Multi fire index examination of future climate change affecting wildfire seasonality and extremes in the continental United States

Climate change is impacting wildfires in the contiguous United States, thus projections of fire weather under climate change have the potential to inform responses to changing wildfire risks. We examine changes in projected fire weather for, and compare the responses of, multiple fire indices across the contiguous United States. We calculate fire indices for thirteen dynamically downscaled regional climate models, then count days exceeding relevant fire danger percentile and midpoint thresholds, and ultimately compare the differences between a reference period and future periods. Additionally, we examine at what point during the year these exceedances occur. The analysis focuses on the midcentury, though the end of the century is also examined. Many regions in the domain experience increases in the number of days exceeding fire danger thresholds by the midcentury. The regions which exhibit agreement across the simulation ensemble on the sign of change, and the magnitude of that change, vary greatly between indices. The timing and frequency of fire danger days throughout the year changes, both in the shoulder season and during existing peaks in fire danger. By the end of the century, most of the domain experiences statistically significant increases in the number of fire danger days. Complex interactions between input variables, and the sensitivities to inputs, affect the response of fire indices under climate change. The projected increase in fire weather risk could place greater demands upon fire management resources, pose elevated hazards for populations exposed to fire, and potentially disrupt landscapes and infrastructure more frequently.