The megadrought that has been devastating the southwestern United States and parts of Mexico over the last two decades is the worst the region has seen in at least 1,200 years, according to a study released Monday.
Researchers with Nature Climate Change analyzed tree ring patterns, which delineate soil moisture levels over periods of time, to conclude that the current megadrought is worse than one that hit the region in the late 1500s and is the most severe since one in 800 AD.
The study, which analyzed a region stretching from southern Montana to northern Mexico and from the Pacific Ocean to the Rocky Mountains, found that human-caused global heating accounts for more than 40% of the severity of the dry spell.