We're locked into warming already, and so the question is how to reduce the worst impacts.
In the long human struggle to live within the rhythms of a changing planet, scientists at the University of Chicago have proposed something audacious: that we might learn to quiet El Niño itself, not by altering the emissions that warm the world, but by teaching clouds to reflect more sunlight at precisely the right moment over the Pacific. The inspiration came not from a laboratory but from catastrophe — the smoke of Australia's great fires accidentally cooled the ocean and bought the world a reprieve, and researchers now ask whether that accident can be made intentional. The proposal is not a solution so much as a question about what responsibilities we bear when the tools to intervene exist, however imperfectly, alongside the suffering that inaction guarantees.
- El Niño events already cost the world trillions of dollars and countless lives through floods, droughts, and heat waves — and the next major cycle looms without any reliable means of prevention.
- A study published by University of Chicago researchers proposes marine cloud brightening over the equatorial Pacific as a targeted intervention capable of reversing most of El Niño's temperature and precipitation effects if deployed between June and February.
- The technology required does not yet exist at scale — perfected nozzles, 2,400 ships operating simultaneously for months — making the gap between the computer model and the real ocean vast and sobering.
- Models also reveal a troubling trade-off: suppressing El Niño could warm parts of Europe and Asia, and repeated interventions over decades might trigger cascading effects in ocean and atmospheric systems that remain poorly understood.
- Lead researcher Jessica Wan argues that refusing to study such interventions is itself a moral failure — not a replacement for emissions cuts, but a parallel responsibility given how much warming is already locked in.
Scientists at the University of Chicago have published research suggesting that a future El Niño — with its attendant floods, droughts, and heat waves — might be interrupted before it fully takes hold, using a method as counterintuitive as it is ambitious: artificially brightening clouds over the Pacific Ocean at precisely the right moment.
The idea traces back to an accident. During Australia's catastrophic bushfires of 2019 and 2020, smoke particles drifted into the atmosphere and made clouds more reflective, inadvertently triggering a multi-year La Niña cooling phase by bouncing solar energy back into space. Researchers asked whether ships equipped with specialized nozzles could engineer the same effect deliberately, spraying sea salt particles into clouds over a carefully chosen equatorial zone.
Computer simulations of the powerful El Niño events of 1997–1998 and 2015–2016 produced striking results. When brightening began in June and continued through February, the models showed most of El Niño's temperature and precipitation effects reversed — regions that would have flooded dried out, global temperatures were substantially blunted, and the droughts and disruptions that ripple across continents were significantly reduced.
The practical obstacles, however, are formidable. The nozzle technology does not yet exist at the required scale, and researchers estimate that even a perfected system would demand roughly 2,400 ships operating simultaneously for months — a fleet larger than most national navies. Beyond the engineering challenge lies a deeper uncertainty: the models also revealed that suppressing El Niño could warm parts of Europe and Asia, and no one yet understands what repeated interventions might do to ocean and atmospheric systems over decades.
Lead researcher Jessica Wan acknowledges these limits but insists the inquiry itself is necessary. She rejects the argument that geoengineering gives polluters cover to keep emitting, framing the question instead as one of parallel responsibility: emissions cuts remain essential, but given how much warming is already locked in, she argues that failing to research every available tool would itself be a form of negligence.
Scientists at the University of Chicago have published research suggesting that the next major El Niño event—the kind that brings devastating heat waves, floods, and droughts across the globe—might be interrupted before it fully takes hold. The mechanism they propose is counterintuitive: artificially brighten clouds over the Pacific Ocean at precisely the right moment, and you could neutralize one of Earth's most influential weather patterns.
The idea emerged from an unexpected source. During Australia's catastrophic bushfires in 2019 and 2020, smoke particles rose into the atmosphere and altered cloud properties, making them more reflective. This natural accident inadvertently triggered a multi-year cooling phase in the Pacific—a La Niña—by bouncing more of the sun's energy back into space. Researchers wondered whether they could engineer the same effect deliberately, using ships equipped with nozzles to spray sea salt particles into clouds over a carefully chosen zone in the equatorial Pacific.
Using sophisticated computer models, the team simulated what would have happened if they'd deployed this intervention during the powerful El Niño events of 1997–1998 and 2015–2016. The results were striking. When the brightening began in June and continued through the following February, the models showed the intervention reversed most of El Niño's temperature and precipitation effects. Regions that would have warmed cooled instead. Areas that would have flooded dried out. The global impacts—the droughts in Australia, the wetter winters in East Africa, the elevated global temperatures—were substantially blunted.
But the practical obstacles are formidable. The nozzle technology needed to spray sea salt at the required scale doesn't yet exist. Even with a perfected design, researchers estimate it would take roughly 2,400 ships operating simultaneously to generate enough impact. That's a fleet larger than most national navies, deployed continuously for months. The engineering alone represents a monumental challenge.
Beyond the hardware problem lies a deeper concern: unintended consequences. The models revealed that while reversing El Niño conditions would help many regions, it would warm parts of Europe and Asia. And no one yet knows what happens if you suppress El Niño repeatedly over years or decades—whether the repeated interventions might trigger cascading effects in ocean and atmospheric systems that scientists don't yet understand.
Jessica Wan, the postdoctoral researcher who led the study, acknowledges these limitations but argues the research itself is necessary. She rejects the common criticism that geoengineering offers polluters an excuse to keep emitting carbon. "We're locked into warming already," she said. The question, as she frames it, isn't whether to pursue emissions cuts—that remains essential—but whether to simultaneously develop tools that could reduce the worst impacts while the world makes that long, difficult transition. In her view, not researching such interventions would be irresponsible given the stakes.
Citações Notáveis
These shorter timescales of interventions could be a very powerful way that geoengineering enters this portfolio of responses to climate change.— Jessica Wan, postdoctoral researcher at the University of Chicago
The reason people would ever care about this is not temperature in a box in the Pacific, but how the impacts translate over land.— Jessica Wan
A Conversa do Hearth Outra perspectiva sobre a história
So the idea is that you could essentially pause an El Niño before it happens?
Not pause it exactly—more like dampen it. The ocean warming that drives El Niño would still occur, but by brightening clouds above it, you'd reflect enough solar energy back to space to reduce the temperature anomaly and its downstream effects.
And this came from watching smoke do it accidentally?
Yes. The Australian bushfires created this natural experiment. Smoke particles seeded the clouds, made them more reflective, and that helped trigger a cooling phase. It showed the mechanism could work.
What's the real barrier—the ships, or something else?
The ships are the obvious one, but honestly the deeper question is what we don't know. If you do this every few years, what happens to ocean currents? To monsoon patterns? We'd be experimenting on a planetary system.
So it's not that it won't work. It's that we don't know what else it might break.
Exactly. And some regions benefit while others get warmed instead. It's not a clean solution. It's a tool with trade-offs we'd have to live with.