Nuclear winter

"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 fireball generated NOx emissions would devastate the ozone layer was losing credibility. In these model scenarios, various soot clouds containing uncertain quantities of soot were assumed to form over cities, oil refineries, and more rural missile silos. Once the quantity of soot is decided upon by the researchers, the climate effects of these soot clouds are then modeled. 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. 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 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 °C (1.8 °F), largely eliminating the magnitude of anthropogenic global warming for the next roughly two or three years. 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. nuclear weapon use during an American-Soviet total war. This larger number of firestorms, which are not in themselves modeled, This cooling would be produced due to a 99% reduction in the natural solar radiation reaching the surface of the planet in the first few years, gradually clearing over the course of several decades. it has been known that firestorms could inject soot smoke and aerosols 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 that they burned in. This is somewhat analogous to the frequent 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 properties of this smoke. 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. Currently, from satellite tracking data, it appears that stratospheric smoke aerosols dissipate in a time span under approximately two months. The existence of a tipping point into a new stratospheric condition where the aerosols would not be removed within this time frame remains to be determined. == Mechanism ==

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. are ignited by nuclear explosions, Although it is common in the climate models to consider city firestorms, these need not be ignited by nuclear devices; 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 rate of energy release from the firestorm's fuel, not the size of an initial nuclear explosion. 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 16-kiloton nuclear bomb from a single B-29 bomber could have been produced instead by the conventional use of about 1.2 kilotons of incendiary bombs from 220 B-29s distributed over the city. While the firestorms of Dresden and Hiroshima and the mass fires of Tokyo and Nagasaki occurred within mere months in 1945, the more intense and 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. and falls out of the atmosphere via gravity-driven dry deposition, and which also occur at greater concentrations when air is heated to high temperatures. Historical data on residence times of aerosols, albeit a 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, however aerosol–atmosphere interactions are still poorly understood. Soot properties Sooty aerosols can have a wide range of properties, as well as complex shapes, making it difficult to determine their evolving atmospheric 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 burning efficiency considered almost "elemental carbon black," while on the more inefficient end of the burning spectrum, greater quantities of 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. 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. == Consequences ==

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.) 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. Alexandrov disappeared in 1985. As of 2016, there remains ongoing speculation by friend, Andrew Revkin, of foul play relating to his work. 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 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", disrupting agricultural production and food gathering in particular in higher latitude countries. 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. 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 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. Nuclear summer A "nuclear summer" is a hypothesized scenario in which, after a nuclear winter caused by aerosols inserted into the atmosphere that would prevent sunlight from reaching lower levels or the surface, has abated, a greenhouse effect then occurs due to carbon dioxide released by combustion and methane released from the decay of the organic matter such as corpses that froze during the nuclear winter. 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 CO2 and other greenhouse gases from burning, followed by more released from the decay of dead organic matter. The detonations would also insert nitrogen oxides into the stratosphere that would then deplete the ozone layer around the Earth. 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. == History ==

Early work detonated as surface bursts. 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. US high-yield upper atmospheric tests, Teak and Orange were also assessed for their ozone destruction potential. 0 = Approx altitude commercial aircraft operate1 = Fat Man2 = Castle Bravo In 1952, a few weeks prior to the Ivy Mike (10.4 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. 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 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." 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. 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, 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." 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". 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 micrometer range. The potential cooling from soil dust was again looked at in 1992, in a US National Academy of Sciences (NAS) report on geoengineering, which estimated that about 1010 kg (10 teragrams) of stratospheric injected soil dust with particulate grain dimensions of 0.1 to 1 micrometer would be required to mitigate the warming from a doubling of atmospheric carbon dioxide, that is, to produce ~2 °C of cooling. In 1969, Paul Crutzen discovered that 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 that due to the creation of atmospheric NOx by nuclear fireballs, 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. In 1975, Hampson's hypothesis "led directly" 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. 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. In total, about 500 Mt were atmospherically detonated between 1945 and 1971, peaking in 1961–1962, when 340 Mt were detonated in the atmosphere by the United States and Soviet Union. 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 × 1034 additional molecules of nitric oxide (about 5,000 tons per Mt, 5 × 109 grams per megaton) 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 caused by other meteorological effects. 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 light leading to the widespread destruction of crops, as advocated by Jonathan Schell in The Fate of the Earth, as highly unlikely. 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 mutants, 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. Anderson went on to publish a novel based partly on this story in 1961, titling it Twilight World. 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". 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 accuracy), the ozone layer danger was "not very significant". 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 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, 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 to explain how Martian dust may be formed and how it may reach global proportions." 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. 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. 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. 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, 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 magazine until late-December 1983. The phrase "nuclear winter" had been coined by Turco just prior to publication. 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. The 1-D radiative-convective models used in these studies produced a range of results, with cooling up to 15–42 °C between 14 and 35 days after the war, with a "baseline" of about 20 °C. Somewhat more sophisticated calculations using 3-D GCMs produced similar results: temperature drops of about 20 °C, though with regional variations. All calculations show large heating (up to 80 °C) at the top of the smoke layer at about ; 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: 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 °C drop in mid-latitudes • 10 °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 °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 °C • Ozone depletion of 50% leading to 200% increase in UV radiation incident on surface. Kuwait wells in the first Gulf War were not just limited to 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. 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. 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. 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. In articles printed in the Wilmington Morning Star and the 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. As threatened, the wells were 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, 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 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 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." Singer, on the other hand, anticipated that the smoke would go to an altitude of about 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, 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. 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. 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." 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 , and when combined with scavenging by clouds the smoke had a short residency time of a maximum of a few days in the atmosphere. 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, 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 °C within 200 km of the source. shows black smoke from the 2005 Buncefield fire, a series of fires and explosions involving approximately 250,000,000 litres 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 °C over the Persian Gulf, but not much smoke reached stratospheric altitudes and Asia was spared." 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. 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: However, the above simulation notably contained the assumption that no dry or wet deposition would occur. == Recent modeling ==

Between 1990 and 2003, commentators noted that no peer-reviewed papers on "nuclear winter" were published. 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. 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: ...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. 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". This study has been contradicted by results in several subsequent studies claiming the 2018 study to be flawed. 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". 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., 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. 2022 (IND) and Pakistan (PAK). "USA-RUS" marks a simulated nuclear war between the US (USA) and Russia (RUS). "PRK" = a simulated nuclear war in which 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. According to a peer-reviewed study published in the journal Nature Food in August 2022, 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 events. 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 of warming by 2100 and by 2500, would send around 12–14% of animal species extinct under the same methodology. 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. the committee was still working on the report. 2025 study - Impact on global agriculture In 2025, researchers at Pennsylvania State University used the Cycles agroecosystem 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. 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%. 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%. 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. To help mitigate such impacts, the authors suggested "agricultural resilience kits," containing seeds of fast-growing, cold-tolerant crops suited to different regions. ==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: • 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 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)? • Darkness and opacity: how much light-blocking effect the assumed quality of the soot reaching the atmosphere would have? 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. Starley L. Thompson's less primitive mid-1980s 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. 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. 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. 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". 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]." The contribution of smoke from the ignition of live non-desert vegetation, living forests, grasses and so on, nearby to many missile silos 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". This reduction in the estimate of the non-urban smoke hazard is supported by the earlier preliminary Estimating Nuclear Forest Fires publication of 1984, and Operation Redwing test series. on 9–10 March 1945, 1,665 tons (1.66 kilotons) of 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 – , the most destructive and deadliest bombing operation in history. , approximately 10 times as much energy as delivered onto Tokyo, yet due in part to the comparative inefficiency of larger bombs, a much smaller area of building destruction occurred when contrasted with the results from Tokyo. Only of Hiroshima was destroyed by blast, fire, and firestorm effects. 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 22-kiloton nuclear bomb dropped on Nagasaki did not result in a firestorm and thus did not do as much fire damage as the conventional airstrikes on Hamburg which did generate a firestorm. 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. 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 shoji paper sliding walls. 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". The nuclear bombing of Nagasaki for example, did not produce a firestorm. 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 fluxes 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 km. Following his investigation into the Siberian fire of 1915, Seitz criticized the "nuclear winter" model results for being based on successive worst-case events: 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 ..." Schneider conceded the issue in 1990, saying "a war in late fall or winter would have no appreciable [cooling] effect". 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". Similarly S. Fred Singer was a long term vocal critic of the hypothesis in the journal and in televised debates with Carl Sagan. In 1986 Seitz also contends that many others are reluctant to speak out for fear of being stigmatized as "closet Dr. Strangeloves"; 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." Emanuel also made an "interesting point" about questioning proponents' objectivity when it came to strong emotional or political views that they hold. and previously mentioned RAMS atmosphere model, had in the 1980s worked on soot rain-out models and supported the predictions made by his own and other nuclear winter models. 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 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". == Policy implications ==

During the Cuban Missile Crisis, Fidel Castro and Che Guevara called on the USSR to launch a nuclear 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". 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. 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. Moreover, total deployed US and Russian strategic weapons increased steadily from 1983 until the Cold War ended. 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, An originally classified 1984 US interagency intelligence assessment states that in both the preceding 1970s and 1980s, the Soviet and US military were already following the "existing trends" in warhead miniaturization, of higher accuracy and lower yield nuclear warheads. This is seen when assessing the most numerous physics packages in the US arsenal, which in the 1960s were the 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. 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 decoys on each missile. Alongside the desire to still destroy 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 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 Stephen Cimbala of Pennsylvania State University argued that the then already developed and deployed smaller, more accurate warheads (e.g. W76), together with 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 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, while also temporarily lofting far more localized fallout when compared to airburst fuzing – the standard mode of employment against un-hardened targets., had a yield about a tenth of the 13 to 16 Kt Hiroshima bomb, 1.2 Kt, and was detonated 5.2 m (17 ft) beneath ground level. No thermal flash of heat energy was emitted to the surroundings in this shallow buried test. The resulting crater was 260 feet (79 m) wide and 53 feet (16 m) deep. 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. 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. 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 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. Therefore, as a consequence of attempting to limit the target fire hazard by reducing the range of thermal radiation with fuzing for surface and 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. 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 development of more accurate, and even lower explosive yield, nuclear weapons. 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. 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. Alleged Soviet exploitation 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." 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. 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 echelon thinking. In 1985, Time magazine noted "the suspicions of some Western scientists that the nuclear winter hypothesis was promoted by Moscow to give anti-nuclear groups in the U.S. and Europe some fresh ammunition against America's arms buildup." 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. 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. 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 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 Soviet Academy of Sciences by Georgii Golitsyn, Nikita Moiseyev and Vladimir Alexandrov concerning the climatic effects of nuclear war. Although it is accepted that the Soviet Union exploited the nuclear winter hypothesis for propaganda purposes, 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 . In an interview in 2009 conducted by the National Security Archive, Vitalii Nikolaevich Tsygichko (a Senior Analyst at the 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. == Mitigation techniques ==

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. The report considered attempting to stop the spread of fires by creating firebreaks by blasting combustible material out of an area, possibly even using nuclear weapons, along with the use of preventative Hazard Reduction Burns. According to the report, one of the most promising techniques investigated was initiation of rain from seeding of mass-fire thunderheads and other clouds passing over the developing, and then stable, firestorm. Producing food without sunlight 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; bark bread, a long-standing famine food using the edible 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; and variations of wood or cellulosic biofuel production, which typically already creates edible sugars/xylitol from inedible cellulose, as an intermediate product before the final step of alcohol generation. 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. 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)." The minimum annual global wheat storage is approximately 2 months. == Climate engineering ==

Despite the name "nuclear winter", nuclear events are not necessary to produce the modeled climatic effect. According to the threshold "nuclear winter" computer models, if one to five teragrams of firestorm-generated soot 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 °C cooling for two to three years; and after 10 years, average global temperatures would still be 0.5 °C lower than before the soot injection. == Potential climatic precedents ==

formation. The asteroid connected with the extinction of the Cretaceous–Paleogene extinction event released an estimated energy of . 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. 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). Similar climatic effects to "nuclear winter" followed historical supervolcano eruptions, which plumed sulfate aerosols high into the stratosphere, with this being known as a volcanic winter. 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. 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. Similarly, extinction-level comet and asteroid impacts are also believed to have generated impact winters by the 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, and "nuclear winter" effects, with the heat of the heavier rock ejecta igniting regional and possibly even global forest firestorms. 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-sized ejecta fragments created can meteorically re-enter the atmosphere forming a hot blanket of global debris high in the air, potentially turning the entire sky red-hot for minutes to hours, and with that, burning the complete global inventory of above-ground carbonaceous material, including rain forests. This hypothesis is suggested as a means to explain the severity of the Cretaceous–Paleogene extinction event, as the 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, Tamara Goldin and Melosh, who had initially supported the hypothesis, with this re-evaluation being dubbed the "Cretaceous-Palaeogene firestorm debate" by Belcher. in much the same manner that the fraction of the material ignited directly by the meteor impact is difficult to determine. == See also ==

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. • 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 (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 (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: 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. • Nuclear Winter is a mini documentary by Retro Report that looks at nuclear winter fears in today's world. == Explanatory notes==

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