Image: Antti Lipponen

Climate change impacts are felt disproportionately around the globe. And it turns out geoengineering—the most radical, and potentially ill-advised solution to climate change—could further turn the world’s weather on its head.

New findings released on Tuesday chronicle how pumping the atmosphere full of tiny particles to reflect sunlight and cool the Earth could have the unintended consequence of altering Atlantic hurricane season. For a variety of reasons, this could be very bad.

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The scientists took a unique approach and looked at what geoengineering half the planet at a time would do. The results paint an unsettling picture of how hacking Earth’s climate system could create winners and losers, and how it could even be weaponized. The authors warn that the study “reemphasizes the perils of unilateral geoengineering” and the need for the world to gets its act together to stop nations from going rogue.

The basic premise of geoengineering is that our planet is overheating and there may come a time when dramatic measures are needed to cool it. One of those ideas is to spray tiny particles called aerosols into the stratosphere to block incoming solar radiation and chill things out just a bit.

The problem is while this may cool the planet and pause some of the effects of climate change, it would likely mess up other parts of the climate system. As we inch closer to dangerous climate change, scientists are scrambling to understand what new problems would arise from this very fraught climate change solution.

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The new study, published in Nature Communications, looks at how aerosols would affect the frequency and intensity of Atlantic hurricanes. The findings are well-timed, as the U.S. is living through one of the most destructive hurricane seasons in years after Harvey, Irma, and Maria left trails of destruction from Texas to Puerto Rico.

The researchers took a novel approach to their study by running a handful of model experiments where aerosols were only sprayed in the northern hemisphere in one scenario, and the southern hemisphere in another. They ran both scenarios out to 2100 using a middle-of-the-road carbon emissions scenario.

Their findings show that spraying only in the northern hemisphere would result in fewer hurricanes, while injecting aerosols into the stratosphere in the southern hemisphere would result in a marked uptick in hurricanes. In all scenarios, they found stopping geoengineering rapidly resulted in a return to business-as usual climate change. In other words, stratospheric aerosols are more like flipping a light switch than a true course correction.

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The reason for the different responses of the northern and southern hemisphere has to do with shifts in the intertropical convergence zone, a band of rain storms that encircles the globe around the equator. It moves north or south of depending on temperature differences between the two hemispheres.

Injecting aerosols into the northern hemisphere stratosphere would cool that hemisphere more than the south, because there would be a higher densities of aerosols there. According to the study’s models that would send the intertropical convergence zone migrating south, making the region where hurricanes form less favorable to storms. The opposite is true if you inject aerosols in the southern hemisphere.

So why not just inject aerosols in the northern hemisphere and be done with it? A cooler planet and fewer hurricanes is a win-win, no?

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Sure, if you live along the Gulf Coast. But not so much if you live in the Sahel, a semi-arid region in Africa. Researchers expect that region to dry out under the northern hemisphere-only scenario, leaving millions of people already living on the edge a step closer to catastrophe.

Because injecting aerosols in the atmosphere is fairly cheap and impact on the climate would be rapid, its also imaginable that a rogue state could take the southern hemisphere route looking to stir up more hurricanes. Or maybe nations in the Sahel find the funds and want to enhance their rainfall, Florida’s fate be damned.

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While these scenarios might sound far-fetched, they show that geoengineering is a fraught process that would create winners and losers.

“Unilateral deployment is likely to favor the interests of the actor doing the deployment, and not those of others,” Janos Pasztor, the executive director of the Carnegie Climate Geoengineering Governance Initiative, told Earther in an email. “Consequently, it is important that governments agree that there be no deployment of solar radiation management until we (the world) know better the expected risks and potential benefits, and until we (the world) had a chance to develop and agree on the governance frameworks necessary for potential deployment.”

There’s one important caveat to the study’s main results, though. In one of their experiments, they used a technique to blend local observations and global climate models. The results showed in fewer hurricanes in all geoengineering scenarios compared to the climate change-only experiments, a discrepancy which they said remains unexplained.

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Overall, the study paints a worrisome picture that messing with geoengineering is like taking a step off a cliff with no clue how far you’re going to fall. It could be 10 feet, in which case you break a leg, or it could be 1,000 feet, in which case you are dead.

While all three geoengineering scenarios also keep the planet cool, causing Arctic sea ice to rebound, there are many uncomfortable questions about unintended consequences and who will suffer collateral damage. Maybe we ought to start cutting our carbon emissions before someone gets desperate enough to try a risky solution that could unleash bigger problems.