If there's one thing more potentially contentious than the international politics of global warming (which the world has spent at least the past 20-plus years dithering about), it's the politics of the most radical suggestion to solve it: geoengineering. After all, he who controls Earth's thermostat may well control Earth. And what's good for one nation (Bangladesh and its shoreline prefer today's climate, fearing sea level rise under a warmer one) may not be good for another (Russia might enjoy a balmier Arctic Circle).

That's exactly what some new computer modeling suggests, as published July 18 in Nature Geoscience. (Scientific American is part of Nature Publishing Group.) Geophysicist Kate Ricke of Carnegie Mellon University and her colleagues show that one of the more feasible geoengineering methods—injecting reflective particles into the atmosphere to mimic the world-cooling effects of a volcanic eruption—will have effects that vary from place to place. So, for example, India might be rendered too cold (and wet) by a level of particle injection that's just right for its neighbor China while setting the levels to India's liking would toast the Middle Kingdom.

What's worse, the computer models that show that such injections might work in the short term also show that they will change global weather patterns by making part of the atmosphere more stable—and therefore less likely to promote storms. That means less rainfall to go around—and these side effects become worse with time.

"The generic results—what's good for the goose may not be good for the gander—is robust," says climate modeler and geoengineering expert Ken Caldeira of Stanford University, whose own computer modeling in the late-1990s proved that such sulfate injection could work, at least in the short term. "I would not believe the specifics regarding India versus China in this one model."

Caldeira notes that Ricke and her fellows relied on just one model to make these predictions. Nor does he think that any geoengineering will be tailored locally: "The world is inextricably linked economically, so the idea that each location will be trying to optimize local weather is not right," he says. "The process of globalization of our economy will lead people to consider a more global optimization of climate."

Of course, international negotiations to cope with climate change—the environmental side-effect of such globalization—have proved intensely regional, national and even classist. And even Caldeira admits that "in the case of a real climate emergency, where leaders are trying to save their citizens from famine and starvation, the leaders will simply deploy a system and treat damage from breaking international guidelines as a cost to be considered."

Or, as economist Gary Yohe of Wesleyan University, puts it: "It's something to have on the shelf in case you look up and say 'We're really going over a cliff here. We have to do something.'"

Image: Mount Pinatubo, the catastrophic eruption of which would-be geoengineers would mimic.