Fire, drought, and El Nino: California in a warming world

The 2014 record drought in California set the government and society scrambling for water managing and firefighting. When it comes to projecting for future extreme events like this past drought, traditional approaches such as mean and median climate help little as far as climate prediction and disaster planning is concerned. This study was developed from our recent paper on the dynamical mechanisms of the California drought, and utilized the new large-member ensemble of the Community Earth System Model (CESM) to study direct links between drought, fire, teleconnection, and climate change. The 2014 California drought was initiated by an anomalous high-amplitude ridge system emerged from continual sources of Rossby wave energy in the western North Pacific that persisted throughout winter. The ridge pattern is linked with a type of El Nino precursor and this link has become stronger since the 1970s. There is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge. Consequently, when projecting for the future, the large-member ensemble simulations of CESM indicated signifiant increases in many wildfire metrics, including fire counts and probability (Figure, top), fire season, and fire intensity. In addition, extreme drought occurrences are projected to triple by the end of 21st century. Both fire and drought variabilities will become increasingly linked to the ENSO cycle (Figure, bottom); however this trend may facilitate seasonal prediction in the future for California's drought and fire occurrences. [ Figure legend: thin lines are individual members of the large-member ensemble, while thick line is the mean ]