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 percent of the Earth’s population, or billions of people.
The new study presented Monday 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 percent, with the north and south poles seeing a 70 percent reduction.
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 effect, said scientist Steve Ghan of the Pacific Northwest National Laboratory.
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