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.
Through studies of tree rings, sediment and other natural evidence, researchers have documented multiple droughts in California that lasted 10 or 20 years in a row during the past 1,000 years — compared to the mere three-year duration of the current dry spell. The two most severe megadroughts make the Dust Bowl of the 1930s look tame: a 240-year-long drought that started in 850 and, 50 years after the conclusion of that one, another that stretched at least 180 years.
“We continue to run California as if the longest drought we are ever going to encounter is about seven years,” said Scott Stine, a professor of geography and environmental studies at Cal State East Bay. “We’re living in a dream world.”
Thirty years ago, the New York Times knew that the 20th century was unusually wet in California, and that the Medieval Warm Period was global.
“Lisa J. Graumlich, who examines the ring patterns of foxtail pine trees and western junipers in the Sierra Nevada, has compiled a detailed record of the year-to-year variation in temperature and precipitation over the last thousand years.
She has seen in the North American trees the feathery but unmistakable signatures of the Medieval Warm Period, a era from 1100 to 1375 A.D. when, according to European writers of the time and other sources, the climate was so balmy that wine grapes flourished in Britain and the Vikings farmed the now-frozen expanse of Greenland; and the Little Ice Age, a stretch of abnormally frigid weather lasting roughly from 1450 to 1850. A Crucial Question
“We can now see that these were global climate phenomena, not regional temperature variations,” she said. “The question is, how did we get those warmer temperatures during pre-industrial times, and what can we learn from those conditions about what is going on today?”
Western landscapes in presettlement era were very smoky places.