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The first rule is that the technology must largely embody the cause-effect relationship connecting problem to solution. In this case, solar radiation management fails because it addresses the effect of higher average global temperatures rather than the cause, which is accumulating concentrations of greenhouse gases in the atmosphere. On the other hand, air capture aims to remove the cause—e.g., greenhouse gases—from the atmosphere thus preventing an increase in temperature.
The second rule is that the effects of the technological fix must be assessable using relatively unambiguous or uncontroversial criteria. Air capture clearly meets this criterion. Pielke notes, "If the accumulation of carbon dioxide in the atmosphere is judged to be a problem, then its removal logically follows as a solution."
The third rule of technological fixes is that research and development is most likely to contribute decisively to solving a social problem when it focuses on improving a standardized technical core that already exists. In this case, Pielke argues that air capture technologies have been developed now that can be refined and deployed with no risk to the climate system.
To assess the costs of air capture Pielke points out that various estimates for reducing the emissions of carbon dioxide might cost between 1 to 3 percent of total global GDP over the next century. Assuming about 3 percent global GDP growth to 2100, Pielke calculates that the cost of air capture at even $500 per ton of carbon would cost 2.7 percent of global GDP if the goal is to make sure that carbon dioxide concentrations do not exceed 450 parts per million. Pielke concludes, "My bottom line is that the geoengineering of the earth system as a way to adapt to increasing concentrations of greenhouse gases is a losing proposition."
Despite the cautions of Smith and Pielke, it is hard to disagree with Bickel and Lane's conclusion on climate engineering: "The results of this initial benefit-cost analysis place the burden of proof squarely on the shoulders of those who would prevent such research."
Note: I will be reporting on the Copenhagen Consensus Center's next series of papers dealing with climate mitigation, adaptation, and green energy research as they are publicly released.
Ronald Bailey is Reason magazine's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is now available from Prometheus Books.
Disclosure: The Copenhagen Consensus Center paid my travel expenses to report on its Consensus 2008 process. The Center exercised no editorial control whatsoever over my reporting.