Chris Lieberman, FISM News
Hot, dry conditions in the southwestern U.S. have led to the worst megadrought in the region since the 800s A.D., according to a new study.
A previous study by the same authors had concluded that between 2000 and 2018, the region had experienced the driest 19-year span since the multi-decade drought of the late 1500s. But after severe conditions in 2021, the researchers have concluded that the last 22 years have now surpassed the 1500s drought, reaching levels unseen since the days of Charlamagne.
To conduct their research, scientists analyzed tree rings, which can help to indicate relative moisture over time. Thicker rings typically indicate years with more moisture, while thinner rings indicate less. When combined with other data samples and historical observations, scientists are able to use this information to construct a climate timeline for a given area.
While the data indicates that the region has experienced several droughts over the past 12 centuries, some of which lasted multiple decades, no previous 22-year period has seen less moisture than the current drought.
Researchers are concerned that this drought seems to show no signs of letting up. “Twenty-two years in, some of these big megadroughts in the past were starting to peter out,” said A. Park Williams, a climate scientist and lead author of the study. “This drought is not petering out. Instead, it’s in full swing and is as strong now as it ever was before.” The study projects that there is a 75% chance the drought lasts at least 30 years.
The drought has already had a major impact on the water supply in the western U.S. Water levels at Lake Mead and Lake Powell, two key reservoirs for the region, have reached their lowest on record. “We have a society that’s relying on there being the amount of water there was in the 1900s,” Williams told NPR. “But now with the number of water molecules available to us declining, it really is time for us to get real about how much water there is for us to use.”
Faith Kearns, a scientist at the California Institute of Water Resources, agreed, saying that the drought will impact U.S. water management going forward. “Water infrastructure in California and much of the western U.S. was developed during a wetter time that was assumed by many to be largely stable,” she wrote in an email to the Washington Post. “I worry about this from an equity perspective and feel that we need to be supporting water operations in integrating climate change into all planning efforts across all water systems, in the western U.S. in particular.”
The study’s authors point to climate change as a major factor behind the record-setting drought. They estimate that 19% of the 2021 drought and 42% of the overall conditions since 2000 are due to what they call anthropogenic climate change, or the impact of human activity on global temperatures. Scientists believe that the higher temperatures create an arid environment, causing the atmosphere to pull more moisture from the ground.
However, Williams also noted that severe droughts have always been present in the region. “The tree rings tell us that there can actually be very, very extreme dryness in the West without the help of climate change at all,” Williams said. “Even without climate change, we can have monumentally severe and long-lasting droughts.”