Schemes to hack the planet and save us from global warming have two layers of obstacles to overcome. First, is it technologically and physically possible to do what’s proposed? And then there’s the second: Is it politically possible to tinker with the planet?

Those who would argue “absolutely not” to the latter got a boost by a new study out in Nature Geoscience. Katharine Ricke and her team modeled the effects of one of the most popular geoengineering plans: seeding the atmosphere with aerosols to reflect away some of the sun’s rays, mimicking the way a massive volcanic eruption can cool the Earth. Ricke found that the effects on rainfall and temperature could vary wildly by region—and that what’s best for one country could spell disaster for another.

For example, Ricke says, her study found that levels of sulphate that kept China closest to its baseline climate were so high that they made India cold and wet. Those that were best for India caused China to overheat. She notes, however, that both countries fared better either way than under a no-geoengineering policy [Nature].

Given the complex connectivity of the climate system, it’s not possible to fix everything to everybody’s liking. While the team’s study shows that geoengineers could control either temperature or precipitation pretty well by fine-tuning their atmospheric seeding, they couldn’t control both at once.

“People won’t agree on what level of geoengineering is desirable,” says Myles Allen of the University of Oxford, who was involved in the study. “It works, but it won’t work the same way for everyone” [New Scientist].

Nevertheless, the drumbeat for geoengineering isn’t quieting. Two books that came out this spring, Jeff Goodell’s “How To Cool the Planet” and Eli Kintisch’s “Hack the Planet”, delved into the idea. Several more out this year try to predict what the Earth will be like in the warmer future, and whether you should go ahead and buy that summer vacation property in Canada. Last September Britain’s Royal Society issued a report calling for investment in geoengineering as a backup plan in case nations fail to constrain their emissions. And that was before the failure of the Copenhagen climate summit.

But, as climate models improve, scientists could get a better picture of the fallout from such a dramatic action as seeding the atmosphere with aerosols, according to climate guru Ken Caldeira.

“I don’t think climate modelling is at the point where we should trust one single model at that scale,” Caldeira says. “But I think the results are robust in the sense that it’s the kind of issue that people will need to face. The qualitative idea is that you’re going to have differential results in different regions, and that’s going to cause people to want different amounts of this stuff up there, if they want any of it up there at all” [Nature].

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