The increase in the number of large western wildfires in recent years may be a result of global warming, researchers say. An analysis of data going back to 1970 indicates the fires increased “suddenly and dramatically” in the 1980s and the wildfire season grew longer, according to scientists in Arizona and California.
“The increase in large wildfires appears to be another part of a chain of reactions to climate warming,” said Dan Cayan, a co-author of the paper and director of the climate research division at Scripps Institution of Oceanography.
He said that while part of the increase may be attributed to natural fluctuations, evidence also links it to the effects of human-induced climate warming. The researchers used the files of the US Forest Service and National Park Service to analyse 1,166 fires of more than about 1,000 acres.
Their findings are published in the journal Science. Beginning about 1987, there was a change from infrequent fires averaging about one week in duration to more frequent ones that often burned five weeks or more, they reported. The length of the wildfire season was extended by 78 days.
The researchers said the changes appear to be linked to annual spring and summer temperatures, with many more wildfires burning in hotter years than in cooler years.