Geoengineering has always had a certain allure. After all, the thinking goes, if we could just remove carbon from the atmosphere or reflect sunlight back into space, maybe we wouldn’t have to make so many pesky sacrifices in the global fight against climate change. Now that global temperatures have crept past the dreaded 1.5 degree Celsius warning line, there’s renewed interest in geoengineering, and it comes with plenty of controversy.
It’s controversial in part because we’re ignorant of what consequences geoengineering might bring, and many environmental groups warn it could make matters worse. Additionally, private actors are increasingly launching their own geoengineering projects—mostly start-ups that are uncoordinated with government actions—which could be a recipe for disaster.
Either way, the kind of large-scale geoengineering projects that might actually make a dent in climate change are nowhere close to underway. Smaller scale geoengineering, on the other hand, could temporarily help nudge local climate systems in a more favorable direction. According to a study published today in Science Advances, it could even be used to forestall super El Niños, like the one currently brewing in the warming Pacific waters.
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“One of the biggest social concerns around geoengineering is the fact that if we use it to reduce long-term climate risks, we have to deploy it continuously for an indefinite period of time,” study co-author Jessica Wan of the Scripps Institution of Oceanography said in a statement. “If we could target natural variability, we could get some of the benefits of geoengineering without having to employ it indefinitely.”
While even small-scale geoengineering experiments could lead to adverse consequences, the brush fires that ravaged Australia during the 2019-2020 wildfire season provided a natural trial of sorts. Prior research showed the smoke contained scads of aerosols that offered a natural cloud brightening effect, reflecting solar radiation and reducing the heat that fuels El Niños. Using data from that study, a team of climatologists modeled what would happen if clouds over the Pacific were artificially brightened during the lead-up to the major El Niños that formed in 2015 and 1997. They found that geoengineering would indeed dampen the severity of the cycles.
“It’s a different way of thinking about geoengineering,” study co-author Katharine Ricke explained. “We need to understand a lot more, but if there is a way to use this in addition to the risk reduction tools to mitigate El Niños, why wouldn’t we consider it?”
With global temperatures rising steadily and carbon emissions remaining stubbornly high, it’s a good question, but still a controversial one. 
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