The southwestern United States is having its worst megadrought in 1,200 years. New research suggests that this drought could persist for decades, as ongoing warming disrupts the region's vital rain cycles. Models suggest continued global temperature rises could keep the Southwest in a dry regime through at least 2100.
The Pacific Decadal Oscillation (PDO) typically brings alternating periods of aridity and wetness to the region. However, new analysis of millennia-old climate records suggests this pattern may be changing. Researchers discovered a similar event thousands of years ago, where warming forced the PDO out of rhythm, causing a millennia-long dry period.
Ancient lake sediment cores reveal that around 6,000 to 9,000 years ago, the region suffered a major dry spell. Winter precipitation feeding major rivers dropped by 20%. Climate models now align with these findings after incorporating ancient global vegetation shifts.
Extensive ancient plant growth across continents darkened Earth's surface. This increased solar absorption, warming the planet and triggered a long-lasting shift in North Pacific patterns, resembling the PDO's dry phase which lasted for thousands of years.
Planning for this Southwest drought as a new reality is essential for effective water management.