Dimming the Sun Could Reduce El Niño Risks, Study Finds
A new study suggests that marine cloud brightening, a form of solar geoengineering, could weaken El Niño events and their global impacts, but experts warn of political and technical challenges.
This year's El Niño is shaping up to be one of the strongest on record, bringing chaotic weather worldwide. A study published Wednesday in Science Advances by researchers from UC San Diego and the Scripps Institution of Oceanography proposes that dimming the sun through marine cloud brightening (MCB) could mitigate some of El Niño's effects.
El Niño occurs naturally every few years in the tropical Pacific when weakened trade winds push warm water toward South America, raising global temperatures, causing droughts, floods, and more Pacific cyclones. Combined with human-induced warming from fossil fuels, a strong El Niño can lead to hundreds of billions in economic losses.
MCB involves spraying seawater into marine clouds to increase their reflectivity. Since large-scale experiments are lacking, the researchers used the 2019–2020 Australian bushfires as a natural analogue. Those fires produced nearly 1 million metric tons of smoke, which previous research linked to a rare triple-dip La Niña—the opposite of El Niño.
Modeling the smoke's MCB-like effects against two historical El Niño events showed that reducing sunlight reaching the Pacific surface would have significantly lessened the magnitude and global impact of those events.
Lead author Katherine Ricke emphasized that this approach rethinks geoengineering: instead of global cooling, it targets regional events like El Niño. However, Texas A&M atmospheric scientist Andrew Dessler called the idea politically risky, noting that unintended consequences could create problems worse than those solved. Ricke acknowledged the need for more modeling before real-world application but argued the research is vital if fossil fuel emissions continue unchecked.
