"The science is clear and confirms what New Mexico's communities have been experiencing for decades—climate change is here, and our water systems are ground zero," Rep. Melanie Stansbury (D-N.M.)
Despite copious amounts of rainfall in parts of the southwest, drought conditions continue unabated. 2020 and 2021 pushed the region over the top for the driest megadrought in over 1200 years.
Researchers have determined this drought started 22 years ago with a certainty of 94% that the deficit will continue this year. They also found that it is likely not to break for at least another eight years by factoring in human-caused climate change. Regardless, megadroughts will follow as temperatures continue to rise unabated. A megadrought is determined when arid conditions persist for at least two decades.
Chelsea Harvey writes in E&E News :
The searing “megadrought” that has gripped the southwest U.S. for more than two decades is the driest 22-year period in at least 1,200 years. The region hasn’t seen a more severe drought since the start of the scientific record around the year 800, according to new research published yesterday.
An arid year in 2021 helped break the record. Before last year, a previous megadrought occurring in the late 1500s was the only other drought known to be worse than today. A megadrought is typically defined as a severe dry period lasting at least a couple of decades.
The current event has been strongly influenced by human-caused climate change, the study said. In fact, without the influence of global warming, today’s conditions probably wouldn’t be classified as a megadrought at all.
The Columbia Climate School in a presser adds some meat to the findings:
University of California Los Angeles geographer Park Williams, the study’s lead author, said with dry conditions likely to persist, it would take multiple wet years to remediate the effects. “It’s extremely unlikely that this drought can be ended in one wet year,” he said. The study was coauthored by Jason Smerdon and Benjamin Cook of the Columbia Climate School.
The researchers calculated the intensity of droughts by analyzing tree rings, which provide insights about soil moisture levels each year over long time spans. They confirmed their measurements by checking findings against historical climate data. Periods of severe drought were marked by high degrees of soil moisture deficit, a metric that describes how much moisture the soil contains compared to its normal saturation.
Since 2000, the average soil moisture deficit was twice as severe as any drought of the 1900s, and greater than it was during even the driest parts of the most severe megadroughts of the past 12 centuries, say the authors.
Studying the area from southern Montana to northern Mexico, and from the Pacific Ocean to the Rocky Mountains, the researchers discovered that megadroughts occurred repeatedly in the region from 800 to 1600. Williams said the finding indicates that dramatic shifts in water availability happened in the Southwest well before the effects of human-caused climate change became apparent in the 20th century.
Existing climate models have shown that the current drought would have been bad even without climate change, but not to the same extent. Human-caused climate change is responsible for about 42 percent of the soil moisture deficit since 2000, the paper found.
Climate change is a threat multiplier for heatwaves' desiccation of plants, leading to agricultural loss and wildfire.
The Nature Climate Change journal study is behind a paywall. The lead author, Park Williams, was interviewed on PBS ON February 15, 2022