Asian pollution may cause American climate shift

WASHINGTON - Pollution from Asian coal power plants could create summer hot spots in the central United States and southern Europe by mid-century, US climate scientists reported on Thursday. The full report is available online at www.climatescience.gov and was released by the US Climate Change Science Program.

Unlike the long-lived greenhouse gas carbon dioxide, the particle and gas pollution cited in this report only stays in the air for a few days or weeks but its warming effect stays over the long term.

"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 Levy of the US National Oceanic and Atmospheric Administration.

"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.

Asian soot and sulfate pollution is likely to make for hotter, drier summers in the American Midwest and the Mediterranean region of southern Europe, Levy said, adding that heating and drying effects are not expected to hit Asia.

The reason for the expected pollution-related warming trend is that sulfate pollution, which has been linked to respiratory problems, is expected to decrease dramatically while soot pollution is forecast to continue increasing in Asia.

Ground-level ozone emitted by US transport vehicles is also a factor, the scientists said.

These pollutants have usually been dealt with as threats to air quality, but should also be considered for their impact on climate change, said Drew Shindell, a climate expert at NASA.

Carbon dioxide, which spurs global warming and is emitted from natural and human-made sources, still is going to dominate the climate change picture in the coming century, but because modern societies are built to emit lots of this substance, change is likely to be slow, Shindell said.

Targeting these air pollutants now makes sense, because of their role in the quality of the air people breathe as well as their impact on global warming, he said.

"It's no substitute for targeting CO2 (carbon dioxide), which in the long run is the main contributor to global warming and has to be tackled, but ... the shorter-term pollutants can have a very large impact," Shindell said.

Climate change could dramatically hurt the US economy.