Thursday, November 1, 2007

fire and feedbacks

Forest fires produce their own greenhouse gases. Lots of them.
That's the news in an AP story today that offers up numbers on emissions from CA fires and fires around the country. In the US, fires annually spit out about 5 percent of what fossil fuel combustion does. In Alaska, it's much higher.
The Western continental United States is responsible for more than one-third of the country's carbon dioxide from fires. But Alaska is king. Alaskan fires produce twice as much of the greenhouse gas than burning fossil fuels in that state. Alaskan fires make up 27 percent of the nation's yearly fire-related carbon dioxide emissions.
This is like a lot of things, where natural and man-made warming lead to more natural warming. Is it still a "natural" source if there's reason to believe it was spurred in part by man-made warming? (Studies project that fires will increase in a warmer world.) Consider the release of methane gases from thawing lakes, or the increased absorption of solar energy with reduced sea ice. Attribution only really matters in the policy debate, but understanding the many feedback loops is important for being able to predict the extent of the warming.
The picture is from a prescribed burn near Fairbanks.

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