Small Nuclear War Would Devastate Global Climate, Scientists Warn
Richard A. Lovett in San Francisco, California
for National Geographic News
|December 13, 2006|
Even a small nuclear conflict would cause long-lasting global devastation that could kill tens of millions, scientists warned this week.
Within a couple of decades, 40 countries could have arsenals large enough to cause such a disaster, the researchers added.
This means the threat of global catastrophe is higher now than it was during the Cold War—even though worldwide stocks of nuclear weapons have declined by a factor of three since the end of the four-decades-long conflict.
The dire predictions came from the first ever study of a regional nuclear exchange, unveiled Monday at the fall meeting of the American Geophysical Union in San Francisco.
Previous studies had looked only at the effects of all-out nuclear war between superpowers.
"This is the greatest danger to survival since the dawn of humanity," said study co-author Owen Toon of the University of Colorado, Boulder.
In an exchange in which each side uses only 50 Hiroshima-size bombs—just 0.3 percent of the world's arsenal—the initial explosions could kill more than 20 million people, the scientists calculate.
(See a National Geographic magazine feature on weapons of mass destruction.)
But more far-reaching would be the resulting fires, which would fill the upper atmosphere with soot—destroying the Earth's ozone layer, blocking sunlight, and reducing average global temperatures by 2 degrees Fahrenheit (1.25 degrees Celsius), said co-author Alan Robock of Rutgers University in New Jersey.
The effect would persist for several years and be stronger at mid-latitudes, including the U.S. and Europe.
"This would be a global climate change unprecedented in recorded history," Robock said.
Smothered in Soot
The increase in people living in urban areas is magnifying the danger, said Richard Turco of the University of California, Los Angeles.
Densely populated "megacities" would be the most likely targets in a small-scale nuclear war.
Firestorms from the detonations would feed on a combination of wood, plastics, asphalt roofing, and petroleum products, injecting a black, sooty smoke high into the air, Turco said.
The soot would absorb sunlight before it reached Earth's surface, reducing temperatures and causing the soot to rise dozens of miles higher.
Eventually the soot would settle into the upper layer of the atmosphere known as the stratosphere, where it would block sunlight for many years.
This would have a devastating impact on agriculture, causing a 10 percent reduction in rainfall and shrinking the growing season in some parts of the globe by as much as 30 days.
The particles would also destroy much of Earth's ozone layer, which protects humans and animals from cancer-causing ultraviolet radiation, the scientists predicted.
Toon referred to the result as "a global ozone hole."
In the 1980s Turco, Toon, and the late Carl Sagan had similar concerns about the effects of an all-out war between the U.S. and the Soviet Union.
They dubbed the resulting scenario "nuclear winter" because of the devastating impact on climate worldwide, including entire years with global temperatures below freezing.
The researchers didn't realize, however, that a smaller nuclear exchange would also have dramatic impacts.
"Regional-scale nuclear war can cause casualties similar to those previously predicted for a strategic attack by the U.S.S.R on the U.S.," Toon said.
The policy implications of the research are clear, the scientists noted.
Stephen Schneider of Stanford University in Palo Alto, California, said, "Nobody can use these things without the effects spilling over to the rest of the planet."
"We're just at the beginning of this work," Robock added.
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