Wildfires Tied to Climate Change

The U.S. House of Representatives Energy and Natural Resources committee held a hearing on wildfire management this week. Fires are burning in California, Colorado, Arizona, New Mexico, Texas, Florida and Oregon. The record-breaking Wala fire in Arizona may have been sparked by a campfire but made worse by a prolonged drought, high temperatures, dry and windy conditions and climate change.

Scientists are careful to separate climate from individual weather events. But trends in the ultra dry desert southwest are pointing to a broader shift.

Rep. Jeff Bingaman, the chair of the House committee released a statement saying, “It’s been a dynamic year of severe weather: intense tornadoes and flooding throughout much of the United States, extreme drought and wildfire activity in the Southwest and much of the South. The overall trend of increasing drought and wildfire in the West and Southwest have been attributed by numerous scientific reports to climate change, including the recent report of our National Academy of Sciences, entitled America’s Climate Choices.”

U.S. Forest Service chief Tom Tidwell testified that he is witnessing longer fire seasons all around the country.

He says, “With this change in climate, we are seeing a much increased frequency in disturbance events such as drought. Not only are droughts more frequent, they are longer in length.”

As a result snow pack in the mountains is melting earlier each year and Forest Service scientists have found the average fire season in the west has been extended about 30 days.

When Tidwell flew over the Wallow fire in Arizona last week he says he was surprised. He’s seen many forest fires but when he saw the west front was a 30-mile stretch of active fire it “topped anything he’d seen before.”

Matt Rollins, who monitors wildfires for the U.S. Geological Survey says, “What we can’t do is definitively tie this to any specific driving factor like climate variability.”

Why not?

Well, fire is a highly complex system that is influenced by a number of variables. Short term weather patterns create dry conditions. Infrequent ground fires allow brush and other fuel to grow so when a fire does arise it’s hot and intense and hard to fight. Windy conditions, insect infestations that kill trees and changes in land use all contribute to making fire hard to pin down.

Some research into big fires has been done. A combined U.S. Forest Service and U.S. Geological survey effort studied fires that burned more than 1,000 acres. The study found that between 1984 and 1999 2.2 million acres burned nationally each year. But between 2000 and 2008 and acreage destroyed jumped to 6.4 million acres.

Stephen J. Pyne from Arizona State University things overgrazing, logging and fire prevention efforts (remember Smoky Bear?) have provided a lot more fuel for wildfires.

He says, “You don’t even have to involve global warming. It’s hot this time of year and all you need is a couple of weeks of really dry weather.”

According to the Associated Press, so far this year 31,350 wildfires have burned more than 4 million acres of land. That’s up from 27,077 fires at the same time last year which burned about one-third as much acreage.

According to research by Anthony Westerling, an engineer at the University of California, Merced the number of large fires began to grow in the mid 1980s. His paper appeared in Science magazine(PDF) in 2006. He says the big Yellowstone fire in 1988 began the era of big wildfires in the west.

The strong La Nina weather pattern this year that just ended contributed to the severity of an existing drought in the desert southwest, where rain has been infrequent and temperatures have been well above normal. With all the factors at play in making a wildfire, climate may play a subtler role, exacerbating conditions that merely fan the flames.

Congressman Bingaman is convinced there is a connection between fire and climate. He says, “Since climate change will continue into the future, we can expect the incidences of severe weather and the further drying-out of the already arid regions of the West to continue.”

Others are content to pin the blame on short term weather conditions, insect infestations and more people living and camping in the woods.

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