The season for large fires in Southern California is projected to lengthen in a changing climate

More frequent large wildfires and a lengthening of the fire season in southern California are projected under future emission and climate scenarios, according to machine learning and climate model projections. Southern California is a biodiversity hotspot and home to over 23 million people. Over recent decades the annual wildfire area in the coastal southern California region has not significantly changed. Yet how fire regime will respond to future anthropogenic climate change remains an important question. Here, we estimate wildfire probability in southern California at station scale and daily resolution using random forest algorithms and downscaled earth system model simulations. We project that large fire days will increase from 36 days/year during 1970-1999 to 58 days/year under moderate greenhouse gas emission scenario (RCP4.5) and 71 days/year by 2070-2099 under a high emission scenario (RCP8.5). The large fire season will be more intense and have an earlier onset and delayed end. Our findings suggest that despite the lack of a contemporary trend in fire regime, projected greenhouse gas emissions will substantially increase the fire danger in southern California by 2099.

Automated summary

Machine learning and climate model projections indicate that southern California will experience more frequent large wildfires and a longer fire season in the future. This has significant implications for the biodiversity hotspot and the densely populated region of southern California.