Climate change resulting from human activities has nearly doubled the area burned by forest fires in the western United States over the past three decades.

John Abatzoglou at the University of Idaho in Moscow and Park Williams at Columbia University in Palisades, New York, used a climate model and data on the dryness of forested areas since 1979 to assess the contribution that climate change has made to wildfires. They found that warming temperatures made the forests drier, increasing fire risk, and expanded the area burned in the western part of the United States between 1984 and 2015 by about 4.2 million hectares.

Climate change also accounted for about half the increase in both the length of the fire season and the number of days with a high risk of fire.

Proc. Natl Acad. Sci. USA http://doi.org/brsj (2016)