Not since Charlemagne was crowned Holy Roman Emperor in 800 A.D. has the American West been so dry. A recent study in Nature Climate Change found the period 2000 to 2021 was the driest 22 years in more than a millennium, attributing a fifth of that anomaly to human-caused climate change. The megadrought has meant more fires, reduced agricultural productivity, and reduced hydropower generation. Last summer, the United States’ two largest reservoirs — Lake Mead and Lake Powell — reached their lowest levels ever, triggering unprecedented cuts in water allocations to Arizona, Nevada, and Mexico.