Relief from drought in southwest U.S. likely isn't coming

The Southwest United States is currently facing its most severe mega drought in over 1,200 years, and a study from the University of Texas at Austin suggests that this dry spell could stretch at least until the century's end. While some scientists are holding out hope that natural climate shifts might bring some relief, new findings indicate that ongoing warming could actually throw critical climate cycles that bring rain to the region out of whack.

One key player in this scenario is the Pacific Decadal Oscillation (PDO), an important ocean climate cycle that swings between drought and wet spells every 20 to 30 years. However, a recent study published in Nature Geoscience looked into the climate history of the area and hinted that this cycle might be changing. Researchers discovered that during a warming phase about 6,000 years ago, the PDO lost its rhythm, leading to an extended drought. The current warming trend linked to climate change seems to echo these past disruptions, as shown by comparisons of ancient climate data with future forecasts.

The research was led by doctoral student Victoria Todd and Associate Professor Timothy Shanahan from UT's Jackson School of Geosciences. They examined lake sediment cores from the Rocky Mountains, which provide insights into ancient climate conditions. Todd found evidence of a significant drought that occurred between 6,000 and 9,000 years ago, which was more intense than previously believed, resulting in a 20% drop in precipitation, particularly impacting winter rains that feed rivers like the Colorado.

To gain a clearer picture of the drought, Todd created a model to differentiate between the effects of summer and winter moisture. The initial climate models didn’t quite capture the severity of the historical drought until her co-authors tweaked them to factor in changes in global vegetation. This adjustment pointed to a drier Southwest, aligning perfectly with Todd's findings.

Increased plant growth in areas like North Africa, Canada, and Eurasia has absorbed more sunlight, contributing to global warming and causing lasting changes in oceanic and atmospheric conditions that resemble the current megadrought. This phase of drought can persist for quite some time.

Reference

by University of Texas at Austin Relief from drought in southwest U.S. likely isn't coming, according to new research

Phys.org Available at- https://phys.org/news/2025-07-relief-drought-southwest-isnt.html

(Assessed: 17th July 2025)