Smog, soot and other particles like the kind often seen hanging over Beijing add to global warming and may raise summer temperatures in the American heartland by three degrees in about 50 years, says a new federal science report released Thursday.
These overlooked, shorter-term pollutants — mostly from burning wood and kerosene and from driving trucks and cars — cause more localized warming than once thought, the authors of the report say.
They contend there should be a greater effort to attack this type of pollution for faster results.
For decades, scientists have concentrated on carbon dioxide, the most damaging greenhouse gas because it lingers in the atmosphere for decades. Past studies have barely paid attention to global warming pollution that stays in the air merely for days.
The new report, written by scientists with NASA and the National Oceanic and Atmospheric Administration, makes a case for tackling the short-term pollutants, while acknowledging that carbon dioxide is still the chief cause of warming.
That concept is also the official policy of the Bush Administration, said assistant secretary of commerce Bill Brennan.
In the United States, this approach would mean cutting car and truck emissions perhaps before restricting coal-burning power plants.
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.
In addition to soot, smog and sulfates, other short-lived pollutants are organic carbon, dust and nitrates. While carbon dioxide is invisible, these are pollutants people can see.
Projected increases in some of these pollutants and decreases in others in Asia will eventually add up to about 20 percent of the already-predicted man-made summer warming in America by 2060, the report said.
"What they do about their pollution can affect our climate," said study co-author Hiram "Chip" Levy, a senior scientist at NOAA's fluid dynamics lab in Princeton, N.J.
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.
In the United States it's "a big blob in the middle of the country" stretching from the Rocky Mountains to the Appalachians, Levy said.
The same analysis also shows about an inch less of yearly rain in middle America because of Asian emissions by about 2060.
As far as American-produced pollution, smog is the main problem.
Reducing diesel emissions and increasing mass transit would prove a more effective and immediate strategy than would limiting power plants, said study co-author Drew Shindell, a climate scientist at NASA's Goddard Institute for Space Studies in New York.
The report make sense, but should also include a strategy for man-made methane, a greenhouse gas which lasts 10 years in the atmosphere, said Michael MacCracken, chief scientist at the Climate Institute in Washington.
Methane mostly comes from landfills, natural gas use, livestock, coal mining and sewage treatment, according to the U.S. Environmental Protection Agency.