Climate Science

Which Emissions to Reduce?

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Science  30 Aug 2013:
Vol. 341, Issue 6149, pp. 939
DOI: 10.1126/science.341.6149.939-a
CREDIT: © SCUBAZOO/SUPERSTOCK/CORBIS

A fierce debate is being waged about the relative merits of controlling the anthropogenic emissions of climate-affecting pollutants with long atmospheric lifetimes, such as carbon dioxide, and those with shorter atmospheric lifetimes, such as methane or black carbon. Both classes of compounds have substantial radiative impacts, and arguments about which is more important to reduce have been made for each. By using a sophisticated global model, Smith and Mizrahi examined the potential climate effects of a strategy to mitigate the short-lived climate-forcing agents methane and black carbon and concluded that the likely benefits of such an approach are much more modest than had been suggested recently. Even assuming the maximally feasible reductions in emissions over the next decades, the rise in global average surface air temperature by the year 2050 would be only about one-half of the previous best estimate. Thus, a policy of focusing on reducing emissions of short-lived climate forcers, attractive to many because of its rapid effect and possibly easier and less costly implementation, may not be the silver bullet some have hoped it might be.

Proc. Natl. Acad. Sci. U.S.A. 110, 10.1073/pnas.1308470110 (2013).

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