A Clever But Questionable Approach to Geoengineering

Technology Review editor David Rotman has an unusually reader-friendly article in the issue just out  on what goes by the name, loosely, of "geoengineering"—deliberate efforts to modify earth's atmosphere to counteract the effects of greenhouse gases. In the March issue, Rotman profiles MIT scientist David Keith, a former atomic physicist, and his idea of injecting sulfuric acid into the upper atmosphere, where the sulfur aerosols would reflect incoming solar radiation back into space.

"One of the startling things about Keith's proposal," writes Rotman, "is just how little sulfur would be required. A few grams of it in the atmosphere will offset the warming caused by a ton of carbon dioxide, according to his estimate."

The idea of pumping sulfate aerosols into the atmosphere is not new as such. What does seem novel in Keith's scheme, however, is the disarmingly simply method he proposes for putting them there: Customize standard Gulfstream business jets and have them fly 20 kilometers up to disperse sulfuric acid, which will combine with water to form the reflective sulfate aerosols.

What's not to like in this scenario? The main objections are just those that my fellow energy blogger David Levitan has identified in this space: The impossibility of accurately predicting what the regional impacts of the sulfur pumping would be, and the complete absence of any understanding of its impact on ocean acidification, one of the most serious consequences of carbon dioxide buildup. "It's not possible to use existing models to know how geoengineering might affect, say, India's monsoons or precipitation in such drought-prone areas as northern Africa," Rotman concedes in the end.

For balance, Technology Review also has in its current issue an excellent short commentary piece that makes the case for energy conservation and efficiency (an editorial strategy Scientific American also has adopted when addressing the delicate subject of geoengineering). It won't be enough to just keep trying to marginally reduce our immense greenhouse gas emissions, writes Jane Long, who chairs a California future energy committee and co-chairs the Bipartisan Policy Center's geoengineering task force. "Our first step should be to to commit to never building another energy-inefficient city, building, vehicle, or industry."

Image: Don Bayley/iStockphoto

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