Scientists Model Sun-Dimming to Tame a Potential Super El Niño

A team of climate scientists from the Scripps Institution of Oceanography and UC San Diego’s School of Global Policy and Strategy published a proof-of-concept analysis in *Science Advances* (Wednesday, 2026). Using a “natural experiment” that isolated the cloud-brightening effect of smoke from Australia’s 2019-2020 “Black Summer” bushfires, the researchers ran climate-model simulations of a comparable marine cloud brightening (MCB) deployment ahead of two historically strong El Niño events (1997 and 2015). The models indicate that targeted MCB could weaken El Niño’s heat, fire and precipitation extremes and amplify the cooling and drying associated with a subsequent La Niña by roughly 40 %, especially when applied early in the El Niño cycle.

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El Niño is a natural Pacific-Ocean oscillation that raises global temperatures and reshapes weather patterns, producing droughts, floods and cyclones worldwide. Climate change has lifted the planet’s baseline temperature, pushing recent El Niño episodes into more extreme territory. The National Oceanic and Atmospheric Administration (NOAA) has warned of a 63 % chance that the 2026-2027 El Niño will exceed a 2 °C temperature increase, a threshold often labeled a “super” El Niño. Such an event could generate hundreds of billions of dollars in economic losses and severe humanitarian impacts.

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• Simulated MCB before the 1997 and 2015 El Niños reduced peak sea-surface-temperature anomalies by about 40 %.

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• The same simulations showed a 40 % boost in La Niña-type cooling and drying following the MCB intervention.

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• Earlier deployment in the El Niño timeline produced proportionally larger mitigation effects.

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Lead author Katherine “Kate” Ricke emphasized that the study does not advocate immediate deployment. She described the work as a “proof of concept” intended to determine whether MCB merits further investigation. Ricke framed MCB as a temporary, targeted tool for “super” El Niño events that cause widespread damage, noting that the approach would avoid locking the world into a permanent geoengineering program. She also highlighted the need to weigh regional trade-offs, such as the benefit of reduced heat against potential disruptions to areas that rely on El Niño-driven rainfall.

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Atmospheric scientists not involved in the study voiced substantial reservations. James Haywood, professor of atmospheric science at the University of Exeter, warned of “many, many unanswered questions and uncertainties” about controlling MCB’s cooling impact and the risk of triggering an overly strong La Niña. David Keith, professor of geophysical sciences at the University of Chicago, noted that existing MCB sprayers operate at rates at least a factor of one hundred too small for practical climate mitigation, and that the necessary technology “simply doesn’t exist.” Both experts stressed ethical dilemmas, including governance of a global solar-dimming tool and the possibility that geoengineering could distract from emissions reductions.

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• Technical feasibility: Current spray-rate capabilities fall far short of model requirements, creating a gap between simulation and real-world deployment.

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• Unintended climate effects: Models suggest a potential for a “mega” La Niña, but the magnitude and regional impacts remain uncertain.

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• Termination shock: Some analysts argue that abruptly ending MCB could cause a rapid temperature rebound, yet empirical evidence is lacking.

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• Absence of field trials: Researchers avoided real-world experiments due to fears of “disastrous unintended consequences,” leaving the concept untested outside of computer models.

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• “it’s not something that you’re locking yourself into.” — Kate Ricke, climate scientist, Scripps Institution of Oceanography

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• “This is just a proof of concept … the only thing we’ve shown is that it’s worth further study,” — Kate Ricke

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• “You have to think very carefully about trade-offs,” — Kate Ricke

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• “is probably best to think about for now in terms of super El Niños, where most people, most places are losers and really extreme, damaging events are most possible,” — Kate Ricke

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• “many, many unanswered questions and uncertainties as to the viability of marine cloud brightening” — James Haywood, professor of atmospheric science, University of Exeter

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• “Almost two decades after research started, marine cloud brightening sprayers have spray rates… that are at least factor of a hundred too small for practical use,” — David Keith, professor of geophysical sciences, University of Chicago

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