Editing Nuclear winter (section)

== 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.