Increasing Water Cycle Extremes in California, the ENSO Cycle, and Global Warming


The ongoing drought in California is causing statewide water stress and severe economic loss and has raised an important scientific question: Will California continue to experience more drought in the coming decades? Using multi-ensemble simulations of the Community Earth System Model (CESM) and multimodel simulations archived in the Coupled Model Intercomparison Project phase 5 (CMIP5), Department of Energy scientists at Pacific Northwest National Laboratory and researchers at Utah State University found that water cycle extremes, including both extreme drought and flood, are projected to increase at least 50 percent to the end of the 21st century. They found that this projected increase in water cycle extremes is associated with a strengthened relationship to El Niño and the Southern Oscillation (ENSO). In particular, the association is with extreme El Niño and La Niña events that modulate California’s climate not only through its warm and cold phases, but also its precursor patterns. Two sets of the sensitivity experiments with CESM substantiated the role of the changing ENSO cycle on the water cycle extremes in California under global warming.


Yoon, J.-H., S.-Y. S. Wang, R. R. Gilles, B. Kravitz, L. Hipps, and P. J. Rasch. 2015. “Increasing Water Cycle Extremes in California and in Relation to ENSO Cycle under Global Warming,” Nature Communications 6(8657), DOI: 10.1038/ncomms9657.