A Radical Experiment Shows Cloud Brightening May Be Our Climate’s White Knight

Darren Orf
Tue, April 16, 2024 


Humans are not doing a great job lowering carbon emissions, so scientists are searching for ways to buy the world time to kick its nasty fossil fuel habit.


One idea is marine cloud brightening (MCB), and a new study says that MCB could also create cloud cover, making it an even better ‘painkiller’ for climate change that previously thought.


However, there’s a lot scientists still don’t know about MCB, including how it could affect ocean circulation patterns and rainfall on land.

Coming as a surprise to no one, 2023 was the warmest year on record. And that’s just another step in an already disturbing trend that sparked the creation of the Paris Climate Accord in 2015. There’s just one problem: the world is falling behind its emission-reducing commitments.

The world is currently on track for 4.8 degrees Celsius warming by the end of the century, which is far above the 2.7 degree Celsius goal. To realize that less-apocalyptic goal, the world needs to cut 28 percent of the greenhouse gas emissions that it’s currently on track to produce, according to NPR. It’s undeniable that the world is in a bit of a time crunch, so some scientists are pursuing a Plan B—solar geoengineering. If successful, it could buy humanity time to fully kick our addiction to fossil fuels and embrace the green energy revolution.


Now, a new study by scientists at the University of Birmingham (in collaboration with other U.S. and European universities) discovered that one of these geoengineering techniques—a technology known as marine cloud brightening (MCB)—could be a more effective “painkiller” for climate change than previously realized. The researchers created a “natural experiment” by closely analyzing cloud behavior as related to the periodic eruptions of Mount Kilauea volcano in Hawaii.

These natural injections of aerosols into the atmosphere mimic the overall goal of marine cloud brightening, which (in simple terms) also injects aerosols—in the case of MCB, hyperfine sea salt particles—into clouds to increase their brightness and reflectiveness. However, the team found that MCB actually gets most of its cooling effect from creating cloud cover. The results were published in the journal Nature Geoscience on Thursday.

“Our findings show that marine cloud brightening could be more effective as a climate intervention than climate models have suggested previously,” University of Birmingham’s Ying Chen, the study’s lead author, said in a press statement. “We must continue to improve fundamental understanding of aerosol’s impacts on clouds, further research on global impacts and risks of MCB, and search for ways to decarbonize human activities.”

Using machine learning to pore over historical satellite and meteorological data, the team created a predictor that showed cloud behavior during inactive volcano periods. Then, the researchers could easily identify how the volcano directly impacted clouds. Turns out, natural aerosols increased cloud cover by 50 percent during volcanic activity, with a cooling effect of -10 watts per square meter (negative is a good thing).

“Our findings suggest that MCB may be quite effective for alleviating climate warming, although it would probably manifest as an increase in cloud cover rather than cloud opacity, as the MCB terminology implies,” the paper reads. “This best practice would be particularly effective in tropical oceans where incoming solar radiation is strong and background environment is clean (that is, clouds are more ‘pristine’).”

While MCB has been around since the 1990s, the idea has been grabbing more headlines as the world continues to warm. The New York Times reported just last week that the University of Washington conducted its first MCB experiment off the coast of Alameda, California.

However, any kind of climate tool under the tech umbrella of “geoengineering” will draw some suspicion. Scientists, for example, aren’t sure how MCB could affect ocean circulation patterns, or if it could increase rainfall in some places while reducing it in others. But proponents emphasize that the world is already being geoengineered by human-created greenhouse gasses, and that the side effects of MCB could potentially be preferable to the the devastating costs of climate change.

There is one area of agreement between both camps—MCB isn’t a solution to climate change—but evidence is growing that it could be one way to lower the planet’s symptomatic fever while we attempt to treat the carbon-induced disease.