US:A limited atomic exchange could still trigger global environmental disorder and serious agricultural disruption, writes John Johnsonin San Francisco
Even a small nuclear conflict could have catastrophic environmental and social consequences, extending the death toll far beyond the number of people killed directly by bombs, according to the first comprehensive climatic analysis of a regional nuclear war.
A few dozen modest Hiroshima-sized nuclear weapons exchanged between India and Pakistan, for example, could produce a globe-encircling pall of smoke, causing temperatures to fall worldwide and disrupting food production for millions of people, according to an analysis presented on Monday at a meeting of the American Geophysical Union.
While a small nuclear exchange might not trigger a life-ending "nuclear winter", it could cause as much death as was once predicted for a nuclear war between the US and the Soviet Union, said Owen Toon, an atmospheric researcher at the University of Colorado.
"These results are quite surprising," Toon said. Regional nuclear conflicts "can endanger entire populations" the way it was once thought only worldwide conflict could.
Toon and co-author Richard Turco, a professor of atmospheric sciences at the University of California, Los Angeles, were part of the team of scientists that developed the concept of nuclear winter in the 1980s.
The analysis was presented in two papers that dealt with the climatic, atmospheric and social consequences of a regional exchange. The studies were published in the online journal Atmospheric Chemistry and Physics Discussions.
Since the 1980s, when the US and Soviet Union began drawing down their nuclear stockpiles, the number of weapons around the world has declined by a factor of three, Toon said. There are now about 10,000 nuclear weapons, and that is expected to drop to 4,000 by 2012.
But the number of potential nuclear-armed nations has gone up dramatically. Toon said 40 countries have the fissile material to build nuclear weapons. Japan, with its large nuclear power industry, could make 20,000 weapons alone.
Many countries that could build nuclear weapons are also unstable or engaged in some level of strife with their neighbours.
In conducting their research, the scientists looked at other global cataclysms, such as the 1815 eruption of Tambora volcano in Indonesia. The eruption triggered the "year without a summer", which caused killing frosts, crop failures and famine in Europe.
The authors said even a limited nuclear conflict would be much worse, killing as many as 17 million people in China alone.
The most significant atmospheric impact from a nuclear exchange would be the accumulation of smoke and soot in the atmosphere, said team member Georgiy Stenchikov, a professor of environmental science at Rutgers University.
Stenchikov estimated that 4.5 million tonnes of soot could be thrown into the air by the explosion of about 100 15-kiloton nuclear weapons. The smoke and soot would ascend into the stratosphere and stay there for up to 10 years, causing temperatures to fall several degrees.
In areas far removed from the site of the explosions, growing seasons could be reduced to a month, said Alan Robock, an environmental professor at Rutgers who worked on the analysis.
Instead of feeling content that the US and Russia are drawing down their nuclear arsenal, people should realise that they "are at a perilous crossroads", Toon said. "Nuclear proliferation and political instability form the greatest danger to human society since the dawn of mankind."
- ( LA Times-Washington Post service)