The American Southwest is being plagued by what scientists call the worst megadrought in 1200 years, and new research suggests there’s likely no relief coming anytime soon.
New research from the University of Texas at Austin predicts it will continue until the end of the century—or even far beyond. While some researchers believe natural climate cycles could eventually bring the needed rain, the study suggests that global warming may be disrupting one of the region’s most vital climate rhythms: the Pacific Decadal Oscillation (PDO).
Similar to El Niño and La Niña, the PDO typically shifts every 20 to 30 years between wet and dry phases. However, researchers now believe that consistent warming is disrupting this natural cycle, causing the Southwest to experience an extended period of drought.
The research was led by doctoral student Victoria Todd and Associate Professor Timothy Shanahan at UT Austin’s Jackson School of Geosciences. Todd’s analysis of ancient lake sediments from the Rocky Mountains revealed a prolonged drought between 6,000 and 9,000 years ago, linked to the last significant warming of the Northern Hemisphere. Her findings showed that rainfall dropped by about 20 percent due to a decline in winter precipitation, a critical seasonal rain that feeds major rivers such as the Colorado.
“This is a drought related to the winter precipitation collapse,” Todd said in a statement. “Then the question is, ‘What causes the precipitation to change?’”
“That’s where the PDO comes in,” Todd added.
To investigate further, researchers compared ancient climate data with simulations of both past and future warming. When they adjusted their models to account for vegetation shifts — such as the greener landscapes that once covered North Africa, Canada, and Eurasia — they found these changes darkened Earth’s surface, absorbing more sunlight and increasing global temperatures. This warming appeared to disrupt oceanic and atmospheric patterns in the North Pacific, mirroring the drought phase of the PDO.
Unlike the typical cycle, however, this megadrought lasted thousands of years.
The team reviewed current climate projections in collaboration with the University of Colorado to determine whether a similar scenario could occur today. Their model showed a long-term North Pacific response, with a reduction in winter precipitation extending through at least 2100.
“If global temperatures keep rising, our models suggest the Southwest could remain in a drought-dominated regime through at least 2100,” Shanahan said, although such conditions could persist for much longer, possibly even centuries.
This spells trouble for the region’s water resources, particularly the Colorado River, which supplies water to nearly 40 million people and has already seen decades of drought.
“Many people still expect the Colorado River to bounce back,” Shanahan added. “But our findings suggest it may not. Water managers need to start planning for the possibility that this drought isn’t just a rough patch—it could be the new reality.”
Todd and the team’s new paper, “North Pacific ocean–atmosphere responses to Holocene and future warming drive Southwest US drought,” appeared in Nature Geoscience on July 9, 2025.
Chrissy Newton is a PR professional and founder of VOCAB Communications. She currently appears on The Discovery Channel and Max and hosts the Rebelliously Curious podcast, which can be found on YouTube and on all audio podcast streaming platforms. Follow her on X: @ChrissyNewton, Instagram: @BeingChrissyNewton, and chrissynewton.com.