Nuclear winter (Encyclopedia of Environmental Issues, Revised Edition)
The nuclear winter theory predicts that a global nuclear war would cause huge amounts of dust and debris to be carried high into the atmosphere, where it could remain for as long as three years. This debris would obstruct incoming sunlight and disrupt photosynthesis, causing the extinction of many plant species. The loss of considerable amounts of plant life would eventually affect the entire food chain. Once the atmosphere cleared, only those species that could survive without sunlight would be left to repopulate the planet.
Discussion of the possibility of nuclear winter began in the early 1980’s as a result of the ever-present fear of global nuclear war. Several prominent scientists, notably Carl Sagan of Cornell University, began to examine the possible effects of total nuclear war on the environment. Using computer simulations, they predicted that an enormous amount of dust and particulate matter from the nuclear explosions and resulting fires would be lifted high into the atmosphere. This debris would be quickly distributed around the globe by the earth’s prevailing winds and would remain in the atmosphere for a minimum of three months to a maximum of three years. It was predicted that, in the event of a nuclear war, the majority of nuclear impacts would take place in the Northern Hemisphere; the Southern Hemisphere would thus experience a six-month “grace period” before it would feel the full effects of the atmospheric...
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Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Ahrens, C. Donald. “Climate Change.” In Essentials of Meteorology: An Invitation to the Atmosphere. 5th ed. Belmont, Calif.: Thomson Learning, 2008.
Cotton, William R., and Roger A. Pielke, Sr. “Nuclear Winter.” In Human Impacts on Weather and Climate. 2d ed. New York: Cambridge University Press, 2007.
Manahan, Stanley E. “Catastrophic Atmospheric Events.” In Environmental Science and Technology: A Sustainable Approach to Green Science and Technology. 2d ed. Boca Raton, Fla.: CRC Press, 2007.
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Definition (Encyclopedia of Global Warming)
“Nuclear winter” was the term coined in the 1980’s to describe the global climatic effects of a major nuclear weapons exchange between the United States and the Soviet Union. The concept arose from scientific theories attempting to explain the extinction of the dinosaurs. Evidence to suggest an unusual geological event was found at the boundary between the Cretaceous and Tertiary periods (65-70 million years ago). An iridium-rich layer of sediment separated the dinosaur-fossil-bearing layers below from the dinosaur-fossil-lacking layers above. It was theorized that this amount of iridium could only have come from a collision with an asteroid-sized object, at least 10 to 16 kilometers in diameter.
If such an object had hit the Earth, the impact would have had a global effect on the planet’s environment. Rock and ash debris would have been thrown high into the atmosphere, and the impact would have ignited huge forest fires. Ash from these fires, combined with the fine dust from the impact, could have remained in the atmosphere for several years and altered the Earth’s albedo. Less sunlight would reach the surface, as the dust-laden atmosphere reflected it back into space. Those life forms surviving the initial impact would have to adapt to a rapidly changing environment. Less sunlight would affect photosynthesis, and the food chain would be disrupted as the Earth entered into a long global winter.
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Significance for Climate Change (Encyclopedia of Global Warming)
The end of World War II in 1945 saw the beginning of the Cold War between the United States and the Soviet Union. During the war, the United States and the Soviet Union had been allies fighting against a common enemy in Nazi Germany. Although the two countries had different political ideals and agendas, they put aside their differences to win the war. Once the war was over, each side began to mistrust the other. What made matters worse was the development and use of the atomic bomb.
The United States was the first country to develop a nuclear bomb, which it used twice to end the war with Japan, bombing the cities of Hiroshima and Nagasaki. Conventional bombing raids over Germany and Japan killed more people and damaged more property than a single atomic bomb. However, the psychological effect of one bomb doing the same amount of damage as thousands of conventional weapons made a difference and motivated Japan to end the war. The bomb blasts had unanticipated, lingering effects on the area, however, in the form of radioactive fallout. Tens of thousands of people may have died from the nuclear blast, while perhaps hundreds of thousands more would later die from radiation poisoning.
The nuclear attacks on Hiroshima and Nagasaki demonstrated to the world the horrors of nuclear war. It was hoped that they would serve as a reason for avoiding any further nuclear conflicts. Throughout the 1950’s, 1960’s,...
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Further Reading (Encyclopedia of Global Warming)
Fisher, David E. Fire and Ice: The Greenhouse Effect, Ozone Depletion, and Nuclear Winter. New York: Harper and Row, 1990. A good introduction to the concept of global climatic change and humankind’s effects upon the environment.
Greene, Owen, Ian Percival, and Irene Ridge. Nuclear Winter: The Evidence and Risks. New York: Polity Press, 1985. One of the first books written to capture the public’s attention to the dangers of climatic change induced by nuclear weapons or natural disasters.
Sagan, Carl, and Richard P. Turco. A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race. New York: Random House, 1990. Coauthor Sagan, a popular scientist, was probably the best-known proponent of the nuclear winter concept.
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Nuclear Winter (World of Earth Science)
Nuclear winter is a theory estimating the global climatic consequences of a nuclear war: prolonged and worldwide cooling and darkening caused by sunlight-blocking smoke and soot entering the atmosphere. During the Cold War after World War II, the concern about nuclear weapons was increasing all over the world. Initially, only the danger of radioactive fallout was recognized, but later also the possible environmental effects of a nuclear war became the subject of several studies. The term nuclear winter was first defined and used by American astronomer Carl Sagan (1934996) and his group of colleagues in their 1983 article (later referred to as the TTAPS-article, from the initials of the authors' family names). This article was the first one to take into consideration not only the direct damage, but also the indirect effects of a nuclear war.
The basic assumption during a nuclear war is that the exploding nuclear warheads would create huge fires, resulting in smoke and soot from burning cities and forests being emitted into the troposphere in vast amounts. This would block the sun's incoming radiation from reaching the surface of Earth, causing cooling of the surface temperatures. The smoke and soot soon would rise because of their high temperature, allowing them to drift at high altitudes for weeks without being washed out. Finally, the particles would settle in the Northern Hemisphere mid-latitudes as a black particle cloud belt, blocking sunshine for several weeks. The darkness and cold, combined with nuclear fallout radiation, would kill most of Earth's vegetation and animal life, which would lead to starvation and diseases for the human population surviving the nuclear war itself. At the same time, the upper troposphere temperatures would rise because the smoke would absorb sunlight and warm it up, creating a temperature inversion, which would keep smog at the lower levels. Another possible consequence is that nuclear explosions would produce nitrogen oxides, which would damage the protective ozone layer in the stratosphere, thus allowing more ultraviolet radiation to reach the earth's surface.
Although the basic findings of the original TTAPS-article have been confirmed by later reports, some later studies report a lesser degree of cooling would occur, only around 25 degrees of temperature drop and only for weeks instead of the initially estimated months. According to different scenarios, depending on the number of nuclear explosions, their spatial distribution, targets, and many other factors, this cloud of soot and dust could remain for many months, reducing sunlight almost entirely, and decrease average temperatures to as low as 0°C in the Northern Hemisphere continents. There are other studies, that mention the possibility of a not so severe nuclear winter as originally estimated, hence it is named a nuclear fall. Other researchers even talk about nuclear summer, stating that a worldwide warming would follow a nuclear war because of the many small contributions to the greenhouse effect from carbon dioxide, water vapor, ozone, and various aerosols entering the troposphere and stratosphere. What all scenarios agree on is that a nuclear war would have a significant effect on the atmosphere and climate of the earth and, consequently, many aspects of life such as food production or energy consumption would be drastically effected.
Opponents of the nuclear winter theory argue that there are many problems with the hypothesized scenarios either because of the model's incorrect assumptions (e.g., the results would be right only if exactly the assumed amount of dust would enter the atmosphere, or the model assumes uniformly distributed, constantly injected particles), or because important effects, processes and/or feedback mechanisms are not taken into consideration (e.g., the moderating effects of the oceans, or small-scale processes are not included, or the biological effects are not addressed), or simply because there are many uncertainties involved in the estimates. The topic even at present day remains controversial, because the exact level of damage, along with the extent and duration of the effects, cannot be agreed upon with full confidence.
See also Atmospheric circulation; Atmospheric composition and structure; Atmospheric inversion layers; Atmospheric lapse rate; Atmospheric pollution