Nuclear winter
Encyclopedia
Nuclear winter is a predicted climatic
effect of nuclear war
. It has been theorized that severely cold weather and reduced sunlight for a period of months or even years could be caused by detonating large numbers of nuclear weapons, especially over flammable
targets such as cities
, where large amounts of smoke
and soot
would be ejected into the Earth
's stratosphere
.
Similar climatic effects can be caused by a comet
or asteroid impact, also sometimes termed an impact winter
, or of a supervolcano
eruption, known as a volcanic winter
.
predicts that the huge fires caused by nuclear explosion
s (from burning urban areas) would loft massive amounts of dense smoke
from the fires, into the upper troposphere
/ stratosphere
. At 10-15 kilometers (6–9 miles) above the Earth's surface, the absorption of sunlight would further heat the smoke, lifting some, or all of it, into the stratosphere
, to where the smoke would persist for years, with no rain to wash it out. This aerosol
of particles would block out much of the sun's light
from reaching the surface, causing surface temperatures to drop drastically.
, is dependent on both chemical and physical removal processes. The physical removal mechanisms affecting the timescale of smoke particle removal are how quickly the particles in the smoke coagulate and fall out of the atmosphere via dry deposition, and to a slower degree, the time it takes for solar radiation pressure
to move the particles to a lower level in the atmosphere. Whether by coagulation
or radiation pressure
, once the particles are at this lower atmospheric level cloud seeding
can begin, permitting precipitation
to wash the smoke aerosol
out of the atmosphere by the wet deposition mechanism. The chemical processes that affect the removal are dependant on the ability of atmospheric chemistry
to oxidize the smoke, via reactions with oxidative species such as ozone
and nitrogen oxides, both of which are found at all levels of the atmosphere. Historical data on residence times of aerosols, albeit a different mixture of aerosols, from megavolcano eruptions appear to be in the 1-2 year time scale. Aerosol
atmosphere interactions are still poorly understood.
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 kiloton each) on major populated 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".
A minor nuclear war with each country using 50 Hiroshima-sized atom bombs as airbursts on urban areas could produce climate change unprecedented in recorded human history. A nuclear war between the United States and Russia today could produce nuclear winter, with temperatures plunging below freezing in the summer in major agricultural regions, threatening the food supply for most of the planet. The climatic effects of the smoke from burning cities and industrial areas would last for several years, much longer than previously thought. New climate model simulations, which are said to have the capability of including the entire atmosphere and oceans, show that the smoke would be lofted by solar heating to the upper stratosphere, where it would remain for years.
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 A.D. 1600 and A.D. 1850). This would take effect instantly, and agriculture would be severely threatened. Larger amounts of smoke would produce larger climate changes, and for the 150 Tg case produce a true nuclear winter, making agriculture impossible for years. In both cases, new climate model simulations show that the effects would last for more than a decade.
in July 2007, Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences, 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 described as being only about a third 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 (1 Tg is equal to 1012 gram
s), 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:
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."
and other scientists predicted that burning oil wells could cause environmental damage comparable to nuclear winter. Nearly 700 oil wells were set ablaze by the retreating Iraqi army and the fires were not fully extinguished until November 6, 1991, eight months after the end of the war. The fires consumed an estimated six million barrels of oil daily.
According to a 1992 study from Peter Hobbs
and Lawrence Radke, daily emissions of sulfur dioxide
were 57% of that from electric utilities in the United States, emissions of carbon dioxide
were 2% of global emissions and emissions of soot
were 3,400 metric tons per day. However, pre-war claims of wide scale, long-lasting, and significant global environmental impacts were not borne out and found to be significantly exaggerated by the media and speculators, with climate models 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. At the peak of the fires, the smoke absorbed 75% to 80% of the sun’s radiation. The particles were never observed to rise above 6 km and when combined with scavenging by clouds gave the smoke a short residency time in the atmosphere and localized its effects; Professor Carl Sagan
of the Turco
, Toon, Ackerman, Pollack, Sagan (TTAPS) study hypothesized in January 1991 that enough smoke from the fires "might get so high as to disrupt agriculture in much of South Asia...." Sagan later conceded in his book The Demon-Haunted World
that this prediction 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 2007 study discussed above 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 or the burning of cities that would be expected to follow a nuclear strike, would loft significant amounts of smoke into the stratosphere:
was published containing a section entitled "Nuclear Bombs and the Weather" (pages 69–71), which 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 debris remaining in the atmosphere after the explosion of even the largest nuclear weapons is probably not more than about 1 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." In 1974, John Hampson suggested that 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, the United States National Research Council
(NRC) reported on ozone depletion following nuclear war, judging that the effect of dust would probably be slight climatic cooling.
As part of a study launched in 1980 by Ambio, a journal of the Royal Swedish Academy of Sciences
, Paul Crutzen and John Birks circulated a draft paper in early 1982 with the first quantitative evidence of alterations in short-term climate after a nuclear war. In 1982, a special issue of Ambio
devoted to the possible environmental consequences of nuclear war included a paper by Crutzen and Birks anticipating the nuclear winter scenario. The paper discussed particulates from large fires, nitrogen oxide, ozone depletion and the effect of nuclear twilight on agriculture. Crutzen and Birks showed that smoke injected into the atmosphere by fires in cities, forests and petroleum reserves could prevent up to 99% of sunlight from reaching the Earth's surface, with major climatic consequences: "The normal dynamic and temperature structure of the atmosphere would therefore change considerably over a large fraction of the Northern Hemisphere, which will probably lead to important changes in land surface temperatures and wind systems." An important implication of their work was that a "first strike" nuclear attack would have severe consequences for the perpetrator.
, Owen Toon
, Thomas P. Ackerman, James B. Pollack
and Carl Sagan
) undertook a computational modeling study of the atmospheric consequences of nuclear war, publishing their results in Science
in December 1983. The phrase "nuclear winter" was coined by Turco just prior to publication. In this early work, TTAPS carried out the first estimates of the total smoke and dust emissions that would result from a major nuclear exchange, and determined quantitatively the subsequent effects on the atmospheric radiation balance and temperature structure. To compute dust and smoke impacts, they employed a one-dimensional microphysics/radiative-transfer model of the Earth's lower atmosphere (to the mesopause), which defined only the vertical characteristics of the global climate perturbation.
Around this time, interest in nuclear war environmental effects also arose in the USSR. After becoming aware of the work of the Swedish Academy and, in particular, papers by N.P.Bochkov and E.I.Chazov
, Russian atmospheric scientist Georgy Golitsyn applied his research on dust-storms to the situation following a nuclear catastrophe. His suggestion that the atmosphere would be heated and that the surface of the planet would cool appeared in The Herald of the Academy of Sciences in September 1983. Upon learning of the TTAPS scenarios, Vladimir Alexandrov
and G. I. Stenchikov soon published a report on the climatic consequences of nuclear war based on simulations with a two-level global circulation model, which produced results consistent with the TTAPS findings.
commissioned Georgy Golitsyn and N. A. Phillips to review the state of the science. They found that studies generally assumed a scenario that half of the world's nuclear weapons would be used, ~5000 Mt
, destroying approximately 1,000 cities, and creating large quantities of carbonaceous smoke - 1–2 × 1014 grams being mostly likely, with a range of 0.2 – 6.4 × 1014 grams (NAS; TTAPS assumed 2.25 × 1014). The smoke resulting would be largely opaque to solar radiation but transparent to infra-red, thus cooling by blocking sunlight but not causing warming from 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 Mt-equivalent of explosion could release up to 5 million ton
s of dust, but most would quickly fall out; high altitude dust is estimated at 0.1-1 million tons per Mt-equivalent of explosion. Burning of crude oil could also contribute substantially.
The 1-D radiative-convective models used in these studies produced a range of results, with coolings 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 GCM
s (Alexandrov and Stenchikov (1983); Covey, Schneider and Thompson (1984); produced similar results: temperature drops of between 20 and 40 °C, though with regional variations.
All calculations show large heating (up to 80 °C) at the top of the smoke layer at about 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.
The report made no attempt to compare the likely human impacts of the post-war cooling to the direct deaths from explosions.
First 1 to 3 months:
Following 1 to 3 years:
The original work by Sagan and others was criticized as a "myth" and "discredited theory" in the 1987 book Nuclear War Survival Skills
, a civil defense
manual by Cresson Kearny
for the Oak Ridge National Laboratory
. Kearny said the maximum estimated temperature drop would be only about by 20 degrees Fahrenheit (11 degrees Celsius), and that this amount of cooling would last only a few days. He also suggested that a global nuclear war would indeed result in millions of deaths from hunger, but primarily due to cessation of international food supplies, rather than due to climate changes.
Kearny, who was not a climate scientist himself, based his conclusions almost entirely on the 1986 paper "Nuclear Winter Reappraised" by Starley Thompson and Stephen Schneider. However, a 1988 article by Brian Martin in Science and Public Policy states that although their paper concluded the effects would be less severe than originally thought, with the authors describing these effects as a "nuclear autumn", other statements by Thompson and Schneider show that they "resisted the interpretation that this means a rejection of the basic points made about nuclear winter". In addition, the authors of the 2007 study above state 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]." And in 2007 Schneider emphasized the danger of serious climate changes from a limited nuclear war of the kind analyzed in the 2006 study above, 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."
. As firestorm
formation is clearly a necessity to generate the form of smoke discussed in the climatology
models, this is the bedrock to all nuclear winter predictions. The 150 Tg carbon
soot aerosol injection into the stratosphere, which the TTAPS paper required to cause nuclear winter, has been criticised on the basis of World War II firestorm
ignition evidence from Japanese and medieval European wooden cities, since unbiased factual evidence exists in survivor testimony from Hiroshima that soot was actually precipitated as rainout during the firestorm-the infamous black rain a natural phenomenon produced by Pyrocumulus cloud
s. At Hiroshima, the infamous black rain formed soon after the bombing, washing large amounts of carbon out of the atmosphere.
Unlike the Japanese wooden cities of 1945 and medieval wooden housing areas of Germany where firestorms occurred, modern cities are not built out of predominantly flammable materials like wood, but built of mostly concrete
and masonry brick
.
The nuclear winter effect from the firestorm in Hiroshima blocked out the sun for 25 minutes (from burst time at 8:15 am until 8:40 am) as shown by the meteorological sunshine records printed in Figure 6 (3H) of the Report of the Joint Commission for the Investigation of the Effects of the Atomic Bomb in Japan, Volume 1, Office of the Air Surgeon, report NP-3036, April 19, 1951, U.S. Atomic Energy Commission. The Hiroshima firestorm soot was hydroscopic, absorbing water and falling out in black rain, which limited the climatic effect. The fact that soot was rapidly precipitated in a self-induced rainout in Hiroshima was in 1983 used as a nuclear winter criticism by J. B. Knox of Lawrence Livermore National Laboratory in report UCRL-89907. No other nuclear explosion ever created a firestorm, including detonations of up to 15 megatons
beside naturally forested islands-Bikini
and Eniwetok Atoll, which failed to ignite the trees due to the high (80%) air humidity and its effects both on ignition and thermal pulse transmission. Targeting oil wells instead of cities, as was done in the final TAPPS paper to compensate for reduced estimates of city firestorm soot emission, reduces the moisture effect, but the soot doesn't rise high enough from burning oil wells for widespread climatic effects, as proved in 1991 when Iraq
set fire to all of Kuwait’s oil fields.
Lastly, there is the question of whether the thermal pulse of a modern nuclear weapon is sufficient to ignite an entire modern city, or simply level most of it to the ground. The generating mechanism for the firestorm
that engulfed Hiroshima was not(as some contend) directly linked to the thermal pulse from the atomic bomb
, but in reality the major causative agent of the firestorm was the timing of the bombing, and to a lesser degree the exceptionally dry weather conditions preceding the bomb run. The fact that the bombing occurred at 08:15 local time meant the bombing occurred right around breakfast time, which importantly implies that the fires were secondary in nature, started from overturned cooking devices when the blast wave
arrived, This is in direct contrast to the atomic bombing of Nagasaki, where no true firestorm
formed.
The originally secret 6 volume U.S. Strategic Bombing Survey reports on Hiroshima and Nagasaki disclose that there had been no significant rain for 3 weeks prior to the Hiroshima bombing, and for 10 days prior to the Nagasaki bombing, except for one light shower on August 5. The May 1947 U.S. Strategic Bombing Survey report on Hiroshima lists all the factors that contributed to the firestorm on pages 4–6: "Six persons who had been in reinforced-concrete buildings within 3,200 feet of air zero stated that black cotton black-out curtains were ignited by flash heat... A large proportion of over 1,000 persons questioned was, however, in agreement that a great majority of the original fires were started by debris falling on kitchen charcoal fires ... There had been practically no rain in the city for about 3 weeks. The velocity of the wind ... was not more than 5 miles per hour.... Hundreds of fires were reported to have started in the centre of the city within 10 minutes after the explosion... almost no effort was made to fight this conflagration ... There were no automatic sprinkler systems in buildings...".
, in response to the comment "In the 1980s, you warned about the unprecedented dangers of nuclear weapons and took very daring steps to reverse the arms race," said "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."
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
effect of nuclear war
Nuclear warfare
Nuclear warfare, or atomic warfare, is a military conflict or political strategy in which nuclear weaponry is detonated on an opponent. Compared to conventional warfare, nuclear warfare can be vastly more destructive in range and extent of damage...
. It has been theorized that severely cold weather and reduced sunlight for a period of months or even years could be caused by detonating large numbers of nuclear weapons, especially over flammable
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....
targets such as cities
City
A city is a relatively large and permanent settlement. Although there is no agreement on how a city is distinguished from a town within general English language meanings, many cities have a particular administrative, legal, or historical status based on local law.For example, in the U.S...
, where large amounts of smoke
Smoke
Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires , but may also be used for pest...
and soot
Soot
Soot is a general term that refers to impure carbon particles resulting from the incomplete combustion of a hydrocarbon. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolyzed fuel particles such as cenospheres,...
would be ejected into the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
.
Similar climatic effects can be caused by a comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
or asteroid impact, also sometimes termed an impact winter
Impact winter
An impact winter is a period of prolonged cold weather caused by the impact on the Earth of a large asteroid or comet. If such an impact occurred on land or the floor of a shallow sea, it could cause large amounts of dust or ash to be thrown into the Earth's atmosphere, blocking the Sun's light...
, or of a supervolcano
Supervolcano
A supervolcano is a volcano capable of producing a volcanic eruption with an ejecta volume greater than 1,000 cubic kilometers . This is thousands of times larger than most historic volcanic eruptions. Supervolcanoes can occur when magma in the Earth rises into the crust from a hotspot but is...
eruption, known as a volcanic winter
Volcanic winter
A volcanic winter is the reduction in temperature caused by volcanic ash and droplets of sulfuric acid obscuring the sun and raising Earth's albedo after a large particularly explosive type of volcanic eruption...
.
Mechanism
The nuclear winter scenarioScenario
A scenario is a synoptical collage of an event or series of actions and events. In the Commedia dell'arte it was an outline of entrances, exits, and action describing the plot of a play that was literally pinned to the back of the scenery...
predicts that the huge fires caused by nuclear explosion
Nuclear explosion
A nuclear explosion occurs as a result of the rapid release of energy from an intentionally high-speed nuclear reaction. The driving reaction may be nuclear fission, nuclear fusion or a multistage cascading combination of the two, though to date all fusion based weapons have used a fission device...
s (from burning urban areas) would loft massive amounts of dense smoke
Smoke
Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires , but may also be used for pest...
from the fires, into the upper troposphere
Troposphere
The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....
/ stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
. At 10-15 kilometers (6–9 miles) above the Earth's surface, the absorption of sunlight would further heat the smoke, lifting some, or all of it, into the stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
, to where the smoke would persist for years, with no rain to wash it out. This aerosol
Aerosol
Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...
of particles would block out much of the sun's light
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
from reaching the surface, causing surface temperatures to drop drastically.
Aerosol removal timescale
The exact timescale for how long this smoke remains, and thus how severely this smoke affects the climate once it reaches the stratosphereStratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
, is dependent on both chemical and physical removal processes. The physical removal mechanisms affecting the timescale of smoke particle removal are how quickly the particles in the smoke coagulate and fall out of the atmosphere via dry deposition, and to a slower degree, the time it takes for solar radiation pressure
Radiation pressure
Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. If absorbed, the pressure is the power flux density divided by the speed of light...
to move the particles to a lower level in the atmosphere. Whether by coagulation
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
or radiation pressure
Radiation pressure
Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. If absorbed, the pressure is the power flux density divided by the speed of light...
, once the particles are at this lower atmospheric level cloud seeding
Cloud seeding
Cloud seeding, a form of intentional weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud...
can begin, permitting precipitation
Precipitation
Precipitation may refer to:* Precipitation , rain, sleet, hail, snow and other forms of water falling from the sky* Precipitation , the condensation of a solid from a solution during a chemical reaction...
to wash the smoke aerosol
Aerosol
Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...
out of the atmosphere by the wet deposition mechanism. The chemical processes that affect the removal are dependant on the ability of atmospheric chemistry
Atmospheric chemistry
Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary field of research and draws on environmental chemistry, physics, meteorology, computer modeling, oceanography, geology and...
to oxidize the smoke, via reactions with oxidative species such as ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
and nitrogen oxides, both of which are found at all levels of the atmosphere. Historical data on residence times of aerosols, albeit a different mixture of aerosols, from megavolcano eruptions appear to be in the 1-2 year time scale. Aerosol
Aerosol
Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...
atmosphere interactions are still poorly understood.
Climatic effects
A study presented at the annual meeting of the American Geophysical UnionAmerican Geophysical Union
The American Geophysical Union is a nonprofit organization of geophysicists, consisting of over 50,000 members from over 135 countries. AGU's activities are focused on the organization and dissemination of scientific information in the interdisciplinary and international field of geophysics...
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
Subtropics
The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...
would each use 50 Hiroshima
Atomic bombings of Hiroshima and Nagasaki
During the final stages of World War II in 1945, the United States conducted two atomic bombings against the cities of Hiroshima and Nagasaki in Japan, the first on August 6, 1945, and the second on August 9, 1945. These two events are the only use of nuclear weapons in war to date.For six months...
-sized nuclear weapons (about 15 kiloton each) on major populated 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
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
, including most of the grain-growing regions. The cooling would last for years, and according to the research could be "catastrophic".
Ozone depletion
A 2008 study published in the Proceedings of the National Academy of Science 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 wreaking environmental havoc for at least a decade. The computer-modeling 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 50 miles (80.5 km) into the stratosphere. The soot would absorb enough solar radiation to heat surrounding gases, setting in motion a series of chemical reactions that would break down the stratospheric ozone layer protecting Earth from harmful ultraviolet radiation.Recent modeling
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.A minor nuclear war with each country using 50 Hiroshima-sized atom bombs as airbursts on urban areas could produce climate change unprecedented in recorded human history. A nuclear war between the United States and Russia today could produce nuclear winter, with temperatures plunging below freezing in the summer in major agricultural regions, threatening the food supply for most of the planet. The climatic effects of the smoke from burning cities and industrial areas would last for several years, much longer than previously thought. New climate model simulations, which are said to have the capability of including the entire atmosphere and oceans, show that the smoke would be lofted by solar heating to the upper stratosphere, where it would remain for years.
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
Little Ice Age
The Little Ice Age was a period of cooling that occurred after the Medieval Warm Period . While not a true ice age, the term was introduced into the scientific literature by François E. Matthes in 1939...
(the period of history between approximately A.D. 1600 and A.D. 1850). This would take effect instantly, and agriculture would be severely threatened. Larger amounts of smoke would produce larger climate changes, and for the 150 Tg case produce a true nuclear winter, making agriculture impossible for years. In both cases, new climate model simulations show that the effects would last for more than a decade.
2007 study on global nuclear war
A study published in the Journal of Geophysical ResearchJournal of Geophysical Research
The Journal of Geophysical Research is a peer-reviewed scientific journal published by the American Geophysical Union 80 times per year. It contains original research on the physical, chemical, and biological processes that contribute to the understanding of the Earth, Sun, and solar system...
in July 2007, Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences, 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 described as being only about a third the size of the world's arsenals twenty years earlier). The authors used a global circulation model
Global climate model
A General Circulation Model is a mathematical model of the general circulation of a planetary atmosphere or ocean and based on the Navier–Stokes equations on a rotating sphere with thermodynamic terms for various energy sources . These equations are the basis for complex computer programs commonly...
, ModelE from the NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
Goddard Institute for Space Studies
Goddard Institute for Space Studies
The NASA Goddard Institute for Space Studies , at Columbia University in New York City, is a component laboratory of NASA's Goddard Space Flight Center Earth-Sun Exploration Division and a unit of The Earth Institute at Columbia University...
, 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 (1 Tg is equal to 1012 gram
Gram
The gram is a metric system unit of mass....
s), 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:
In addition, they found that this cooling caused a weakening of the global hydrological cycle, reducing global precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of 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."
Kuwait wells in the first Gulf War
Following Iraq's invasion of Kuwait, Carl SaganCarl Sagan
Carl Edward Sagan was an American astronomer, astrophysicist, cosmologist, author, science popularizer and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books...
and other scientists predicted that burning oil wells could cause environmental damage comparable to nuclear winter. Nearly 700 oil wells were set ablaze by the retreating Iraqi army and the fires were not fully extinguished until November 6, 1991, eight months after the end of the war. The fires consumed an estimated six million barrels of oil daily.
According to a 1992 study from Peter Hobbs
Peter V. Hobbs
Peter Victor Hobbs was a British-born professor of Atmospheric Sciences and Director of the Cloud and Aerosol Research Group at the University of Washington. His research interests were in the physics and chemistry of the atmosphere, focusing on the roles played by aerosols, clouds, and...
and Lawrence Radke, daily emissions of sulfur dioxide
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
were 57% of that from electric utilities in the United States, emissions of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
were 2% of global emissions and emissions of soot
Soot
Soot is a general term that refers to impure carbon particles resulting from the incomplete combustion of a hydrocarbon. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolyzed fuel particles such as cenospheres,...
were 3,400 metric tons per day. However, pre-war claims of wide scale, long-lasting, and significant global environmental impacts were not borne out and found to be significantly exaggerated by the media and speculators, with climate models 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. At the peak of the fires, the smoke absorbed 75% to 80% of the sun’s radiation. The particles were never observed to rise above 6 km and when combined with scavenging by clouds gave the smoke a short residency time in the atmosphere and localized its effects; Professor Carl Sagan
Carl Sagan
Carl Edward Sagan was an American astronomer, astrophysicist, cosmologist, author, science popularizer and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books...
of the Turco
Richard P. Turco
Richard Peter Turco is an American atmospheric scientist, and Professor at the Institute of the Environment, Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles. He won an award in 1986, from MacArthur Fellows Program....
, Toon, Ackerman, Pollack, Sagan (TTAPS) study hypothesized in January 1991 that enough smoke from the fires "might get so high as to disrupt agriculture in much of South Asia...." Sagan later conceded in his book The Demon-Haunted World
The Demon-Haunted World
The Demon-Haunted World: Science as a Candle in the Dark is a book by astrophysicist Carl Sagan, which was first published in 1995.The book is intended to explain the scientific method to laypeople, and to encourage people to learn critical or skeptical thinking...
that this prediction 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 2007 study discussed above 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
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
, but that smoke from fires covering a large area, like some forest fires or the burning of cities that would be expected to follow a nuclear strike, would loft significant amounts of smoke into the stratosphere:
Early work
In June 1957, The Effects of Nuclear Weapons by Samuel GlasstoneSamuel Glasstone
Samuel Glasstone authored 40 popular textbooks on physical chemistry, reaction rates, nuclear weapons effects, nuclear reactor engineering, Mars, space sciences, the environmental effects of nuclear energy and nuclear testing...
was published containing a section entitled "Nuclear Bombs and the Weather" (pages 69–71), which states: "The dust raised in severe volcanic eruptions
Volcanic Eruptions
Volcanic Eruptions is a company owned by Crispin Glover. The company produces and issues Glover's work: It has released two films to date, What Is It? and its sequel, It is Fine! EVERYTHING IS FINE . Its current plans include releasing the final film in the trilogy titled It Is Mine...
, such as that at Krakatoa
Krakatoa
Krakatoa is a volcanic island made of a'a lava in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island , and the volcano as a whole. The island exploded in 1883, killing approximately 40,000 people, although some estimates...
in 1883, is known to cause a noticeable reduction in the sunlight reaching the earth ... The amount of debris remaining in the atmosphere after the explosion of even the largest nuclear weapons is probably not more than about 1 percent or so of that raised by the Krakatoa
Krakatoa
Krakatoa is a volcanic island made of a'a lava in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island , and the volcano as a whole. The island exploded in 1883, killing approximately 40,000 people, although some estimates...
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." In 1974, John Hampson suggested that 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, the United States National Research Council
United States National Research Council
The National Research Council of the USA is the working arm of the United States National Academies, carrying out most of the studies done in their names.The National Academies include:* National Academy of Sciences...
(NRC) reported on ozone depletion following nuclear war, judging that the effect of dust would probably be slight climatic cooling.
1982
In 1981, William J. Moran began discussions and research in the NRC on the dust effects of a large exchange of nuclear warheads. An NRC study panel on the topic met in December 1981 and April 1982.As part of a study launched in 1980 by Ambio, a journal of the Royal Swedish Academy of Sciences
Royal Swedish Academy of Sciences
The Royal Swedish Academy of Sciences or Kungliga Vetenskapsakademien is one of the Royal Academies of Sweden. The Academy is an independent, non-governmental scientific organization which acts to promote the sciences, primarily the natural sciences and mathematics.The Academy was founded on 2...
, Paul Crutzen and John Birks circulated a draft paper in early 1982 with the first quantitative evidence of alterations in short-term climate after a nuclear war. In 1982, a special issue of Ambio
Ambio
AMBIO: A Journal of the Human Environment is a multidisciplinary English language academic journal published by the Royal Swedish Academy of Sciences since 1972. It is published eight times a year....
devoted to the possible environmental consequences of nuclear war included a paper by Crutzen and Birks anticipating the nuclear winter scenario. The paper discussed particulates from large fires, nitrogen oxide, ozone depletion and the effect of nuclear twilight on agriculture. Crutzen and Birks showed that smoke injected into the atmosphere by fires in cities, forests and petroleum reserves could prevent up to 99% of sunlight from reaching the Earth's surface, with major climatic consequences: "The normal dynamic and temperature structure of the atmosphere would therefore change considerably over a large fraction of the Northern Hemisphere, which will probably lead to important changes in land surface temperatures and wind systems." An important implication of their work was that a "first strike" nuclear attack would have severe consequences for the perpetrator.
1983
In 1982, the so-called TTAPS team (Richard P. TurcoRichard P. Turco
Richard Peter Turco is an American atmospheric scientist, and Professor at the Institute of the Environment, Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles. He won an award in 1986, from MacArthur Fellows Program....
, Owen Toon
Owen Toon
Owen Brian Toon is professor of Atmospheric and Oceanic Sciences and a fellow at the Laboratory for Atmospheric and Space Physics at the University of Colorado. He received his Ph.D. from Cornell University in 1975; his adviser was Carl Sagan. His research interest is in cloud physics, atmospheric...
, Thomas P. Ackerman, James B. Pollack
James B. Pollack
James B. Pollack was an American astrophysicist who worked for NASA's Ames Research Center.Pollack was born on 9 July 1938, and was brought up in Woodmere, Long Island by a Jewish family that was in the women's garment business. He was a high school valedictorian and graduated from Princeton...
and Carl Sagan
Carl Sagan
Carl Edward Sagan was an American astronomer, astrophysicist, cosmologist, author, science popularizer and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books...
) undertook a computational modeling study of the atmospheric consequences of nuclear war, publishing their results in Science
Science Magazine
Science Magazine was a half-hour television show produced by the Canadian Broadcasting Corporation from 1975 to 1979.The show was hosted by geneticist David Suzuki, who previously hosted the daytime youth programme Suzuki On Science...
in December 1983. The phrase "nuclear winter" was coined by Turco just prior to publication. In this early work, TTAPS carried out the first estimates of the total smoke and dust emissions that would result from a major nuclear exchange, and determined quantitatively the subsequent effects on the atmospheric radiation balance and temperature structure. To compute dust and smoke impacts, they employed a one-dimensional microphysics/radiative-transfer model of the Earth's lower atmosphere (to the mesopause), which defined only the vertical characteristics of the global climate perturbation.
Around this time, interest in nuclear war environmental effects also arose in the USSR. After becoming aware of the work of the Swedish Academy and, in particular, papers by N.P.Bochkov and E.I.Chazov
Yevgeniy Chazov
Yevgeniy Ivanovich Chazov is a prominent physician of the Soviet Union and Russia, specializing in cardiology, Chief of the Fourth Directorate of the Ministry of Health of the USSR, Academician of the Russian Academy of Sciences and Russian Academy of Medical Sciences, a recipient of numerous...
, Russian atmospheric scientist Georgy Golitsyn applied his research on dust-storms to the situation following a nuclear catastrophe. His suggestion that the atmosphere would be heated and that the surface of the planet would cool appeared in The Herald of the Academy of Sciences in September 1983. Upon learning of the TTAPS scenarios, Vladimir Alexandrov
Vladimir Alexandrov
Vladimir Valentinovich Alexandrov was a Russian physicist who created a mathematical model for the nuclear winter theory. He disappeared in 1985 while at a nuclear winter conference in Madrid and his ultimate fate remains unknown.-Research:...
and G. I. Stenchikov soon published a report on the climatic consequences of nuclear war based on simulations with a two-level global circulation model, which produced results consistent with the TTAPS findings.
1986
In 1984 the WMOWorld Meteorological Organization
The World Meteorological Organization is an intergovernmental organization with a membership of 189 Member States and Territories. It originated from the International Meteorological Organization , which was founded in 1873...
commissioned Georgy Golitsyn and N. A. Phillips to review the state of the science. They found that studies generally assumed a scenario that half of the world's nuclear weapons would be used, ~5000 Mt
TNT equivalent
TNT equivalent is a method of quantifying the energy released in explosions. The ton of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT...
, destroying approximately 1,000 cities, and creating large quantities of carbonaceous smoke - 1–2 × 1014 grams being mostly likely, with a range of 0.2 – 6.4 × 1014 grams (NAS; TTAPS assumed 2.25 × 1014). The smoke resulting would be largely opaque to solar radiation but transparent to infra-red, thus cooling by blocking sunlight but not causing warming from enhancing the greenhouse effect
Greenhouse effect
The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere...
. The optical depth
Optical depth
Optical depth, or optical thickness, is a measure of transparency. Optical depth is defined by the negative logarithm of the fraction of radiation that is not scattered or absorbed on a path...
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 Mt-equivalent of explosion could release up to 5 million ton
Ton
The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight, and as a unit of volume. It can also be used as a measure of energy, for truck classification, or as a colloquial term.It is derived from...
s of dust, but most would quickly fall out; high altitude dust is estimated at 0.1-1 million tons per Mt-equivalent of explosion. Burning of crude oil could also contribute substantially.
The 1-D radiative-convective models used in these studies produced a range of results, with coolings 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 GCM
Global climate model
A General Circulation Model is a mathematical model of the general circulation of a planetary atmosphere or ocean and based on the Navier–Stokes equations on a rotating sphere with thermodynamic terms for various energy sources . These equations are the basis for complex computer programs commonly...
s (Alexandrov and Stenchikov (1983); Covey, Schneider and Thompson (1984); produced similar results: temperature drops of between 20 and 40 °C, though with regional variations.
All calculations show large heating (up to 80 °C) at the top of the smoke layer at about 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.
The report made no attempt to compare the likely human impacts of the post-war cooling to the direct deaths from explosions.
1990
In 1990, in a paper entitled "Climate and Smoke: An Appraisal of Nuclear Winter," TTAPS give a more detailed description of the short- and long-term atmospheric effects of a nuclear war using a three-dimensional model:First 1 to 3 months:
- 10 to 25% of soot injected is immediately removed by precipitation, while the rest is transported over the globe in 1 to 2 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 1 to 3 years:
- 25 to 40% of injected smoke is stabilised in atmosphere (NCAR). Smoke stabilised for approximately 1 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.
Criticism and debate
The TTAPS study was widely reported and criticized in the media. Later model runs in some cases predicted less severe effects, but continued to support the overall conclusion of significant global cooling. Recent studies (2006) substantiate that smoke from urban firestorms in a regional war would lead to long lasting global cooling but in a less dramatic manner than the nuclear winter scenario, while a 2007 study of the effects of global nuclear war supported the conclusion that it would lead to full-scale nuclear winter.The original work by Sagan and others was criticized as a "myth" and "discredited theory" in the 1987 book Nuclear War Survival Skills
Nuclear war survival skills
Nuclear War Survival Skills or NWSS by Cresson Kearny is a civil defense manual. It contains information gleaned from research performed at Oak Ridge National Laboratory during the Cold War, as well as from Kearny's extensive jungle living and international travels.The book aims to provide a...
, a civil defense
Civil defense
Civil defense, civil defence or civil protection is an effort to protect the citizens of a state from military attack. It uses the principles of emergency operations: prevention, mitigation, preparation, response, or emergency evacuation, and recovery...
manual by Cresson Kearny
Cresson Kearny
Cresson Henry Kearny wrote several survival related books based primarily on research performed at Oak Ridge National Laboratory.-Career:Kearny attended Texas Military Institute in the 1930s, where he became the commanding officer of the cadet corps, a champion runner and rifle shot, and...
for the Oak Ridge National Laboratory
Oak Ridge National Laboratory
Oak Ridge National Laboratory is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle. ORNL is the DOE's largest science and energy laboratory. ORNL is located in Oak Ridge, Tennessee, near Knoxville...
. Kearny said the maximum estimated temperature drop would be only about by 20 degrees Fahrenheit (11 degrees Celsius), and that this amount of cooling would last only a few days. He also suggested that a global nuclear war would indeed result in millions of deaths from hunger, but primarily due to cessation of international food supplies, rather than due to climate changes.
Kearny, who was not a climate scientist himself, based his conclusions almost entirely on the 1986 paper "Nuclear Winter Reappraised" by Starley Thompson and Stephen Schneider. However, a 1988 article by Brian Martin in Science and Public Policy states that although their paper concluded the effects would be less severe than originally thought, with the authors describing these effects as a "nuclear autumn", other statements by Thompson and Schneider show that they "resisted the interpretation that this means a rejection of the basic points made about nuclear winter". In addition, the authors of the 2007 study above state 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]." And in 2007 Schneider emphasized the danger of serious climate changes from a limited nuclear war of the kind analyzed in the 2006 study above, 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."
Firestorm formation
All of the papers begin with the common premise: a large quantity of carbon aerosol has found its way into the stratosphereStratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
. As firestorm
Firestorm
A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires...
formation is clearly a necessity to generate the form of smoke discussed in the climatology
Climatology
Climatology is the study of climate, scientifically defined as weather conditions averaged over a period of time, and is a branch of the atmospheric sciences...
models, this is the bedrock to all nuclear winter predictions. The 150 Tg carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
soot aerosol injection into the stratosphere, which the TTAPS paper required to cause nuclear winter, has been criticised on the basis of World War II firestorm
Firestorm
A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires...
ignition evidence from Japanese and medieval European wooden cities, since unbiased factual evidence exists in survivor testimony from Hiroshima that soot was actually precipitated as rainout during the firestorm-the infamous black rain a natural phenomenon produced by Pyrocumulus cloud
Pyrocumulus cloud
A pyrocumulus, or literally fire cloud, is a dense cumuliform cloud associated with fire or volcanic activity.A pyrocumulus is similar dynamically in some ways to a firestorm, and the two phenomena may occur in conjunction with each other...
s. At Hiroshima, the infamous black rain formed soon after the bombing, washing large amounts of carbon out of the atmosphere.
Unlike the Japanese wooden cities of 1945 and medieval wooden housing areas of Germany where firestorms occurred, modern cities are not built out of predominantly flammable materials like wood, but built of mostly concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
and masonry brick
Brick
A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...
.
The nuclear winter effect from the firestorm in Hiroshima blocked out the sun for 25 minutes (from burst time at 8:15 am until 8:40 am) as shown by the meteorological sunshine records printed in Figure 6 (3H) of the Report of the Joint Commission for the Investigation of the Effects of the Atomic Bomb in Japan, Volume 1, Office of the Air Surgeon, report NP-3036, April 19, 1951, U.S. Atomic Energy Commission. The Hiroshima firestorm soot was hydroscopic, absorbing water and falling out in black rain, which limited the climatic effect. The fact that soot was rapidly precipitated in a self-induced rainout in Hiroshima was in 1983 used as a nuclear winter criticism by J. B. Knox of Lawrence Livermore National Laboratory in report UCRL-89907. No other nuclear explosion ever created a firestorm, including detonations of up to 15 megatons
Castle Bravo
Castle Bravo was the code name given to the first U.S. test of a dry fuel thermonuclear hydrogen bomb device, detonated on March 1, 1954 at Bikini Atoll, Marshall Islands, as the first test of Operation Castle. Castle Bravo was the most powerful nuclear device ever detonated by the United States ,...
beside naturally forested islands-Bikini
Bikini Atoll
Bikini Atoll is an atoll, listed as a World Heritage Site, in the Micronesian Islands of the Pacific Ocean, part of Republic of the Marshall Islands....
and Eniwetok Atoll, which failed to ignite the trees due to the high (80%) air humidity and its effects both on ignition and thermal pulse transmission. Targeting oil wells instead of cities, as was done in the final TAPPS paper to compensate for reduced estimates of city firestorm soot emission, reduces the moisture effect, but the soot doesn't rise high enough from burning oil wells for widespread climatic effects, as proved in 1991 when Iraq
Iraq
Iraq ; officially the Republic of Iraq is a country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert....
set fire to all of Kuwait’s oil fields.
Lastly, there is the question of whether the thermal pulse of a modern nuclear weapon is sufficient to ignite an entire modern city, or simply level most of it to the ground. The generating mechanism for the firestorm
Firestorm
A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires...
that engulfed Hiroshima was not(as some contend) directly linked to the thermal pulse from the atomic bomb
Little boy
Little boy may refer to:* Little Boy, the codename of the atomic bomb dropped on Hiroshima* Little Boy: The Arts of Japan's Exploding Subculture, a book about Japanese postwar culture* Helen Littleboy, documentary director...
, but in reality the major causative agent of the firestorm was the timing of the bombing, and to a lesser degree the exceptionally dry weather conditions preceding the bomb run. The fact that the bombing occurred at 08:15 local time meant the bombing occurred right around breakfast time, which importantly implies that the fires were secondary in nature, started from overturned cooking devices when the blast wave
Blast wave
A blast wave in fluid dynamics is the pressure and flow resulting from the deposition of a large amount of energy in a small very localised volume. The flow field can be approximated as a lead shock wave, followed by a 'self-similar' subsonic flow field. In simpler terms, a blast wave is an area of...
arrived, This is in direct contrast to the atomic bombing of Nagasaki, where no true firestorm
Firestorm
A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires...
formed.
The originally secret 6 volume U.S. Strategic Bombing Survey reports on Hiroshima and Nagasaki disclose that there had been no significant rain for 3 weeks prior to the Hiroshima bombing, and for 10 days prior to the Nagasaki bombing, except for one light shower on August 5. The May 1947 U.S. Strategic Bombing Survey report on Hiroshima lists all the factors that contributed to the firestorm on pages 4–6: "Six persons who had been in reinforced-concrete buildings within 3,200 feet of air zero stated that black cotton black-out curtains were ignited by flash heat... A large proportion of over 1,000 persons questioned was, however, in agreement that a great majority of the original fires were started by debris falling on kitchen charcoal fires ... There had been practically no rain in the city for about 3 weeks. The velocity of the wind ... was not more than 5 miles per hour.... Hundreds of fires were reported to have started in the centre of the city within 10 minutes after the explosion... almost no effort was made to fight this conflagration ... There were no automatic sprinkler systems in buildings...".
Policy implications
In an interview in 2000, Mikhail GorbachevMikhail Gorbachev
Mikhail Sergeyevich Gorbachev is a former Soviet statesman, having served as General Secretary of the Communist Party of the Soviet Union from 1985 until 1991, and as the last head of state of the USSR, having served from 1988 until its dissolution in 1991...
, in response to the comment "In the 1980s, you warned about the unprecedented dangers of nuclear weapons and took very daring steps to reverse the arms race," said "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."
See also
- Doomsday deviceDoomsday deviceA doomsday device is a hypothetical construction — usually a weapon, or collection of weapons — which could destroy all life on a planet, particularly the Earth, or destroy the planet itself, bringing "doomsday", a term used for the end of planet Earth...
- Nuclear darknessNuclear darknessNuclear darkness refers to a predicted by a global stratospheric smoke layer created by the burning of cities and industrial areas following a nuclear conflict...
- Nuclear summerNuclear summerA Nuclear summer is a hypothetical scenario resulting from nuclear warfare that would follow a nuclear winter, caused by aerosols inserted into the atmosphere that would prevent sunlight from reaching lower levels or the surface...
- Impact eventImpact eventAn impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Throughout recorded history, hundreds of minor impact events have been reported, with some occurrences causing deaths, injuries, property damage or other significant...
- SupervolcanoSupervolcanoA supervolcano is a volcano capable of producing a volcanic eruption with an ejecta volume greater than 1,000 cubic kilometers . This is thousands of times larger than most historic volcanic eruptions. Supervolcanoes can occur when magma in the Earth rises into the crust from a hotspot but is...
- Volcanic winterVolcanic winterA volcanic winter is the reduction in temperature caused by volcanic ash and droplets of sulfuric acid obscuring the sun and raising Earth's albedo after a large particularly explosive type of volcanic eruption...
External links
- The Encyclopedia of Earth, Nuclear Winter Lead Author: Alan Robock. Last Updated: July 31, 2008
- Global Atmospheric Consequences of Nuclear War, the 1983 study conducted by TTAPS.
- Nuclear Winter Simulation Animation
- New studies of climatic consequences of regional nuclear conflict from Alan Robock, including links to new studies published in 2007.