Nuclear winter is a term used to describe the potential environmental and climate effects resulting from a large-scale nuclear war. On December 23, 1983, five scientists, Richard P. Turco, Owen B. Toon, Thomas P. Ackerman, James B. Pollack, and Carl Sagan, published a paper in the journal Science that has come to be known as the TTAPS Study. The paper raised concern over the shortterm and long-term consequences of dust, smoke, radioactivity, and toxic vapors that would be generated by a nuclear war. Although with the end of the Cold War in the 1980s, the threat of nuclear war has subsided, it should never be dismissed completely.
In the article, the five scientists concluded that exploding just one half of the combined nuclear weapons of the United States and the former Soviet Union would throw billions of metric tons of dust, soot, smoke, and ash into the atmosphere. In each explosion, most of this dust would be carried up by the nuclear fireball itself, and some of it would be sucked up the stem of the mushroom cloud. Even a more modest explosion on or above cities would produce massive fires like those in Hiroshima and Nagasaki at the end of World War II. These fires would consume wood, natural gas, and a wide variety of combustibles. The resulting smoke would be far more dangerous to the earth’s climate than the dust; the smoke, the scientists argued, could produce a blanket of air pollution so thick that it would have the potential to block more than 80% of the sunlight that would otherwise reach the northern hemisphere.
As a result, they claimed, severe worldwide climate changes could occur, including prolonged periods of darkness and below-freezing temperatures, making the average land cool to 10°C to 20°C; continental interiors could cool by up to 20°C to 40°C, with subzero temperatures possible even in summer. There would also be the potential for violent windstorms. The combination of cold temperatures, dryness, and lack of sunlight would also cripple agricultural production and destroy ecosystems, putting most of the world’s population at risk of starvation, according to the 1985 report by the International Council of Scientific Unions. Other studies suggest that even a small nuclear war would devastate the earth.
Severe climate change may have been a factor in the demise of the dinosaurs toward the end of the Mesozoic era. There is evidence that the end of the Mesozoic era saw changes in climate resulting in a pronounced drop in temperatures, similar to a nuclear winter. Major volcanic eruptions may have produced enormous quantities of smoke and ash that blocked the sunlight over major portions of the earth’s land mass; alternatively, as some geological evidence suggests, an extraterrestrial object, most likely a meteor or asteroid, may have struck the earth, throwing up huge quantities of debris into the atmosphere and blocking out sunlight for a time. Such an event would have created a winter condition that killed plants and larger animals. This scenario is similar to that of a nuclear winter that could follow a major nuclear war.
The nuclear winter theory has been the subject of some controversy. Efforts were made by government and military scientists to play down the possible consequences. They argued that the effects would not be nearly so severe and began talking of a “nuclear autumn.” In 1984, the U.S. National Research Council publicly stated that it agreed with the ideas advanced in the Science article; however, in 1985, the U.S. Department of Defense issued a report saying that while the nuclear winter theory might be valid, it would not change defense policies.
Today, although the threat of nuclear war has receded somewhat, the continued existence of nuclear weapons is a reminder that the possibility of a nuclear winter cannot be entirely dismissed.
Patricia Sedor
See also Dinosaurs; Ecology; Extinction, Mass;
Extinction and Evolution; Sagan, Carl
Further Readings
Fisher, D. E. (1990). Fire and ice: The greenhouse effect, ozone depletion and nuclear winter. New York: HarperCollins.
Grinspoon, L. (1986). The long darkness: Psychological and moral perspectives on nuclear winter. New Haven, CT: Yale University Press.
Rowan-Robinson, M. (1985). Fire and ice: The nuclear winter. New York: Longman.
Sagan, C., & Turco, R. (1990). A path where no man thought. New York: Random House.
