The Last Time California Was This Dry, People Thought the Sun Revolved
Around the Earth
--By Luke Whelan
Mother Jones, Wed September 16, 2015 6:00 AM EDT
http://www.motherjones.com/blue-marble/2015/09/crazy-statist-puts-californias-drought-historic-perspective
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.
We're Obliterating Global Temperature Records, and There's No End in Sight
Luke Whelan is an editorial fellow at Mother Jones whose work has appeared
in Grist and Vermont's Burlington Free Press. He enjoys road biking and
working on his Chinese. RSS | Twitter
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