A new study published in the journal Science Advances suggests that dimming the sun could mitigate some of the most devastating impacts of El Niño. The research, led by Katherine Ricke at the University of California San Diego and Scripps Institution of Oceanography, proposes using a technique called marine cloud brightening (MCB) to selectively cool the Pacific Ocean and moderate the intensity of El Niño events before they become too strong.
El Niño is a natural climate phenomenon that develops every few years in the tropical Pacific, caused by weakened trade winds that push ocean heat toward the coast of South America. It tilts the odds toward above-average global temperatures, droughts in some regions, intense rains and floods in others, and more cyclones in the Pacific. When piled on top of warming from fossil fuels, a strong El Niño can cause hundreds of billions in economic losses.
A new frontier for regional solar geoengineering
Marine cloud brightening works by spraying seawater into marine clouds to enhance their reflectivity, thereby deflecting some sunlight back into space. Unlike other solar geoengineering techniques such as stratospheric aerosol injection which have global effects, MCB can be applied regionally. This would allow direct intervention in the Pacific area where El Niño forms, reducing the risk of unintended consequences on a planetary scale.
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The researchers modeled the effect of MCB using a natural event that mimicked it: the 2019–2020 Australian bushfire season. Over 10,000 fires produced nearly 1 million metric tons of smoke, triggering a rare triple-dip La Niña (the opposite phase of El Niño) thanks to reflective particles in soot. This provided a model to test MCB's efficacy against two historical El Niño events. The results showed that reducing sunlight reaching the Pacific surface would have significantly lowered the magnitude of those events and their global impact.
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Political risks and scientific unknowns of climate intervention
Despite the scientific promise, practical implementation of MCB raises serious concerns. Andrew Dessler, professor of atmospheric science at Texas A&M University, calls the study's thesis reasonable but warns that executing such an intervention would be a political nightmare, with potential for conflict if something goes wrong. Climate models are imperfect, and there is a possibility of creating an unpredictable problem worse than the one intended to solve. Ricke herself acknowledges that much needs to be understood from models before trying in the real world, but stresses that this research is crucial for a future where humanity fails to address fossil fuel pollution.
Source: https://www.wired.com/story/dimming-the-sun-would-lower-risks-of-el-nino
