Anthropogenic megadrought

Human-driven climate warming worsens an otherwise moderate drought Historical documents from the Spanish Entrada on the northern frontier of New Spain (now the U.S. Southwest) include anecdotal evidence for unusual aridity in the late 16th century ( 1 ). However, a quantitative record of the 16th-century megadrought has only recently been obtained from hundreds of exactly dated and moisture-sensitive tree-ring chronologies developed across Canada, the United States, and Mexico. On page 314 of this issue, Williams et al. ( 2 ) provide a new assessment of proxy climate data from the U.S. Southwest. They determine that the 16th-century megadrought was the worst multidecadal drought episode in the Southwest over the past 1200 years, and that the second-worst event occurred from 2000 to 2018 over southwestern North America (SWNA) and may be ongoing. The study also pinpoints substantial anthropogenic (human) contribution to the severity of the current drought.