Percentiles of potential evapotranspiration (ETo) during Water Year 2014 with respect to 1979 to 2012 climatology. If WY 2014 temperatures resembled California's 1916–2012 climatology, there would have been at least an 86 percent chance that winter snow water equivalent and spring-summer soil moisture and runoff deficits would have been less severe than the observed conditions. Graphic: Shukla, et al., 2015

By Greg Laden
22 May 2015 (Science Blogs) – […] A paper just out in Geophysical Research Letters uses modeling and historic data to confirm that the current California drought is very likely an effect of climate change. The paper is “Temperature Impacts on the Water Year 2014 Drought in California“, by Shraddhanand Shukla, Mohammad Safeeq, Amir Aghkouchak, Kaiyu Guan, and Chris Funk. Here is the abstract, which is pretty self explanatory and understandable:

California is experiencing one of the worst droughts on record. Here we use a hydrological model and risk assessment framework to understand the influence of temperature on the water year (WY) 2014 drought in California and examine the probability that this drought would have been less severe if temperatures resembled the historical climatology. Our results indicate that temperature played an important role in exacerbating the WY 2014 drought severity. We found that if WY 2014 temperatures resembled the 1916-2012 climatology, there would have been at least an 86% chance that winter snow water equivalent and spring-summer soil moisture and runoff deficits would have been less severe than the observed conditions. We also report that the temperature forecast skill in California for the important seasons of winter and spring is negligible, beyond a lead-time of one month, which we postulate might hinder skillful drought prediction in California. [more]

California Drought Caused By Climate Change