineering/ozone-depletion-intro/24-Will-commercial-supersonic-aircraft-damage-the-ozone-laye.html |title=24 Will commercial supersonic aircraft damage the ozone layer?|first=Stas |last=Bekman |website=stason.org|access-date=2014-10-03|url-status=live|archive-url=https://web.archive.org/web/20160606051736/http://stason.org/TULARC/science-engineering/ozone-depletion-intro/24-Will-commercial-supersonic-aircraft-damage-the-ozone-laye.html|archive-date=2016-06-06}}</ref>

==== Science fiction ====
The first published suggestion that cooling of the climate could be an effect of a nuclear war, appears to have been originally put forth by [[Poul Anderson]] and F. N. Waldrop in their story "Tomorrow's Children", in the March 1947 issue of the ''[[Astounding Science Fiction]]'' magazine. The story, primarily about a team of scientists hunting down [[mutant (fiction)|mutants]],<ref>{{cite book |author=Ashley |first=Michael |title=The History of the Science Fiction Magazine |volume=1 |page=186 |language=en-us}}</ref> warns of a "[[Fimbulwinter]]" caused by dust that blocked sunlight after a recent nuclear war and speculated that it may even trigger a new Ice Age.<ref>{{Cite encyclopedia |title=Nuclear Winter|encyclopedia=Science Fiction Encyclopedia |url=http://www.sf-encyclopedia.com/entry/nuclear_winter#sthash.x25SIeys.dpuf|access-date=2018-09-13 |archive-url=https://web.archive.org/web/20180728074452/http://www.sf-encyclopedia.com/entry/nuclear_winter#sthash.x25SIeys.dpuf|archive-date=2018-07-28|url-status=live}}</ref><ref name=autogenerated5>{{cite web|url=http://www.aip.org/history/climate/Winter.htm#N_1_|title=Wintry Doom |website=www.aip.org|access-date=2014-09-23|archive-url=https://web.archive.org/web/20140929134255/http://www.aip.org/history/climate/Winter.htm#N_1_|archive-date=2014-09-29|url-status=live}}</ref> Anderson went on to publish a novel based partly on this story in 1961, titling it ''Twilight World''.<ref name=autogenerated5 /> Similarly in 1985 it was noted by T. G. Parsons that the story "Torch" by C. Anvil, which also appeared in ''Astounding Science Fiction'' magazine, but in the April 1957 edition, contains the essence of the "Twilight at Noon"/"nuclear winter" hypothesis. In the story, a nuclear warhead ignites an oil field, and the soot produced "screens out part of the sun's radiation", resulting in Arctic temperatures for much of the population of North America and the Soviet Union.<ref name="babel.hathitrust.org" />

=== 1980s ===
The 1988 Air Force Geophysics Laboratory publication, ''An assessment of global atmospheric effects of a major nuclear war'' by H. S. Muench, et al., contains a chronology and review of the major reports on the nuclear winter hypothesis from 1983 to 1986. In general, these reports arrive at similar conclusions as they are based on "the same assumptions, the same basic data", with only minor model-code differences. They skip the modeling steps of assessing the possibility of fire and the initial fire plumes and instead start the modeling process with a "spatially uniform soot cloud" which has found its way into the atmosphere.<ref name="babel.hathitrust.org" />

Although never openly acknowledged by the multi-disciplinary team who authored the most popular 1980s TTAPS model, in 2011 the [[American Institute of Physics]] states that the TTAPS team (named for its participants, who had all previously worked on the phenomenon of dust storms on Mars, or in the area of asteroid [[impact event]]s: [[Richard P. Turco]], [[Owen Toon]], Thomas P. Ackerman, [[James B. Pollack]] and [[Carl Sagan]]) announcement of their results in 1983 "was with the explicit aim of promoting international arms control".<ref name="history.aip.org">{{cite web|title=Wintry Doom |url=http://history.aip.org/history/climate/Winter.htm|website=history.aip.org|access-date=2016-12-02 |archive-url=https://web.archive.org/web/20161202235031/http://history.aip.org/history/climate/Winter.htm |archive-date=2016-12-02|url-status=live}}</ref> However, "the computer models were so simplified, and the data on smoke and other aerosols were still so poor, that the scientists could say nothing for certain".<ref name="history.aip.org"/>

In 1981, William J. Moran began discussions and research in the [[National Research Council (United States)|National Research Council]] (NRC) on the airborne soil/dust effects of a large exchange of nuclear warheads, having seen a possible parallel in the dust effects of a war with that of the asteroid-created [[K-T boundary]] and its popular analysis a year earlier by [[Luis Walter Alvarez|Luis Alvarez]] in 1980.{{sfn|Committee on the Atmospheric Effects of Nuclear Explosions|1985|loc="Appendix: Evolution of Knowledge About Long-Term Nuclear Effects"|p=186}} An NRC study panel on the topic met in December 1981 and April 1982 in preparation for the release of the NRC's ''The Effects on the Atmosphere of a Major Nuclear Exchange'', published in 1985.{{sfn|Committee on the Atmospheric Effects of Nuclear Explosions |1985|p={{page needed|date=September 2021}}}}

As part of a study on the creation of [[Oxidizing agent|oxidizing species]] such as NOx and ozone in the troposphere after a nuclear war,<ref name="Nuclear Winter Documentary 1984">{{Citation |title=On the 8th Day – Nuclear Winter Documentary |date=1984 |url=https://www.youtube.com/watch?v=WCTKcd2Ko98 |access-date=2023-12-15 |language=en}}.</ref> launched in 1980 by ''[[Ambio]]'', a journal of the [[Royal Swedish Academy of Sciences]], [[Paul J. Crutzen]] and [[John W. Birks]] began preparing for the 1982 publication of a calculation on the effects of nuclear war on stratospheric ozone, using the latest models of the time. However, they found that as a result of the trend towards more numerous but less energetic, sub-megaton range nuclear warheads (made possible by the march to increase ICBM warhead [[Circular Error Probable|accuracy]]), the ozone layer danger was "not very significant".<ref name="bmartin.cc1"/>

It was after being confronted with these results that they "chanced" upon the notion, as "an afterthought"<ref name="Nuclear Winter Documentary 1984" /> of nuclear detonations igniting massive fires everywhere and, crucially, the smoke from these conventional fires then going on to absorb sunlight, causing surface temperatures to plummet.<ref name="bmartin.cc1"/> In early 1982, the two circulated a draft paper with the first suggestions of alterations in short-term climate from fires presumed to occur following a nuclear war.{{sfn|Committee on the Atmospheric Effects of Nuclear Explosions |1985|p={{page needed|date=September 2021}}}} Later in the same year, the special issue of ''[[Ambio]]'' devoted to the possible environmental consequences of nuclear war by Crutzen and Birks was titled "The Atmosphere after a Nuclear War: Twilight at Noon", and largely anticipated the nuclear winter hypothesis.<ref name="crutzen" /> The paper looked into fires and their climatic effect and discussed particulate matter from large fires, nitrogen oxide, ozone depletion and the effect of nuclear twilight on agriculture. Crutzen and Birks' calculations suggested that smoke particulates injected into the atmosphere by fires in cities, forests and petroleum reserves could prevent up to 99 percent of sunlight from reaching the Earth's surface. This darkness, they said, could exist "for as long as the fires burned", which was assumed to be many weeks, with effects such as: "The normal dynamic and temperature structure of the atmosphere would...change considerably over a large fraction of the Northern Hemisphere, which will probably lead to important changes in land surface temperatures and wind systems."<ref name=crutzen /> An implication of their work was that a successful nuclear [[decapitation strike]] could have severe climatic consequences for the perpetrator.

After reading a paper by N. P. Bochkov and [[Yevgeniy Chazov|E. I. Chazov]],<ref>{{cite book |author=Chazov |first1=E. I. |title=The Aftermath: the human and ecological consequences of nuclear war |last2=Vartanian |first2=M. E. |date=1983 |publisher=Pantheon Books |isbn=978-0-394-72042-5 |editor=Peterson |editor-first=Jeannie |location=New York |pages=[https://archive.org/details/aftermathhuman00pete/page/155 155–163] |language=en |chapter=Effects on human behaviour |chapter-url=https://archive.org/details/aftermathhuman00pete |chapter-url-access=registration}}</ref> published in the same edition of ''Ambio'' that carried Crutzen and Birks's paper "Twilight at Noon", Soviet atmospheric scientist [[Georgy Golitsyn]] applied his research on [[Climate of Mars#Effect of dust storms|Mars dust storms]] to soot in the Earth's atmosphere. The use of these influential Martian dust storm models in nuclear winter research began in 1971,<ref name="Vladimir Gubarev 2001">{{cite journal |author=Gubarev |first=Vladimir |author-link=Vladimir Gubarev |date=2001 |title=Tea Drinking in The Academy. Academician G. S. Golitsyn: Agitations Of The Sea And Earth |url=http://www.nkj.ru/archive/articles/5755/ |url-status=live |journal=Science and Life |language=ru |volume=3 |archive-url=https://web.archive.org/web/20110522025535/http://www.nkj.ru/archive/articles/5755/ |archive-date=2011-05-22 |access-date=2009-10-11}}</ref> when the Soviet spacecraft [[Mars 2]] arrived at the red planet and observed a global dust cloud. The orbiting instruments together with the 1971 [[Mars 3]] lander determined that temperatures on the surface of the red planet were considerably colder than temperatures at the top of the dust cloud. Following these observations, Golitsyn received two telegrams from astronomer [[Carl Sagan]], in which Sagan asked Golitsyn to "explore the understanding and assessment of this phenomenon". Golitsyn recounts that it was around this time that he had "proposed a theory{{which|date=December 2016}} to explain how Martian dust may be formed and how it may reach global proportions."<ref name="Vladimir Gubarev 2001"/>

In the same year Alexander Ginzburg,<ref name="journals.co-action.net">{{cite journal |last1=Golitsyn |first1=G. S. |last2=Ginsburg |first2=Alexander S. |date=1985 |title=Comparative estimates of climatic consequences of Martian dust storms and of possible nuclear war |journal=Tellus |volume=378 |issue=3 |pages=173–181 |bibcode=1985TellB..37..173G |doi=10.3402/tellusb.v37i3.15015 |doi-access=free}}</ref> an employee in Golitsyn's institute, developed a model of dust storms to describe the cooling phenomenon on Mars. Golitsyn felt that his model would be applicable to soot after he read a 1982 Swedish magazine dedicated to the effects of a hypothetical nuclear war between the USSR and the US.<ref name="Vladimir Gubarev 2001"/> Golitsyn would use Ginzburg's largely unmodified dust-cloud model with soot assumed as the aerosol in the model instead of soil dust and in an identical fashion to the results returned, when computing dust-cloud cooling in the Martian atmosphere, the cloud high above the planet would be heated while the planet below would cool drastically. Golitsyn presented his intent to publish this Martian-derived Earth-analog model to the [[Andropov]] instigated ''Committee of Soviet Scientists in Defence of Peace Against the Nuclear Threat'' in May 1983, an organization that Golitsyn would later be appointed vice-chairman. The establishment of this committee was done with the expressed approval of the Soviet leadership with the intent "to expand controlled contacts with Western [[nuclear disarmament|"nuclear freeze" activists]]".<ref>{{cite magazine |author=Zubok |first=Vladislav M. |date=April 1, 2000 |title=Gorbachev's Nuclear Learning |work=Boston Review |url=https://bostonreview.net/world/vladislav-m-zubok-gorbachevs-nuclear-learning |url-status=live |archive-url=https://web.archive.org/web/20160818075324/http://bostonreview.net/world/vladislav-m-zubok-gorbachevs-nuclear-learning |archive-date=18 August 2016 |access-date=21 December 2016}}</ref> Having gained this committees approval, in September 1983, Golitsyn published the first computer model on the nascent "nuclear winter" effect in the widely read ''[[Herald of the Russian Academy of Sciences]]''.<ref name="Тяжелая пыль">{{Cite web |author=Shumeyko |first=Igor |date=2003-10-08 |title=Тяжелая пыль "ядерной зимы" |trans-title=Heavy dust 'nuclear winter' |url=http://www.ng.ru/science/2003-10-08/14_winter.html |url-status=live |archive-url=https://web.archive.org/web/20110617081632/http://www.ng.ru/science/2003-10-08/14_winter.html |archive-date=2011-06-17 |access-date=2009-10-27 |language=ru}}</ref>

On 31 October 1982, Golitsyn and Ginsburg's model and results were presented at the conference on "The World after Nuclear War", hosted in [[Washington, D.C.]]<ref name="journals.co-action.net"/>

Both Golitsyn<ref name="Тяжелая пыль"/> and Sagan<ref>{{cite thesis |author=Rubinson |date=2008 |title=Containing Science: The U.S. National Security State and Scientists' Challenge to Nuclear Weapons during the Cold War |url=https://www.lib.utexas.edu/etd/d/2008/rubinsonp66913/rubinsonp66913.pdf |archive-url=https://web.archive.org/web/20140924041711/https://www.lib.utexas.edu/etd/d/2008/rubinsonp66913/rubinsonp66913.pdf |archive-date=2014-09-24 |type=PhD |first=Paul Harold}}</ref> had been interested in the cooling on the dust storms on the planet Mars in the years preceding their focus on "nuclear winter". Sagan had also worked on [[Project A119]] in the 1950s–1960s, in which he attempted to model the movement and longevity of a plume of lunar soil.

After the publication of "Twilight at Noon" in 1982,{{Sfn | Badash |2009 | p = {{page needed|date=September 2021}}}} the TTAPS team have said that they began the process of doing a 1-dimensional computational modeling study of the atmospheric consequences of nuclear war/soot in the stratosphere, though they would not publish a paper in ''[[Science (journal)|Science]]'' magazine until late-December 1983.<ref name="CITEREFTurcoToonAckermanPollack1983">{{cite journal |last1=Turco |first1=R. P. |last2=Toon |first2=O. B. |last3=Ackerman |first3=T. P. |last4=Pollack |first4=J. B. |last5=Sagan |first5=Carl |date=December 23, 1983 |title=Nuclear Winter: Global Consequences of Multiple Nuclear Explosions |journal=Science |volume=222 |issue=4630 |pages=1283–1292 |bibcode=1983Sci...222.1283T |doi=10.1126/science.222.4630.1283 |pmid=17773320 |s2cid=45515251}}</ref> The phrase "nuclear winter" had been coined by Turco just prior to publication.<ref>{{cite journal |author=Dörries |first=Matthias |date=2011 |title=The Politics of Atmospheric Sciences: "Nuclear Winter" and Global Climate Change |url=https://univoak.eu/islandora/object/islandora%3A62598 |journal=Osiris |volume=26 |issue=1 |pages=198–223 |doi=10.1086/661272 |jstor=10.1086/661272) |pmid=21936194 |s2cid=23719340}}</ref> In this early paper, TTAPS used assumption-based estimates on the total smoke and dust emissions that would result from a major nuclear exchange, and with that, began analyzing the subsequent effects on the atmospheric [[radiation balance]] and temperature structure as a result of this quantity of assumed smoke. To compute dust and smoke effects, they employed a one-dimensional microphysics/radiative-transfer model of the Earth's lower atmosphere (up to the mesopause), which defined only the vertical characteristics of the global climate perturbation.

Interest in the environmental effects of nuclear war, however, had continued in the Soviet Union after Golitsyn's September paper, with [[Vladimir Alexandrov]] and G. I. Stenchikov also publishing a paper in December 1983 on the climatic consequences, although in contrast to the contemporary TTAPS paper, this paper was based on simulations with a three-dimensional global circulation model.<ref name="Alexandrov, V. V 1983" /> (Two years later Alexandrov disappeared under mysterious circumstances). Richard Turco and Starley L. Thompson were both critical of the Soviet research. Turco called it "primitive" and Thompson said it used obsolete US computer models.{{Sfn | Badash |2009 | p = 219}} Later they were to rescind these criticisms and instead applauded Alexandrov's pioneering work, saying that the Soviet model shared the weaknesses of all the others.<ref name="babel.hathitrust.org"/>

In 1984, the [[World Meteorological Organization]] (WMO) commissioned Golitsyn and N. A. Phillips to review the state of the science. They found that studies generally assumed a scenario where half of the world's nuclear weapons would be used, ~5000 Mt, destroying approximately 1,000 cities, and creating large quantities of carbonaceous smoke – 1–{{val|2|e=14|u=g}} being most likely, with a range of 0.2–{{val|6.4|e=14|u=g}} (NAS; TTAPS assumed {{val|2.25|e=14}}). The smoke resulting would be largely opaque to solar radiation but transparent to infrared, thus cooling the Earth by blocking sunlight, but not creating warming by enhancing the greenhouse effect. The optical depth of the smoke can be much greater than unity. Forest fires resulting from non-urban targets could increase aerosol production further. Dust from near-surface explosions against hardened targets also contributes; each megaton-equivalent explosion could release up to five million tons of dust, but most would quickly fall out; high altitude dust is estimated at 0.1–1 million tons per megaton-equivalent of explosion. Burning of crude oil could also contribute substantially.<ref>Golitsyn, G. S. and Phillips, N. A. (1986) "Possible climatic consequences of a major nuclear war", ''[[World climate research programme|WCRP]]'', World Meteorological Organization, WCP-113, WMO/TD #99.</ref>

The 1-D radiative-convective models used in these{{which|date=October 2016}} studies produced a range of results, with cooling up to 15–42&nbsp;°C between 14 and 35 days after the war, with a "baseline" of about 20&nbsp;°C. Somewhat more sophisticated calculations using 3-D [[Global climate model|GCMs]] produced similar results: temperature drops of about 20&nbsp;°C, though with regional variations.<ref name="Alexandrov, V. V 1983"/><ref>{{cite journal |last1=Covey |first1=C. |last2=Schneider |first2=S. |last3=Thompson |first3=S. |title=Global atmospheric effects of massive smoke injections from a nuclear war: results from general circulation model simulations |journal=Nature |volume=308 |pages=21–25 |date=March 1984 |issue=5954 |doi=10.1038/308021a0 |bibcode=1984Natur.308...21C |s2cid=4326912 |url=http://climate.envsci.rutgers.edu/pdf/CoveySchneiderThompson.pdf |access-date=2021-09-04 |archive-date=2021-09-04  |archive-url=https://web.archive.org/web/20210904215009/http://climate.envsci.rutgers.edu/pdf/CoveySchneiderThompson.pdf |url-status=live }}</ref>

All{{which|date=October 2016}} calculations show large heating (up to 80&nbsp;°C) at the top of the smoke layer at about {{Cvt|10|km|}}; this implies a substantial modification of the circulation there and the possibility of [[advection]] of the cloud into low latitudes and the southern hemisphere.

=== 1990 ===
In a 1990 paper entitled "Climate and Smoke: An Appraisal of Nuclear Winter", TTAPS gave a more detailed description of the short- and long-term atmospheric effects of a nuclear war using a three-dimensional model:<ref name="autogenerated1">{{cite Q|Q63169455}}</ref>

First one to three months:
* 10–25% of soot injected is immediately removed by precipitation, while the rest is transported over the globe in one to two weeks
* SCOPE figures for July smoke injection:
** 22&nbsp;°C drop in mid-latitudes
** 10&nbsp;°C drop in humid climates
** 75% decrease in rainfall in mid-latitudes
** Light level reduction of 0% in low latitudes to 90% in high smoke injection areas
* SCOPE figures for winter smoke injection:
** Temperature drops between 3 and 4&nbsp;°C

Following one to three years:
* 25–40% of injected smoke is stabilised in atmosphere (NCAR). Smoke stabilised for approximately one year.
* Land temperatures of several degrees below normal
* Ocean surface temperature between 2 and 6&nbsp;°C
* Ozone depletion of 50% leading to 200% increase in UV radiation incident on surface.

=== Kuwait wells in the first Gulf War ===
{{main|Kuwaiti oil fires}}
[[File:F-14A VF-114 over burning Kuwaiti oil well 1991.JPEG|thumb| The [[Kuwaiti oil fires]] were not just limited to [[oil well fire|burning oil wells]], one of which is seen here in the background, but burning "oil lakes", seen in the foreground, also contributed to the smoke plumes, particularly the sootiest/blackest of them.<ref name="gulflink.osd.mil">{{cite web |website=GulfLINK |url=http://www.gulflink.osd.mil/owf_ii/owf_ii_s04.htm#IV.%20AIR%20POLLUTANTS%20FROM%20OIL%20FIRES%20AND%20OTHER%20SOURCES |title=IV. Air Pollutants From Oil Fires and Other Sources |access-date=2014-06-11 |archive-url=https://web.archive.org/web/20150924024302/http://www.gulflink.osd.mil/owf_ii/owf_ii_s04.htm#IV.%20AIR%20POLLUTANTS%20FROM%20OIL%20FIRES%20AND%20OTHER%20SOURCES |archive-date=2015-09-24 |url-status=live}}</ref>]]
[[File:KuwaitiOilFires-STS037-152-91-(2).jpg|thumb|Smoke plumes from a few of the [[Kuwaiti Oil Fires]] on April 7, 1991. The maximum assumed extent of the combined plumes from over six hundred fires during the period of February 15 – May 30, 1991, are available.<ref name="gulflink.osd.mil"/><ref>{{cite web |url=http://www.gulflink.osd.mil/owf_ii/owf_ii_tabj.htm#TAB%20J%20%E2%80%93%20Plume%20Configurations |title=Tab J – Plume Configurations |website=GulfLINK |access-date=2014-06-11 |archive-url=https://web.archive.org/web/20150924024306/http://www.gulflink.osd.mil/owf_ii/owf_ii_tabj.htm#TAB%20J%20%E2%80%93%20Plume%20Configurations |archive-date=2015-09-24 |url-status=live}}</ref> Only about 10% of all the fires, mostly corresponding with those that originated from "oil lakes" produced pure black soot filled plumes, 25% of the fires emitted white to grey plumes, while the remaining emitted plumes with colors between grey and black.<ref name="gulflink.osd.mil"/>]]

One of the major results of TTAPS' 1990 paper was the re-iteration of the team's 1983 model that 100 [[oil refinery]] fires would be sufficient to bring about a small scale, but still globally deleterious nuclear winter.<ref name="sgr.org.uk">{{cite web|url=http://www.sgr.org.uk/resources/does-anybody-remember-nuclear-winter|title=Does anybody remember the Nuclear Winter? |website=www.sgr.org.uk|access-date=2016-02-13 |archive-url=https://web.archive.org/web/20160216064753/http://www.sgr.org.uk/resources/does-anybody-remember-nuclear-winter|archive-date=2016-02-16|url-status=live}}</ref>

Following Iraq's [[invasion of Kuwait]] and Iraqi threats of igniting the country's approximately 800 oil wells, speculation on the cumulative climatic effect of this, presented at the [[World Climate Conference]] in Geneva that November in 1990, ranged from a nuclear winter type scenario, to heavy [[acid rain]] and even short term immediate global warming.<ref name="Tahir Husain">{{cite journal |author=Husain |first=Tahir |date=July 1994 |title=Kuwaiti oil fires—Modeling revisited |journal=Atmospheric Environment |volume=28 |issue=13 |pages=2211–2226 |bibcode=1994AtmEn..28.2211H |doi=10.1016/1352-2310(94)90361-1 |issn=1352-2310}}</ref>

In articles printed in the [[Star-News|''Wilmington Morning Star'']] and the [[The Baltimore Sun|''Baltimore Sun'']] newspapers in January 1991, prominent authors of nuclear winter papers – Richard P. Turco, John W. Birks, Carl Sagan, Alan Robock and Paul Crutzen – collectively stated that they expected catastrophic nuclear winter like effects with continental-sized effects of sub-freezing temperatures as a result of the Iraqis going through with their threats of igniting 300 to 500 pressurized oil wells that could subsequently burn for several months.<ref>{{cite web |author=Roylance |first=Frank D. |date=January 23, 1991 |title=Burning oil wells could be disaster, Sagan says |url=https://www.baltimoresun.com/1991/01/23/burning-oil-wells-could-be-disaster-sagan-says/ |url-status=live |archive-url=https://web.archive.org/web/20141006144456/http://articles.baltimoresun.com/1991-01-23/news/1991023131_1_kuwait-saddam-hussein-sagan |archive-date=October 6, 2014 |access-date=June 11, 2014 |work=Baltimore Sun |page=1}}</ref><ref>{{cite news |author=Evans |first=David |date=January 20, 1991 |title=Burning oil wells could darken U.S. skies |work=Wilmington Morning Star |url=https://news.google.com/newspapers?id=6tEVAAAAIBAJ&sjid=RBQEAAAAIBAJ&pg=6851,2148654&dq=world-climate-conference+oil+fires&hl=en |url-status=live |archive-url=https://web.archive.org/web/20160312090836/https://news.google.com/newspapers?id=6tEVAAAAIBAJ&sjid=RBQEAAAAIBAJ&pg=6851,2148654&dq=world-climate-conference+oil+fires&hl=en |archive-date=2016-03-12}}</ref>

As threatened, the wells were [[Kuwaiti oil fires|set on fire]] by the retreating Iraqis in March 1991, and the 600 or so burning oil wells were not fully extinguished until November 6, 1991, eight months after the end of the war,<ref>{{cite web|url=http://www.gulflink.osd.mil/owf_ii/owf_ii_tabc.htm|title=TAB C – Fighting the Oil Well Fires |website=GulfLINK |access-date=2009-10-26|url-status=live|archive-url=https://web.archive.org/web/20150220213449/http://www.gulflink.osd.mil/owf_ii/owf_ii_tabc.htm|archive-date=2015-02-20}}</ref> and they consumed an estimated six million barrels of oil per day at their peak intensity.

When [[Operation Desert Storm]] began in January 1991, coinciding with the first few oil fires being lit, Dr. [[S. Fred Singer]] and [[Carl Sagan]] discussed the possible environmental effects of the Kuwaiti petroleum fires on the [[ABC News (United States)|ABC News]] program ''[[Nightline (US news program)|Nightline]]''. Sagan again argued that some of the effects of the smoke could be similar to the effects of a nuclear winter, with smoke lofting into the stratosphere, beginning around {{convert|48000|ft|m}} above sea level in Kuwait, resulting in global effects. He also argued that he believed the net effects would be very similar to the [[1815 eruption of Mount Tambora]] in Indonesia, which resulted in the year 1816 being known as the "[[Year Without a Summer]]".

Sagan listed modeling outcomes that forecast effects extending to South [[Asia]], and perhaps to the Northern Hemisphere as well. Sagan stressed this outcome was so likely that "It should affect the war plans."<ref>{{cite web|url=https://www.cfa.harvard.edu/~scranmer/SPD/crichton.html|archive-url=https://web.archive.org/web/20120119014904/https://www.cfa.harvard.edu/~scranmer/SPD/crichton.html|archive-date=19 January 2012|title=A lecture by Michael Crichton|date=19 January 2012}}</ref> Singer, on the other hand, anticipated that the smoke would go to an altitude of about {{convert|3000|ft|m}} and then be rained out after about three to five days, thus limiting the lifetime of the smoke. Both height estimates made by Singer and Sagan turned out to be wrong, albeit with Singer's narrative being closer to what transpired, with the comparatively minimal atmospheric effects remaining limited to the Persian Gulf region, with smoke plumes, in general,<ref name="gulflink.osd.mil"/> lofting to about {{convert|10,000|ft|m}} and a few as high as {{convert|20,000|ft|m}}.<ref>{{cite web|title=The Kuwaiti Oil Fires |last=Hirschmann|first=Kris|publisher=Facts on File |url=https://www.scribd.com/doc/4960296/The-Kuwaiti-Oli-Fires|archive-url=https://web.archive.org/web/20140102193647/http://www.scribd.com/doc/4960296/The-Kuwaiti-Oli-Fires |archive-date=2014-01-02|via=Scribd}}</ref><!--The reference for this is a hardcopy transcript of the episode, excerpts on the Fred Singer talk page.--><ref>{{cite episode |title=First Israeli Scud Fatalities, Oil Fires in Kuwait |series=Nightline |series-link=Nightline (US news program) |network=ABC |air-date=1991-01-22 |transcript=yes}}</ref>

Sagan and his colleagues expected that a "self-lofting" of the sooty smoke would occur when it absorbed the sun's heat radiation, with little to no scavenging occurring, whereby the black particles of soot would be heated by the sun and lifted/lofted higher and higher into the air, thereby injecting the soot into the stratosphere, a position where they argued it would take years for the sun-blocking effect of this aerosol of soot to fall out of the air, and with that, catastrophic ground level cooling and agricultural effects in Asia and possibly the Northern Hemisphere as a whole.<ref>{{cite web |author=Roylance |first=Frank D. |date=January 23, 1991 |title=Burning oil wells could be disaster, Sagan says |url=https://www.baltimoresun.com/1991/01/23/burning-oil-wells-could-be-disaster-sagan-says/ |url-status=live |archive-url=https://web.archive.org/web/20141006144456/http://articles.baltimoresun.com/1991-01-23/news/1991023131_1_kuwait-saddam-hussein-sagan |archive-date=October 6, 2014 |access-date=June 11, 2014 |work=Baltimore Sun |page=2}}</ref> In a 1992 follow-up, [[Peter V. Hobbs]] and others had observed no appreciable evidence for the nuclear winter team's predicted massive "self-lofting" effect and the oil-fire smoke clouds contained less soot than the nuclear winter modelling team had assumed.<ref>{{cite web|url=https://www.orlandosentinel.com/1992/07/26/kuwait-fires-failed-to-bring-doomsday/|title=Kuwait Fires Failed To Bring Doomsday|date=July 26, 1992 |access-date=2016-12-05|archive-url=https://web.archive.org/web/20170202053517/http://articles.orlandosentinel.com/1992-07-26/news/9207260223_1_nuclear-winter-carbon-dioxide-smoke|archive-date=2017-02-02|url-status=live}}</ref>

The atmospheric scientist tasked with studying the atmospheric effect of the Kuwaiti fires by the [[National Science Foundation]], Peter V. Hobbs, stated that the fires' modest impact suggested that "some numbers [used to support the Nuclear Winter hypothesis]... were probably a little overblown."<ref>{{cite web |url=http://www.nationalcenter.org/dos7124.htm |title=Dossier, A publication providing succinct biographical sketches of environmental scientists, economists, "experts", and activists released by The National Center for Public Policy Research. Environmental Scientist: Dr. Carl Sagan|archive-url=https://web.archive.org/web/20140714131601/http://www.nationalcenter.org/dos7124.htm |archive-date=2014-07-14 }}</ref>

Hobbs found that at the peak of the fires, the smoke absorbed 75 to 80% of the sun's radiation. The particles rose to a maximum of {{convert|20,000|ft|m}}, and when combined with scavenging by clouds the smoke had a short residency time of a maximum of a few days in the atmosphere.<ref name="ReferenceA">{{cite journal |first1=Peter V. |last1=Hobbs |first2=Lawrence F. |last2=Radke |title=Airborne Studies of the Smoke from the Kuwait Oil Fires |journal=Science |date=May 15, 1992 |doi=10.1126/science.256.5059.987 |volume=256 |issue=5059 |pages=987–991 |pmid=17795001 |bibcode=1992Sci...256..987H |s2cid=43394877 |url=https://zenodo.org/record/1231018 |access-date=2018-09-13  |archive-date=2020-07-28  |archive-url=https://web.archive.org/web/20200728023037/https://zenodo.org/record/1231018 |url-status=live }} [http://europepmc.org/article/MED/17795001 Full text via Europe PMC] {{Webarchive|url=https://web.archive.org/web/20210905005958/http://europepmc.org/article/MED/17795001 |date=2021-09-05  }}</ref>

Pre-war claims of wide scale, long-lasting, and significant global environmental effects were thus not borne out, and found to be significantly exaggerated by the media and speculators,<ref>{{cite journal |author=Khordagu |first1=Hosny |last2=Al-Ajmi |first2=Dhari |date=July 1993 |title=Environmental impact of the Gulf War: An integrated preliminary assessment |journal=Environmental Management |volume=17 |issue=4 |pages=557–562 |bibcode=1993EnMan..17..557K |doi=10.1007/bf02394670 |s2cid=153413376}}</ref> with climate models by those not supporting the nuclear winter hypothesis at the time of the fires predicting only more localized effects such as a daytime temperature drop of ~10&nbsp;°C within 200&nbsp;km of the source.<ref>{{Cite journal |doi = 10.1038/351363a0|title = Environmental effects from burning oil wells in Kuwait|journal = Nature|volume = 351|issue = 6325|pages = 363–367|year = 1991|last1 = Browning|first1 = K. A.|last2 = Allam|first2 = R. J.|last3 = Ballard|first3 = S. P.|last4 = Barnes|first4 = R. T. H.|last5 = Bennetts|first5 = D. A.|last6 = Maryon|first6 = R. H.|last7 = Mason|first7 = P. J.|last8 = McKenna|first8 = D.|last9 = Mitchell|first9 = J. F. B.|last10 = Senior|first10 = C. A.|last11 = Slingo|first11 = A.|last12 = Smith|first12 = F. B.|bibcode = 1991Natur.351..363B|s2cid = 4244270}}</ref>

[[File:Hemel Hempstead fuel explosion map.jpg|thumb|This satellite photo of the south of [[United Kingdom|Britain]] shows black smoke from the 2005 [[Buncefield fire]], a series of fires and explosions involving approximately 250,000,000 [[litre]]s of [[fossil fuels]]. The plume is seen spreading in two main streams from the explosion site at the apex of the inverted 'v'. By the time the fire had been extinguished the smoke had reached the [[English Channel]]. The orange dot is a marker, not the actual fire. Although the smoke plume was from a single source, and larger in size than the individual [[oil well]] fire plumes in Kuwait 1991, the Buncefield smoke cloud remained out of the stratosphere.]]

Sagan later conceded in his book ''[[The Demon-Haunted World]]'' that his predictions obviously did not turn out to be correct: "it ''was'' pitch black at noon and temperatures dropped 4–6&nbsp;°C over the Persian Gulf, but not much smoke reached stratospheric altitudes and Asia was spared."<ref>{{cite book |author=Sagan, Carl |title=The demon-haunted world: science as a candle in the dark |publisher=Random House |location=New York |date=1996 |page=257 |isbn=978-0-394-53512-8 }}</ref>

The idea of oil well and oil reserve smoke pluming into the stratosphere serving as a main contributor to the soot of a nuclear winter was a central idea of the early climatology papers on the hypothesis; they were considered more of a possible contributor than smoke from cities, as the smoke from oil has a higher ratio of black soot, thus absorbing more sunlight.<ref name="crutzen">{{cite journal |author=Crutzen |first1=P. |last2=Birks |first2=J. |date=1982 |title=The atmosphere after a nuclear war: Twilight at noon |journal=Ambio |volume=11 |issue=2 |pages=114–125 |jstor=4312777}}</ref><ref name=CITEREFTurcoToonAckermanPollack1983/> Hobbs compared the papers' assumed "emission factor" or soot generating efficiency from ignited oil pools and found, upon comparing to measured values from oil pools at Kuwait, which were the greatest soot producers, the emissions of soot assumed in the nuclear winter calculations were still "too high".<ref name="ReferenceA"/> Following the results of the Kuwaiti oil fires being in disagreement with the core nuclear winter promoting scientists, 1990s nuclear winter papers generally attempted to distance themselves from suggesting oil well and reserve smoke will reach the stratosphere.

In 2007, a nuclear winter study noted that modern computer models have been applied to the Kuwait oil fires, finding that individual smoke plumes are not able to loft smoke into the stratosphere, but that smoke from fires covering a large area, like some forest fires, can lift smoke into the stratosphere, and recent evidence suggests that this occurs far more often than previously thought.<ref name="agu.org"/><ref name="Fire-Breathing Storm Systems"/><ref>{{cite web |url=http://www.nasa.gov/mission_pages/fires/main/siberia-smoke.html |url-status=live |archive-url=https://web.archive.org/web/20120717141349/http://www.nasa.gov/mission_pages/fires/main/siberia-smoke.html |archive-date=2012-07-17 |title=Satellite Sees Smoke from Siberian Fires Reach the U.S. Coast |date=2012-06-11 |publisher=NASA}}</ref><ref>{{cite web |title=NRL scientist seeing clearly the effects of pyrocumulonimbus |url=http://www.eurekalert.org/pub_releases/2010-08/nrl-nss082610.php |url-status=live |archive-url=https://web.archive.org/web/20130129195204/http://www.eurekalert.org/pub_releases/2010-08/nrl-nss082610.php |archive-date=2013-01-29 |date=August 26, 2010 |website=EurekAlert!}}</ref> The study also suggested that the burning of the comparably smaller cities, which would be expected to follow a nuclear strike, would also loft significant amounts of smoke into the stratosphere:

{{blockquote|Stenchikov et al. [2006b]<ref name="Georgiy Stenchikov">{{cite journal|last1=Stenchikov|first1=G. L. |last2=Fromm|first2=M.|last3=Robock|first3=A.|date=2006|url=http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm06&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm06%2Ffm06&maxhits=200&=%22U14A-05%22 |title=Regional Simulations of Stratospheric Lofting of Smoke Plumes |journal=EOS Trans. |publisher=AGU |volume=87 |issue=52 Fall Meet. Suppl |bibcode=2006AGUFM.U14A..05S |at=Abstract U14A-05 |archive-url=https://web.archive.org/web/20080124034046/http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm06&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm06%2Ffm06&maxhits=200&=%22U14A-05%22 |archive-date=2008-01-24}} <!--The following may be helpful if you are willing to install whatever they are selling-->{{cite web |title=Slides |access-date=2014-08-08 |url= http://www.slidefinder.net/s/stenchikov_nwinter_agu_8short/stenchikov_nwinter_agu_8short/29710541 |archive-url=https://web.archive.org/web/20140810030820/http://www.slidefinder.net/s/stenchikov_nwinter_agu_8short/stenchikov_nwinter_agu_8short/29710541|archive-date=2014-08-10 }}</ref> conducted detailed, high-resolution smoke plume simulations with the RAMS regional climate model [e.g., Miguez-Macho, et al., 2005]<ref>{{cite web|url=http://www.envsci.rutgers.edu/~gera/papers_downscaling/GonzaloJC2005.pdf |last1=Miguez-Macho|first1=G. |last2=Stenchikov|first2=G. L.|last3=Robock|first3=A.|date=15 April 2005 |title=Regional Climate Simulations over North America: Interaction of Local Processes with Improved Large-Scale Flow |access-date=2008-01-24 |archive-date=2008-04-10|archive-url=https://web.archive.org/web/20080410131929/http://www.envsci.rutgers.edu/~gera/papers_downscaling/GonzaloJC2005.pdf}}</ref> and showed that individual plumes, such as those from the Kuwait oil fires in 1991, would not be expected to loft into the upper atmosphere or stratosphere, because they become diluted. However, much larger plumes, such as would be generated by city fires, produce large, undiluted mass motion that results in smoke lofting. New [[large eddy simulation]] model results at much higher resolution also give similar lofting to our results, and no small scale response that would inhibit the lofting [Jensen, 2006].<ref>{{cite journal |last=Jensen|first=E. J.|date=2006|url=http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm06&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm06%2Ffm06&maxhits=200&=%22U14A-06%22 |title=Lofting of Smoke Plumes Generated by Regional Nuclear Conflicts |journal=EOS Trans. |publisher=AGU |volume=87 |issue=52 Fall Meet. Suppl |bibcode=2006AGUFM.U14A..06J|at=Abstract U14A-06 |archive-url=https://web.archive.org/web/20080124034052/http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm06&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm06%2Ffm06&maxhits=200&=%22U14A-06%22 |archive-date=2008-01-24 }}</ref>}}

However, the above simulation notably contained the assumption that no dry or wet deposition would occur.<ref name="Georgiy Stenchikov"/>

== Recent modeling ==
Between 1990 and 2003, commentators noted that no peer-reviewed papers on "nuclear winter" were published.<ref name="sgr.org.uk"/>

Based on new work published in 2007 and 2008 by some of the authors of the original studies, several new hypotheses have been put forth, primarily the assessment that as few as 100 firestorms would result in a nuclear winter.<ref name="2008physicstoday"/><ref name=autogenerated3/> However, far from the hypothesis being "new", it drew the same conclusion as earlier 1980s models, which similarly regarded 100 or so city firestorms as a threat.{{sfn|Goure|1986|p=7}}<ref>{{harvnb|Toon|Turco|Robock|Bardeen|2007|p=1989}}. "At that time, significant climate effects were expected from 100 high yield weapons being used on 100 cities, but given the large numbers of weapons then available such a scenario did not seem likely. Here we estimate the smoke generated from 100 low yield weapons being used on 100 targets."</ref>

Compared to climate change for the past millennium, even the smallest exchange modeled would plunge the planet into temperatures colder than the [[Little Ice Age]] (the period of history between approximately 1600 and 1850 AD). This would take effect instantly, and agriculture would be severely threatened. Larger amounts of smoke would produce larger climate changes, making agriculture impossible for years. In both cases, new climate model simulations show that the effects would last for more than a decade.<ref name="Robock Toon 2012"/>

=== 2007 study on global nuclear war ===
A study published in the ''[[Journal of Geophysical Research]]'' in July 2007, titled "Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences",<ref name="Robock"/> used current climate models to look at the consequences of a global nuclear war involving most or all of the world's current nuclear arsenals (which the authors judged to be one similar to the size of the world's arsenals twenty years earlier). The authors used a global circulation model, ModelE from the [[NASA]] [[Goddard Institute for Space Studies]], which they noted "has been tested extensively in global warming experiments and to examine the effects of volcanic eruptions on climate". The model was used to investigate the effects of a war involving the entire current global nuclear arsenal, projected to release about 150 Tg of smoke into the atmosphere, as well as a war involving about one third of the current nuclear arsenal, projected to release about 50 Tg of smoke. In the 150 Tg case they found that:

{{blockquote|A global average surface cooling of −7 °C to −8 °C persists for years, and after a decade the cooling is still −4 °C (Fig. 2). Considering that the global average cooling at the depth of the last ice age 18,000 yr ago was about −5 °C, this would be a climate change unprecedented in speed and amplitude in the history of the human race. The temperature changes are largest over land .... Cooling of more than −20 °C occurs over large areas of North America and of more than −30 °C over much of Eurasia, including all agricultural regions.}}

In addition, they found that this cooling caused a weakening of the global hydrological cycle, reducing global precipitation by about 45%. As for the 50 Tg case involving one third of current nuclear arsenals, they said that the simulation "produced climate responses very similar to those for the 150 Tg case, but with about half the amplitude," but that "the time scale of response is about the same". They did not discuss the implications for agriculture in depth, but noted that a 1986 study which assumed no food production for a year projected that "most of the people on the planet would run out of food and starve to death by then" and commented that their own results show that, "This period of no food production needs to be extended by many years, making the impacts of nuclear winter even worse than previously thought."

=== 2014 ===
In 2014, Michael J. Mills (at the US [[National Center for Atmospheric Research]], NCAR), et al., published "Multi-decadal global cooling and unprecedented ozone loss following a regional nuclear conflict" in the journal ''Earth's Future''.<ref>{{cite journal |last1=Mills |first1=Michael J. |last2=Toon |first2=O. B. |last3=Lee-Taylor |first3=J. |last4=Robock |first4=A. |date=2014 |title=Multi-decadal global cooling and unprecedented ozone loss following a regional nuclear conflict |journal=Earth's Future |volume=2 |issue=4 |pages=161–176 |bibcode=2014EaFut...2..161M |doi=10.1002/2013EF000205|s2cid=9582735 |doi-access=free }}</ref> The authors used computational models developed by NCAR to simulate the climatic effects of a soot cloud that they suggest would be a result of a regional nuclear war in which 100 "small" (15 Kt) weapons are detonated over cities. The model had outputs, due to the interaction of the soot cloud:

<blockquote>...global ozone losses of 20–50% over populated areas, levels unprecedented in human history, would accompany the coldest average surface temperatures in the last 1000 years. We calculate summer enhancements in UV indices of 30–80% over Mid-Latitudes, suggesting widespread damage to human health, agriculture, and terrestrial and aquatic ecosystems. Killing frosts would reduce growing seasons by 10–40 days per year for 5 years. Surface temperatures would be reduced for more than 25 years, due to thermal inertia and albedo effects in the ocean and expanded sea ice. The combined cooling and enhanced UV would put significant pressures on global food supplies and could trigger a global nuclear famine.</blockquote>

=== 2018 ===
Researchers at [[Los Alamos National Laboratory]] published the results of a multi-scale study of the climate impact of a regional nuclear exchange, the same scenario considered by Robock et al. and by Toon et al. in 2007. Unlike previous studies, this study simulated the processes whereby black carbon would be lofted into the atmosphere and found that very little would be lofted into the stratosphere and, as a result, the long-term climate impacts were much lower than those studies had concluded. In particular, "none of the simulations produced a nuclear winter effect", and "the probability of significant global cooling from a limited exchange scenario as envisioned in previous studies is highly unlikely".<ref name="LANL2018">{{cite journal |author=Reisner |first=Jon |display-authors=et al |year=2018 |title=Climate Impact of a Regional Nuclear Weapons Exchange: An Improved Assessment Based On Detailed Source Calculations |journal=Journal of Geophysical Research: Atmospheres |volume=123 |issue=5 |pages=2752–2772 |bibcode=2018JGRD..123.2752R |doi=10.1002/2017JD027331 |s2cid=134771643 |doi-access=free}}</ref> This study has been contradicted by results in several subsequent studies claiming the 2018 study to be flawed.<ref name="Robock Toon Bardeen 2019 pp. 12953–12958">{{cite journal |last1=Robock |first1=Alan |last2=Toon |first2=Owen B. |last3=Bardeen |first3=Charles G. |date=2019-12-09 |title=Comment on "Climate Impact of a Regional Nuclear Weapon Exchange: An Improved Assessment Based on Detailed Source Calculations" by Reisner et al. |journal=Journal of Geophysical Research: Atmospheres |publisher=American Geophysical Union |volume=124 |issue=23 |pages=12953–12958 |doi=10.1029/2019jd030777 |issn=2169-897X |doi-access=free|bibcode=2019JGRD..12412953R }}</ref><ref name="Wagman Lundquist Tang Glascoe 2020 p.">{{cite journal |last1=Wagman |first1=Benjamin M. |last2=Lundquist |first2=Katherine A. |last3=Tang |first3=Qi |last4=Glascoe |first4=Lee G. |last5=Bader |first5=David C. |date=2020-12-14 |title=Examining the Climate Effects of a Regional Nuclear Weapons Exchange Using a Multiscale Atmospheric Modeling Approach |journal=Journal of Geophysical Research: Atmospheres |publisher=American Geophysical Union |volume=125 |issue=24 |page= |doi=10.1029/2020jd033056 |issn=2169-897X |doi-access=free|bibcode=2020JGRD..12533056W }}</ref><ref name="Redfern Lundquist Toon Muñoz‐Esparza 2021 p.">{{cite journal |last1=Redfern |first1=Stephanie |last2=Lundquist |first2=Julie K.|author2-link=Julie Lundquist |last3=Toon |first3=Owen B. |last4=Muñoz-Esparza |first4=Domingo |last5=Bardeen |first5=Charles G. |last6=Kosović |first6=Branko |date=2021-12-07 |title=Upper Troposphere Smoke Injection From Large Areal Fires |journal=Journal of Geophysical Research: Atmospheres |publisher=American Geophysical Union |volume=126 |issue=23 |page= |arxiv=2012.07246 |doi=10.1029/2020jd034332 |bibcode=2021JGRD..12634332R |issn=2169-897X}}</ref><ref name="Tarshish Romps 2022 p.">{{cite journal |last1=Tarshish |first1=Nathaniel |last2=Romps |first2=David M. |date=2022-09-12 |title=Latent Heating Is Required for Firestorm Plumes to Reach the Stratosphere |journal=Journal of Geophysical Research: Atmospheres |publisher=American Geophysical Union |volume=127 |issue=18 |page= |doi=10.1029/2022jd036667 |bibcode=2022JGRD..12736667T |s2cid=251852245 |issn=2169-897X}}</ref>

Research published in the peer-reviewed journal ''Safety'' suggested that no nation should possess more than 100 nuclear warheads because of the blowback effect on the aggressor nation's own population because of "nuclear autumn".<ref>{{Cite web |date=2018-06-13 |title=Morbid Researchers Imagine a 'Best-Case Scenario' for Nuclear War, and the Results Are Grim |url=https://gizmodo.com/morbid-researchers-imagine-a-best-case-scenario-for-nuc-1826776856 |access-date=2023-12-16 |website=Gizmodo |language=en}}</ref><ref>{{Cite journal|last1=Denkenberger|first1=David|last2=Pearce|first2=Joshua|last3=Pearce|first3=Joshua M.|last4=Denkenberger|first4=David C.|date=June 2018|title=A National Pragmatic Safety Limit for Nuclear Weapon Quantities|journal=Safety|volume=4|issue=2|page=25|doi=10.3390/safety4020025|doi-access=free}}</ref>

=== 2019 ===
2019 saw the publication of two studies on nuclear winter that build on previous modeling and describe new scenarios of nuclear winter from smaller exchanges of nuclear weapons than have been previously simulated.

As in the 2007 study by Robock ''et al.'',<ref name="Robock"/> a 2019 study by Coupe ''et al.'' models a scenario in which 150 Tg of black carbon is released into the atmosphere following an exchange of nuclear weapons between the United States and Russia where both countries use all of the nuclear weapons [[New START|treaties]] permit them to.<ref name=":0">{{Cite journal|last1=Coupe|first1=Joshua|last2=Bardeen|first2=C.|last3=Robock|first3=A.|last4=Toon|first4=O.|date=2019|title=Nuclear Winter Responses to Nuclear War Between the United States and Russia in the Whole Atmosphere Community Climate Model Version 4 and the Goddard Institute for Space Studies ModelE|journal=Journal of Geophysical Research: Atmospheres|volume=124|issue=15|pages=8522–8543|doi=10.1029/2019JD030509|bibcode=2019JGRD..124.8522C|s2cid=200047350}}</ref> This amount of black carbon far exceeds that which has been emitted in the atmosphere by all volcanic eruptions in the past 1,200 years but is less than the asteroid impact which caused a mass extinction event 66 million years ago.<ref name=":0" /> Coupe ''et al.'' used the "[[Whole Atmosphere Community Climate Model|whole atmosphere community climate model]] version 4" (WACCM4), which has a higher resolution and is more effective at simulating [[aerosol]]s and stratospheric chemistry than the ModelE simulation used by Robock ''et al''.<ref name=":0" />

The WACCM4 model simulates that black carbon molecules increase to ten times their normal size when they reach the stratosphere. ModelE did not account for this effect. This difference in black carbon particle size results in a greater [[optical depth]] in the WACCM4 model across the world for the first two years after the initial injection due to greater [[Absorption (chemistry)|absorption]] of sunlight in the stratosphere.<ref name=":0" /> This will have the effect of increasing stratospheric temperatures by 100K and result in ozone depletion that is slightly greater than ModelE predicted.<ref name=":0" /> Another consequence of the larger particle size is accelerating the rate at which black carbon molecules fall out of the atmosphere; after ten years from the injection of black carbon into the atmosphere, WACCM4 predicts 2 Tg will remain, while ModelE predicted 19 Tg.<ref name=":0" />

The 2019 model and the 2007 model both predict significant temperature decreases across the globe, however the increased [[Optical resolution|resolution]] and particle simulation in 2019 predict a greater temperature anomaly in the first six years after injection but a faster return to normal temperatures. Between a few months after the injection to the sixth year of anomaly, the WACCM4 predicts cooler global temperatures than ModelE, with temperatures more than 20K below normal leading to freezing temperatures during the summer months over much of the northern hemisphere leading to a 90% reduction in agricultural growing seasons in the midlatitudes, including the midwestern United States.<ref name=":0" /> WACCM4 simulations also predict a 58% reduction in global annual precipitation from normal levels in years three and four after injection, a 10% higher reduction than predicted in ModelE.<ref name=":0" />

Toon ''et al.'' simulated a nuclear scenario in 2025 where [[India]] and [[Pakistan]] engage in a nuclear exchange in which 100 urban areas in Pakistan and 150 urban areas in India are attacked with nuclear weapons ranging from 15 kt to 100 kt and examined the effects of black carbon released into the atmosphere from [[Air burst|airburst]]-only detonations.<ref name=":1"/> The researchers modeled the atmospheric effects if all weapons were 15 kt, 50 kt, and 100 kt, providing a range where a nuclear exchange would likely fall into given the recent nuclear tests performed by both nations. The ranges provided are large because neither India nor Pakistan is obligated to provide information on their nuclear arsenals, so their extent remains largely unknown.<ref name=":1" />

Toon ''et al.'' assume that either a [[firestorm]] or [[conflagration]] will occur after each detonation of the weapons, and the amount of black carbon inserted into the atmosphere from the two outcomes will be equivalent and of a profound extent;<ref name=":1" /> in Hiroshima in 1945, it is predicted that the firestorm released 1,000 times more energy than was released during the nuclear explosion.{{sfn|Toon|Turco|Robock|Bardeen|2007}} Such a large area being burned would release large amounts of black carbon into the atmosphere. The amount released ranges from 16.1 Tg if all weapons were 15 kt or less to 36.6 Tg for all 100 kt weapons.<ref name=":1" /> For the 15 kt and 100kt range of weapons, the researchers modeled global precipitation reductions of 15% to 30%, temperature reductions between 4K and 8K, and ocean temperature decreases of 1K to 3K.<ref name=":1" /> If all weapons used were 50 kt or more, [[Hadley cell]] circulation would be disrupted and cause a 50% decrease in precipitation in the American midwest. [[Primary sector of the economy|Net primary productivity]] (NPP) for oceans decreases from 10% to 20% for the 15 kt and 100 kt scenarios, respectively, while land NPP decreases between 15% and 30%; particularly affected are midlatitude agricultural regions in the United States and Europe, experiencing 25-50% reductions in NPP.<ref name=":1" /> As predicted by other literature, once the black carbon is removed from the atmosphere after ten years, temperatures and NPP will return to normal.<ref name=":1" />

=== 2021 ===
Coupe et al. report the simulation of a [[El Niño]] effect lasting several years after six nuclear scenarios ranging from 5 to 150 Tg soot under the CESM-WACCM4 model. They term the change a "Nuclear Niño" and describe various changes in the ocean currents.<ref>{{cite journal |author=Coupe |first1=J. |last2=Stevenson |first2=S. |last3=Lovenduski |first3=N. S. |display-authors=etal |year=2021 |title=Nuclear Niño response observed in simulations of nuclear war scenarios. |journal=Commun Earth Environ |volume=2 |issue=18 |page=18 |bibcode=2021ComEE...2...18C |doi=10.1038/s43247-020-00088-1 |doi-access=free}}</ref>

=== 2022 ===

[[File:Percent of the world's population dead from a nuclear war.svg|thumb|Percent of the world's population dead from a nuclear war per simulations by Xia et al. (2022, see esp. their Table 1)<ref name=Xia2022/> with models fit thereto. The vertical axis is the percent of the world's population expected to die within a few years after a one-week long nuclear war that injects between 1.5 and 150 Tg (teragrams = million metric tons) of smoke (soot) into the stratosphere, shown on the top axis.<ref>Xia et al. (2022, Table 1) reported "Number of direct fatalities" and "Number of people without food at the end of year 2" out of a total population of 6.7 billion for their simulated year 2010.  Two issues with this:  First, Xia et al. (2022, Fig. 1) show that the climate impact does not start recovering until year 5 after the nuclear war and has not yet fully recovered 9 years after the war.  Thus, few people still alive without food at the end of year 2 will not likely live to year 9.  Second, the percentages plotted here are the sums of those two numbers divided by 6.7 billion.  The Wikipedia article on [[w:World population|World population]] said the world population in 2010 was 6,985,603,105 -- 7 billion (accessed 12 August 2023).  The difference between 6.7 and 7 billion seems so slight that it can be safely ignored, especially given the uncertainty inherent in these simulations and the likelihood that the small populations excluded were probably not substantively different from those included.</ref> The bottom axis is the total megatonnage (number of nuclear weapons used times average yield) simulated to produce the quantity of soot plotted on the top axis. "IND-PAK" marks a range of hypothetical nuclear wars between [[w:India and weapons of mass destruction|India]] (IND) and [[w:Pakistan and weapons of mass destruction|Pakistan]] (PAK).  "USA-RUS" marks a simulated nuclear war between [[w:Nuclear weapons of the United States|the US]] (USA) and [[w:Russia and weapons of mass destruction|Russia]] (RUS).  "PRK" = a simulated nuclear war in which [[w:North Korea and weapons of mass destruction|North Korea]] (the People's Republic of Korea, PRK) used their existing nuclear arsenal estimated at 30 weapons with an average yield of 17 kt<ref>Estimates of North Korea's nuclear weapons stockpile vary widely, as summarized in the Wikipedia article on [[w:North Korea and weapons of mass destruction|North Korea and weapons of mass destruction]], accessed 2023-08-07.  The estimate of 30 weapons averaging 17 kt each seems not far from the middle of the estimate cited in that article.  That totals 510 kt (0.51 megatons), roughly a third of smallest nuclear war simulated by Xia et al. (2022).</ref> ''without nuclear retaliation by an adversary''.<ref>See also [[Wikiversity:Responding to a nuclear attack]].</ref>]]

According to a peer-reviewed study published in the journal ''[[Nature Food]]'' in August 2022,<ref name=Xia2022/> a full-scale nuclear war between the [[United States]] and [[Russia]], which together hold more than 90% of the world's nuclear weapons, would kill 360 million people directly and more than 5 billion indirectly by starvation during a nuclear winter.<ref>{{cite news |last1=Diaz-Maurin |first1=François |date=20 October 2022 |title=Nowhere to hide: How a nuclear war would kill you – and almost everyone else |work=[[Bulletin of the Atomic Scientists]] |url=https://thebulletin.org/2022/10/nowhere-to-hide-how-a-nuclear-war-would-kill-you-and-almost-everyone-else/}}</ref><ref>{{cite news |title=World Nuclear war between the U.S. and Russia would kill more than 5 billion people – just from starvation, study finds |url=https://www.cbsnews.com/news/nuclear-war-5-billion-people-starvation-deaths-study/ |work=CBS News |date=16 August 2022}}</ref>

Another paper published that year, from the [[Tohoku University]] Earth science scholar Kunio Kaiho, compared the impact of nuclear winter scenarios on marine and terrestrial [[animal]] life with that of historical [[extinction event]]s. Kaiho estimated that a ''minor'' [[nuclear war]] (which he defined as a nuclear exchange between [[India]] and [[Pakistan]] or an event of equivalent magnitude) would cause extinctions of 10–20% of species on its own, while a ''major'' nuclear war (defined as a nuclear exchange between [[United States]] and [[Russia]]) would cause the extinctions of 40–50% of animal species, which is comparable to some of the "Big Five" mass extinction events. For comparison, what he considered the most likely scenario of anthropogenic [[climate change]], with {{convert|3|C-change|F-change}} of warming by 2100 and {{convert|3.8|C-change|F-change}} by 2500, would send around 12–14% of animal species extinct under the same methodology.<ref name="Kaiho2022">{{Cite journal |last1=Kaiho |first1=Kunio |date=23 November 2022 |title=Extinction magnitude of animals in the near future |journal=Scientific Reports |volume=12 |issue=1 |page=19593 |language=en |doi=10.1038/s41598-022-23369-5 |pmid=36418340 |pmc=9684554 |bibcode=2022NatSR..1219593K }}</ref>

=== 2023 ===
Since 2023, the U.S. National Academies of Science, Engineering, and Medicine has established an Independent Study on Potential Environmental Effects of Nuclear War. The aim is to evaluate all research on nuclear winter, and the final report was planned for a 2024 release date.<ref name="National Academies">{{cite web | access-date=28 May 2025 | url=https://www.nationalacademies.org/our-work/independent-study-on-potential-environmental-effects-of-nuclear-war | title=Independent Study on Potential Environmental Effects of Nuclear War | publisher=National Academy of Sciences}}</ref>

{{as of|2025|03|12|post=,}} the committee was still working on the report.{{r|name="National Academies"|at="Past Events"|q="The following topics were discussed in the closed sessions: Discussing state of report and timeline. Drafting of the report as well."}}

=== 2025 study - Impact on global agriculture ===

In 2025, researchers at Pennsylvania State University used the Cycles [[agroecosystem]] [[Agroecosystem analysis|model]] to simulate how a nuclear winter could impact global corn yields (''Zea mays''), treating corn as a proxy for global staple crops. The study modeled production across 38,572 locations under six scenarios of soot injection into the upper atmosphere, ranging from about 5 million to 165 million tonnes.<ref name="PSU2025">{{cite web |title=Simulating the unthinkable: Models show nuclear winter food production plunge |url=https://www.psu.edu/news/research/story/simulating-unthinkable-models-show-nuclear-winter-food-production-plunge/ |website=Pennsylvania State University |date=22 July 2025 |access-date=11 August 2025}}</ref><ref name=":3">{{Cite journal |last=Shi |first=Yuning |last2=Montes |first2=Felipe |last3=Di Gioia |first3=Francesco |last4=Xia |first4=Lili |last5=Bardeen |first5=Charles G. |last6=Anderson |first6=Charles T. |last7=Gil |first7=Yolanda |last8=Khider |first8=Deborah |last9=Ratnakar |first9=Varun |last10=Kemanian |first10=Armen R. |date=2025-06-01 |title=Adapting agriculture to climate catastrophes: the nuclear winter case |url=http://www.scopus.com/inward/record.url?scp=105005164732&partnerID=8YFLogxK |journal=Environmental Research Letters |volume=20 |issue=6 |doi=10.1088/1748-9326/adcfb5 |issn=1748-9326|doi-access=free }}</ref>

A regional nuclear war (~5.5 Mt soot) could reduce worldwide corn production by about 7%, while a full-scale global conflict (~165 Mt soot) might cut yields by around 80%.<ref name="ScienceAlert2025">{{cite news |last=Fisher |first=Theresa |title=A nuclear winter could destroy much of the world's food supply |url=https://www.sciencealert.com/a-nuclear-winter-could-destroy-much-of-the-worlds-food-supply |work=ScienceAlert |date=24 July 2025 |access-date=11 August 2025}}</ref><ref>{{Cite web |last=Irving |first=Michael |date=2025-08-08 |title=A Nuclear Winter Could Destroy Much of The World's Food Supply |url=https://www.sciencealert.com/a-nuclear-winter-could-destroy-much-of-the-worlds-food-supply |access-date=2025-08-11 |website=ScienceAlert |language=en-US}}</ref>

The researchers also estimated that ozone depletion following a large-scale conflict would increase ultraviolet-B radiation, peaking six to eight years later, causing an additional ~7 % decline in corn yields. In the worst-case scenario, this would bring the total reduction to roughly 87%.<ref name="PSU2025" /><ref>{{Cite web |title=New Study Reveals How Nuclear War Could Starve The World |url=https://www.ndtv.com/science/new-study-reveals-how-nuclear-war-could-starve-the-world-9053608 |access-date=2025-08-11 |website=www.ndtv.com |language=en}}</ref>

Global agricultural recovery was projected to take between seven and twelve years, depending on the severity of the conflict and location, with longer delays at higher latitudes.<ref name="ScienceAlert2025" /> To help mitigate such impacts, the authors suggested "agricultural resilience kits," containing seeds of fast-growing, cold-tolerant crops suited to different regions.<ref name="PSU2025" /><ref name=":3" />

==Criticism and debate==
The five major and largely independent underpinnings that the nuclear winter concept has and continues to receive criticism over are regarded as:<ref name="LANL2018"/><ref name="nytimes.com">{{cite news|url=https://www.nytimes.com/1990/01/23/science/nuclear-winter-theorists-pull-back.html?pagewanted=2|title=Nuclear Winter Theorists Pull Back|first=Malcolm W.|last=Browne|access-date=2017-02-11|archive-url=https://web.archive.org/web/20170519073506/http://www.nytimes.com/1990/01/23/science/nuclear-winter-theorists-pull-back.html?pagewanted=2|archive-date=2017-05-19|url-status=live|newspaper=The New York Times|date=1990-01-23}}</ref>

* Would cities readily [[firestorm]], and if so how much soot would be generated?
* ''Atmospheric'' longevity: would the quantities of soot assumed in the models remain in the atmosphere for as long as projected or would far more soot precipitate as [[firestorm|black rain]] much sooner?
* ''Timing'' of events: how reasonable is it for the modeling of firestorms or war to commence in late spring or summer (this is done in almost all US-Soviet nuclear winter papers, thereby giving rise to the largest possible degree of modeled cooling)?
* ''[[Optical depth#Atmospheric sciences|Darkness and opacity]]'': how much light-blocking effect the assumed quality of the soot reaching the atmosphere would have?<ref name="nytimes.com"/>
* ''Lofting'': how much soot would be lofted into the stratosphere?<ref name="LANL2018"/>

While the highly popularized initial 1983 TTAPS 1-dimensional model forecasts were widely reported and criticized in the media, in part because every later model predicts far less of its "apocalyptic" level of cooling,<ref name="textfiles.com">{{cite news |author=Seitz |first=Russell |date=November 5, 1986 |title=The Melting of 'Nuclear Winter |work=The Wall Street Journal |url=http://www.textfiles.com/survival/nkwrmelt.txt |url-status=live |archive-url=https://web.archive.org/web/20160912140621/http://www.textfiles.com/survival/nkwrmelt.txt |archive-date=2016-09-12}}</ref> most models continue to suggest that some deleterious global cooling would still result, under the assumption that a large number of fires occurred in the spring or summer.<ref name="sgr.org.uk"/><ref name="Martin">{{cite journal |author=Martin |first=Brian |date=October 1988 |title=Nuclear winter: science and politics |url=http://www.uow.edu.au/~bmartin/pubs/88spp.html |url-status=live |journal=Science and Public Policy |volume=15 |issue=5 |pages=321–334 |doi=10.1093/spp/15.5.321 |archive-url=https://web.archive.org/web/20140129144432/http://www.uow.edu.au/%7Ebmartin/pubs/88spp.html |archive-date=2014-01-29 |access-date=2014-06-11 |via=www.uow.edu.au}}</ref> Starley L. Thompson's less primitive mid-1980s [[global climate models|3-dimensional]] model, which notably contained the very same general assumptions, led him to coin the term "nuclear autumn" to more accurately describe the climate results of the soot in this model, in an on camera interview in which he dismisses the earlier "apocalyptic" models.<ref>{{cite web |title=Nuclear Winter |others=Produced by Kit Roane |date=4 April 2016 |publisher=Pulitzer Center |url=http://www.retroreport.org/video/nuclear-winter |access-date=4 April 2016 |via=Retro Report |archive-url=https://web.archive.org/web/20160410163333/http://www.retroreport.org/video/nuclear-winter|archive-date=10 April 2016}}</ref>

A major criticism of the assumptions that continue to make these model results possible appeared in the 1987 book ''[[Nuclear War Survival Skills]]'' (''NWSS''), a [[civil defense]] manual by [[Cresson Kearny]] for the [[Oak Ridge National Laboratory]].<ref name="ORNL">{{cite book |last=Kearny |first=Cresson |url=http://www.oism.org/nwss/ |title=Nuclear War Survival Skills |date=1987 |publisher=Oregon Institute of Science and Medicine |isbn=978-0-942487-01-5 |location=Cave Junction, Oregon |pages=17–19 |language=en-us |author-link=Cresson Kearny |access-date=2008-04-29 |archive-url=https://web.archive.org/web/20080515172145/http://www.oism.org/nwss/ |archive-date=2008-05-15 |url-status=live}}</ref> According to the 1988 publication ''An assessment of global atmospheric effects of a major nuclear war'', Kearny's criticisms were directed at the excessive amount of soot that the modelers assumed would reach the stratosphere. Kearny cited a Soviet study that modern cities would not burn as firestorms, as most flammable city items would be buried under non-combustible rubble and that the TTAPS study included a massive overestimate on the size and extent of non-urban wildfires that would result from a nuclear war.<ref name="babel.hathitrust.org" /> The TTAPS authors responded that, amongst other things, they did not believe target planners would intentionally blast cities into rubble, but instead argued fires would begin in relatively undamaged suburbs when nearby sites were hit, and partially conceded his point about non-urban wildfires.<ref name="babel.hathitrust.org" /> Dr. Richard D. Small, director of thermal sciences at the Pacific-Sierra Research Corporation similarly disagreed strongly with the model assumptions, in particular the 1990 update by TTAPS that argues that some 5,075 Tg of material would burn in a total US-Soviet nuclear war, as analysis by Small of blueprints and real buildings returned a maximum of 1,475 Tg of material that could be burned, "assuming that all the available combustible material was actually ignited".<ref name="nytimes.com"/>

Although Kearny was of the opinion that future more accurate models would, "indicate there will be even smaller reductions in temperature", including future potential models that did not so readily accept that firestorms would occur as dependably as nuclear winter modellers assume, in ''NWSS'' Kearny summarized the comparatively moderate cooling estimate of no more than a few days,<ref name="ORNL" /> from the 1986 ''Nuclear Winter Reappraised'' model by Starley Thompson and [[Stephen Schneider (scientist)|Stephen Schneider]].<ref>{{cite journal |last1=Thompson |first1=Starley L. |last2=Schneider |first2=Stephen H. |title=Nuclear Winter Reappraised |journal=Foreign Affairs |volume=64 |issue=5 |date=Summer 1986 |pages=981–1005 |jstor=20042777 |url=http://www.foreignaffairs.org/19860601faessay7798/starley-l-thompson-stephen-h-schneider/nuclear-winter-reappraised.html |doi=10.2307/20042777  | archive-url=https://web.archive.org/web/20090119010758/http://www.foreignaffairs.org/19860601faessay7798/starley-l-thompson-stephen-h-schneider/nuclear-winter-reappraised.html |archive-date=2009-01-19}}</ref> This was done in an effort to convey to his readers that contrary to the popular opinion at the time, in the conclusion of these two climate scientists, "on scientific grounds the global apocalyptic conclusions of the initial nuclear winter hypothesis can now be relegated to a vanishing low level of probability".<ref name="ORNL" />

However, a 1988 article by Brian Martin in ''Science and Public Policy''<ref name="Martin" /> states that—although ''Nuclear Winter Reappraised'' concluded the US-Soviet "nuclear winter" would be much less severe than originally thought, with the authors describing the effects more as a "nuclear autumn"—other statements by Thompson and Schneider<ref>{{cite news |author=Schneider |first=Stephen H. |date=25 November 1986 |title=letter |work=Wall Street Journal}}</ref><ref>'Severe global-scale nuclear war effects reaffirmed', statement resulting from SCOPE-ENUWAR workshop in Bangkok, 9–12 February 1987.</ref> show that they, "resisted the interpretation that this means a rejection of the basic points made about nuclear winter". In the Alan Robock et al. 2007 paper, they write that, "because of the use of the term 'nuclear autumn' by Thompson and Schneider [1986], even though the authors made clear that the climatic consequences would be large, in policy circles the theory of nuclear winter is considered by some to have been exaggerated and disproved [e.g., Martin, 1988]."<ref name="Robock"/> In 2007 Schneider expressed his tentative support for the cooling results of the limited nuclear war (Pakistan and India) analyzed in the 2006 model, saying, "The sun is much stronger in the tropics than it is in mid-latitudes. Therefore, a much more limited war [there] could have a much larger effect, because you are putting the smoke in the worst possible place", and "anything that you can do to discourage people from thinking that there is any way to win anything with a nuclear exchange is a good idea".<ref>{{cite web |author=Lee |first=Brian D. |date=8 January 2007 |title=Climate scientists describe chilling consequences of a nuclear war |url=http://news.stanford.edu/news/2007/january10/schneidersr-011007.html |url-status=live |archive-url=https://web.archive.org/web/20110731151700/http://news.stanford.edu/news/2007/january10/schneidersr-011007.html |archive-date=2011-07-31 |work=Stanford Report}}</ref>

The contribution of smoke from the ignition of live non-desert vegetation, living forests, grasses and so on, nearby to many [[missile silo]]s is a source of smoke originally assumed to be very large in the initial "Twilight at Noon" paper, and also found in the popular TTAPS publication. However, this assumption was examined by Bush and Small in 1987 and they found that the burning of live vegetation could only conceivably contribute very slightly to the estimated total "nonurban smoke production".<ref name="babel.hathitrust.org" /> With the vegetation's potential to sustain burning only probable if it is within a [[Nuclear weapon yield#Yield limits|radius]] or two from the surface of the nuclear fireball, which is at a distance that would also experience extreme [[blast wave|blast winds]] that would influence any such fires.<ref>{{cite journal|doi=10.1080/00102208708952566 |volume=52 |issue=1–3 |title=A Note on the Ignition of Vegetation by Nuclear Weapons |year=1987 |journal=Combustion Science and Technology |pages=25–38 |last1=Bush |first1=B. W. |last2=Small |first2=R. D.}}</ref> This reduction in the estimate of the non-urban smoke hazard is supported by the earlier preliminary ''Estimating Nuclear Forest Fires'' publication of 1984,<ref name="babel.hathitrust.org" /> and by the 1950–1960s in-field examination of surface-scorched, [[Operation Blowdown|mangled]] but never burnt-down tropical forests on the surrounding islands from the shot points in the [[Operation Castle]]<ref>{{cite report |url=http://www.hss.energy.gov/HealthSafety/IHS/marshall/collection/data/ihp1d/49309z.pdf |title=Operation Castle, Project 3.3, Blast Effects on Tree Stand |last1=Fons |first1=W. L. |last2=Storey |first2=Theodore G. |date=March 1955 |publisher=U.S. Department of Agriculture, Forest Service, Division of Fire Research |id=WT-921 |access-date=2014-10-16 |archive-url=https://web.archive.org/web/20141023114936/http://www.hss.energy.gov/HealthSafety/IHS/marshall/collection/data/ihp1d/49309z.pdf |archive-date=2014-10-23}}</ref> and [[Operation Redwing]]<ref>{{cite report |title=Operation Redwing, Technical Summary of Military Effects, Programs 1–9 (Pacific Proving Grounds, May – July 1956) |id=WT-1344(EX) |date=15 May 1981 |orig-date=April 25, 1961 |page=219 |url=https://documents.theblackvault.com/documents/nuclear/ADA995132.pdf |access-date=2021-09-02 |via=The Black Vault |archive-date=2021-09-02  |archive-url=https://web.archive.org/web/20210902190754/https://documents.theblackvault.com/documents/nuclear/ADA995132.pdf |url-status=live }}</ref><ref>{{cite web |author=Greenewald |first=John |date=March 1, 2015 |title=Operation Redwing |url=https://www.theblackvault.com/documentarchive/operation-redwing/ |url-status=live |archive-url=https://web.archive.org/web/20210902190754/https://www.theblackvault.com/documentarchive/operation-redwing/ |archive-date=2021-09-02 |access-date=2021-09-03 |website=The Black Vault}}</ref> test series.

[[Image:Tokyo 1945-3-10-1.jpg|thumb|During the [[Bombing of Tokyo|''Operation Meeting House'' firebombing of Tokyo]] on 9–10 March 1945, 1,665 tons (1.66 kilotons) of [[wikt:incendiary|incendiary]] and [[high-explosive]] bombs in the form of [[bomblets]] were dropped on the city, causing the destruction of over 10,000 [[acres]] of buildings – {{convert|16|sqmi|km2}}, the most destructive and deadliest bombing operation in history.<ref>{{cite web |author=Vance |first=Laurence M. |date=14 August 2009 |title=Bombings Worse than Nagasaki and Hiroshima |url=http://www.fff.org/comment/com0908j.asp |archive-url=https://web.archive.org/web/20121113021343/http://fff.org/comment/com0908j.asp |archive-date=13 November 2012 |access-date=8 August 2011 |website=The Future of Freedom Foundation}}</ref><ref>{{cite news |author=Coleman |first=Joseph |date=10 March 2005 |title=1945 Tokyo Firebombing Left Legacy of Terror, Pain |publisher=CommonDreams.org |agency=Associated Press |url=http://www.commondreams.org/headlines05/0310-08.htm |url-status=live |access-date=8 August 2011 |archive-url=https://web.archive.org/web/20150103023353/http://www.commondreams.org/headlines05/0310-08.htm |archive-date=3 January 2015}}</ref>]]
[[File:Hiroshima aftermath.jpg|thumb|The first nuclear bombing in history used a [[little boy|16-kiloton nuclear bomb]], approximately 10 times as much energy as delivered onto Tokyo, yet due in part to the [[nuclear holocaust#"Overkill" and comparisons to WWII|comparative inefficiency of larger bombs]],<ref group="note" name="external">"This relation arises from the fact that the destructive power of a bomb does not vary linearly with the yield. The volume the weapon's energy spreads into varies as the cube of the distance, but the destroyed area varies at the square of the distance"</ref><ref>{{cite web|title=The Energy from a Nuclear Weapon |website=www.atomicarchive.com |url=http://www.atomicarchive.com/Effects/effects1.shtml|access-date=2016-10-14|archive-url=https://web.archive.org/web/20161017221016/http://www.atomicarchive.com/Effects/effects1.shtml|archive-date=2016-10-17|url-status=live}}</ref> a much ''smaller'' area of building destruction occurred when contrasted with the results from Tokyo. Only {{convert|4.5|sqmi|km2}} of Hiroshima was destroyed by blast, fire, and [[firestorm]] effects.<ref name="Firestorms. pg 53">{{cite web |url=http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=AD0616638 |title=Exploratory Analysis of Fire Storms |website=Dtic.mil |access-date=2016-05-11 |archive-url=https://web.archive.org/web/20121008110454/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0616638&Location=U2&doc=GetTRDoc.pdf |archive-date=2012-10-08  }}</ref> Similarly, Major Cortez F. Enloe, a surgeon in the [[USAAF]] who worked with the [[United States Strategic Bombing Survey]] (USSBS), noted that the even more energetic [[Fat Man|22-kiloton nuclear bomb]] dropped on [[Nagasaki]] did not result in a firestorm and thus did not do as much fire damage as the [[Bombing of Hamburg in World War II|conventional airstrikes on Hamburg]] which did generate a firestorm.<ref>{{cite magazine |title=News in Brief |url=http://www.flightglobal.com/pdfarchive/view/1946/1946%20-%200061.html |date=10 January 1946 |magazine=Flight |page=33 |access-date=14 October 2016 |url-status=live |archive-url=https://web.archive.org/web/20160514010720/https://www.flightglobal.com/pdfarchive/view/1946/1946%20-%200061.html |archive-date=14 May 2016}}</ref> Thus, whether a city will firestorm depends primarily not on the size or type of bomb dropped, but rather on the density of fuel present in the city.{{Citation needed|date=December 2020}} Moreover, it has been observed that firestorms are not likely in areas where modern buildings (constructed of bricks and concrete) have totally collapsed. By comparison, Hiroshima, and Japanese cities in general in 1945, had consisted of mostly densely-packed wooden houses along with the common use of [[Shōji|''shoji'' paper sliding walls]].<ref name="Firestorms. pg 53"/><ref name="osti.gov">{{cite journal |url=http://www.osti.gov/bridge/product.biblio.jsp?osti_id=4421057 |title=Medical Effects of Atomic Bombs, The Report of the Joint Commission for the Investigation of the Effects of the Atomic Bomb in Japan |volume=1 (Technical Report) |publisher=SciTech Connect |website=Osti.gov |date=1951-04-19 |doi=10.2172/4421057 |access-date=2016-05-11 |archive-url=https://web.archive.org/web/20130723230457/http://www.osti.gov/bridge/product.biblio.jsp?osti_id=4421057 |archive-date=2013-07-23 |url-status=live |last1=Oughterson |first1=A. W. |last2=Leroy |first2=G. V. |last3=Liebow |first3=A. A. |last4=Hammond |first4=E. C. |last5=Barnett |first5=H. L. |last6=Rosenbaum |first6=J. D. |last7=Schneider |first7=B. A. |doi-access=free }}</ref> The fire hazard construction practices present in cities that have historically firestormed are now illegal in most countries for general safety reasons, and therefore cities with firestorm potential are far rarer than was common at the time of World War II.]]

A paper by the [[United States Department of Homeland Security]], finalized in 2010, states that after a nuclear detonation targeting a city "If fires are able to grow and coalesce, a firestorm could develop that would be beyond the abilities of firefighters to control. However experts suggest in the nature of modern US city design and construction may make a raging firestorm unlikely".<ref>{{cite web |date=June 2010 |url= http://hpschapters.org/sections/homeland/documents/Planning_Guidance_for_Response_to_a_Nuclear_Detonation-2nd_Edition_FINAL.pdf |title=Planning Guidance for Response to a Nuclear Detonation |edition=2nd |archive-url=https://web.archive.org/web/20140403100050/http://hpschapters.org/sections/homeland/documents/Planning_Guidance_for_Response_to_a_Nuclear_Detonation-2nd_Edition_FINAL.pdf|archive-date=3 April 2014}}</ref> The nuclear bombing of Nagasaki for example, did not produce a firestorm.<ref>[http://www.fourmilab.ch/etexts/www/effects/eonw_7.pdf Glasstone & Dolan (1977) Thermal effects Chapter] {{Webarchive|url=https://web.archive.org/web/20140309024211/http://www.fourmilab.ch/etexts/www/effects/eonw_7.pdf |date=2014-03-09 }} p. 304</ref> This was similarly noted as early as 1986–1988, when the assumed quantity of fuel "mass loading" (the amount of fuel per square meter) in cities underpinning the winter models was found to be too high and intentionally creates [[heat flux]]es that loft smoke into the lower stratosphere, yet assessments "more characteristic of conditions" to be found in real-world modern cities, had found that the fuel loading, and hence the heat flux that would result from efficient burning, would rarely loft smoke much higher than 4&nbsp;km.<ref name="babel.hathitrust.org" />

Russell Seitz, Associate of the Harvard University Center for International Affairs, argues that the winter models' assumptions give results which the researchers want to achieve and is a case of "worst-case analysis run amok".<ref name="Martin"/> In September 1986, Seitz published "Siberian fire as 'nuclear winter' guide" in the journal ''Nature'', in which he investigated the 1915 Siberian fire, which started in the early summer months and was caused by the worst drought in the region's recorded history. The fire ultimately devastated the region, burning the world's largest [[boreal forest]], the size of Germany. While approximately 8˚C of daytime summer cooling occurred under the smoke clouds during the weeks of burning, no increase in potentially devastating agricultural night frosts occurred.<ref>{{cite journal |journal=Nature |volume=323 |issue=6084 |title=Siberian fire as "nuclear winter" guide |pages=116–117 |year=1986 |last1=Seitz |first1=Russell |doi=10.1038/323116a0 |bibcode=1986Natur.323..116S |s2cid=4326470}}</ref> Following his investigation into the Siberian fire of 1915, Seitz criticized the "nuclear winter" model results for being based on successive worst-case events:

{{blockquote| The improbability of a string of 40 such coin tosses coming up heads approaches that of a pat [[royal flush (poker hand)|royal flush]].  Yet it was represented as a "sophisticated one-dimensional model" – a usage that is oxymoronic, unless applied to [the British model Lesley Lawson] [[Twiggy]].<ref name="textfiles.com" />|author=|title=|source=}}

Seitz cited Carl Sagan, adding an emphasis: "''In almost any realistic case'' involving nuclear exchanges between the superpowers, global environmental changes sufficient to cause an extinction event equal to or more severe than that of the close of the [[Cretaceous]] when the dinosaurs and many other species died out are likely." Seitz comments: "The ominous [[rhetoric]] italicized in this passage puts even the 100 megaton [the original 100 city firestorm] scenario ... on a par with the 100 million megaton blast of an asteroid striking the Earth. This [is] astronomical mega-hype ..."<ref name="textfiles.com"/> Seitz concludes:

{{blockquote|As the science progressed and more authentic sophistication was achieved in newer and more elegant models, the postulated effects headed downhill. By 1986, these worst-case effects had melted down from a year of arctic darkness to warmer temperatures than the cool months in [[Palm Beach, Florida|Palm Beach]]! A new [[paradigm]] of broken clouds and cool spots had emerged. The once global hard [[frost]] had retreated back to the northern [[tundra]]. Mr. Sagan's elaborate conjecture had fallen prey to [[Murphy's Law|Murphy's]] lesser-known Second Law: If everything MUST go wrong, don't bet on it.<ref name="textfiles.com"/>}}

Seitz's opposition caused the proponents of nuclear winter to issue responses in the media. The proponents believed it was simply necessary to show only the possibility of climatic catastrophe, often a worst-case scenario, while opponents insisted that to be taken seriously, nuclear winter should be shown as likely under "reasonable" scenarios.{{Sfn | Badash |2009 | p = 251}} One of these areas of contention, as elucidated by Lynn R. Anspaugh, is upon the question of which season should be used as the backdrop for the US-USSR war models. Most models choose the summer in the Northern Hemisphere as the start point to produce the maximum soot lofting and therefore eventual winter effect. However, it has been pointed out that if the same number of firestorms occurred in the autumn or winter months, when there is much less intense sunlight to loft soot into a stable region of the stratosphere, the magnitude of the cooling effect would be negligible, according to a January model run by Covey et al.<ref name=autogenerated2>{{cite book |url=http://books.nap.edu/openbook.php?record_id=940&page=570|title=The Medical Implications of Nuclear War |date=1986|doi=10.17226/940|pmid=25032468|isbn=978-0-309-07866-5|author1=Institute of Medicine (US) Steering Committee for the Symposium on the Medical Implications of Nuclear War|editor-last1=Solomon|editor-first1=F. |editor-last2=Marston |editor-first2=R. Q.|access-date=22 September 2014|archive-url=https://web.archive.org/web/20140924040629/http://books.nap.edu/openbook.php?record_id=940&page=570 |archive-date=24 September 2014|url-status=live}}</ref> Schneider conceded the issue in 1990, saying "a war in late fall or winter would have no appreciable [cooling] effect".<ref name="nytimes.com"/>

Anspaugh also expressed frustration that although a managed forest fire in Canada on 3 August 1985 is said to have been lit by proponents of nuclear winter, with the fire potentially serving as an opportunity to do some basic measurements of the optical properties of the smoke and smoke-to-fuel ratio, which would have helped refine the estimates of these critical model inputs, the proponents did not indicate that any such measurements were made.<ref name=autogenerated2 /> [[Peter V. Hobbs]], who would later successfully attain funding to fly into and sample the smoke clouds from the Kuwait oil fires in 1991, also expressed frustration that he was denied funding to sample the Canadian, and other forest fires in this way.<ref name="babel.hathitrust.org" /> Turco wrote a 10-page memorandum with information derived from his notes and some satellite images, claiming that the smoke plume reached 6&nbsp;km in altitude.<ref name="babel.hathitrust.org" />

In 1986, atmospheric scientist [[Joyce E. Penner|Joyce Penner]] from the [[Lawrence Livermore National Laboratory]] published an article in ''Nature'' in which she focused on the specific variables of the smoke's optical properties and the quantity of smoke remaining airborne after the city fires. She found that the published estimates of these variables varied so widely that depending on which estimates were chosen the climate effect could be negligible, minor or massive.<ref>{{cite journal |doi=10.1038/324222a0 |title=Uncertainties in the smoke source term for 'nuclear winter' studies |volume=324 |issue=6094 |journal=Nature |pages=222–226 |year=1986 |last1=Penner |first1=Joyce E. |author-link1=Joyce E. Penner |bibcode=1986Natur.324..222P |s2cid=4339616 |url=https://zenodo.org/record/1233051 |access-date=2018-09-13  |archive-date=2020-07-28  |archive-url=https://web.archive.org/web/20200728023015/https://zenodo.org/record/1233051 |url-status=live }}</ref> The assumed optical properties for black carbon in more recent nuclear winter papers in 2006 are still "based on those assumed in earlier nuclear winter simulations".<ref name="Robock"/>

[[John Maddox]], editor of the journal ''[[Nature (journal)|Nature]]'', issued a series of skeptical comments about nuclear winter studies during his tenure.<ref>{{cite journal |last1=Maddox |first1=John |year=1984 |title=From Santorini to armageddon |journal=Nature |volume=307 |issue=5947| page=107 |doi=10.1038/307107a0| bibcode = 1984Natur.307..107M| s2cid = 4323882 }}</ref><ref>{{cite journal |last1=Maddox |first1=John |year=1984 |title=Nuclear winter not yet established |journal=Nature |volume=308 |issue=5954| page=11 |doi=10.1038/308011a0| bibcode=1984Natur.308...11M| s2cid=4325677}}</ref> Similarly S. Fred Singer was a long term vocal critic of the hypothesis in the journal and in televised debates with Carl Sagan.<ref>{{cite journal |last1=Singer |first1=S. Fred |year=1984 |title=Is the 'nuclear winter' real? |journal=Nature |volume=310 |issue=5979| page=625 |doi=10.1038/310625a0| bibcode=1984Natur.310..625S| s2cid=4238816| doi-access=free}}</ref><ref>{{cite journal |last1=Singer |first1=S. Fred |year=1985 |title=On a 'nuclear winter' (letter) |journal=Science |volume=227 |issue=4685| page=356 |pmid=17815709 |doi=10.1126/science.227.4685.356 |bibcode=1985Sci...227..356S}}</ref><ref name="babel.hathitrust.org"/>

===Critical response to the more modern papers===
In a 2011 response to the more modern papers on the hypothesis, Russell Seitz published a comment in ''Nature'' challenging Alan Robock's claim that there has been no real scientific debate about the "nuclear winter" concept.<ref>{{cite journal | doi = 10.1038/475037b | pmid=21734694 | volume=475 | issue=7354 | title=Nuclear winter was and is debatable | journal=Nature | page=37 | year=2011 | last1 = Seitz | first1 = Russell| doi-access=free }}</ref> In 1986 Seitz also contends that many others are reluctant to speak out for fear of being stigmatized as "closet [[Dr. Strangelove]]s"; physicist [[Freeman Dyson]] of Princeton for example stated "It's an absolutely atrocious piece of science, but I quite despair of setting the public record straight."<ref name="textfiles.com"/> According to the Rocky Mountain News, Stephen Schneider had been called a fascist by some disarmament supporters for having written his 1986 article "Nuclear Winter Reappraised."<ref name="ORNL" /> [[MIT]] meteorologist [[Kerry Emanuel]] similarly wrote in a review in ''Nature'' that the winter concept is "notorious for its lack of scientific integrity" due to the unrealistic estimates selected for the quantity of fuel likely to burn, the imprecise global circulation models used. Emanuel ends by stating that the evidence of other models point to substantial scavenging of the smoke by rain.<ref>{{cite journal |url=http://texmex.mit.edu/ftp/pub/emanuel/PAPERS/nuclear.pdf |title=Nuclear winter: Towards a scientific exercise |last=Emanuel |first=K. |journal=Nature |volume=319 |page=259 |date=23 Jan 1986 |issue=6051 |doi=10.1038/319259a0 |bibcode=1986Natur.319..259E |s2cid=7405296 |doi-access=free |access-date=2021-09-04  |archive-date=2021-09-04  |archive-url=https://web.archive.org/web/20210904215009/http://texmex.mit.edu/ftp/pub/emanuel/PAPERS/nuclear.pdf |url-status=live }}</ref> Emanuel also made an "interesting point" about questioning proponents' objectivity when it came to strong emotional or political views that they hold.<ref name="babel.hathitrust.org" />

[[William R. Cotton]], Professor of Atmospheric Science at Colorado State University, specialist in [[cloud physics]] modeling and co-creator of the highly influential<ref>{{cite journal|title=A comprehensive meteorological modeling system—RAMS|first1=R. A.|last1=Pielke|first2=W. R.|last2=Cotton|first3=R. L. |last3=Walko|first4=C. J.|last4=Tremback|first5=W. A.|last5=Lyons|first6=L. D.|last6=Grasso|first7=M. E. |last7=Nicholls|first8=M. D.|last8=Moran |first9=D. A.|last9=Wesley|first10=T. J.|last10=Lee|first11=J. H. |last11=Copeland|date=March 1992|journal=Meteorology and Atmospheric Physics|volume=49|issue=1–4|pages=69–91 |s2cid=3752446 |doi=10.1007/BF01025401 |bibcode=1992MAP....49...69P |url=https://www.academia.edu/5920131 |access-date=2021-09-04}}</ref><ref>{{cite web|website=Google Scholar |url=https://scholar.google.com/scholar?hl=en&as_sdt=5%2C48&sciodt=0%2C48&cites=13921324745783044190&scipsc=&q=A+comprehensive+meteorological+modeling+system%E2%80%94RAMS&btnG= |access-date=2021-09-04 |title=Search results: A comprehensive meteorological modeling system—RAMS|archive-url=https://web.archive.org/web/20210904200312/https://scholar.google.com/scholar?hl=en&as_sdt=5%2C48&sciodt=0%2C48&cites=13921324745783044190&scipsc=&q=A+comprehensive+meteorological+modeling+system%E2%80%94RAMS&btnG= |archive-date=2021-09-04}} {{as of|2021|September}}, over 2500 papers have referenced the original RAMS paper.</ref> and previously mentioned [[Regional Atmospheric Modeling System|RAMS atmosphere model]], had in the 1980s worked on soot rain-out models<ref name="babel.hathitrust.org" /> and supported the predictions made by his own and other nuclear winter models.{{Sfn | Badash |2009 | pp = 184–185}} However, he has since reversed this position, according to a book co-authored by him in 2007, stating that, amongst other systematically examined assumptions, far more rain out/wet deposition of soot will occur than is assumed in modern papers on the subject: "We must wait for a new generation of [[General Circulation Model|GCMs]] to be implemented to examine potential consequences quantitatively". He also states that, in his view, "nuclear winter was largely politically motivated from the beginning".<ref name=autogenerated4/><ref name="assets.cambridge.org"/>

== Policy implications ==
During the [[Cuban Missile Crisis]], [[Fidel Castro]] and [[Che Guevara]] called on the USSR to launch a nuclear [[Pre-emptive nuclear strike|first strike]] against the US in the event of a US invasion of Cuba. In the 1980s, Castro was pressuring the Kremlin to adopt a harder line against the US under President [[Ronald Reagan]], even arguing for the potential use of nuclear weapons. As a direct result of this, a Soviet official was dispatched to Cuba in 1985 with an entourage of "experts", who detailed the ecological effect on Cuba in the event of nuclear strikes on the United States. Soon after, the Soviet official recounts, Castro lost his prior "nuclear fever".<ref>{{cite book |first=Andrian |last=Danilevich |chapter=3 |title=Evolution of soviet strategy|page=24|chapter-url=http://nsarchive.gwu.edu/nukevault/ebb285/doc02_I_ch3.pdf |access-date=2016-12-05|archive-url=https://web.archive.org/web/20161101014139/http://nsarchive.gwu.edu/nukevault/ebb285/doc02_I_ch3.pdf |archive-date= 2016-11-01 |url-status=live}}</ref><ref>{{cite web |date=September 11, 2009 |editor-last=Burr |editor-first=William |editor2=Savranskaya |editor2-first=Svetlana |title=Previously Classified Interviews with Former Soviet Officials Reveal U.S. Strategic Intelligence Failure Over Decades |url=http://www.gwu.edu/~nsarchiv//nukevault/ebb285/ |url-status=live |archive-url=https://web.archive.org/web/20110805060352/http://www.gwu.edu/~nsarchiv/nukevault/ebb285/ |archive-date=2011-08-05 |work=National Security Archive}}</ref> In 2010, Alan Robock was summoned to Cuba to help Castro promote his new view that nuclear war would bring about Armageddon. Robock's 90 minute lecture was later aired on the nationwide state-controlled television station in the country.<ref>{{cite web |author=Roane |first=Kit R. |date=April 6, 2016 |title=Nuclear Winter's Cuban Connection |url=http://pulitzercenter.org/reporting/nuclear-winters-cuban-connection |url-status=live |archive-url=https://web.archive.org/web/20161202165746/http://pulitzercenter.org/reporting/nuclear-winters-cuban-connection |archive-date=2016-12-02 |website=Pulitzer Center}}</ref><ref name="nature">{{cite web |url= http://climate.envsci.rutgers.edu/pdf/NatureNuclearWinterComment.pdf |title= Comment |date=19 May 2011 |volume=473 |website=Nature |page=275 |access-date=11 June 2014 |archive-url= https://web.archive.org/web/20131001213509/http://climate.envsci.rutgers.edu/pdf/NatureNuclearWinterComment.pdf |archive-date= 1 October 2013 |url-status= live}}</ref>

However, according to Robock, insofar as getting US government attention and affecting nuclear policy, he has failed. In 2009, together with [[Owen Toon]], he gave a talk to the [[United States Congress]], but nothing transpired from it and the then-presidential science adviser, [[John Holdren]], did not respond to their requests in 2009 or at the time of writing in 2011.<ref name="nature"/>
[[File:US and USSR nuclear stockpiles.svg|thumb|United States and Soviet Union nuclear stockpiles. The effects of trying to make others believe the results of the models on nuclear winter, does not appear to have decreased either country's nuclear stockpiles in the 1980s,{{Sfn | Badash |2009 | p = 315}} only the failing [[Soviet economy]] and the [[dissolution of the Soviet Union|dissolution of the country between 1989 and 1991]] which marks the end of the [[Cold War]] and with it the relaxation of the "[[arms race]]", appears to have had an effect. The effects of the electricity generating [[Megatons to Megawatts]] program can also be seen in the mid-1990s, continuing the trend in Russian reductions. A similar chart focusing solely on quantity of warheads in the multi-megaton range is also available.<ref>{{Cite web |last=Johnston |first=William Robert |title=Multimegaton Weapons |url=http://www.johnstonsarchive.net/nuclear/multimeg.html |access-date=2023-12-16 |website=www.johnstonsarchive.net}}</ref> Moreover, total deployed US and Russian [[strategic weapon]]s increased steadily from 1983 until the Cold War ended.<ref>Hans M. Kristensen 2012, [http://krepon.armscontrolwonk.com/archive/3524/worth-the-wait "Estimated US-Russian Nuclear Warhead Inventories 1977–2018.] {{webarchive|url=https://web.archive.org/web/20150112224012/http://krepon.armscontrolwonk.com/archive/3524/worth-the-wait|date=2015-01-12}}".</ref>]]

In a 2012 "Bulletin of the Atomic Scientists" feature, Robock and Toon, who had routinely mixed their disarmament advocacy into the conclusions of their "nuclear winter" papers,<ref name="Robock"/> argue in the political realm that the hypothetical effects of nuclear winter necessitates that the doctrine they assume is active in Russia and US, "[[mutually assured destruction]]" (MAD), should instead be replaced with their own "self-assured destruction" (SAD) concept,<ref name="Robock Toon 2012"/> because, regardless of whose cities burned, the effects of the resultant nuclear winter that they advocate would be, in their view, catastrophic. In a similar vein, in 1989 [[Carl Sagan]] and [[Richard P. Turco|Richard Turco]] wrote a policy implications paper that appeared in ''[[Ambio]]'' that suggested that as nuclear winter is a "well-established prospect", both superpowers should jointly reduce their nuclear arsenals to "[[Minimal deterrence|Canonical Deterrent Force]]" levels of 100–300 individual warheads each, such that in "the event of nuclear war [this] would minimize the likelihood of [extreme] nuclear winter."<ref>{{cite journal |last1=Turco |first1=Richard |last2=Sagan |first2=Carl |date=13 September 1989 |title=Policy Implications of Nuclear Winter |journal=Ambio |volume=18 |issue=7 |pages=372–376 |jstor=4313618}}</ref>

An originally classified 1984 US [[United States Intelligence Community|interagency intelligence]] assessment states that in both the preceding 1970s and 1980s, the Soviet and US military were already following the "''existing trends''" in [[Nuclear weapon design#Fusion-boosted fission weapons|warhead miniaturization]], of higher accuracy and lower yield nuclear warheads.{{sfn|Interagency Intelligence Assessment |1984|p=20}} This is seen when assessing the most numerous [[physics package]]s in the US arsenal, which in the 1960s were the [[B28 nuclear bomb|B28]] and [[W31]], however, both quickly became less prominent with the 1970s mass production runs of the 50 Kt [[W68]], the 100 Kt [[W76]] and in the 1980s, with the [[B61 nuclear bomb|B61]].<ref>{{cite web|title=Yield-to-weight ratios|website=Nuclear secrecy |url=http://nuclearsecrecy.com/betas/yieldtoweight/ |access-date= 2016-12-18|archive-url= https://web.archive.org/web/20161025101934/http://nuclearsecrecy.com/betas/yieldtoweight/|archive-date=2016-10-25|url-status=live}}</ref> This trend towards miniaturization, enabled by advances in [[inertial guidance]] and accurate [[GPS]] navigation etc., was motivated by a multitude of factors, namely the desire to leverage the physics of equivalent megatonnage that miniaturization offered; of freeing up space to fit more [[MIRV]] warheads and [[Penetration aid|decoys]] on each missile. Alongside the desire to still destroy [[missile silo|hardened targets]] but while reducing the severity of fallout [[collateral damage]] depositing on neighboring, and potentially friendly, countries. As it relates to the likelihood of nuclear winter, the range of potential [[Effects of nuclear explosions|thermal radiation]] ignited fires was already reduced with miniaturization. For example, the most popular nuclear winter paper, the 1983 TTAPS paper, had described a 3000 Mt [[counterforce]] attack on [[ICBM]] sites with each individual warhead having approximately one Mt of energy; however not long after publication, Michael Altfeld of [[Michigan State University]] and [[Political Scientist|political scientist]] Stephen Cimbala of [[Pennsylvania State University]] argued that the then already developed and deployed smaller, more accurate warheads (e.g. W76), together with [[airburst|lower detonation heights]], could produce the same counterforce strike with a total of only 3 Mt of energy being expended. They continue that, ''if'' the nuclear winter models prove to be representative of reality, then far less climatic-cooling would occur, even if firestorm prone areas existed in the [[Single Integrated Operational Plan|target list]], as lower fusing heights such as surface bursts would also limit the range of the burning thermal rays due to terrain masking and shadows cast by buildings,{{Sfn | Badash |2009 | p = 235}} while also temporarily lofting far more [[nuclear fallout|localized fallout]] when compared to [[airburst]] fuzing – the standard mode of employment against un-hardened targets.[[File:UncleNuclearTest1951.jpg|thumb|left|The 1951 [[Operation Buster-Jangle|''Shot Uncle'' of Operation ''Buster-Jangle'']], had a yield about a tenth of the 13 to 16 Kt Hiroshima bomb, 1.2 Kt,<ref name="Jangle Uncle 2001">Some sources refer to the test as ''Jangle Uncle'' (e.g., Adushkin, 2001) or ''Project Windstorm'' (e.g., DOE/NV-526, 1998). Operation ''Buster'' and Operation ''Jangle'' were initially conceived as separate operations, and ''Jangle'' was at first known as ''Windstorm'', but the AEC merged the plans into a single operation on 19 June 1951. See Gladeck, 1986.</ref> and was detonated 5.2 m (17 ft) beneath ground level.<ref>{{cite web |last1=Adushkin |first1=Vitaly V. |last2=Leith |first2=William |date=September 2001 |title=USGS Open File Report 01-312: Containment of Soviet underground nuclear explosions |url=https://geology.er.usgs.gov/eespteam/pdf/USGSOFR01312.pdf |archive-url=https://web.archive.org/web/20130509080818/http://geology.er.usgs.gov/eespteam/pdf/USGSOFR01312.pdf |archive-date=2013-05-09 |publisher=US Department of the Interior Geological Survey}}</ref> No thermal flash of heat energy was emitted to the surroundings in this shallow buried test.<ref name="Jangle Uncle 2001"/> The explosion resulted in a cloud that rose to 3.5 km (11,500 ft).<ref>{{cite book |title=Shots Sugar and Uncle: The final tests of the Buster-Jangle series (DNA 6025F) |first= Jean |last=Ponton |display-authors= etal |date=June 1982 |publisher=Defense Nuclear Agency |url= http://www.dtra.mil/rd/programs/nuclear_personnel/docs%5CT24299.PDF|archive-url= https://web.archive.org/web/20070710110311/http://www.dtra.mil/rd/programs/nuclear_personnel/docs%5CT24299.PDF|archive-date= 2007-07-10}}</ref> The resulting crater was 260 feet (79 m) wide and 53 feet (16 m) deep.<ref>{{cite web |title=Operation Buster-Jangle |publisher=The Nuclear Weapons Archive |url= http://nuclearweaponarchive.org/Usa/Tests/Busterj.html |access-date=2014-11-04 |archive-url=https://web.archive.org/web/20141014123759/http://nuclearweaponarchive.org/Usa/Tests/Busterj.html |archive-date=2014-10-14 |url-status= live}}</ref> The yield is similar to that of an [[Atomic Demolition Munition]]. Altfeld and Cimbala argue that true belief in nuclear winter might lead nations towards building greater arsenals of weapons of this type.{{Sfn | Badash | 2009 | p = 242}} However, despite being complicated due to the advent of [[Dial-a-yield]] technology, data on these low yield nuclear weapons suggests that they, as of 2012, make up about a tenth of the arsenal of the US and Russia, and the fraction of the stockpile that they occupy has diminished since the 1970–1990s, not grown.<ref>{{cite web|url= https://fas.org/_docs/Non_Strategic_Nuclear_Weapons.pdf|title=Non-strategic nuclear weapons, Hans M. Kristensen, Federation of American Scientists, 2012|access-date=2016-06-04|archive-url=https://web.archive.org/web/20160423194001/http://fas.org/_docs/Non_Strategic_Nuclear_Weapons.pdf|archive-date=2016-04-23|url-status=live}}</ref> A factor in this is that very thin devices with yields of approximately one kiloton of energy are nuclear weapons that make very inefficient use of their nuclear materials, e.g. [[two-point implosion]]. Thus a more [[psychological warfare|psychologically detering]] higher efficiency/higher yield device, can instead be constructed from the same mass of [[fissile material]].]] This logic is similarly reflected in the originally classified 1984 ''Interagency Intelligence assessment'', which suggests that targeting planners would simply have to consider target combustibility along with yield, height of burst, timing and other factors to reduce the amount of smoke to safeguard against the potentiality of a nuclear winter.{{sfn|Interagency Intelligence Assessment |1984|p=20}} Therefore, as a consequence of attempting to limit the target fire hazard by reducing the range of thermal radiation with fuzing for surface and [[Robust Nuclear Earth Penetrator|sub-surface bursts]], this will result in a scenario where the far more concentrated, and therefore deadlier, ''local'' fallout that is generated following a surface burst forms, as opposed to the comparatively dilute ''global'' fallout created when nuclear weapons are fuzed in air burst mode.{{Sfn | Badash |2009 | p = 235}}<ref>{{Cite book |last1=Solomon |first1=Fredric |url=https://books.google.com/books?id=NUUrAAAAYAAJ&pg=PA106 |title=The Medical Implications of Nuclear War |last2=Marston |first2=Robert Q. |date=1986-01-01 |publisher=National Academies Press |isbn=978-0-309-03692-4 |page=106 |language=en-us}}</ref>

Altfeld and Cimbala also argued that belief in the possibility of nuclear winter would actually make nuclear war more likely, contrary to the views of Sagan and others, because it would serve yet further motivation to follow the ''existing trends'', towards the [[Circular error probable|development of more accurate]], and even lower explosive yield, nuclear weapons.{{Sfn | Badash | 2009 | p = 242}} As the winter hypothesis suggests that the replacement of the then Cold War viewed [[strategic nuclear weapons]] in the multi-megaton yield range, with weapons of explosive yields closer to [[tactical nuclear weapons]], such as the [[Robust Nuclear Earth Penetrator]] (RNEP), would safeguard against the nuclear winter potential. With the latter capabilities of the then, largely still conceptual RNEP, specifically cited by the influential nuclear warfare analyst [[Albert Wohlstetter]].{{Sfn | Badash | 2009 | pp = 238–239}} Tactical nuclear weapons, on the low end of the scale have yields that overlap with large [[conventional weapons]] and are therefore often viewed "as blurring the distinction between conventional and nuclear weapons", making the prospect of using them "easier" in a conflict.<ref>{{cite web|title=Nuclear Weapon Initiatives: Low-Yield R&D, Advanced Concepts, Earth Penetrators, Test Readiness |website= Congressional research |url= http://congressionalresearch.com/RL32130/document.php|access-date=2014-11-01|url-status=live|archive-url=https://web.archive.org/web/20141109095233/http://congressionalresearch.com/RL32130/document.php |archive-date=2014-11-09}}</ref><ref>[http://capitolwords.org/date/2005/07/22/S8717_national-defense-authorization-act-for-fiscal-year/ National Defense Authorization Act For Fiscal Year 2006] {{webarchive |url=https://web.archive.org/web/20150805023431/http://capitolwords.org/date/2005/07/22/S8717_national-defense-authorization-act-for-fiscal-year/ |date=2015-08-05}}</ref>

===Alleged Soviet exploitation===
{{See also|Soviet influence on the peace movement#Claims of wider Soviet influence}}
In an interview in 2000 with [[Mikhail Gorbachev]] (the leader of the Soviet Union from 1985 to 1991), the following statement was posed to him: "In the 1980s, you warned about the unprecedented dangers of nuclear weapons and took very daring steps to reverse the arms race", with Gorbachev replying "Models made by Russian and American scientists showed that a nuclear war would result in a nuclear winter that would be extremely destructive to all life on Earth; the knowledge of that was a great stimulus to us, to people of honor and morality, to act in that situation."<ref>[http://dir.salon.com/story/news/feature/2000/09/07/gorbachev/ Mikhail Gorbachev explains what's rotten in Russia] {{webarchive|url= https://web.archive.org/web/20090210165853/http://dir.salon.com/story/news/feature/2000/09/07/gorbachev/ |date=2009-02-10}}</ref>

However, a 1984 US Interagency Intelligence Assessment expresses a far more skeptical and cautious approach, stating that the hypothesis is not scientifically convincing. The report predicted that Soviet [[nuclear policy]] would be to maintain their strategic nuclear posture, such as their fielding of the high [[throw-weight]] [[SS-18]] missile and they would merely attempt to exploit the hypothesis for propaganda purposes, such as directing scrutiny on the US portion of the [[nuclear arms race]]. Moreover, it goes on to express the belief that if Soviet officials did begin to take nuclear winter seriously, it would probably make them demand exceptionally high standards of scientific proof for the hypothesis, as the implications of it would undermine their [[military doctrine]] – a level of scientific proof which perhaps could not be met without field experimentation.{{sfn|Interagency Intelligence Assessment |1984|pp=18–19}} The un-redacted portion of the document ends with the suggestion that substantial increases in Soviet Civil defense food stockpiles might be an early indicator that Nuclear Winter was beginning to influence Soviet upper [[wikt:echelon|echelon]] thinking.{{sfn|Interagency Intelligence Assessment |1984|p=20}}

In 1985, ''[[Time magazine|Time]]'' magazine noted "the suspicions of some Western scientists that the nuclear winter hypothesis was promoted by Moscow to give [[campaign for nuclear disarmament|anti-nuclear groups]] in the U.S. and Europe some fresh ammunition against America's arms buildup."<ref>{{Cite web |last1=Lamar Jr. |first1=Jacob V. |last2=Aikman |first2=David |last3=Amfitheatrof |first3=Erik |name-list-style=amp |date=2007-09-30 |orig-date=October 7, 1985 |title=Another Return From the Cold -- Printout -- TIME |url=http://www.time.com/time/magazine/printout/0,8816,960025,00.html |access-date=2023-12-16 |archive-url=https://web.archive.org/web/20070930040755/http://www.time.com/time/magazine/printout/0,8816,960025,00.html |archive-date=September 30, 2007 }}</ref> In 1985, the [[United States Senate]] met to discuss the science and politics of nuclear winter. During the congressional hearing, the influential analyst [[Leon Gouré]] presented evidence that perhaps the Soviets have simply echoed Western reports rather than producing unique findings. Gouré hypothesized that Soviet research and discussions of nuclear war may serve only Soviet political agendas, rather than to reflect actual opinions of Soviet leadership.<ref>United States. Congress. Senate. Committee on Armed Services. ''Nuclear Winter and Its Implications Hearings before the Committee on Armed Services, United States Senate, Ninety-Ninth Congress, First Session, October 2 and 3, 1985.'' U.S. G.P.O., 1986.</ref>

In 1986, the [[Defense Nuclear Agency]] document ''An update of Soviet research on and exploitation of Nuclear winter 1984–1986'' charted the minimal [public domain] research contribution on, and Soviet propaganda usage of, the nuclear winter phenomenon.{{sfn|Goure|1986|p={{page needed|date=September 2021}}}}

There is some doubt as to when the Soviet Union began modelling fires and the atmospheric effects of nuclear war. Former Soviet intelligence officer [[Sergei Tretyakov (intelligence officer)|Sergei Tretyakov]] claimed that, under the directions of [[Yuri Andropov]], the [[KGB]] invented the concept of "nuclear winter" in order to stop the deployment of NATO [[Pershing II]] missiles. They are said to have distributed to peace groups, the environmental movement and the journal ''Ambio'' disinformation based on a faked "doomsday report" by the [[Russian Academy of Sciences|Soviet Academy of Sciences]] by Georgii Golitsyn, [[Nikita Moiseyev]] and Vladimir Alexandrov concerning the climatic effects of nuclear war.<ref name="Comrade J">Pete Earley, "Comrade J: The Untold Secrets of Russia's Master Spy in America After the End of the Cold War", Penguin Books, 2007, {{ISBN|978-0-399-15439-3}}, pp. 167–177.</ref> Although it is accepted that the Soviet Union exploited the nuclear winter hypothesis for propaganda purposes,{{sfn|Goure|1986|p={{page needed|date=September 2021}}}} Tretyakov's inherent claim that the KGB funnelled disinformation to ''Ambio'', the journal in which Paul Crutzen and John Birks published the 1982 paper "Twilight at Noon", has not been corroborated {{As of|2009|lc= y}}.{{Sfn | Badash |2009 | p = {{page needed|date=September 2021}}}} In an interview in 2009 conducted by the [[National Security Archive]], Vitalii Nikolaevich Tsygichko (a Senior Analyst at the [[Academy of Sciences of the USSR|Soviet Academy of Sciences]] and military mathematical modeler) stated that Soviet military analysts were discussing the idea of "nuclear winter" years before U.S. scientists, although they did not use that exact term.<ref>{{cite web|url= http://www.gwu.edu/~nsarchiv//nukevault/ebb285/ |title=Candid Interviews with Former Soviet Officials Reveal U.S. Strategic Intelligence Failure Over Decades | publisher = GWU |access-date= 2012-05-06 |archive-url= https://web.archive.org/web/20110805060352/http://www.gwu.edu/~nsarchiv/nukevault/ebb285/ |archive-date= 2011-08-05|url-status= live}}</ref>

== Mitigation techniques ==
{{See also|Conflict Resolution}}
A number of solutions have been proposed to mitigate the potential harm of a nuclear winter if one appears inevitable. The problem has been attacked at both ends; some solutions focus on preventing the growth of fires and therefore limiting the amount of smoke that reaches the stratosphere in the first place, and others focus on food production with reduced sunlight, with the assumption that the very worst-case analysis results of the nuclear winter models prove accurate and no other mitigation strategies are fielded.

=== Fire control ===
In a report from 1967, techniques included various methods of applying liquid nitrogen, dry ice, and water to nuclear-caused fires.<ref>W. E. Shelberg and E. T. Tracy. "Countermeasure Concepts for Use Against Urban Mass Fires From Nuclear Weapon Attack" U.S. Naval Radiological Defense Laboratory, San Francisco, California 1967.</ref> The report considered attempting to stop the spread of fires by creating [[firebreak]]s by blasting combustible material out of an area, possibly even using nuclear weapons, along with the use of preventative [[Controlled burn|Hazard Reduction Burns]]. According to the report, one of the most promising techniques investigated was [[cloud seeding|initiation of rain from seeding]] of mass-fire thunderheads and other clouds passing over the developing, and then stable, firestorm.

=== Producing food without sunlight ===
{{See also|Impact Winter#Agriculture}}
In the book ''[[Feeding Everyone No Matter What]]'', under the worst-case scenario predictions of nuclear winter, the authors present various unconventional food possibilities. These include natural-gas-digesting bacteria, the most well known being ''[[Methylococcus capsulatus]]'', that is presently used as a feed in [[fish farming]];<ref>- [http://www.unibio.dk/] {{Webarchive|url=https://web.archive.org/web/20150212000141/http://www.unibio.dk/|date=2015-02-12}} "UniBio A/S – turns NG to fish food"</ref> [[bark bread]], a long-standing [[famine food]] using the edible [[Phloem|inner bark]] of trees, and part of Scandinavian history during the [[Little Ice Age]]; increased [[fungiculture]] or mushrooms such as the [[honey fungi]] that grow directly on moist wood without sunlight;<ref>Hazeltine, B. & Bull, C. 2003 ''Field Guide to Appropriate Technology''. San Francisco: Academic Press.</ref> and variations of wood or [[cellulosic biofuel]] production, which typically already creates edible [[sugar]]s/[[xylitol]] from inedible cellulose, as an intermediate product before the final step of alcohol generation.<ref>{{Cite web |url=https://www.plant.ca/general/biofuel-process-to-develop-sugar-substitute-cellulose-ethanol-304/ |title=Biofuel process to develop sugar substitute, cellulose ethanol. SunOpta BioProcess Inc. 2010 |access-date=2018-10-18 |archive-url=https://web.archive.org/web/20181019042641/https://www.plant.ca/general/biofuel-process-to-develop-sugar-substitute-cellulose-ethanol-304/ |archive-date=2018-10-19 |url-status=live }}</ref><ref>{{cite journal |last1=Langan |first1=P. |last2=Gnanakaran |first2=S. |last3=Rector |first3=K. D. |last4=Pawley |first4=N. |last5=Fox |first5=D. T. |last6=Chof |first6=D. W. |last7=Hammelg |first7=K. E. |year=2011 |title=Exploring new strategies for cellulosic biofuels production |journal=Energy & Environmental Science |volume=4 |issue=10 |pages=3820–3833 |doi=10.1039/c1ee01268a |bibcode=2011EnEnS...4.3820L |s2cid=94766888}}</ref> One of the book's authors, mechanical engineer David Denkenberger, states that mushrooms could theoretically feed everyone for three years. Seaweed, like mushrooms, can also grow in low-light conditions. Dandelions and tree needles could provide Vitamin C, and bacteria could provide Vitamin E. More conventional cold-weather crops such as potatoes might get sufficient sunlight at the equator to remain feasible.<ref>{{cite news |last1=Bendix |first1=Aria |title=A full-scale nuclear winter would trigger a global famine. A disaster expert put together a doomsday diet to save humanity. |url=https://www.businessinsider.com/how-to-survive-after-nuclear-war-what-to-eat-2020-1 |access-date=20 March 2020 |work=Business Insider |date=2020 |archive-date=2020-03-20  |archive-url=https://web.archive.org/web/20200320052438/https://www.businessinsider.com/how-to-survive-after-nuclear-war-what-to-eat-2020-1 |url-status=live }}</ref>

=== Large-scale food stockpiling ===
To feed portions of civilization through a nuclear winter, large stockpiles of food storage prior to the event would have to be accomplished. Such stockpiles should be placed underground, at higher elevations and near the equator to mitigate high altitude UV and radioactive isotopes. Stockpiles should also be placed near populations most likely to survive the initial catastrophe. One consideration is who would sponsor the stockpiling. "There may be a mismatch between those most able to sponsor the stockpiles (i.e., the pre-catastrophe wealthy) and those most able to use the stockpiles (the pre-catastrophe rural poor)."<ref>{{cite journal |last1=Maher |first1=T. M. Jr. |last2=Baum |first2=S. D. |year=2013 |title=Adaptation to and recovery from global catastrophe |journal=Sustainability |volume=5 |issue=4 |pages=1461–79 |doi=10.3390/su5041461 |doi-access=free|bibcode=2013Sust....5.1461J }}</ref> The minimum annual global wheat storage is approximately 2 months.<ref>Thien Do, Kim Anderson, B. Wade Brorsen. "The World's wheat supply." ''Oklahoma Cooperative Extension Service.''</ref>

== Climate engineering ==
{{Main|Climate engineering}}
Despite the name "nuclear winter", nuclear events are not necessary to produce the modeled climatic effect.{{Sfn | Badash |2009 | pp = 242–244}}<ref name="climate.envsci.rutgers.edu" /> In an effort to find a quick and cheap solution to the global warming projection of at least 2 ˚C of surface warming as a result of the doubling in CO<sub>2</sub> levels within the atmosphere, through [[solar radiation management]] (a form of climate engineering) the underlying nuclear winter effect has been looked at as perhaps holding potential. Besides the more common suggestion to inject [[stratospheric sulfur injection|sulfur compounds into the stratosphere]] to approximate the effects of a volcanic winter, the injection of other chemical species such as the release of a particular type of soot particle to create minor "nuclear winter" conditions, has been proposed by Paul Crutzen and others.<ref>{{Cite journal |title=Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma? |quote=release soot particles to create minor "nuclear winter" conditions |doi=10.1007/s10584-006-9101-y |volume=77 |year=2006 |journal=Climatic Change|pages=211–220|last1=Crutzen|first1=Paul J.|issue=3–4|doi-access=free|bibcode=2006ClCh...77..211C}}</ref><ref>{{Cite journal |title=Climate engineering: A critical review of approaches to modify the global energy balance |quote=Besides sulfur injections some other chemical species have been proposed for injection into the stratosphere. For instance the injection of soot particles as a consequence of a nuclear conflict has been studied in "nuclear winter" scenarios... (p. 87) |doi=10.1140/epjst/e2009-01149-8 |volume=176 |year=2009 |journal=The European Physical Journal Special Topics |pages=81–92 |last1=Feichter |first1=J. |last2=Leisner |first2=T. |issue=1 |bibcode=2009EPJST.176...81F |doi-access=free}}</ref> According to the threshold "nuclear winter" computer models,<ref name="2008physicstoday"/><ref name="news.nationalgeographic.com"/> if one to five teragrams of firestorm-generated soot<ref name=pnas.0710058105/> is injected into the low stratosphere, it is modeled, through the anti-greenhouse effect, to heat the stratosphere but cool the lower troposphere and produce 1.25&nbsp;°C cooling for two to three years; and after 10 years, average global temperatures would still be 0.5&nbsp;°C lower than before the soot injection.<ref name="news.nationalgeographic.com"/>

== Potential climatic precedents ==
{{See also|Tunguska event}}
[[File:Chicxulub-animation.gif|thumb|left|upright=1.2|An animation depicting a massive asteroid–Earth impact and subsequent [[impact crater]] formation. The asteroid connected with the extinction of the [[Cretaceous–Paleogene extinction event]] released an estimated energy of {{convert|100|TtTNT|ZJ|lk=on}}.<ref>{{cite journal |last1=Schulte |first1=P. |display-authors=1 |date=5 March 2010 |title=The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary |journal=[[Science (journal)|Science]] |volume=327 |issue=5970 |pages=1214–1218 |doi=10.1126/science.1177265 |pmid=20203042 |s2cid=2659741 |bibcode=2010Sci...327.1214S |first30=E. |last30=Pierazzo |first29=R. D. |last29=Norris |first28=D. J. |last28=Nichols |first27=C. R. |last27=Neal |first26=J. V. |last26=Morgan |first25=A. |last25=Montanari |first24=J. |last24=Melosh |first23=T. |last23=Matsui |first22=K. G. |last22=MacLeod |first21=D. A. |last21=Kring |first20=C. |last20=Koeberl |first19=W. |last19=Kiessling |first18=K. R. |last18=Johnson |first17=S. P. S. |last17=Gulick |first16=R. A. F. |last16=Grieve |first15=J. M. |last15=Grajales-Nishimura |first14=K. |last14=Goto |first13=T. J. |last13=Goldin |first12=A. |last12=Deutsch |first11=G. S. |last11=Collins |first10=C. S. |last2=Alegret |first2=L. |last3=Arenillas |first3=I. |last10=Cockell |last4=Arz |first4=J. A. |last5=Barton |first5=P. J. |last6=Bown |first6=P. R. |last7=Bralower |first7=T. J. |last8=Christeson |first8=G. L. |last9=Claeys |first9=P. |url=http://doc.rero.ch/record/210367/files/PAL_E4389.pdf |access-date=20 April 2018 |archive-url=https://web.archive.org/web/20170921215225/http://doc.rero.ch/record/210367/files/PAL_E4389.pdf |archive-date=21 September 2017 |url-status=live}}</ref> corresponding to 100,000,000 Mt of energy, roughly 10,000 times the maximum combined arsenals of the US and Soviet Union in the Cold War.<ref>{{cite web |url=http://ocw.nd.edu/physics/nuclear-warfare/notes/lecture-18 |title=University of Notre Dame |author=ENR/PAZ |website=University of Notre Dame |access-date=2014-11-06|archive-url=https://web.archive.org/web/20141010114324/http://ocw.nd.edu/physics/nuclear-warfare/notes/lecture-18 |archive-date=2014-10-10|url-status=live}}</ref> This is hypothesized to have produced sufficient ground-energy coupling to have caused severe [[mantle plume]] (volcanism) at the [[antipodal point]] (the opposite side of the world).<ref>{{cite journal |last1=Hagstrum |first1=Jonathan T. |title=Antipodal Hotspots and Bipolar Catastrophes: Were Oceanic Large-body Impacts the Cause? |journal=[[Earth and Planetary Science Letters]] |volume=236 |issue=1–2 |pages=13–27 |url=http://www.mantleplumes.org/WebDocuments/Antip_hot.pdf |date=2005 |doi=10.1016/j.epsl.2005.02.020 |bibcode=2005E&PSL.236...13H |access-date=2014-11-06 |archive-url=https://web.archive.org/web/20071128195943/http://www.mantleplumes.org/WebDocuments/Antip_hot.pdf |archive-date=2007-11-28 |url-status=live}}</ref>]]
Similar climatic effects to "nuclear winter" followed historical [[supervolcano]] eruptions, which plumed [[sulfate aerosol]]s high into the stratosphere, with this being known as a [[volcanic winter]].<ref>{{cite news |author=Kirby |first=Alex |date=February 3, 2000 |title=Supervolcanoes could trigger global freeze |work=BBC News |url=http://news.bbc.co.uk/2/hi/science/nature/628515.stm |url-status=live |access-date=April 28, 2008 |archive-url=https://web.archive.org/web/20071014214504/http://news.bbc.co.uk/2/hi/science/nature/628515.stm |archive-date=October 14, 2007}}</ref> The effects of smoke in the atmosphere (short wave absorption) are sometimes termed an "antigreenhouse" effect, and a strong analog is the hazy atmosphere of [[Titan (moon)|Titan]]. Pollack, Toon and others were involved in developing models of Titan's climate in the late 1980s, at the same time as their early nuclear winter studies.<ref>{{cite book |last=Lorenz |first=Ralph |date=2019 |title=Exploring Planetary Climate: A History of Scientific Discovery on Earth, Mars, Venus and Titan |publisher=Cambridge University Press |page=36 |isbn=978-1-108-47154-1}}</ref>

Similarly, extinction-level [[Impact event|comet and asteroid impacts]] are also believed to have generated [[impact winter]]s by the [[rock crusher|pulverization]] of massive amounts of fine rock dust. This pulverized rock can also produce "volcanic winter" effects, if [[sulfate]]-bearing rock is hit in the impact and lofted high into the air,<ref>{{cite news |author=Airhart |first=Marc |date=January 1, 2008 |title=Seismic Images Show Dinosaur-Killing Meteor Made Bigger Splash |url=http://www.jsg.utexas.edu/news/2008/01/seismic-images-show-dinosaur-killing-meteor-made-bigger-splash/ |url-status=live |access-date=November 6, 2014 |archive-url=https://web.archive.org/web/20141220175132/http://www.jsg.utexas.edu/news/2008/01/seismic-images-show-dinosaur-killing-meteor-made-bigger-splash/ |archive-date=December 20, 2014}}</ref> and "nuclear winter" effects, with the heat of the heavier rock [[ejecta]] igniting regional and possibly even global forest firestorms.<ref>{{cite journal |title=Comet Caused Nuclear Winter |journal=Discover |date=January 2005 |url=http://discovermagazine.com/2005/jan/comet-caused-nuclear-winter |access-date=2008-04-28 |archive-url=https://web.archive.org/web/20080517085337/http://discovermagazine.com/2005/jan/comet-caused-nuclear-winter |archive-date=2008-05-17 |url-status=live }}</ref><ref>{{cite magazine |author=Asaravala |first=Amit |date=May 26, 2004 |title=A Fiery Death for Dinosaurs? |url=https://www.wired.com/science/discoveries/news/2004/05/63613 |url-status=live |magazine=Wired |archive-url=https://web.archive.org/web/20140130010854/http://www.wired.com/science/discoveries/news/2004/05/63613 |archive-date=January 30, 2014 |access-date=March 10, 2017}}</ref>

This global "impact firestorms" hypothesis, initially supported by Wendy Wolbach, H. Jay Melosh and Owen Toon, suggests that as a result of massive impact events, the small [[sand grain|sand-grain]]-sized ejecta fragments created can [[meteor]]ically [[re-entry|re-enter]] the atmosphere forming a hot blanket of global debris high in the air, potentially turning the entire sky [[incandescence|red-hot]] for minutes to hours, and with that, burning the complete global inventory of above-ground carbonaceous material, including [[rain forests]].<ref name="geology.gsapubs.org">Belcher, Clair M. [http://geology.gsapubs.org/content/37/12/1147.short Reigniting the Cretaceous-Palaeogene Firestorm Debate] {{Webarchive|url=https://web.archive.org/web/20150125233941/http://geology.gsapubs.org/content/37/12/1147.short|date=2015-01-25}}, Journal of Geology, {{doi|10.1130/focus122009.1}}. vol. 37, no. 12, pp. 1147–1148. Open access.</ref><ref name="Robertson, D.S. 2013">{{cite journal |author=Robertson |first1=D. S. |last2=Lewis |first2=W. M. |last3=Sheehan |first3=P. M. |last4=Toon |first4=Owen B. |name-list-style=amp |date=2013 |title=K/Pg extinction: re-evaluation of the heat/fire hypothesis |journal=Journal of Geophysical Research: Biogeosciences |volume=118 |issue=1 |page=329 |bibcode=2013JGRG..118..329R |doi=10.1002/jgrg.20018 |doi-access=free}}</ref> This hypothesis is suggested as a means to explain the severity of the Cretaceous–Paleogene extinction event, as the [[Chicxulub impact|earth impact of an asteroid about 10 km wide]] which precipitated the extinction is not regarded as sufficiently energetic to have caused the level of extinction from the initial impact's energy release alone.

The global firestorm winter, however, has been questioned in more recent years (2003–2013) by Claire Belcher,<ref name="geology.gsapubs.org" /><ref>{{cite news |author=Rincon |first=Paul |date=9 December 2003 |title=No fiery extinction for dinosaurs |work=BBC News |url=http://news.bbc.co.uk/2/hi/science/nature/3295539.stm |url-status=live |access-date=6 November 2014 |archive-url=https://web.archive.org/web/20141106100231/http://news.bbc.co.uk/2/hi/science/nature/3295539.stm |archive-date=6 November 2014}}</ref><ref>{{cite journal |last1=Belcher |first1=C. M. |last2=Collinson |first2=M. E. |last3=Scott |first3=A. C. |year=2005 |title=Constraints on the thermal energy released from the Chicxulub impactor: new evidence from multi-method charcoal analysis |journal=Journal of the Geological Society |volume=162 |issue=4 |pages=591–602 |bibcode=2005JGSoc.162..591B |doi=10.1144/0016-764904-104 |s2cid=129419767}}</ref> Tamara Goldin<ref>{{cite thesis |type=PhD |url=http://www.geo.arizona.edu/Antevs/Theses/GoldenPHD08.pdf |last=Goldin |first=Tamara Joan |date=2008 |title=Atmospheric Interactions During Global Deposition of Chicxulub Impact Ejecta |archive-url=https://web.archive.org/web/20180221232820/https://www.geo.arizona.edu/Antevs/Theses/GoldenPHD08.pdf |archive-date=2018-02-21 |url-status=live}}</ref><ref>{{cite web |author=Hecht |first=Jeff |date=7 December 2009 |title=Dinosaur-killing impact set Earth to broil, not burn |url=https://www.newscientist.com/article/dn18246-dinosaurkilling-impact-set-earth-to-broil-not-burn.html#.VFqi21cTGlA |url-status=live |archive-url=https://web.archive.org/web/20150423105034/http://www.newscientist.com/article/dn18246-dinosaurkilling-impact-set-earth-to-broil-not-burn.html#.VFqi21cTGlA |archive-date=2015-04-23 |work=New Scientist}}</ref><ref>{{cite book |chapter=Impact firestorms |first=Tamara |last=Goldin |publisher=Springer |title=Encyclopedia of Natural Hazards |series=Encyclopedia of Earth Sciences Series |year=2013 |page=525 |doi=10.1007/978-1-4020-4399-4_187|isbn=978-90-481-8699-0 }}</ref> and Melosh, who had initially supported the hypothesis,<ref name="geology.geoscienceworld.org">{{cite journal|title=Self-shielding of thermal radiation by Chicxulub impact ejecta: Firestorm or fizzle?|first1=T. J.|last1=Goldin|first2=H. J.|last2=Melosh|date=1 December 2009|journal=Geology |volume=37|issue=12|pages=1135–1138|doi=10.1130/G30433A.1|bibcode=2009Geo....37.1135G}}</ref><ref>{{cite web |author=Than |first=Ker |date=28 December 2009 |title=Dinosaur-Killing Firestorm Theory Questioned |url=http://www.space.com/7710-dinosaur-killing-firestorm-theory-questioned.html |url-status=live |archive-url=https://web.archive.org/web/20141106044650/http://www.space.com/7710-dinosaur-killing-firestorm-theory-questioned.html |archive-date=2014-11-06 |access-date=2014-11-06 |work=Space.com}}</ref> with this re-evaluation being dubbed the "Cretaceous-Palaeogene firestorm debate" by Belcher.<ref name="geology.gsapubs.org" />
[[File:Meteoroid - Meteor (Bolide) - Meteorite.gif|thumb|upright=2|Depending on the size of the meteor, it will either burn up high in the atmosphere or reach lower levels and explode in an air burst akin to the [[Chelyabinsk meteor]] of 2013, which approximated the thermal effects of a nuclear explosion.]]
The issues raised by these scientists in the debate are the perceived low quantity of soot in the sediment beside the fine-grained [[Cretaceous–Paleogene boundary|iridium-rich asteroid dust layer]], if the quantity of re-entering ejecta was perfectly global in blanketing the atmosphere, and if so, the duration and profile of the re-entry heating, whether it was a high thermal pulse of heat or the more prolonged and therefore more incendiary "[[oven]]" heating,<ref name="geology.geoscienceworld.org"/> and finally, how much the "self-shielding effect" from the first wave of now-cooled meteors in [[Dark flight (astronomy)|dark flight]] contributed to diminishing the total heat experienced on the ground from later waves of meteors.<ref name="geology.gsapubs.org"/>

In part due to the [[Cretaceous period]] being a high-[[Paleoclimatology|atmospheric-oxygen era]], with concentrations above that of the present day, Owen Toon et al. in 2013 were critical of the re-evaluations the hypothesis is undergoing.<ref name="Robertson, D.S. 2013" />

It is difficult to successfully ascertain the percentage contribution of the soot in this period's [[stratigraphy|geological sediment]] record from living plants and fossil fuels present at the time,<ref>{{cite journal|title=Soot in Cretaceous-Paleogene boundary clays worldwide: is it really derived from fossil fuel beds close to Chicxulub?|first=Pavle|last=Premović|date=1 January 2012|journal=Open Geosciences|volume=4|issue=3|page=383|doi=10.2478/s13533-011-0073-8|bibcode=2012CEJG....4..383P|s2cid=128610989|doi-access=free}}</ref> in much the same manner that the fraction of the material ignited directly by the meteor impact is difficult to determine.

== See also ==
* [[1883 eruption of Krakatoa]], which caused approximately 1 [[kelvin]] of global cooling for 2 years due to sulfate emissions.
* [[Dalton Minimum]], 1790 to 1830, a period of prolonged [[solar cycle|solar minimum]] activity, resulting in Earth receiving lower insolation values.
* [[Doomsday device]]
* [[Global dimming]], global reduction in ground insolation, due to the atmospheric injection of aerosols from various sources.
* [[Impact winter]]
* [[Laki]], 1783 eruption of an Icelandic volcano which produced continentally localized cooling for 1–2 years.
* [[List of states with nuclear weapons]]
* [[Little Ice Age]], a period of low temperatures from the sixteenth to the nineteenth centuries, partially overlapping with the [[Maunder Minimum]] of solar activity, 1645 to 1715.
* [[Nuclear famine]]
* [[Nuclear holocaust]]
* [[Nuclear terrorism]]
* [[Toba catastrophe theory]], a controversial hypothesis that a volcanic winter produced by the eruption of a volcano in [[Lake Toba|Toba]], [[Indonesia]], created a human [[population bottleneck]] approximately 80,000 years ago.
* [[Volcanic winter]]
* [[Year Without a Summer]], 1816, created by a volcanic eruption in Tambora.
* [[Younger Dryas impact hypothesis]], a controversial hypothesis that an impact event and fires triggered the last ice age.

== Literature ==
=== Non-fiction ===
* ''[[The Fate of the Earth]]'' (1982) by [[Jonathan Schell]] - Influential examination of nuclear war consequences that helped introduce nuclear winter concepts to the public
* ''[[The Cold and the Dark: The World after Nuclear War]]'': A book co-authored by Carl Sagan in 1984 which followed his co-authoring of the TTAPS study in 1983.
* ''A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race'': A book authored by Richard P. Turco and Carl Sagan, published in 1990; it explains the nuclear winter hypothesis and, with that, advocates nuclear disarmament.<ref name="path">{{cite book |last1=Sagan |first1=Carl |url=https://archive.org/details/pathwherenomanth00saga |title=A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race |last2=Turco |first2=Richard P. |date=1990 |publisher=Random House |isbn=978-0-394-58307-5 |location=New York |language=en-us |url-access=registration}}</ref>
* ''[[Nuclear War: A Scenario]]'' (2024) by [[Annie Jacobsen]] - Contemporary minute-by-minute analysis of nuclear escalation leading to nuclear winter and global famine

=== Fiction ===
* [[On the Beach (novel)|On the Beach]] (1957) by [[Nevil Shute]] - Post-nuclear war novel depicting gradual extinction of humanity
* [[Warday]] (1984) by [[Whitley Strieber]] and [[James Kunetka]] - Speculative account of America five years after limited nuclear exchange
* [[The Road]] (2006) by [[Cormac McCarthy]] - Post-apocalyptic novel set in ash-covered world resembling nuclear winter
* [[Alas, Babylon]] (1959) by [[Pat Frank]] - Early nuclear war survival story depicting societal breakdown
* [[Level 7 (novel)|Level 7]] (1959) by [[Mordecai Roshwald]] - Underground bunker narrative during nuclear holocaust
* [[Z for Zachariah]] (1974) by [[Robert C. O'Brien]] - Young adult novel about nuclear winter survivor

== Media ==
* ''[[Threads (1984 film)|Threads]]'': A 1984 [[docu-drama]] that Carl Sagan assisted in an advisory capacity. This film was the first of its kind to depict a nuclear winter.
* ''On the 8th Day'' – Nuclear winter documentary (1984) filmed by the [[BBC]] and available on Internet video hosting websites; chronicles the rise of the hypothesis, with lengthy interviews of the prominent scientists who published the nascent papers on the subject.<ref>On the 8th Day – Nuclear winter documentary (1984).</ref>
* [http://www.retroreport.org/video/nuclear-winter/ Nuclear Winter] is a mini documentary by [[Retro Report]] that looks at nuclear winter fears in today's world.

== Explanatory notes==
{{reflist|group=note}}

== General references ==
{{Refbegin|30em}}
* {{Cite book |last1=Badash |first1=Lawrence |date=2009-07-10 |title=A Nuclear Winter's Tale |publisher=Massachusetts Institute of Technology |isbn=978-0-26225799-2 |url=https://books.google.com/books?id=y8M5vx-Lrk0C |access-date=2016-06-04 |archive-date=2014-01-12  |archive-url=https://web.archive.org/web/20140112051702/http://books.google.com/books?id=y8M5vx-Lrk0C |url-status=live }}
* {{cite book |author-link1=Mikhail Budyko |last1=Budyko |first1=M. I. |author-link2=Georgy Golitsyn |first2=G. S. |last2=Golitsyn |first3=Y. A. |last3=Izrael |title=Global Climatic Catastrophes |publisher=Springer |date=September 1988 |isbn=978-0-387-18647-4 |url-access=registration |url=https://archive.org/details/globalclimaticca0000budy }}
* {{Cite book |author=Committee on the Atmospheric Effects of Nuclear Explosions |title=The Effects on the Atmosphere of a Major Nuclear Exchange |place=Washington D.C. |publisher=National Academy Press |doi=10.17226/540 |year=1985 |isbn=978-0-309-03528-6 |url-access=registration |url=https://archive.org/details/effectsonatmosph0000nati |access-date=2009-10-11 }}
* {{cite journal |author-link1=Paul J. Crutzen |first1=Paul J. |last1=Crutzen |first2=John W. |last2=Birks |title=The Atmosphere After a Nuclear War: Twilight at Noon |journal=Ambio |volume=11 |issue=2–3 |page=114 |date=1982 }}
* {{cite report |last=Goure |first=Leon |date=1985-06-05 |title=Soviet exploitation of the 'nuclear winter' hypothesis |id=DNA-TR-84-373 |url=http://apps.dtic.mil/dtic/tr/fulltext/u2/a165794.pdf |access-date=2016-02-15 |archive-url=https://web.archive.org/web/20160223213627/http://www.dtic.mil/dtic/tr/fulltext/u2/a165794.pdf |archive-date=2016-02-23 |url-status=live }}
* {{cite report |last=Goure |first=L. |date=1986-09-16 |title=An update of Soviet research on and exploitation of 'nuclear winter', 1984–1986 |id=DNA-TR-86-404 |url=http://apps.dtic.mil/dtic/tr/fulltext/u2/a191488.pdf |access-date=2014-06-12 |archive-url=https://web.archive.org/web/20140714212740/http://www.dtic.mil/dtic/tr/fulltext/u2/a191488.pdf |archive-date=2014-07-14 |url-status=live }}
* {{cite book |author=Harwell, Mark A. |title=Nuclear Winter: The Human and Environmental Consequences of Nuclear War |publisher=Springer |date=November 1984 |isbn=978-0-387-96093-7 |url-access=registration |url=https://archive.org/details/nuclearwinterhum0000harw }}
* {{cite report|author=Interagency Intelligence Assessment|year=1984|title=The Soviet Approach to Nuclear Winter|url=http://www.foia.cia.gov/sites/default/files/document_conversions/89801/DOC_0000284025.pdf|access-date=2014-06-12|archive-url=https://web.archive.org/web/20130718020015/http://www.foia.cia.gov/sites/default/files/document_conversions/89801/DOC_0000284025.pdf|archive-date=2013-07-18|url-status=live}}
* {{cite journal |last1=Mills|first1=Michael J.|last2=Toon|first2=Owen B.|last3=Turco|first3=Richard P. |last4=Kinnison |first4=Douglas E. |last5=Garcia |first5=Rolando R. |title=Massive global ozone loss predicted following regional nuclear conflict |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=105 |issue=14 |pages=5307–12 |date=2008 |pmid=18391218 |pmc=2291128 |doi=10.1073/pnas.0710058105 |bibcode=2008PNAS..105.5307M |doi-access=free }}
* {{cite journal |last1=Mills|first1=Michael J.|last2=Toon|first2=Owen B.|last3=Lee-Taylor|first3=Julia |last4=Robock |first4=Alan |title=Multi-decadal global cooling and unprecedented ozone loss following a regional nuclear conflict |journal=Earth's Future |volume=2 |issue=4 |pages=161–76 |date=2014 |doi=10.1002/2013EF000205 |bibcode=2014AGUFMGC41C0580M |s2cid=9582735 |doi-access=free }}
* {{cite book |author-link1=Nikita Moiseyev |first1=N. N. |last1=Moiseyev |title=Man, nature and the future of civilization: "nuclear winter" and the problem of a "permissible threshold" |publisher=Novosti Press Agency |location=Moscow |year=1986 |oclc=15504635}}
* {{cite journal |last1=Robock |first1=Alan |last2=Oman |first2=Luke |last3=Stenchikov |first3=Georgiy L. |last4=Toon |first4=Owen B. |last5=Bardeen |first5=Charles |last6=Turco |first6=Richard P. |name-list-style=amp |title=Climatic consequences of regional nuclear conflicts |journal=Atmos. Chem. Phys. |volume=7 |issue=8 |pages=2003–12 |date=2007 |url=http://climate.envsci.rutgers.edu/pdf/acp-7-2003-2007.pdf |bibcode=2007ACP.....7.2003R |doi=10.5194/acp-7-2003-2007 |doi-access=free |access-date=2007-12-05  |archive-date=2013-06-29  |archive-url=https://web.archive.org/web/20130629153655/http://climate.envsci.rutgers.edu/pdf/acp-7-2003-2007.pdf |url-status=live }}
* {{cite journal |last1=Robock |first1=Alan |last2=Oman |first2=Luke |last3=Stenchikov |first3=Georgiy L. |name-list-style=amp |title=Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences |journal=J. Geophys. Res. |volume=112 |pages=D13107 |date=2007 |issue=D13 |doi=10.1029/2006JD008235 |url=http://climate.envsci.rutgers.edu/pdf/RobockNW2006JD008235.pdf |bibcode=2007JGRD..11213107R |doi-access=free |access-date=2007-12-05  |archive-date=2011-09-28  |archive-url=https://web.archive.org/web/20110928005224/http://climate.envsci.rutgers.edu/pdf/RobockNW2006JD008235.pdf |url-status=live }}
* {{cite journal |doi=10.5194/acp-7-1973-2007 |last1=Toon |first1=Owen B. |last2=Turco |first2=Richard P. |last3=Robock |first3=Alan |last4=Bardeen |first4=Charles |last5=Oman |first5=Luke |last6=Stenchikov |first6=Georgiy L. |name-list-style=amp |title=Atmospheric effects and societal consequences of regional scale nuclear conflicts and acts of individual nuclear terrorism |journal=Atmos. Chem. Phys. |volume=7 |issue=8 |pages=1973–2002 |date=2007 |url=http://climate.envsci.rutgers.edu/pdf/acp-7-1973-2007.pdf |bibcode=2007ACP.....7.1973T |doi-access=free |archive-date=2011-09-28 |archive-url=https://web.archive.org/web/20110928005320/http://climate.envsci.rutgers.edu/pdf/acp-7-1973-2007.pdf }}
* {{cite journal |last1=Toon |first1=Owen B. |last2=Robock |first2=Alan |last3=Turco |first3=Richard P. |last4=Bardeen |first4=Charles |last5=Oman |first5=Luke |last6=Stenchikov |first6=Georgiy L. |name-list-style=amp |title=Consequences of regional-scale nuclear conflicts |journal=Science |volume=315 |issue=5816 |pages=1224–25 |date=2007 |doi=10.1126/science.1137747 |pmid=17332396 |s2cid=129644628 |url=http://climate.envsci.rutgers.edu/pdf/SciencePolicyForumNW.pdf |access-date=2007-12-05  |archive-date=2011-09-28  |archive-url=https://web.archive.org/web/20110928005359/http://climate.envsci.rutgers.edu/pdf/SciencePolicyForumNW.pdf |url-status=live }}
* {{cite journal |last1=Toon |first1=Owen B. |last2=Robock |first2=Alan |last3=Turco |first3=Richard P. |title=Environmental consequences of nuclear war |journal=Physics Today |volume=61 |issue= 12|pages=37–42 |date=December 2008 |doi=10.1063/1.3047679 |bibcode=2008PhT....61l..37T |doi-access=free}}
* {{cite journal |last1=Turco |first1=R.P. |last2=Toon |first2=O.B. |last3=Ackerman |first3=T.P. |last4=Pollack |first4=J.B. |last5=Sagan |first5=C. |title=Nuclear Winter: Global Consequences of Multiple Nuclear Explosions |journal=Science |volume=222 |issue=4630 |pages=1283–1292 |date=December 23, 1983 |doi=10.1126/science.222.4630.1283 |bibcode=1983Sci...222.1283T |s2cid=45515251 |pmid=17773320 }}
* {{cite journal |last1=Turco |first1=R.P. |last2=Toon |first2=O.B. |last3=Ackerman |first3=T.P. |last4=Pollack |first4=J.B. |last5=Sagan |first5=C. |title=Climate and Smoke: An Appraisal of Nuclear Winter |journal=Science |volume=247 |issue=4939 |pages=167–168 |date=January 12, 1990 |doi=10.1126/science.11538069 |bibcode=1990Sci...247..166T |citeseerx=10.1.1.584.8478 |pmid=11538069 }}
{{Refend}}

=== Citations ===
{{Reflist|refs=
<ref name="Robock Toon 2012">{{Cite journal |last1=Robock |first1=Alan |last2=Toon |first2=Owen Brian |date=September–October 2012 |title=Self-assured destruction: The climate impacts of nuclear war |journal=Bulletin of the Atomic Scientists |volume=68 |issue=5 |pages=66–74 |doi=10.1177/0096340212459127 |bibcode=2012BuAtS..68e..66R |s2cid=14377214 |via=SAGE |url=https://journals.sagepub.com/doi/full/10.1177/0096340212459127 |access-date=13 February 2016 |archive-url=https://web.archive.org/web/20210224141904/https://journals.sagepub.com/doi/full/10.1177/0096340212459127 |archive-date=24 February 2021 |url-status=live |url-access=subscription }} [http://climate.envsci.rutgers.edu/pdf/RobockToonSAD.pdf Alternative PDF] {{Webarchive|url=https://web.archive.org/web/20190903152416/http://climate.envsci.rutgers.edu/pdf/RobockToonSAD.pdf |date=2019-09-03  }}</ref>
<ref name=autogenerated3>{{cite web |author=Alan Robock |title=Climatic Consequences of Nuclear Conflict |url=http://climate.envsci.rutgers.edu/nuclear/ |website=climate.envsci.rutgers.edu |access-date=2007-12-05  |archive-date=2011-09-28  |archive-url=https://web.archive.org/web/20110928005214/http://climate.envsci.rutgers.edu/nuclear/ }}{{unreliable source?|date=June 2015}}{{clarify|date=September 2021|reason=Which article?}}{{better source needed|date=September 2021|reason=This is a dynamic (changing) web page that consists of references to other pages and articles.}}</ref>
}}

== External links ==
* [http://www.eoearth.org/article/Nuclear_winter The Encyclopedia of Earth, Nuclear Winter] Lead Author: Alan Robock. Last Updated: July 31, 2008
* [http://www.atomicarchive.com/Movies/Movie6.shtml Nuclear Winter Simulation Animation]
* [http://climate.envsci.rutgers.edu/nuclear/ Studies of climatic consequences of regional nuclear conflict] from [http://envsci.rutgers.edu/~robock Alan Robock]

{{Doomsday}}
{{Pollution}}

[[Category:Climate forcing]]
[[Category:Climatology]]
[[Category:Nuclear doomsday]]
[[Category:Environmental impact of nuclear power]]
[[Category:Environmental impact of war]]
[[Category:Nuclear warfare]]
[[Category:Nuclear weapons]]
[[Category:Carl Sagan]]
[[Category:Theories of history]]