New Study Says Marine Cloud Brightening Could Weaken El Niño. The Science Is Still Early.

Researchers at UC San Diego and the Scripps Institution of Oceanography published a study in Science Advances arguing that a solar geoengineering technique called marine cloud brightening (MCB) could reduce the severity of El Niño events. The lead climate scientist on the paper, Katherine Ricke, described El Niño to Wired as "an ultimate pressure point in the climate system" — one that reshapes global atmospheric energy patterns for an entire year.

El Niño forms when trade winds in the tropical Pacific weaken, pushing accumulated ocean heat toward South America's coast. The result: higher global average temperatures, droughts in some regions, floods and intense rainfall in others, and more frequent Pacific cyclones. Stack that on top of baseline warming from fossil fuel combustion and a strong El Niño can cost hundreds of billions of dollars in economic damage.

The MCB approach would spray fine seawater particles into low-lying marine clouds over the Pacific, increasing those clouds' reflectivity and bouncing more sunlight back into space. Unlike stratospheric aerosol injection — which requires aircraft to seed the upper atmosphere and operates globally — MCB is designed as a regional intervention. That distinction matters. A regional tool, in theory, could be targeted and adjusted. A global one cannot.

Because real-world MCB trials have only been conducted at very small scales, Ricke and her coauthors turned to a natural analogue: the catastrophic 2019–2020 Australian bushfire season. Over 10,000 fires burned across the continent, injecting close to 1 million metric tons of smoke into the atmosphere — one of the largest such events recorded by satellite.

Previous research had already linked that smoke, which included reflective particles, to a rare triple-dip La Niña, the opposite climate phase from El Niño. Ricke's team built a model based on that real-world data to estimate what a deliberate, sustained MCB effort over the Pacific might do to El Niño dynamics. Their conclusion: targeted solar dimming could cool enough ocean surface area to reduce El Niño intensity before it peaks.

Using a wildfire disaster as a proxy for a deliberate geoengineering program is methodologically creative. It's also a significant inferential leap. Smoke from bushfires is chemically complex, geographically diffuse, and temporally uncontrolled. Engineered MCB would need to be precise, sustained, and reversible. Whether those two scenarios are actually comparable enough to validate the model is a question the researchers acknowledge but cannot fully resolve without larger trials.

The strongest objection to this line of research is not scientific — it's political and logistical. Who decides when and where to dim the sun over the Pacific? MCB applied to benefit drought-prone Australia or drought-prone Central America might simultaneously reduce monsoon rainfall somewhere else. Regional interventions in a globally connected atmosphere do not stay regional.

Critics of solar geoengineering research — and there are serious scientists among them — argue that even studying these techniques creates a "moral hazard": governments and industries use the existence of a potential technological fix as a reason to delay cutting emissions. That concern is worth taking seriously. A model showing MCB could moderate El Niño is a long way from a deployable system, and framing it as a near-term solution risks misdirecting both attention and funding.

Ricke's framing, at least as presented in the Wired coverage, stays appropriately cautious. The paper does not claim MCB is ready for deployment. It claims regional interventions can affect global climate patterns — which is itself a scientifically significant finding, separate from any policy question about whether they should.

The study advances a specific, narrow scientific question: can regional cooling influence a planetary-scale climate oscillation? The answer, according to this model, appears to be yes. That's useful to know.

What it does not answer is how MCB would be governed, funded, or coordinated internationally. It does not answer how to handle unintended regional consequences. It does not resolve the moral hazard debate. And it does not replace the foundational physics: El Niño events are becoming more economically damaging partly because background temperatures from greenhouse gas accumulation are rising. MCB does not address that root cause.

The next concrete test of the technique's viability will come from larger-scale controlled trials, which as of July 2026 have not yet been conducted. Without that data, models built on wildfire analogues remain exactly that — models.