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Blotting Out the Sun to Save the Earth? Seriously?

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Gorancakmazovic / Getty Images

By Jeff Turrentine

Science fiction doesn't always stay fictional. Space exploration, robots and self-driving cars are just a few of the modern-day wonders that once existed only as plot devices or fantastical theories. Our capacity for turning science-fictional notions into the stuff of everyday life has grown with each new generation of scientists and microchips, such that more and more ideas previously deemed too far "out there" are now actually here, or at least technologically plausible.


To this list we can now add geoengineering—whether we want to or not. As broadly defined by the science-fiction author and environmentalist Kim Stanley Robinson, geoengineering is the "deliberate planned attempt by human beings to mitigate the damages of climate change, of carbon dioxide and methane buildup in the atmosphere, and of ecological damage generally, by way of some action that is large-scale." In theory, geoengineering might look like any number of things: engaging in mass, worldwide reforestation; dumping iron dust into the oceans to encourage the growth of carbon-eating plankton; "brightening" clouds to make them more reflective; dotting the planet with millions of industrial-strength carbon scrubbers.

Geoengineering ideas are as numerous and varied as the scientific imaginations that spawn them. What usually ties them together is the goal of dramatically reducing global temperatures and/or carbon emissions over a short period of time. Scale and speed are what separate most geoengineering schemes from other, less risky, more tried-and-true attempts at climate mitigation, such as building seawalls or boosting energy efficiency. But increasingly, many who once disparaged geoengineering are now citing its scale and speed as the two main reasons why it may be our best hope for fighting climate change—the biggest and most immediate threat to life on earth as we currently know it.

The latest geoengineering conversation has been sparked in part by a study published last week in the journal Nature that acknowledges the potential benefits of solar radiation management (SRM)—as well as the very real risks that would come along with it. One much-discussed iteration of SRM would involve saturating Earth's atmosphere with sulfur-laden aerosols to reflect solar light back into space, cooling the planet in the process. Support for the theory began to swell among geoengineering proponents after the discovery that global temperatures fell by as much as 0.6 degrees Celsius following giant volcanic eruptions in Mexico and the Philippines that spewed millions of tons of sulfur dioxide into the atmosphere.

The summit of the Mount Pinatubo volcano in the Philippines, 15 days after its eruption in 1991. Global temperatures fell slightly after the volcano's eruption sent vast quantities of sulfur dioxide into the atmosphere.United States Geological Survey

If we could mimic the effects of these volcanoes (so the theory goes) by strategically injecting sulfate aerosols into the atmosphere, the researchers propose that we might be able to effectively "shade" the entire planet and save vulnerable crops from frying under the sun. The problem with that scenario, though? While crops might not wither and die from heat, the ever-cloudy conditions under sulfur-laden skies would also severely stunt the crops' growth, causing them to yield far less food. Whatever gains realized from the lower temperatures, in other words, would be more than offset by losses resulting from the dearth of direct sunlight.

Though they do not state it explicitly in the "Conclusions" section of their study, the researchers confirm a hypothesis that nearly everyone who has looked at geoengineering already accepts: There are no risk-free scenarios. At its core, geoengineering is really just a globally scaled hack, a work-around born of exigency as much as industriousness. And like any hack, it's less than ideal.

Every geoengineering proposal that's been put forth so far, in fact, has come with its own bold-print caveat that we ignore at our peril. Adding iron ore to the oceans, for instance, carries the risk of over-oxygenating water and destroying bacteria crucial to the marine food chain, or of generating dangerous amounts of nitrous oxide, a greenhouse gas. As for cloud brightening, even those who support more research into this approach admit that it could alter precipitation patterns in unexpected and quite possibly harmful ways.

But what's telling is the evolution of the scientific community's response to geoengineering over the past few decades—from outright alarm to qualified alarm to extreme hesitation. This response tracks our understanding of just how much trouble our carbon pollution has gotten us into. Ask any climate scientist, and she'll tell you that the only surefire way to save ourselves is to immediately cut carbon emissions and transition to a clean-energy economy. But she may also be more willing today than she was five or ten years ago to entertain the idea of further research into solar radiation management, cloud brightening, and the like.

Geoengineering is extraordinarily risky. In a perfect world—or even in an imperfect but climatologically hospitable one—we would never even consider it, for fear that our actions could usher in the dystopia we've seen in countless science-fiction movies. But we need to be honest about where we are in the story of humanity and climate change. It's the third act. And while we'd have to be desperate to try to geoengineer our way to a happy ending, there's just not that much time left to argue over the definition of the word desperate.

Reposted with permission from our media associate onEarth.

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