Anthropogenic warming impacts on California snowpack during drought

Simulates Sierra Nevada climate and snowpack during the period of extreme drought from 2011 to 2015
Compares first simulation to another that is identical except for the removal of the twentieth century anthropogenic warming
Results show that anthropogenic warming reduced average snowpack levels by 25%, with middle-to-low elevations experiencing reductions between 26 and 43%
In terms of event frequency, return periods associated with anomalies in 4 year 1 April snow water equivalent are estimated to have doubled, and possibly quadrupled, due to past warming
Concludes that past human emissions of greenhouse gases are already negatively impacting statewide water resources during drought