September 5, 2008

Asian Pollution Could Heat Up America

A new federal science report noted heavy smog hanging over Beijing could heat up the weather in the American Midwest by three degrees over the next 50 years.

The report said unlike the long-lived greenhouse gas carbon dioxide, the particle and gas pollution only stays in the air for a few days or weeks but its warming effect on the climate half a world away could last for decades.

"We found that these short-lived pollutants have a greater influence on the Earth's climate throughout the 21st century than previously thought," said Hiram "Chip" Levy of the U.S. National Oceanic and Atmospheric Administration.

For decades, scientists have focused almost solely on carbon dioxide, the most damaging greenhouse gas because it lingers in the atmosphere for decades. In the past, studies have barely noted global warming pollution that stays in the air for days.

Scientists with NASA and the National Oceanic and Atmospheric Administration wrote the report. They encouraged policy makers to fight the short-term pollutants, while acknowledging that carbon dioxide is still the chief cause of warming.

Levy estimated that by 2050, "two of the three climate models we use found that changes in short-lived pollutants will contribute 20 percent of the predicted global warming."

By 2100, that figure goes up to 25 percent.

The short-lived pollution that can cause long-term warming comes from soot, also known as the black carbon particles that result from fires, and sulfate particles, which are emitted by power plants. Soot particles are dark and absorb heat; sulfates are light and reflect heat, actually cooling things down.

To cut down on short term pollutants, in the United States, car and truck emissions would have to be cut perhaps before restricting coal-burning power plants.

Researchers say in the developing world, especially Asia, it would mean shifting to cleaner energy sources, more like those used in the Western world. Much of this type of pollution in Asia comes from burning kerosene and biofuels, such as wood and animal dung.

"What they do about their pollution can affect our climate," said Levy.

This pollution will likely create three "hot spots" in the world: the central United States, Europe around the Mediterranean Sea, and Kazakhstan, which borders Russia and China.

According to Levy, in the United States it's "a big blob in the middle of the country" stretching from the Rocky Mountains to the Appalachians.

In America, smog is the main problem. Reducing diesel emissions and increasing mass transit would prove a more effective and immediate strategy over limiting power plants, said study co-author Drew Shindell, a climate scientist at NASA's Goddard Institute for Space Studies in New York.


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