Embrace Geoengineering

May 20, 2015
Embrace Geoengineering

By David Keith

Writers, Scientists, and Climate Experts Discuss How to Save the World from Climate Change

David Keith: Imagine a doctor refusing to administer chemotherapy to a stage III lung-cancer patient out of fear that it would reduce his incentive to cut his smoking habit from two packs to one pack a day. That, in a nutshell, is the morally obtuse thinking that has undermined humanity's best bet to curb climate change: solar and carbon geoengineering. 

The first scientific fact to know about climate change is that carbon is (almost) forever. Suppose I pump out a ton of carbon dioxide by flying across the Atlantic. The additional warming from my trip rises over a few decades and then remains constant for more than a century. A millennium hence, about a fifth of my ton will still be in the atmosphere causing climate change, unless humanity does something to remove it. 

Many scientists regard geoengineering as the only viable method to roll back—not just delay—carbon's climate impacts. Solar geoengineering technologies could partially and temporarily reduce climate risks by reflecting some sunlight back to space, imperfectly offsetting the heat-trapping effects of greenhouse gases. Carbon geoengineering technologies could remove carbon dioxide from the atmosphere and transfer it back to geologic reservoirs, reversing the geologic footprint humanity causes by extracting coal, gas, and oil. 

Solar geoengineering is fast and cheap but also risky and impermanent. Carbon geoengineering, on the other hand, is slow and expensive, but once humanity cuts emissions by switching to carbon-free energy sources like solar or nuclear, it could allow future generations to put the carbon genie back into the bottle. 

But geoengineering's vanishingly small role in this year's major climate talks is a classic case of sacrificing scientific approaches at the altar of policy orthodoxy. Policymakers fear the public will only back emissions cuts if they're deemed the sole answer. Even advocates for climate geoengineering present it as a last-ditch response. In the words of science writer Eli Kintisch, geoengineering is "a bad idea whose time has come." 

Emissions must be cut, but I fail to understand how the only policy that could plausibly enable a major reduction in climate risks this century is a bad idea. Even if the world succeeds in cooperating on aggressive emissions reductions, the carbon cycle's inertia means that—at least for a long human lifetime—cutting emissions will only stop making the problem worse. Furthermore, nothing about solar geoengineering changes the need to cut emissions. The only pathway to a stable climate is to bring the net emission of greenhouse gases to zero. But a combination of solar geoengineering and reduced emissions would allow the world to reduce climate change over a single human lifetime. To stop sea level rise. To reverse the increase in extreme precipitation and heat waves.

Our descendants could use carbon geoengineering to gradually restore the world's carbon balance. The amount of solar geoengineering needed to stabilize the climate would decrease as carbon was reduced, and the climate could eventually be restored to a reasonable approximation of its preindustrial state. 

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See also: David Keith, Op-Ed