Short-term geoengineering strategies, like enhancing cloud brightness over the eastern Pacific, have the potential to mitigate El Niño’s impacts and safeguard the global economy, potentially saving trillions of dollars. However, these interventions may disrupt natural cycles, leading to uneven consequences.

El Niño is a climate phenomenon where weakened easterly winds allow warm water from the western Pacific to flow eastward, raising global temperatures significantly and impacting economic growth.

Currently, a strong El Niño, possibly a “super” El Niño, is observed in the eastern Pacific. However, climate models indicate that future warming might be mitigated through ocean cloud brightening, a geoengineering method.

This method involves dispersing tiny seawater droplets into the atmosphere beneath low-level stratocumulus clouds. As the number of droplets increases, the clouds become whiter, reflecting more sunlight back into space.

If the cloud brightness is enhanced in the Niño 3.4 region, it could disrupt the feedback loop that sustains El Niño. This leads to a decrease in sea surface temperatures, reinforcing trade winds that push warm water back to the western Pacific, resulting in colder water surfacing in the eastern Pacific.

“By brightening ocean clouds, we can effectively prevent the cascading effects from escalating,” states Jessica Wang, a researcher from the University of California, San Diego. “We’re beginning to reverse the cycle.”

Wang’s team drew inspiration from Australia’s catastrophic 2019-2020 bushfires, followed by La Niña, a climate pattern that cools global temperatures. Their research proposes that smoke particles from these fires inadvertently enhanced cloud brightness, cooling the eastern Pacific and prolonging the “triple bottom” La Niña from 2020 for three consecutive winters.

The study assessed the impact of cloud brightness on past Super El Niño events (1997-1998 and 2015-2016) and found that increasing seawater spray for nine months could reduce the temperature rise in the Niño 3.4 region from over 2 degrees Celsius to slightly above 1 degree Celsius. This would effectively shorten the El Niño event significantly.

However, implementing this hypothetical cloud-brightening mission would require an estimated 2,400 ships spraying seawater—a scale beyond current nozzle technology. Nonetheless, this intervention could downgrade a super El Niño to a moderate one.

Despite starting only in June, as El Niño conditions began to develop, Wang expressed surprise at the impact observed.

Meanwhile, Matt Collins, a researcher from the University of Exeter, cautioned that such results may not be applicable in real-world scenarios. Warming oceans typically lead to the dissipation of lower clouds, intensifying warming through feedback loops.

“Models suggesting stronger cloud feedback necessitate higher aerosol injection,” he warned. “The experiment may have reached its operational capacity.”

Wang acknowledged potential unintended consequences, as simulations only predict impacts for up to two years. In both scenarios assessed, La Niña approached promptly after El Niño, with the 2015-2016 cycle producing stronger cooling periods, due in part to diminished rainfall during strong La Niña events, which contributed to widespread starvation.

Nevertheless, she affirmed the approach merits further exploration. Unlike long-term geoengineering strategies aimed at cooling the Earth, short-term measures can be paused without incurring drastic temperature spikes.

“This study paves the way for innovative geoengineering research focused on climate change and El Niño mitigation,” Wang emphasized. “It holds significant potential as it avoids long-term risks.”