Hotter and drier fire seasons increase risk of severe wildfires in western US forests

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To understand trends in fire severity and area burned, researchers analyzed satellite images taken before and after each fire in western US forests from 1985 to 2022. They classified areas as high severity when at least 95% of the tree canopy was lost according to a satellite-derived fire severity metric called the Composite Burn Index. To understand climate’s role, they combined three key indicators during the summer fire season (vapor pressure deficit, maximum temperature, and climate water deficit) into a single metric called fire season aridity to capture how hot and dry each fire season was. This same method was used to model future fire conditions, projecting changes in total and high-severity burn areas through the mid-21st century under a 2°C warming scenario.