Current Post-2000 Drought In Southwest Matches Or Exceeds Worst Droughts Going Back 1,200 Years
A severe drought that has gripped the American Southwest since 2000 is as bad as or worse than long-lasting droughts in the region over the past 1,200 years, and climate change has helped make it that way, scientists said Thursday.
The researchers described the current drought, which has helped intensify wildfire seasons and threatened water supplies for people and agriculture, as an “emerging megadrought.” Although 2019 was a relatively wet year, and natural climate variability could bring good luck in the form of more wet years that would end the drought, global warming increases the odds that it will continue. “We know that this drought has been encouraged by the global warming process,” said Park Williams, a bioclimatologist at Lamont-Doherty Earth Observatory at Columbia University, and lead author of a study published Thursday in Science. “As we go forward in time it’s going to take more and more good luck to pull us out of this.”
While the term megadrought has no strict definition, it is generally considered to be a severe dry period persisting for several decades or longer. Many climate researchers and hydrologists have long thought that a Southwestern megadrought was highly likely. A 2016 study put the probability of one occurring this century at 70 percent or higher.
Dr. Williams and his colleagues reconstructed drought conditions in the Southwest for every year back to 800 A.D., using tree growth as a proxy for soil moisture content. Examining nearly 1,600 tree-ring records, they found four periods of more than two decades each during which soil moisture content was far below the baseline for the entire 1,200 years, indicating severe drought conditions of lack of precipitation and increased dryness. One of these megadroughts, in the 13th century, lasted more than 90 years. Their analysis showed that, as measured by soil moisture content, the current drought is more severe than three of the ancient ones. Only one in the late 1500s was worse, and not by much, the researchers said.
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https://www.nytimes.com/2020/04/16/climate/drought-southwest-climate-change.html
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