Yosemite high country last February. Notice anything missing? National Weather Service.
A new study of blue oak tree rings in the Sierra Nevada finds that last winter's snowpack was probably the lowest in 500 years. The study, published in Nature Climate Change, comes via researchers at several institutions, including the Laboratory of Tree-Ring Research at the University of Arizona in Tucson. Tree rings have proven to be a valuable measure of past climatic activity in California.
"Our reconstruction reveals that the 2015 low is unprecedented in the context of the past 500 years," the journal report says. "There is a possibility that a few (primarily sixteenth century) years exceeded the 2015 low," but probably not based on the research. This past winter's snowpack was so low, about five percent of the historical average on April 1, that the state stopped sending out the snow measurement teams. Snowpack matters, of course, because in normal times the snow across the Sierra acts as a natural reservoir that replenishes the rivers that flow into the man-made reservoirs up and down the state.