US fires release large amounts of carb...(/p Although last week's fires in sou...)

Although last week's fires in southern California broke out after the paper was written, Wiedinmyer applied the new computer model to analyze their emissions. Her preliminary estimates indicate that the fires emitted 7.9 million metric tons of carbon dioxide in just the one-week period of October 19-26, the equivalent of about 25 percent of the average monthly emissions from all fossil fuel burning throughout California.

"Enormous fires like this pump a large amount of carbon dioxide quickly into the atmosphere," Wiedinmyer says. "This can complicate efforts to understand our carbon budget and ultimately fight global warming."

Carbon dioxide emissions from fires pose a significant challenge as policymakers focus on limiting greenhouse gases because of concerns over climate change. Some jurisdictions, such as California, have not yet decided whether to include wildfire emissions when setting targets to reduce greenhouse gases.

The impacts of fires on climate change are complex and difficult to predict. Long after a fire sweeps through an area, new vegetation over the course of several decades to a century may absorb as much carbon dioxide as was released during the blaze. But fires are likely to become more frequent and widespread as temperatures warm around much of the globe, which means that more carbon dioxide may be released into the atmosphere. The fires could complicate government efforts to rely on forests to help absorb carbon dioxide.

"The fires that are burning today in the United States are part of the legacy of the past century of fire suppression," says Neff, an assistant professor of environmental studies. "Our attempts to control fire have had the unintended benefit of sequestering more carbon in our forests and reducing the impact of human combustion of fossil fuels. But as these forests now begin to burn, that stored twentieth century carbon is movin
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