Overview

• The study analyzed more than 500 climate model simulations to isolate the human fingerprint on the Pacific Decadal Oscillation.
• Researchers detected that mid-20th-century aerosol pollution drove a temporary wet phase before post-1980s aerosol declines and greenhouse gas increases pushed the PDO into a persistent drought-favoring mode.
• This prolonged negative PDO pattern has suppressed winter rainfall across the western United States, intensifying a two-decade megadrought and driving Lakes Mead and Powell to record lows.
• Geological records from roughly 6,000 years ago corroborate that high temperatures can lock the North Pacific into extended drought phases.
• Experts warn that the drought-inducing PDO phase is likely to persist for decades under continued warming, underscoring the need for aggressive emissions cuts and revamped water management.