Wildfire response to changing daily temperature extremes in California's Sierra Nevada

Burned area has increased across California, especially in the Sierra Nevada range. Recent fires there have had devasting social, economic, and ecosystem impacts. To understand the consequences of new extremes in fire weather, here we quantify the sensitivity of wildfire occurrence and burned area in the Sierra Nevada to daily meteorological variables during 2001-2020. We find that the likelihood of fire occurrence increases nonlinearly with daily temperature during summer, with a 1 degrees C increase yielding a 19 to 22% increase in risk. Area burned has a similar, nonlinear sensitivity, with 1 degrees C of warming yielding a 22 to 25% increase in risk. Solely considering changes in summer daily temperatures from climate model projections, we estimate that by the 2040s, fire number will increase by 51 +/- 32%, and burned area will increase by 59 +/- 33%. These trends highlight the threat posed to fire management by hotter and drier summers.

Automated summary

The study shows that the likelihood of fire occurrence and burned area in the Sierra Nevada range increases nonlinearly with daily temperature during summer. A 1 degrees C increase in temperature leads to a 19 to 22% increase in fire risk and a 22 to 25% increase in burned area risk. Climate model projections suggest that by the 2040s, fire numbers will increase by 51 +/- 32% and burned area will increase by 59 +/- 33%, emphasizing the threat posed by hotter and drier summers to fire management.