El this year Niño is shaping up to be one of them strongest on recordand is designed to create a climate of chaos around the world.
New research suggests there may be a way to mitigate some of the effects of future El Niños and global warming: reducing the sun.
El Niño develops naturally in the tropical Pacific every few years, caused by weak trade winds that push heat from the ocean toward the South American coast. This points to the possibility of higher-than-average global temperatures, as well as droughts in some areas, heavy rains and floods in others, and more hurricanes in the Pacific. Stacked on top of warming driven by fossil fuel burning, a severe El Niño could mean hundreds of billions in economic losses.
The new study says that solar energy deviations can cool the oceans and help control El Niño events before they become too strong, thereby preventing the worst effects.
“El Niño is one of these things where something happens in the tropical Pacific, and then it reprograms how the rest of the world’s atmosphere holds energy that year,” says Katherine Ricke, co-author of the study published Wednesday in the journal Science Advances and a climate scientist at UC San Diego and the Scripps Institution of Oceanography. “It’s the last pressure in the climate system.”
Ricke and his co-authors looked at using marine cloud brightening, or MCB, as a means of reducing sunlight in the Pacific. This technique involves spraying sea water on the sea clouds to increase the brightness of the clouds. Although some pilot projects and randomized controlled trials have tested the effectiveness of this approach, they have been on very small scales.
MCB is one of the few that are different methods of solar engineering intended to reflect sunlight back into space. Other methods, such as using birds to inject themselves aerosols in the stratosphereit can only work worldwide. But the MCB has the potential to be a regional cooling solution.
To counter the lack of MCB testing, the researchers looked at a recent natural phenomenon that simulated it: Australia’s devastating 2019-2020 bushfire season. More than 10,000 forest fires spread across the country, causing approx 1 million tons of smoke. That represents one of the largest inputs of smoke into the atmosphere that humans have seen with satellite technology.
Although the effects of this large amount of smoke were complex, preliminary research suggests that it helped cause the unusual triple dip. A girl—a different phase of El Niño—thanks in part to reflective particles in the smoke.
This event, Ricke says, enabled him and his colleagues to finally address a question they’d had for years about whether regional intervention could help reduce the stress events like El Niño put on the global climate system. The researchers built a model based on the MCB effects of Australian bushfires, and ran it against two different historical El Niño events to see the effects. The model showed that reducing the amount of sunlight reaching the surface of the Pacific would significantly reduce the intensity of these El Niño events and their impact on the world.
Geoengineering techniques have traditionally been considered a way to cool the entire planet, acting as a countermeasure to humanity’s use of fossil fuels—albeit a highly controversial one. New research suggests that some forms of geoengineering could be better used to target regional events, like El Niño. Doing so has the potential to avoid—or at least reduce the risk of—a combination of El Niño effects stacked on top of rising temperatures due to human activity.
“The idea of continuing geoengineering indefinitely gives many people pause—we all understand that cooperation on that scale would be very difficult in the world we live in,” Ricke says. “This is a completely different way of thinking about geoengineering.”
