After four years of drought California is now at its driest for 500 years, scientists have found. The heat has left the Golden State with almost no snowpack in the mountains, which is critical for replenishing the state’s water reservoirs.
An analysis of blue oak tree rings in the state’s Central Valley has led scientists to “astonishing” results.
Scientists have compared their measurements of tree-ring data to previous Sierra Nevada snowpack level recordings that have been recorded since the 1930’s and found that oak trees’ growth seem to accurately reflect the lowest snowpack seasons.
“We combined an extensive compilation of blue oak tree-ring series that reflects large-scale California winter precipitation anomalies with a California February-March temperature reconstruction in a reconstruction that explains 63 percent of the Sierra Nevada snow water equivalent variance over the instrumental period,” the scientists wrote.
The answer lies in the rings of Blue oaks that show high winter rain levels with wide bands in the rings, while low levels result in narrow bands.
It became clear after analysis of the new core samples and those taken in previous years that 2015 had the lowest snowpack levels in 500 years.
“The results were astonishing,” Valerie Trouet, an associate professor at the University of Arizona, a senior author for the study, told the Wall Street Journal. “We knew it was an all-time low over a historical period, but to see this as a low for the last 500 years, we didn’t expect that. There’s very little doubt about it.”