Climate models presented at AGU meeting project drier conditions and increased fire risk across the U.S. in coming decades.

SAN FRANCISCO, CA, Dec. 4, 2012 — Fire seasons in the U.S. like the one seen this past summer and fall typically occur once a decade. But by mid-century, two to four fire seasons out of every ten are expected to bring intense and frequent fires.

That’s what scientists reported on Tuesday at the annual AGU meeting in San Francisco.

The analysis, presented by Doug Morton of NASA’s Goddard Space Flight Center in Greenbelt, Md., was based on current fire trends and predicted levels of greenhouse gas emissions in coming decades. Morton and his colleagues prepared it for the upcoming Fifth Assessment Report of the United Nations Intergovernmental Panel on Climate Change (IPCC).

The researchers calculated results for scenarios that estimated both low and high levels of greenhouse gas emissions in coming decades. Both showed longer and more intense fire seasons across the country over the next 30 to 50 years.

To get an idea of what two to four fire seasons a decade like the one in 2012 would look like, consider a few stats from this year:

By the end of August of this year, fires had consumed more than 6 million acres. That number tops the total number of acres burned during 12 of the last 15 years.

The amount of land scorched by fire has jumped significantly over the past quarter century, and the amount of CO2 emissions from those fires has more than doubled since 1980, the researchers said.

Chris Williams of Clark University in Worcester, Mass., and his colleagues estimated that carbon emissions from fires across the U.S. have increased from an average of 8.8 million tons per year from 1984 to 1995, to an average of 22 million tons per year from 1996 to 2008.

With more high-fire seasons projected, the amount of CO2 emissions from those fires is expected to trend upward, Williams said.

Separate research by Hsiao-wen Lin of the University of California at Irvine shows that agricultural and prescribed fires account for a huge percentage of the total number of active fires in the continental U.S. — as much as 70 percent. Agriculture fires have increased 30 percent over the last decade.

Bruce Lieberman

Bruce Lieberman, a long-time journalist, has covered climate change science, policy, and politics for nearly two decades. A newspaper reporter for 20 years, Bruce worked for The San Diego Union-Tribune...