Climate Change Blamed for Western U.S. Wildfires

Climate Change Blamed for Western U.S. Wildfires

7 July 2006

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Here’s another thing to blame on climate change — wildfires, those forest and grass fires that have threatened communities across the U.S. West, according to research published Thursday.

And a warming climate will only cause more.

“We show that large wildfire activity increased suddenly and dramatically in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations and longer wildfire seasons,” the researchers at the University of Arizona in Tucson and the Scripps Institution of Oceanography in La Jolla, California wrote in the journal Science.

“I see this as one of the first big indicators of climate change impacts in the continental United States,” said Arizona’s Thomas Swetnam, who worked on the government-funded study that tied warming and earlier springs to frequent large forest fires.

“Lots of people think climate change and the ecological responses are 50 to 100 years away. But it’s not 50 to 100 years away — it’s happening now in forest ecosystems through fire,” added Swetnam.

Swetnam said he did not at first believe climate change affected forest fires. But he changed his mind as he and his colleagues studied 1,166 forest wildfires between 1970 and 2003 that had burned at least 1,000 acres.

“The length of the fire season has increased almost two-and-one-half months compared with 1970 to 1986,” he said.

Such fires have made recent headlines because they have burned entire communities and forced the evacuation of hundreds of households at a time.

As of Thursday, the National Fire Information Center reported 412 new fires nationally and six large ones in Montana, Texas, Idaho, Nevada and Wyoming.

Last month, a fire blackened 4,300 acres near Sedona, about 90 miles north of Phoenix, before it was contained.

This week at least 5,500 people were evacuated in the Canadian provinces of Alberta and British Columbia.

The frequency of wildfires appear to be strongly linked to annual spring and summer temperatures and to the timing of spring snowmelt, said Anthony Westerling of Scripps.

“At higher elevations what really drives the fire season is the temperature,” Westerling said in a statement.

“When you have a warm spring and early summer, you get rapid snowmelt. With the snowmelt coming out a month earlier, areas get drier overall. There is a longer season in which a fire can be started and more opportunity for ignition.”

As global temperatures rise, the researchers suggest more severe fires could change forest composition so drastically that the western forests, which currently store atmospheric carbon dioxide, could start adding carbon to the atmosphere. This in turn would drive temperatures even higher.


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