Seawater cloud brightening halves super El Niño warming
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- Marine cloud brightening over the eastern Pacific could prevent super El Niños, with each event estimated to cost the global economy trillions in lost growth.
- Jessica Wan at the University of California, San Diego led the modelling study, simulating cloud brightening against the 1997-1998 and 2015-2016 super El Niños.
- Nine months of seawater spraying would have nearly halved warming in the Niño 3.4 region — from 2°C or more to just over 1°C — and ended each El Niño by January rather than letting it run its natural course.
- A hypothetical mission would require an estimated 2,400 ships delivering spray volumes that exceed what current nozzle technology can produce.
- Mat Collins at the University of Exeter warned that real-world cloud feedback erodes low-level clouds, meaning the model likely underestimates how much aerosol injection would actually be needed.
- In both simulations, La Niña started earlier after El Niño subsided, a potential disaster for drought-prone regions like the Horn of Africa where strong La Niñas have historically contributed to famine.
- The research drew on Australia's 2019-2020 "black summer" bushfires, whose drifting smoke particles brightened clouds and prolonged a "triple dip" La Niña through three winters instead of one or two.
Why it matters: The study reframes geoengineering's appeal: short-term interventions aimed at disrupting individual climate events like El Niño sidestep the "termination shock" risk of permanent cooling schemes, yet a 2,400-ship deployment and unintended La Niña shifts reveal how far the technique remains from real-world viability.
