Cooling the Pacific with a little salt? Scientists unveil a daring plan to tame Super El Niño

What if the next devastating El Niño could be weakened before it ever takes shape? 

A team of scientists believes it may be possible — not by cooling the entire planet, but by making clouds over the Pacific Ocean slightly brighter.

Using advanced climate simulations, researchers found that artificially increasing the reflectivity of marine clouds could cool ocean waters enough to suppress the formation of a powerful El Niño, potentially reducing the floods, droughts and heatwaves that ripple across the globe.

The proposal, however, also revives one of climate science's most contentious debates: should humans deliberately intervene in Earth's weather systems? 

The study, published in Science Advances, explores a form of geoengineering known as marine cloud brightening, a technique that involves spraying tiny sea salt particles into low-lying clouds over the ocean. These particles create a greater number of smaller water droplets, making the clouds whiter and more reflective. As brighter clouds bounce more sunlight back into space, the ocean surface below cools. 

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Unlike broader solar geoengineering proposals that aim to reduce global temperatures by reflecting sunlight across the planet, marine cloud brightening is designed to target specific regions. In this case, researchers focused on the tropical Pacific Ocean — the birthplace of El Niño. 

Using climate models, the team simulated how the technique would have affected previous major El Niño events. The results suggested that cooling the eastern Pacific at the right time could significantly weaken the warming that drives the phenomenon, reducing the likelihood of a "Super El Niño." 

Why El Niño matters 

El Niño is the warm phase of the naturally occurring El Niño-Southern Oscillation (ENSO), a climate pattern that periodically reshapes weather worldwide. 

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As trade winds weaken, warm water spreads eastward across the Pacific, disrupting atmospheric circulation. The consequences can be felt thousands of kilometres away, bringing drought to Australia and Southeast Asia, heavy rainfall to parts of the Americas, shifts in monsoon patterns, and a temporary rise in global temperatures. 

Scientists have warned that climate change could make extreme El Niño events more damaging, increasing the risks of crop failures, water shortages, destructive flooding and record-breaking heat. 

Nature offered an unexpected clue 

The research was inspired in part by an unusual natural experiment. Australia's devastating 2019-20 bushfires injected massive amounts of smoke particles into the atmosphere. Earlier studies suggested those aerosols may have contributed to the rare three-year La Niña event that followed by reflecting sunlight and cooling parts of the Pacific Ocean. 

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Researchers wanted to know whether a similar cooling effect could be produced intentionally — and in a controlled manner — using sea salt instead of wildfire smoke. 

Promise — and plenty of uncertainty 

Despite the encouraging model results, scientists emphasise that the proposal remains theoretical. 

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Marine cloud brightening has only been tested on a very limited scale, and many questions remain about how it could affect regional rainfall, marine ecosystems, atmospheric circulation and neighbouring countries. Altering cloud cover in one part of the world could have unintended consequences elsewhere. 

The idea also raises difficult political and ethical questions. Who gets to decide when to manipulate clouds? Who would be responsible if the intervention produced unexpected weather extremes in another region? And should humanity rely on geoengineering instead of accelerating efforts to reduce greenhouse gas emissions?