Climate scientists describe chilling consequences of a nuclear war

National Archives A mushroom cloud rises more than 60,000 feet over Nagasaki, Japan.

A mushroom cloud rises more than 60,000 feet over Nagasaki, Japan, on Aug. 9, 1945, as a result of the second—and last—atom bomb used in warfare.

Beyond the immediate devastation of a large-scale nuclear war, a growing number of scientists are concerned about the aftermath of "nuclear winter," which could result in famine for billions of people across the globe. On Dec. 11, several climate experts discussed the long-term effects of atomic warfare at the annual meeting of the American Geophysical Union (AGU) in San Francisco.

While the threat of mutual annihilation by the superpowers has diminished, the risk of nuclear combat has increased, said AGU panelist Stephen Schneider, the Melvin and Joan Lane Professor in Interdisciplinary Environmental Studies at Stanford and a senior fellow at the Woods Institute for the Environment.

"Now we have almost no likelihood of a large-scale nuclear war between Russia and the West, but a much higher probability of a limited number of weapons being used in the next 30 years by rogue states," he said.

Schneider spoke at the AGU session titled "Environmental Consequences of Regional Nuclear Conflicts," which came on the heels of the Nov. 16 vote by the U.S. Senate to endorse a plan that reverses decades of U.S. anti-proliferation policy by allowing the government to ship civilian nuclear fuel and technology to India. Critics of the Senate plan argue that it would augment India's nuclear arsenal and spark a regional arms race with Pakistan and China.

"Not only do we have a higher probability of the use of nuclear weapons, they are much more likely to be used in the tropics, not in the high latitudes," Schneider said. "It has changed from a big war in the North to smaller explosions in the political South."

Detonation of nuclear weapons in the tropics could have harsher effects than a war in the northern latitudes, Schneider explained, because heat from the sun could loft plumes of smoke higher into the atmosphere, where it could have a longer cooling effect on the Earth. "The sun is much stronger in the tropics than it is in mid-latitudes," he said. "Therefore, a much more limited war [there] could have a much larger effect, because you are putting the smoke in the worst possible place."

The AGU session was moderated by Alan Robock of Rutgers University and Richard Turco of the University of California-Los Angeles. Robock, Turco and colleagues from the University of Colorado-Boulder used computer models to forecast the climatic effects of the smoke produced in a regional conflict in the subtropics between two opposing nations, each using 50 Hiroshima-size nuclear weapons to attack the other's most populated urban areas. According to their analysis, such a war could produce as many direct fatalities as all of World War II and disrupt the global climate for a decade or more, with environmental effects that could be devastating for everyone on Earth.

"The whole nature of the potential conflict has changed," Schneider noted. "Anything that you can do to discourage people from thinking that there is any way to win anything with a nuclear exchange is a good idea. You still have to be mega-insane to think there is any political objective for which a nuclear explosion is going to do you any good."

Brian D. Lee is a science-writing intern with the Stanford News Service.