Global Warming Causing More Destructive Wildfires

Global warming may be largely to blame for the increasingly destructive wildfires in the Western United States. Scientists find that longer and fiercer wildfire seasons since 1986 are closely associated with warmer summer temperatures, the earlier arrival of spring, and earlier snowmelts in the West.

The study provides additional evidence of the destructive impacts of global warming, following papers published in 2005 in the journals Nature and Science that linked climate change to increases in hurricane intensity since 1970.

Anthony L. Westerling of the Scripps Institution of Oceanography, the study's lead author, and his colleagues analyzed a government database of forest fires larger than 1,000 acres in the West since 1970. They found a dramatic increase in wildfires after 1986, with large fires four times more frequent than during the preceding years, and burning through 6.5 times more area. The length of the average wildfire season increased by 2.5 months.

Scientists had previously believed that increased wildfire activity resulted from changes in land use practices that provide more fuel for fires. But the new study shows that most of the increase in wildfires has occurred in the Northern Rocky Mountains, where few land-use changes have occurred. Also, the scientists found that 66 percent of the yearly variation in forest fires could be explained by temperature changes alone, with hotter years producing more fires. The wildfires were also much more common in years with an early snowmelt, the researchers reported. When snow melts earlier, it allows more time for soil and vegetation to dry out, permitting fires to begin earlier in the season.


Naila Moreira, “Study Links Increase in Wildfires to Global Warming,” Boston Globe, 7 July 2006.