Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity

• Compiles a comprehensive database of large wildfires in western United States forests since 1970 and compared it with hydroclimatic and land-surface data
• Shows that large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons
• Finds the greatest increases occurred in mid-elevation, Northern Rockies forests, where land-use histories have relatively little effect on fire risks and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt

Open source PDF available here