A super El Niño could heighten the risk of extreme weather events in fall and winter 2026. Warming ocean temperatures in the equatorial Pacific Ocean likely foreshadow potential heavy flooding in the U.S. and droughts across parts of Africa and Asia; as the world braces for this El Niño impact, scientists are busy contemplating solutions to dampen the effects of future El Niño events — one controversial plan, marine cloud brightening, stands at the forefront.
A new study published in Science Advances has explored the possible benefits of marine cloud brightening (MCB), a geoengineering approach that would involve spraying tiny sea salt particles into the air to brighten clouds. While the viability of MCB is questioned, one “natural experiment” has provided much-needed insight: A series of Australian bushfires in 2019 and 2020 naturally brightened clouds over the South Pacific, giving scientists a chance to see how MCB could theoretically tackle a super El Niño.
“It is my hope that this study catalyzes progress for research and starts conversations on the possibility of targeted, short-term approaches as part of the climate risk mitigation portfolio,” study first author Jessica Wan, currently a postdoctoral research fellow at the University of Chicago, told Discover.
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Counteracting a Super El Niño
The goal of MCB is to brighten clouds by spraying microscopic sea salt aerosols into the atmosphere, causing the clouds to reflect more sunlight and reducing the heat absorbed by the water below.
While many scientists see MCB as a promising opportunity to weaken El Niño events, some say it could trigger unpredictable effects on global climate, according to a statement about the new study.
Wan says many geoengineering concepts tend to focus on sustained deployment to cool the planet for decades, but these long-term strategies could have unintended consequences.
“If such a large-scale deployment were to suddenly cease (technological failures, political conflict, global pandemic, etc.), there could be huge warming rebound effects worse than the rate of global warming itself,” Wan told Discover.
The new study instead proposes implementing MCB for a shorter period (up to 9 months), which could deliver benefits without incurring the risks of long-term deployment, Wan said.
A Natural Experiment
The new study used the 2019 and 2020 Australian bushfire seasons (often referred to as the "Black Summer") to show that MCB could be an effective way to reduce El Niño’s impact. The aerosols emitted by these fires were transported across the South Pacific and brightened stratocumulus clouds in the Southeast Subtropical Pacific region; this, in turn, led to a La Niña effect from 2020 to 2023 — cooling ocean temperatures, the opposite of what El Niño does.
Knowing that the Australian bushfires cooled ocean temperatures in the Pacific, acting as a natural analog to MCB, researchers simulated what could have happened if a similar event had occurred before a very strong El Niño, which is when the surface waters of the Pacific Ocean around the equator are more than 2 degrees C (3.6 degrees F) warmer than average, according to the Columbia Climate School.
Using a seasonal forecasting model, they tested how MCB would have affected two strong El Niño events: the 1997 to 1998 El Niño and the 2015 to2016 El Niño. They found with this model that MCB would have weakened both events, and that if deployed over the central Pacific Ocean, MCB could increase the cooling and drying effects associated with La Niña by more than 40 percent.
The researchers suggest, though, that aerosols would need to be implemented after the spring predictability barrier, a period from March through May when it becomes difficult to accurately predict El Niño events due to seasonal changes in climate.
Evaluating Marine Cloud Brightening
Although short-term MCB deployment could offset El Niño, many questions remain about the concept.
The process could exacerbate climate impacts in regions outside its deployment range and disrupt normal climate patterns, causing La Niña events to start earlier and become stronger.
Much more research is needed on MCB before it can be reliably implemented, Wan said.
“The best nozzles to generate the correct size and rate of sea spray for MCB are two orders of magnitude below what is required to have a substantial climate effect, and the energy requirements are prohibitively high,” Wan told Discover. “We would need a technological breakthrough to move forward with MCB via sea salt, or start considering alternative materials to brighten clouds that might have lower engineering barriers.”
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from the Columbia Climate School: You Asked: What Exactly Is a ‘Super’ El Niño?
- This article references information from a study published in Science Advances: Targeted marine cloud brightening weakens subsequent El Niño
