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During the 1980s, Carl Sagan and other scientists used the theory of nuclear winter to criticize the arms race. Historians have largely dismissed nuclear winter as a political movement. In fact, nuclear winter influenced debate over nuclear weapons in the United States, despite contentious scientific and political arguments. In addition, an analysis of nuclear winter's reception in the Soviet Union reveals that the theory resonated on both sides of the Iron Curtain. The global debate over nuclear winter shows the potency of scientific arguments against nuclear weapons during the Cold War, and demonstrates the complex relationship between science and politics.

This chapter looks at the nuclear winter project, an outcome of global modeling. The idea that the Earth could be plunged into a “nuclear winter” as the catastrophic outcome of a nuclear war was announced by a group of leading climate and environment scientists from the United States, Western Europe, and the Soviet Union shortly after Ronald Reagan delivered his “Star Wars” speech in March 1983. Drawing on experiments with data-based computer models, these scholars claimed that a nuclear war, unlike the two world wars, would be not simply a regional, but a truly global disaster. Nuclear missiles, detonated over urban areas, would ignite massive fire storms, which in turn would propel soot particles and aerosols into high levels of the atmosphere. As a result, the computer models predicted, a dust shield would emerge that would be transported by air currents to both the Northern and Southern hemispheres.

Carl Sagan is a public intellectual and the best-selling author of Cosmos, The Demon-Haunted World: Science as a Candle in the Dark, The Dragons of Eden: Speculations on the Evolution of Human Intelligence, and many other books. His science fiction novel, Contact, was made into a popular, major motion picture in 1997. Sagan is well known for his interests in extra-terrestrial life and is closely linked to the SETI (Search for Extra Terrestrial Intelligence). As a scientist, Sagan educated the public about “Nuclear Winter”, the idea that a nuclear war could precipitate an unprecedented ice age that might render the Earth largely uninhabitable. Sagan became notorious in certain circles for his forays into religion, which he viewed with skepticism.

On December 11, 1984, the National Academy of Sciences (NAS) issued its final report on nuclear winter. The report was a vindication of sorts for Carl Sagan and his TTAPS team of Richard Turco, Owen Brian Toon, Thomas Ackerman, and James Pollack. The NAS concluded that nuclear-lofted dust could cause climatic problems, but the more serious was the shroud of smoke that could initially obscure 99 percent of sunlight over large areas. Those who argued that the NAS report validated the nuclear winter phenomenon also believed that it supported their long-held opposition to the nuclear arms race. The resumption of the much delayed arms-control negotiations between the United States and the Soviet Union in Geneva in January 1985 increased the public’s consciousness about nuclear weapons. The Royal Society of Canada, the Royal Society of New Zealand, the United Nations, and the International Council of Scientific Unions’s Scientific Committee on Problems of the Environment each released their own report on nuclear winter in 1985.

In March 1986, the General Accounting Office submitted a report to Congress detailing the technical uncertainties surrounding the long-term effects of nuclear war. Titled “Nuclear winter: Uncertainties surround the long-term effects of nuclear war,” the report was drafted by a committee headed by Alan Hecht of the National Oceanic and Atmospheric Administration and comprised of several scientists. The GAO report was reviewed by other government agencies involved with nuclear winter, including the Defense Nuclear Agency. In May 1986, the Department of Defense issued its own report to Congress. Five years later, nuclear winter theory gave way to experiment when most of Kuwait’s 1,250 oil wells were torched in the wake of the Persian Gulf War. This chapter examines the politics and policy issues surrounding the nuclear winter debate.

Nuclear winter did not seem to affect the policy of the Reagan administration. With the dissolution of the Soviet Union, it even disappeared from talks about strategy. The consequences of nuclear explosions were rarely mentioned, and only superficially. There was no evidence of climatic effects, suicidal action, or the demise of agriculture that were supposed to happen due to nuclear winter. Nuclear winter was also ignored in discussions about the diminished nuclear arms race. However, some nuclear winter scientists provided circumstantial evidence to support their claim that the issue actually had an impact on public policy. For example, they cited the peak in the number of nuclear warheads in the Soviet Union in 1986 and the slow decline of the American stockpile for many years. The overwhelming sense of the scientific community is that the nuclear winter phenomenon is possible.

The fact that some of the computer models used in nuclear winter research were derived from others raised concern that many scientists were reaching the same conclusions. Those who studied the nuclear war scenarios, the physical and chemical effects, and the climatic consequences generally viewed their research as independent and were thus confident of its direction. Aside from the independence of models used in the research, another issue was their intrinsic value—that is, whether they were worth believing. In early 1985, better results were obtained from interactive models, which supplanted the one-dimensional representation used by the TTAPS team of Richard Turco, Owen Brian Toon, Thomas Ackerman, James Pollack, and Carl Sagan and the two- and three-dimensional models, which were unable to move smoke around. A number of fire studies were conducted to verify or challenge the TTAPS findings. New research on the biological and ecological implications of nuclear war also appeared.

During the 1980s, peace and environmental advocates such as the Audubon Society and the Council for a Livable World Education Fund made a common stand concerning nuclear winter. In 1984, Carl Sagan received the SANE Peace Award for his nuclear winter efforts and Paul Crutzen received the Discover-Rolex Scientist of the Year Award. The following year, ten conservation groups issued a report criticizing the federal government’s policies on clean air, automobile fuel efficiency, and nuclear weapons (including nuclear winter). However, both the peace movement and the environmental movement did not view nuclear winter as an overwhelmingly significant issue. Even world leaders, from Indira Gandhi of India to Olof Palme of Sweden, Julius Nyerere of Tanzania, and Miguel de la Madrid of Mexico, were conspicuously silent about nuclear winter. This chapter explores the various reactions to the nuclear winter issue and looks at the controversy surrounding the Antipodes as well as New Zealand’s position on nuclear weapons.

Nuclear winter scientists not only attended meetings of the bodies that undertook studies on the phenomenon, but also participated in lectures and conferences. For example, Richard Turco and Owen Brian Toon were present during a Scientific Committee on Problems of the Environment session in Tokyo in February 1985 and during a three-day conference sponsored by the Defense Nuclear Agency (DNA) in Santa Barbara later that month. Although many scientists appeared to despise the federal government’s nuclear weapons policies, they felt obliged to attend such events in case something novel was announced and in order to showcase each laboratory’s accomplishments. This chapter focuses on the conferences held in the United States and abroad to discuss nuclear winter. It also discusses the controversies sparked by the nuclear winter issue, the use of computer models in nuclear winter research, fire studies, and biological and ecological research.

The nuclear winter did not generate excitement among the public, but spurred nuclear analysts and policy experts to contemplate on the issues. Carl Sagan and his fellow nuclear winter proponents ultimately failed to convince the federal government to study the political consequences of the phenomenon. Nevertheless, it sparked a large and rich outpouring of policy ideas and analyses and gave planners the option to pursue nuclear arms expansion, arms control, or do nothing. This chapter examines some of the policy issues in the debate over nuclear winter. It looks at S. Fred Singer’s views about a threshold for climatic effects as well as strategic and tactical nuclear weapons. It also discusses Ronald Reagan’s Strategic Defense Initiative.

In addition to diplomatic and strategic consequences, nuclear winter brought to light other policy issues, including large- and small-scale military concerns. According to J. J. Gertler of the Rand Corporation, sophisticated conventional weapons might become a popular option in times of war. The nuclear winter may also increase the complexity of the military’s Single Integrated Operational Plan (SIOP), which prioritized nuclear targets. Moreover, the military might think twice about using nuclear weapons for fear that the damage would boomerang on their own country. Two political scientists, Michael Altfeld and Stephen Cimbala, predicted that both the United States and the Soviet Union will adopt smaller and more accurate nuclear warheads. Nuclear winter also might spur the countries to improve their ballistic-missile defense and civil defense.

Freeman Dyson, a physicist and an author, was one of the few who raised the issue of morality in the nuclear winter debate. Virtually silent regarding the subject were the Roman Catholic bishops, theologians, and scholars who had recently addressed concepts of just war, deterrence, and various aspects of the nuclear arms race. The various American “peace” groups were also surprisingly silent, apparently waiting out the technical controversy over nuclear winter before jumping into the political fray. However, nuclear winter would soon get entangled with politics. This chapter examines the politics of the nuclear arms race and the political implications of the work of the TTAPS team at the U.S. National Aeronautics and Space Administration (comprised of Richard Turco, Owen Brian Toon, Thomas Ackerman, James Pollack, and Carl Sagan).

Freeman Dyson disagreed with the notion that the research goal was to narrow the range of possibilities for the many ingredients of nuclear winter. While he believed in the evils of nuclear war, Dyson argued that there was a need for greater precision. The nuclear winter predictions made by the TTAPS team (comprised of Richard Turco, Owen Brian Toon, Thomas Ackerman, James Pollack, and Carl Sagan) and others had spurred a flurry of scientific activity. In late 1982, the National Academy of Sciences’s (NAS) National Research Council submitted a proposal for research on nuclear winter to the Defense Nuclear Agency (DNA). The DNA expressed concern that results of both the NAS and the TTAPS studies would be “unrealistically pessimistic.” This chapter examines the bureaucracy and bickering related to the research on nuclear winter, focusing on the reactions of conservative and liberal critics as well as government agencies such as the Department of Defense.

Through 1983 and well into 1984, research on nuclear winter was primarily financed by “discretionary” funds from various government agencies such as the Department of Defense (DoD), the Department of Energy, the National Science Foundation, and the National Aeronautics and Space Administration. As revealed by the private Natural Resources Defense Council, however, the government’s response to nuclear winter remained largely ad hoc. This prompted Congress to call for an organized response, which actually began in February 1984, when John Byrne and Alan Hecht, administrator of the National Oceanic and Atmospheric Administration (NOAA) and director of NOAA’s National Climate Project Office, respectively, received orders from George Keyworth, the presidential science advisor, to formulate a plan. The following year, the DoD released a report which emphasized the significant uncertainties in estimates of climatic responses to nuclear explosions. Congressional hearings were held to discuss the DoD report, first in the House in March 1985, then in the Senate in October 1985.

Whereas nuclear winter was widely reported in the news media in the United States after the phenomenon was announced publicly in October 1983, it received little attention in the Soviet Union until mid-1984. This can be attributed to increasing concern about the climatic consequences of nuclear war by the country’s political leaders. The superpowers’ top leaderships also differed in their reactions to nuclear winter. Nevertheless, Soviet scientists were not unprepared for nuclear winter investigations. In May 1983, an organization calling itself the Soviet Scientists’ Committee for the Defense of Peace Against Nuclear Threat (SSC) was established in response to heightened tensions caused by U.S. President Ronald Reagan’s plans for a Strategic Defense Initiative and his administration’s apparently cavalier attitude toward nuclear war. The U.S. Department of State was seemingly not interested in expanding scientific contact with the Soviets. In 1985, the Soviet nuclear winter program took a hit when its leading investigator, Vladimir Aleksandrov, disappeared in Spain.

Since prehistoric times, severe weather and climatic conditions have been linked to human transgressions, such as a failed offering to the gods or a violation of a taboo. By the mid-twentieth century, scientific evidence seemed to support the connection between widespread disaster and human activities. In particular, nuclear weapons were assumed to wipe out civilization due to blast, heat, and radioactivity. That humans could influence climate conditioned the possibility of a nuclear winter phenomenon. This chapter examines the origin of nuclear winter, with an emphasis on its relationship with ozone depletion. It also discusses the research conducted by Carl Sagan and colleagues at the U.S. National Aeronautics and Space Administration using data from the Mariner 9 spacecraft to determine how much atmospheric warming and surface cooling a specified amount of dust from Mars should cause. Finally, it looks at the conference organized by the TTAPS team (comprised of Richard Turco, Owen Brian Toon, Thomas Ackerman, James Pollack, and Sagan) in April 1983 in Cambridge to announce their findings.

In 1983, Carl Sagan, a planetary astronomer and a renowned science popularizer, coined the phrase “nuclear winter” to describe the effects on Earth’s climate of the explosion of nuclear weapons. This book examines one of the effects of nuclear explosions: decreased temperature and illumination caused by reduced sunlight. As an introduction, this chapter looks at attempts to predict certain climatic consequences of nuclear war and considers the obscuration of sunlight as the main mechanism, with ozone depletion and the altered reflection of sunlight as additional paths. It also examines some of the effects of nuclear weapons, from electromagnetic pulse and ozone depletion to radioactive fallout, global incineration, and climate change. These effects appear to be disparate, but are nevertheless linked by the geographical extent of their consequences.

The nuclear winter phenomenon generated public interest much faster than most other scientific subjects and rapidly polarized those involved. Several congressional hearings were held, a number of lawmakers got involved, and the federal government made its own research and even used the Strategic Defense Initiative as a major argument to support its stand regarding nuclear war. It was evident that politics was at play in the nuclear winter debate. Nuclear winter was a product of scientific research initiated by scientists who did not work at nuclear weapons laboratories. These scientists relied on various scientific disciplines—from particle microphysics and atmospheric chemistry to weapons effects, volcanic eruptions, ozone depletion, fire and smoke studies, planetary studies, and dinosaur extinction—to reveal the potential effects of fires triggered by nuclear explosions. Thus, nuclear winter research was a clear illustration of the increasing interdisciplinarity of science.

Many non-governmental organizations have expressed concern over the threat of nuclear war in the decades since the bombing of Hiroshima and Nagasaki. The twentieth century was characterized by significant environmental activism in the United States, spurred in particular by the threatened depredations of the Reagan administration. The Henry P. Kendall Foundation focused their attention on nuclear winter, first by funding the April 1983 private scientific review held by the TTAPS team at the U.S. National Aeronautics and Space Administration (comprised of Richard Turco, Owen Brian Toon, Thomas Ackerman, James Pollack, and Carl Sagan) in Cambridge. They also launched a media blitz to generate publicity. During the summer of 1983, Paul Ehrlich organized a group of about twenty scientists to discuss the biological implications of large-area decreases in temperature and light intensity. Later that year, the TTAPS team published a formal paper Science.