The Last Time California Was This Dry, People Thought the Sun Revolved Around the Earth

NASA/MODISNASA's Aqua satellite captured these images of the Sierra Nevadas showing the mountain range's snowcover before the drought began (left) and then again earlier this year (right).

For indispensable reporting on the coronavirus crisis and more, subscribe to Mother Jones' newsletters.


California’s historic drought may be even more exceptional than we thought.

In a study published yesterday, scientists made a startling discovery about the severity of California’s dry spell: They estimated that the Sierra Nevada mountain range’s snowpack levels this year are the lowest they’ve been for 500 years. That’s right, since roughly the year 1500.

This is bad news for Californians: Snowfall in the mountains can account for as much as one-third of the state’s water supply during a normal year.

Last spring, measurements showed that levels were at their lowest point in the 75 years they’ve been recorded. (That period is shown in red on the graph below.) But scientists had to get creative in order to determine how much snow had fallen over the centuries before snowpack measurements were taken. Paleoclimatologists from the University of Arizona’s Laboratory of Tree-Ring Research analyzed studies that used tree rings to reconstruct historical rainfall and temperatures in California’s mountains. By combining this data, they were able to estimate spring snowpack levels going back half a millennium, as represented in the graphic below. (SWE stands for “snow water equivalent,” which means snowpack).

University of Arizona’s Laboratory of Tree-Ring Research and Nature Climate Change

They found that while there have been many bad years for snow in the mountains, the last time the snowpack sank to this year’s levels was around the year 1500.

This spring, the snowpack reached just 5 percent of average yearly levels.

According to Greg Corbin, a meteorologist at the National Oceanic and Atmospheric Administration, the state’s water system can only store a limited amount of rain runoff, so it relies on snowpack to replenish water reserves. Until it starts snowing again, California has “a long, long way to go,” to restore its water, he says.

Thank you!

We didn't know what to expect when we told you we needed to raise $400,000 before our fiscal year closed on June 30, and we're thrilled to report that our incredible community of readers contributed some $415,000 to help us keep charging as hard as we can during this crazy year.

You just sent an incredible message: that quality journalism doesn't have to answer to advertisers, billionaires, or hedge funds; that newsrooms can eke out an existence thanks primarily to the generosity of its readers. That's so powerful. Especially during what's been called a "media extinction event" when those looking to make a profit from the news pull back, the Mother Jones community steps in.

The months and years ahead won't be easy. Far from it. But there's no one we'd rather face the big challenges with than you, our committed and passionate readers, and our team of fearless reporters who show up every day.

Thank you!

We didn't know what to expect when we told you we needed to raise $400,000 before our fiscal year closed on June 30, and we're thrilled to report that our incredible community of readers contributed some $415,000 to help us keep charging as hard as we can during this crazy year.

You just sent an incredible message: that quality journalism doesn't have to answer to advertisers, billionaires, or hedge funds; that newsrooms can eke out an existence thanks primarily to the generosity of its readers. That's so powerful. Especially during what's been called a "media extinction event" when those looking to make a profit from the news pull back, the Mother Jones community steps in.

The months and years ahead won't be easy. Far from it. But there's no one we'd rather face the big challenges with than you, our committed and passionate readers, and our team of fearless reporters who show up every day.

We Recommend

Latest

Sign up for our newsletters

Subscribe and we'll send Mother Jones straight to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate

We have a new comment system! We are now using Coral, from Vox Media, for comments on all new articles. We'd love your feedback.