Worried About a Five-Decade Mega-Drought? How About 2,000 Years?

Tuesday, October 06, 2015

A year ago, it seemed like scientists were competing to predict the worst possible future climate for California. One strong contender projected a 5-10% chance of a 50-year megadrought.

“This will be worse than anything seen during the last 2,000 years and would pose unprecedented challenges to water resources in the region,” Toby Ault, lead researcher told the Cornell Chronicle. He was also talking about the 80% chance of a 10-year drought and 20-50% chance of a 35-year megadrought.

All of those would be worse than anything in California since the birth of Christ. But they are nothing compared to what the state has already experienced, if you go back far enough in time.

A recently-published report by California State University, Fullerton  researchers in the journal Quaternary Science Reviews says California once suffered through a series of megadroughts strung together to produce 2,000 years of deprivation. Fortunately, for humans, they were not here.

This occurred 27,500 years ago, turning a sprawling region of pine trees and juniper, where mammoths roamed, into shrubs and chaparral. Eventually pines and juniper returned.

The scientists figured this out by analyzing ancient pollen found in sediments from beneath Lake Elsinore near Los Angeles. They were able to create a continuous terrestrial record, demarcated by decade rather than century, from 32,000 years ago to 9,000 years ago.

Their findings correlated with records of ocean sediment that show the water off Santa Barbara was warm. The warmer water diverted away moisture-carrying air currents and the combination of dryness and heat was devastating—like now, only not as potentially bad back then.

“This was happening during a glacial period when it was already cool and wet―cooler and wetter than it is now,” paleoecologist and co-author Jonathan Nichols said. “If we got a drought like this now, it would be putting a big drought on top of a time which is already warm and dry.”

It won’t take a 2,000-year drought for Californians to realize that reducing residential water use by 25% from 2013 levels isn’t going to make much of a difference. Even less meaningful would be last week’s hand-wringing, or back patting, depending on who you talk to, over the state beating Governor Brown’s arbitrary 25% conservation target by two percentage points in August but falling short of July’s 31.4%.

What might still be meaningful, though, is if some gazillionaire uses 11.8 million gallons of water a month to maintain his estate in the posh L.A. community of Bel Air, enough for 900 families.

Midway through a 2,000-year drought, the state might change its policy about not identifying individual water users.

–Ken Broder      


To Learn More:

California Once Had a 2,000-Year-Long Dry Spell (by Patrick J. Kiger, Discovery)

California’s Current Drought Could Last for 2,000 Years (by Dashel Pierson, Intertia)

Ancient Pollen Points to Mega-Droughts in California Thousands of Years Ago (Lamont-Doherty Earth Observatory)

80% Chance of 10-Year Drought in Southwest; 50% for a Megadrought (by Ken Broder, AllGov California)

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