June 29, 2005
Wednesday

Wildfires that burned more than 11 million acres of Alaska and Canada last summer put about as much carbon monoxide into the atmosphere as did tailpipes and smokestacks in the United States during the same period, according to a new study.

Researchers from the National Center for Atmospheric Research in Boulder, Colo., used a combination of airborne and satellite instruments, computer models and numerical techniques that allowed them to sort out carbon monoxide coming from the wildfires and other sources.

11 million - Number of acres burned in Alaska and northwest Canada during summer of 2004. 33 million - Tons of carbon monoxide released by the fires. Researchers say this is virtually the same amount of the toxic gas that was released by tailpipes and other human sources in the continental United States during June through August of last year.

Wildfires in Alaska, British Columbia and the Yukon were particularly intense last summer, one of the warmest and driest on record, with most of the fires sparked by thousands of "dry" lightning strikes from thunderstorms that yielded little rain.

The team concluded that in charring an area roughly the size of Maryland and Connecticut combined, the fires released about 33 million tons of carbon monoxide from June through August. And because of the wildfires, ground-level concentrations of ozone increased by 25 percent or more in parts of the northern United States and by 10 percent as far away as Europe.

With continuing dry conditions in much of Alaska and the western states, this year's fire season is again off to a dangerous start, with more than 1.6 million acres burned thus far in 2005, including several hundred thousand in Alaska, according to the National Fire Information Center.

"It is important to see how the influence of these fires can reach large parts of the atmosphere, perhaps even over the entire Northern Hemisphere," said Gabriele Pfister, a scientist at the center and lead author of the study, published in the June issue of Geophysical Research Letters. "This has significant implications as societies take steps to improve air quality."

Carbon monoxide is a toxic gas that can affect human health even at low levels. It is emitted from combustion of any carbon-containing fuels that don't completely burn.

Ground-level ozone is formed by reactions between carbon monoxide and other pollutants and sunlight. Ozone both irritates the respiratory system and may increase the risk of heart attacks. It also can damage the growth of plants and have long-term effects on the climate.

Although the EPA monitors both pollutants, scientists have been unable to determine the regional sources of emissions or the extent to which human and natural activities each contribute to concentrations in the air.

For their study, which was funded by NASA and the National Science Foundation, the NCAR team relied on a remote pollution-sensing instrument mounted on NASA's Terra environmental satellite to quantify emissions from the fires. Then they used models to simulate transport of the pollutants and the resulting production of ozone downwind.

In addition to comparing the model results with more measurements from the satellite, the researchers got further confirmation from aircraft-mounted instruments that were taking part in a separate project over North America and Europe last summer.

Pfister said the team is continuing to look at data taken last year from observing stations as far away as the Azores in order to further track the movement of pollutants from the wildfires.

In a follow-up study, she and colleagues plan to use the same techniques to track carbon monoxide emissions from wildfire and human-related sources in South America.

On the Net: www.ucar.edu

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