Nuclear Winter in the Post-Cold War Era

Abstract

1. Nuclear Winter: The Decade-Long Debate In the early 1980s, there were some 60,000 nuclear weapons on the planet - all but a few thousand in the hands of the USA and the then Soviet Union. Between 10,000 and 13,000 on each side were strategic weapons that could be carried by missile or aircraft halfway around the world. The remainder were less potent theater or tactical weapons, most of which nevertheless had a higher explosive yield than the bombs that obliterated Hiroshima and Nagasaki. This was also the moment when we were hearing - mainly from US strategists and politicians - that nuclear war was 'survivable' and even 'winnable'. At just the same time, atmospheric and planetary scientists accidentally discovered that as bad as the prompt and local effects of nuclear war would be - the delayed and global consequences might be much worse. In 1982, Paul Crutzen and John Birks noted that forest fires ignited in a such a war could generate enough smoke to obscure the sun and perturb the atmosphere over large areas. The following year, we and our colleagues - Turco, Toon, Ackerman, Pollack, and Sagan (TTAPS) - recognized that the smoke from the burning of modern cities would provide a still more serious threat, and quantified the resulting climatic effects from various sources of soot and dust and for a wide range of possible nuclear war scenarios. Provided cities were targeted, even a 'small' nuclear war could have disastrous climatic consequences; a global war, we calculated, might lower average planetary temperatures by 15 to 20?C, darken the skies sufficiently to compromise green plant photosynthesis, produce a witches' brew of chemical and radioactive poisons, and significantly deplete the protective ozone layer. (The climate is thought to recover several years later.) These effects, which had been almost wholly overlooked by the world's military establishments, we described as 'nuclear winter'. Considering how profound a challenge nuclear winter presented to prevailing nuclear