The Southwest is in a megadrought, one of the world’s leading climate hydrologists has concluded following his most extensive study of climactic conditions in the West.
A. Park Williams is a climate hydrologist at UCLA, having earned his Ph.D. in 2009 from the University of California, Santa Barbara. He was a postdoctoral researcher at UC-Santa Barbara and Los Alamos National Laboratory, after which he undertook research at the Lamont-Doherty Earth Observatory. From 2015 until 2018 he taught at Columbia University. He has authored or co-authored of over 20 published scientific treatises.
Having done extensive surveys of climate and weather change over differing spans of time, Williams more recently dug into the quintessence at the heart of the global warming debate, considering whether the drying of the soil that accompanies the gradual heating of the planet that has been observed and confirmed over the last 35 years is attributable to human activity or is a feature of other global cycles independent of mankind.
While there are individuals and groups contesting the concept of global warming, reliable scientific data indicates the phenomenon is both real and quantifiable. According to the National Aeronautics and Space Administration, “The global average surface temperature rose 0.6 to 0.9 degrees Celsius (1.1 to 1.6° Fahrenheit) between 1906 and 2005, and the rate of temperature increase has nearly doubled in the last 50 years.”
Williams utilized 29 scientific frameworks to create an overarching model of the planet involving no human-caused warming, which he compared with actual weather and climate data to hypothesize whether the extreme weather events recently observed were caused by climate change.
Along the way, he made two rather grave findings. The megadrought the West, and particularly California, is involved in is the worst in at least 1,200 years, surpassing what was previously considered to be the most prolonged drought period in the 1500s. Moreover, his model demonstrated, human-caused warming is the basis for no less than 42 percent of the current drought condition.
In 2002, the Southwest, already caught in a drought, experienced what was reckoned to be the driest year ever recorded for the entire region. In the years since, overall precipitation in the Southwest has remained scattered and scarce, such that the region is in what the scientific community recognizes as a megadrought. In 2019, there seemed to be a respite in that state of affairs, as California and most of the rest of the Southwest experienced what is considered to be in keeping with the traditional pattern of rain and snowfall. But with 2020, the dearth of rain resumed. Then in 2021, the conditions of 2002 were virtually replicated, qualifying the 22-year-long megadrought as the driest extended period known, that is going back to the point where such phenomenon can be measured by the tools available today, to around the Year 800.
Williams used tree rings and other indicators in his analysis, from which he was able to extrapolate soil moisture levels on a year-to-year basis going back roughly 1,200 years.
“A previous reconstruction back to 800 CE indicated that the 2000–2018 soil moisture deficit in southwestern North America was exceeded during one megadrought in the late-1500s. Here, we show that after exceptional drought severity in 2021, ~19% of which is attributable to anthropogenic climate trends, 2000–2021 was the driest 22-year period since at least 800,” Williams and his co-authors Benjamin I. Cook and Jason E. Smerdon wrote in the study, titled Rapid Intensification of the Emerging Southwestern North American Megadrought in 2020–2021. “Southwestern North America has been experiencing lower than average precipitation and higher temperatures since 2000. This emerging megadrought, spanning 2000-2001, has been the driest 22-year period since the year 800 and 19 percent of the drought severity in 2021 can be attributed to climate change. This drought will very likely persist through 2022, matching the duration of the late-1500s megadrought.”
Williams went beyond the 19 percent figure for human contribution to the 2021 drought conditions, stating that 42 percent of the current megadrought can be laid at the feet of human-caused climate change. It is through climate change that the Southwest is becoming ever drier, Williams said, and he predicted that what is already approaching a worst-case scenario might grow worse. He said with the deterioration of the Southwest’s ecology as a consequence of the megadrought, people will need to expand their conception of how bad things will get.
“Western North America has seen near-persistent drought since the year 2000,” Williams said. “We used climate observations, tree-ring records, land-surface modeling, and climate model simulations to find that human-caused warming put an otherwise moderate drought onto a megadrought trajectory in the first two decades of the 21st Century. Tree rings tell us that natural climate variability will continue to cause wild swings in western North American water availability. Climate models project that over the long term, drying baseline conditions will make it increasingly easy to slide into severe drought and increasingly difficult to emerge from severe drought.”
Williams’ assessment is more pessimistic now than it was previously. In 2015 he did not use the term megadrought, rather characterizing what he saw at that time as a typical drought within the context of rising temperatures globally.
“We find that this drought, like any drought, is primarily caused by natural climate variability,” he said in September 2015. “But the drought is worse because of global warming. Warming causes the atmosphere’s ability to take water out of ecosystems to go up. The last four years of drought in California can be blamed about 15 percent on human-induced global warming, and the other 85 percent is due to natural variability.”
Nevertheless, in September 2015, Williams was relatively confident things would bounce back, saying that regions tend to display “low-frequency variability in their rainfall, meaning that if it’s wet, it’s generally wet for a decade or more. If it’s dry, it’s usually dry for a decade or more. Now, the Southwest may have just finished what was a 16-year dry period, where everybody in the Southwest was thinking, “Oh my God, climate change is awful. It’s made it so dry and hot here.” But if we switch into a more El Niño type of climate for the next several years, then the southwest is going to get very wet, and suddenly there’s going to be a lot of water that was not available before.”
Nearly six-and-a-half years and several surveys of the climate later, Williams is less sanguine.
Williams addressed the challenge of being a harbinger of bad news derived through his scientific endeavors in a circumstance in which a large segment of the public is, by its social, economic and political orientation, disinclined to hear what he has to report.
“As more and more people have learned about global warming, the issue has become increasingly politicized,” Williams said. “It’s very hard to be immune to that. It is almost as if you can accurately predict somebody’s opinion about global warming based purely on which political party they align with. And that’s too bad, because it’s alienating many of us. The research is obviously very important, and we need a lot of people working on it, but it’s becoming increasingly difficult to do the research, because the political situation has made it tougher to be funded. There are people in government who don’t want to see this research done, and they have actively eliminated funding from us. They even take pride in cutting earth science budgets. It’s something to brag about. Unfortunately, it’s borderline corruption to do that.”
-Mark Gutglueck