The megadrought is coming. Scientists appear to be united in their assessment that changing climate patterns will hit the Southwest hard — including Southern California. On July 24th, Columbia University cientists detailed their findings in the academic journal Science Advances. And it is a sobering report: due to global warming, the American Southwest is going to experience a megadrought, like the one that caused most native Americans to leave the Southwest from the 800s to the 1400s.
During that period in history, the Southwest experienced numerous decade-long droughts that collasped most of the native civilizations in that part of the continent. The researchers claim that they have successfully developed “a comprehensive theory for why there were megadroughts in the American Southwest, and why they stopped. They reconstructed aquatic and climate data and sea-surface temperatures spanning the past 2,000 years. In so doing, they were able to identify 14 droughts lasting more than a decade, all of which took place before 1600. The scientists found three key factors:
- Positive radiative forcing — that is, a rise in the amount of energy that Earth absorbed from the sun.
- Warming in the North Atlantic Ocean.
- Severe and frequent La Niña events — unusually cool waters across the equatorial Pacific Ocean that trigger floods, heat waves, blizzards and hurricanes worldwide.
During medieval times in the American Southwest, a drop in volcanic activity — which would have spewed out ash to block the sun — along with an increase in solar activity such as solar flares likely increased the amount of heat the area absorbed (positive radiative forcing). The overall rise in heat would have dried out the area. At the same time, warmer Atlantic conditions combined with strong, frequent La Niñas could have reduced rainfall. As a result of the earth’s heating, the Columbia scientists expect a return of the decade-long droughts. The Southwest will change in ways that none of its residents desire.
In the same week as the megadrought paper was released, a Santa Barbara professor released her findings after studying water wells in the U.S. Her conclusions were similarly troubling: wells across the US have generally been getting deeper since 1950. This trend toward deeper wells showed up across the majority of areas that were included in the database. Deeper wells and depleting groundwater may be related, but it’s not necessarily that simple. There are other reasons why people might drill deeper wells—to avoid contamination in shallower wells, for example, or because improved technology or laxer legislation makes it possible where it wasn’t before.