SAN JOSE, Calif. — California’s current drought is being billed as the driest period in the state’s recorded rainfall history. But scientists who study the West’s long-term climate patterns say the state has been parched for much longer stretches before that 163-year historical period began.
And they worry that the “megadroughts” typical of California’s earlier history could come again.
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Bill Patzert, a research scientist and oceanographer at NASA’s Jet Propulsion Laboratory in Pasadena, says that the West is in a 20-year drought that began in 2000. He cites the fact that a phenomenon known as a “negative Pacific decadal oscillation” is underway — and that historically has been linked to extreme high-pressure ridges that block storms.
Such events, which cause pools of warm water in the North Pacific Ocean and cool water along the California coast, are not the result of global warming, Patzert said. But climate change caused by the burning of fossil fuels has been linked to longer heat waves. That wild card wasn’t around years ago.
“Long before the Industrial Revolution, we were vulnerable to long extended periods of drought. And now we have another experiment with all this CO2 in the atmosphere where there are potentially even more wild swings in there,” said Graham Kent, a University of Nevada geophysicist who has studied submerged ancient trees in Fallen Leaf Lake near Lake Tahoe.