Climate Central: Despite a recent influx of snow and rain this past weekend, extremely low snowpack in the Sierra Nevada has conspired with warm temperatures to keep the state in the grips of one its worst droughts on record for at least another year. The precipitation has been the key ingredient to start the drought, but heat has played an important role in maintaining and intensifying it. A new paper published Monday in the Proceedings of the National Academy of Science shows that human greenhouse gas emissions...