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Nuclear winter (also known as atomic winter) is a hypothetical climatic effect, most often considered a potential threat following a countervalue, or city-targeted, nuclear war. Climate models suggest that the ignition of 100 firestorms that are comparable in intensity to that observed in Hiroshima in 1945 would produce a small nuclear winter. The burning of these firestorms would result in the injection of soot(specifically Black carbon) into the Earth's stratosphere, producing an anti-greenhouse effect, that lowers the Earth's surface temperature. With the models concluding that the size of this effect, from the cumulative products of 100 of these firestorms, would unmistakably cool the global climate by approximately 1 °C for two to three years; with which the authors speculate, but do not model, would have global agricultural losses as a consequence. Whereas a much larger number of firestorms, which are assumed to be the result of any city-targeted, US-Russia total war, is modeled to cause a much deeper nuclear winter, with catastrophic summer cooling by about 20 °C in core agricultural regions of the US, Europe and China, and by as much as 35 °C in Russia.〔http://climate.envsci.rutgers.edu/nuclear/〕 On the fundamental level, it is known that firestorms can inject soot smoke/aerosols into the stratosphere, as each natural occurrence of a wildfire firestorm has been found to "surprisingly frequently" produce minor nuclear winter effects, with short-lived drops in surface temperatures, confined to the global hemisphere that they burned in.〔(Fire-Breathing Storm Systems. NASA )〕〔(Russian Firestorm: Finding a Fire Cloud from Space. NASA Earth Observatory, 2010 )〕 This is somewhat analogous to the frequent volcanic eruptions that inject sulfates into the stratosphere and thereby produce minor 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 properties of this smoke.〔(NASA to study how pollution, storms and climate mix 2013 )〕〔(Wildfires Smoke Crosses the Atlantic July 2, 2013 NASA )〕〔(Canadian and Siberian Boreal Fire Activity during ARCTAS Spring and Summer Phases. American Geophysical Union, Fall Meeting 2009, (Conference paper) )〕 Information regarding all of these properties is necessary to truly ascertain the length and depth of the cooling effect of firestorms, independent of the nuclear winter computer model projections. Presently, from satellite tracking data, stratospheric smoke aerosols are removed in a time span under approximately two months,〔 and the existence of any hint of a tipping point into a new stratospheric condition where the aerosols would not be removed within this timeframe, remains to be determined.〔 == Mechanism == (詳細はfirestorms〔(Massive global ozone loss predicted following regional nuclear conflict 2008 ) "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..."〕〔(Atmospheric effects and societal consequences of regional scale nuclear conflicts and acts of individual nuclear terrorism. ''Atmos ChemPhys'' 7:1973–2002 ) pg 1994 "the injection height of the smoke is controlled by the energy release from the burning fuel not from the nuclear explosion."〕 are ignited by the nuclear explosions of a nuclear war,〔http://bos.sagepub.com/content/68/5/66.abstract Self-assured destruction: The climate impacts of nuclear war. Alan Robock, Owen Brian Toon. Bulletin of the Atomic Scientists, September/October 2012; vol. 68, 5: pp. 66-74〕 and the firestorms lift large enough amounts of sooty smoke into the upper troposphere and lower stratosphere, soot lifted by the movement offered by the pyrocumulonimbus clouds that form during a firestorm. At 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 block out a portion of the sun's light from reaching the surface, causing surface temperatures to drop drastically, and with that, it is predicted surface air temperatures would be akin to, or colder than, a given region's winter for months to years on end. The modeled stable inversion layer of hot soot between the troposphere and high stratosphere that produces the anti-greenhouse effect was dubbed the "Smokeosphere" by Stephen Schneider et al. in their 1988 paper.〔"A Nuclear Winter's Tale By Lawrence Badas" pg 184〕〔(William R. Cotton, Roger A. Pielke, Sr Cambridge University Press, 2007, pg 216 )〕〔http://assets.cambridge.org/97805218/40866/frontmatter/9780521840866_frontmatter.pdf〕 Although it is common in the climate models for the city firestorms to be ignited by nuclear explosions, they need not be ignited by nuclear devices;〔(''A Nuclear Winter's Tale: Science and Politics in the 1980s'', Lawrence Badash ), page 242-244〕 more conventional ignition sources can instead be the spark of the firestorms. As prior to the previously mentioned solar heating effect, the soot's injection height is controlled by the rate of energy release from the firestorm's fuel, not the size, or lack thereof, of an initial nuclear explosion.〔 For example, the mushroom cloud from the 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.〔(Atmospheric effects and societal consequences of regional scale nuclear conflicts and acts of individual nuclear terrorism ) pg 1994. Altitudes of smoke columns.〕 While the firestorm of Dresden and Hiroshima and the mass fires of Tokyo and Nagasaki occurred with mere months separating them in 1945, the more intense and conventionally lit Hamburg firestorm occurred in 1943. Despite this, these five fires potentially placed five percent as much smoke into the stratosphere as the hypothetical 100 nuclear-ignited fires of modern models.〔(Atmospheric effects and societal consequences of regional scale nuclear conflicts and acts of individual nuclear terrorism ) pg 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."〕 While it is believed that the effects of the mass of soot emitted by 100 firestorms (one to five teragrams) would have been detectable with technical instruments in WWII, only five percent of that would not have been possible to observe at that time.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「nuclear winter」の詳細全文を読む スポンサード リンク
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