Global warming pushing US Southwest drought into a megadrought

Posted Apr 17, 2020 by Karen Graham
A severe drought that has engulfed the American Southwest since the year 2000 is likely to soon be the most severe drought since the 800s, according to a new study.
Drought Impacts in the Southwestern Region
Drought Impacts in the Southwestern Region
Global warming has pushed what would have been a moderate drought in southwestern North America into megadrought territory, according to a team of researchers from Columbia University. Their findings were published in the online journal Science on April 17, 2020.
"This appears to be just the beginning of a more extreme trend toward megadrought as global warming continues," the authors wrote in the study, according to EcoWatch.
The scientists focused on an area stretching across nine U.S. states from Oregon down to New Mexico. Their research found that a “megadrought” appears to be emerging in the western U.S., fueled in part by anthropogenic - or human-caused - climate change.
United States Drought Monitor
The researchers go on to say that the 20-year drought being experienced now in the Southwestern U.S. is as bad or worse than any in the past 1,200 years.
To be transparent, nothing is really guaranteed. The year 2019 was actually a fairly wet year, a sign of unpredictable climate variability. But one wet year is not a perfect indicator that the drought will soon be over.
Lead author A. Park Williams, a bioclimatologist at Lamont-Doherty Earth Observatory at Columbia University explains, according to USAToday: "Because the background is getting warmer, the dice are increasingly loaded toward longer and more severe droughts. We may get lucky, and natural variability will bring more precipitation for a while."
"But going forward, we'll need more and more good luck to break out of the drought, and less and less bad luck to go back into drought," he said.
The Colorado River Storage Project provides for the comprehensive development of the Upper Colorado ...
The Colorado River Storage Project provides for the comprehensive development of the Upper Colorado River Basin. The project furnishes the long-term regulatory storage needed to permit States in the upper basin to meet their flow obligation at Lees Ferry, Arizona, as defined in the Colorado River Compact and still use their apportioned water.
Bureau of Reclamation / USBR
The study was far-reaching
To conduct the study, researchers did a comprehensive long-term analysis of thousands of square miles, stretching across nine states from Oregon and Montana down through California, Arizona, New Mexico and part of northern Mexico.
Additionally, 1,200 years worth of tree-ring data was analyzed, with the team pinpointing dozens of droughts across the region dating back to 800AD. Four of the droughts they identified can be classified as a "megadrought," with extreme dryness that lasted for decades.
Four megadroughts stand out as being extreme - in the late 800s, the mid-1100s, the 1200s, and the late 1500s. The team then compared these four megadroughts to soil moisture records from the years 2000 to 2018.
Fissures due to land subsidence can occur when groundwater supplies are depleted.
Fissures due to land subsidence can occur when groundwater supplies are depleted.
S.R. Anderson / USGS
The researchers found that the current drought in the Southwestern U.S. ranked as the second-driest, already outdoing the three earliest ones and on par with the fourth period which spanned from 1575 to 1603, according to CBS News.
These latest findings are consistent with previous studies. A study published last year in "Nature" also found that humans were to blame for droughts and that they will continue to worsen.
The main takeaway from the 2019 study is that it provides evidence that human activities could continue to influence droughts in the future. "The human consequences of this, particularly drying over large parts of North America and Eurasia, are likely to be severe," that 2019 study concluded, predicting many more droughts.