Low snowfall in California sets record

Ars Technica : Over the past two years, the Sierra Nevada range in California has had very little snow. In fact, this recent snow total may be the lowest in the past 500 years. The reason is twofold: less precipitation and warmer winters. Human-measured snow records only go back to 1930, so researchers studied tree rings to try to determine temperatures and precipitation from earlier centuries. From that information they were able to estimate the snowfall and resulting snowpack going back to 1500. Although they found that a few years in the 1500s may have had as little snow as the winter of 2015, they say such a severe snow deficit should probably occur only once every 3100 years. Because the residents of California draw 30% of their water supply from Sierra Nevada snowpack, its disappearance could have devastating long-term effects.