PerspectiveClimate Change

Climate's Dark Forcings

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Science  19 Apr 2013:
Vol. 340, Issue 6130, pp. 280-281
DOI: 10.1126/science.1235731

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The black soot coming out of the tailpipes of diesel trucks is a nuisance familiar to every highway traveler. Soot also endangers the health of untold numbers of women and their families exposed to smoke from traditional cookstoves burning biofuels and coal. But in addition to irritating our noses and lungs, this pollutant, also known as black carbon (BC), is the strongest absorber of solar radiation in the atmosphere. The magnitude of global warming from BC, as well as its regional effects, has been the subject of intense debate. In a recent comprehensive assessment, Bond et al. (1) have synthesized available model results and observations, and propose a "best estimate" for BC's global climate forcing. Their estimate is almost twice as high as values commonly discussed (2). What causes such large discrepancies between estimates, and what are the implications for the global and regional climate effects of BC?