Small nuclear war could lead to cooldown

Updated 12/12/2006 3:32 PM ET

By Alicia Chang, The Associated Press

SAN FRANCISCO — Some of the scientists who first advanced the controversial "nuclear winter" theory more than two decades ago have come up with another bleak forecast: Even a regional nuclear war would devastate the environment.

Using modern climate and population models, researchers estimated that a small-scale nuclear conflict between two warring nations would cause 3 million to 17 million immediate casualties and lead to a marked cooldown of the planet that could lead to crop failures and further misery.

As dire as the predictions seem, they fall short of nuclear winter. That theory says that smoke and dust from an atomic war between the superpowers would blot out the sun, plunge the Earth into the deep freeze and cause mass starvation, wiping out 90% of the Earth's population, or billions of people.

The new scenario offers no estimate of the number of deaths from the environmental effects of a regional nuclear war.

Still, scientists said the scenario points to the danger of small nuclear states obtaining atomic warheads.

The study, presented Monday at an American Geophysical Union meeting in San Francisco, was described as the first to document in detail the climatic effects of a nuclear war on a regional scale.

Some climate experts not connected with the research questioned some of the assumptions made in the studies.

For example, the studies assume that smoke is mostly made up of soot. But other organic particles could cause smoke to scatter and not stay aloft in the atmosphere as long, lessening the impact, said scientist Steve Ghan of the Pacific Northwest National Laboratory.

"I think the effects of the smoke are exaggerated, but it does give people pause to think about," Ghan said. "It suggests that anyone who is contemplating attacking another country is not going to be immune to the impacts on their own countries."

The late astronomer Carl Sagan and four colleagues developed the nuclear winter theory, calculating in 1983 the possible effects of an all-out nuclear attack between the United States and the former Soviet Union. Other scientists have disputed the degree of damage to the Earth.

The superpowers' nuclear stockpiles have shrunk considerably since the end of the Cold War. But some of the scientists behind the nuclear winter theory — including Brian Toon of the University of Colorado at Boulder and Richard Turco of the University of California, Los Angeles — decided to revisit the topic in light of more recent world tensions.

In October, North Korea announced that it had tested a nuclear bomb. Iran is also pursuing the development of nuclear weapons. Other members or presumed members of the nuclear club include India, Pakistan and Israel.

The new studies looked at the consequences if two nations dropped 50 Hiroshima-size bombs on each other's big cities. By analyzing population data and distance from blast, scientists predicted a regional nuclear war would kill 3 million people in Israel and up to 17 million in China. The U.S. would see 4 million blast deaths.

But the researchers say black soot from the fires would linger in the atmosphere, blocking the sun's rays and causing average global surface temperatures to drop about 2 degrees Fahrenheit in the first three years. Although the planet would see a gradual warming within a decade, it would still be colder than it was before the war, the scientists said.

The cooldown would shorten the growing season by about a month in parts of North America, Europe and Asia. Normal rainfall patterns such as summer monsoons in Africa and Southeast Asia would be disrupted, possibly causing huge crop failures.

In addition, the ozone layer, which keeps out harmful ultraviolet radiation, would shrink more than 20%, with the poles seeing a 70% reduction.

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