Cactus and Climate · May 2026
The Ocean Is Talking.
Is the Desert Listening?
The tropical Pacific has always set the rules for desert water.
Climate change is rewriting them.
Photo: Rebekah Blocker / Unsplash
The Pacific sets the rules.
The desert follows them.
El Niño and La Niña are opposite phases of ENSO — the El Niño-Southern Oscillation, driven by temperature swings in the tropical Pacific. Normally, trade winds push warm water westward across the equatorial Pacific, piling it up near Australia. When those winds weaken or reverse, that warm water sloshes back east, rewiring global weather patterns from the top of the atmosphere down. That’s El Niño. When sea surface temperatures in that band run cooler than normal, you get La Niña.
For the desert Southwest, no climate pattern matters more. La Niña raises the odds of below-average precipitation by more than 50% during the cool season — California, Nevada, Arizona, and Utah among the most consistently affected states. Five of the last six winters brought La Niña conditions.1
El Niño probability now sits at 82% for May–July 2026, rising to 96% through winter 2026–27.2 For the Southwest, a strong El Niño winter typically means above-average precipitation across Arizona, New Mexico, and Southern California.
winter 2026–27
La Niña conditions
precipitation under La Niña
El Niño and La Niña explained — NASA Scientific Visualization Studio
The ocean isn’t just a thermostat.
It’s a heat sink.
The ocean absorbs roughly 90% of the excess heat generated by rising greenhouse gas emissions.6 That’s why global sea surface temperatures jumped to record levels in 2023–24 and have remained near those records throughout 2025 and into 2026. The heat doesn’t stay put — it alters the very climate patterns the Southwest has long depended on to forecast its water future.
This past March made the argument in real time. A high-pressure system trapped heat from unusually warm Pacific waters and drove temperatures across the desert Southwest to historic levels — against the backdrop of the warmest winter on record and significant drought.5 Nationally, between March 16–23, over 1,500 daily high temperature records fell. 660 of them were all-time March records.
The river’s fate is written
in the ocean.
Despite originating in the landlocked Rockies, the Colorado’s water supply is readable from the ocean. A 2020 study by researchers at Utah State University, published in Communications Earth & Environment, found that severe water shortages on the Colorado can be forecast several years in advance — simply by tracking sea surface temperatures in three ocean regions: a cooling tropical Pacific, a warming North Pacific, and a warming southern tropical Atlantic.3
The paleoclimate record extends the stakes further. Research published in Paleoceanography and Paleoclimatology confirmed a dry period lasting roughly from 9,800 to 5,400 years ago — triggered by a warming Pacific and shrinking Arctic sea ice. The researchers found that the same ocean conditions driving that ancient aridification are now reasserting themselves, pushed this time by greenhouse gas emissions rather than orbital shifts.4
Some scientists now prefer aridification over drought for what’s unfolding in the Southwest, because drought implies something temporary. What the ocean record suggests looks less like a dry spell and more like a fundamental reset of baseline conditions.
A reprieve is possible.
A solution is not.
Drought is expected to persist across much of the West through mid-year.7 The summer will be hot and dry across the interior West regardless of El Niño, whose wetter effects on the Southwest won’t arrive until late fall at the earliest.
The one summer wildcard is the monsoon. Forecasters project a stronger-than-normal Southwest monsoon beginning as early as June.8 The intense heat already building may reinforce that signal, deepening the low-pressure system that draws monsoon moisture inland. But monsoon rain isn’t snowpack — it falls hard, drains fast, and often evaporates before it reaches a reservoir.
The real question is winter and whether El Niño, now projected at 96% probability through early 2027, delivers what the Pacific occasionally promises. One good wet season would be a reprieve. It wouldn’t be a solution.
SW monsoon projected
through mid-2026
winter 2026–27
“Protecting the ocean isn’t just a coastal concern. For anyone living in the desert Southwest, it’s a water issue.“
The ocean has always governed life in the desert Southwest. The Colorado River’s water budget is set in the Pacific. The monsoon’s strength is negotiated in the Gulf. The winter snowpack is delivered by storm tracks the ocean steers.
None of that is new. But the consequences of ignoring it are.
Sources
