California and West suffering worst ‘megadrought’ in centuries, study of tree rings shows
Officially, California’s most recent drought lasted five painful years and ended in 2017. But a new study released Thursday says California and the rest of the West are enduring a continuing megadrought that ranks among the worst on record.
Despite the occasional wet year, researchers at Columbia University said the period starting in 2000 has been about as bad as any of four lengthy droughts recorded since the late 800s. While the study period ended in 2018, researchers said the West remains trapped in what they called a historic megadrought.
“We now have enough observations of current drought and tree-ring records of past drought to say that we’re on the same trajectory as the worst prehistoric droughts,” said Park Williams, a bioclimatologist at Columbia’s Lamont-Doherty Earth Observatory, in a prepared statement.
While the Columbia research data contains some uncertainty, the study said the current drought might the second-worst of the past 1,200 years. The worst spanned from 1575 to 1603, nearly three decades.
The study added that the prolonged dry spell has been intensified by climate change. Hotter weather, combined with the lack of rain and snow, put additional stress on trees and plants.
The latest megadrought “has been made much worse than it would have been because of climate change,” said scientist Benjamin Cook, one of the study’s co-authors. The researchers noted that the current drought has affected a much wider area than previous droughts, “a fingerprint of global warming.”
Analysis of tree rings
The dismal report comes as California winds up a drier-than-usual winter. About 35 percent of the state is experiencing moderate to severe drought conditions, according to a federal research project called the U.S. Drought Monitor. However, the state’s overall water supply is still fairly healthy — as measured by storage in Shasta, Folsom and other major reservoirs — thanks to a relatively wet winter in 2019.
The study, published in the journal Science, was based on an analysis of thousands of tree rings in nine Western states and Mexico. Other scientists who’ve studied historic droughts said the findings appear plausible.
“There is no doubt we’re in a drought; this is an extended drought,” said water policy expert Jeff Mount of the Public Policy Institute of California. “People tend to think year to year, which is a mistake.”
Jay Lund, of the UC Davis Center for Watershed Sciences, agreed that global warming is intensifying the effect of droughts. “The dryness from climate change will make even moderate droughts worse,” Lund said.
Lund added that a megadrought that last 20 years or longer would severely strain California’s — and test the state’s ability to augment its water supplies. “You don’t build infrastructure for these types of droughts,” he said. “You curtail water use.”
Besides endangering plant life — California’s last five-year drought wiped out millions of trees — prolonged droughts and climate change are believed to be worsening the West’s wildfire risk.
At its worst, the five-year drought dried up thousands of acres of California farmland and forced cities to cut back water consumption by an average of 25 percent. It forced farmers to draw down aquifers to keep their crops going, which exacerbated the literal sinking of parts of the Central Valley floor. The Legislature responded by passing a law that restricts groundwater pumping.
It wasn’t until the winter of 2017, one of the wettest on record, that former Gov. Jerry Brown declared an official end to the drought.
This story was originally published April 16, 2020 at 2:58 PM with the headline "California and West suffering worst ‘megadrought’ in centuries, study of tree rings shows."