Greater temperature and precipitation extremes intensify Western US droughts, wildfire severity, and Sierra Nevada tree mortality

We analyzed gridded daily climate (temperature, precipitation and climatic water deficit) data to identify and characterize the spatiotemporal evolution of the largest Western United States droughts of the last 100 years. Droughts of the last 15 years (2000-2002, 2012-2014) had more extremes of climatic water deficit than earlier droughts, driven by greater temperature and precipitation extremes. Comparing fire extent and severity before, during and after drought events using the Monitoring Trends in Burn Severity dataset (1984-2014), we found fire size and high severity burn extent were greater during droughts than before or after. Similarly, recent Sierra Nevada forest mortality was greatest in drought–affected locations immediately after the drought. Climate simulations anticipate greater extremes in temperature and precipitation in a warming world: droughts and related impacts of the last 15 years may presage the effects of these extremes