(341e) Black Carbon and Its Role in Climate

Black carbon in soot is the dominant absorber of visible solar radiation in the atmosphere. Black carbon is often transported over long distances, mixing with other aerosols along the way. The aerosol mix can form transcontinental plumes of atmospheric brown clouds, with vertical extents of 3 to 5 km. Because of the combination of high absorption, a regional distribution roughly aligned with solar irradiance, and the capacity to form widespread atmospheric brown clouds in a mixture with other aerosols, emissions of black carbon are the second strongest contribution to current global warming, after carbon dioxide emissions. The interception of solar radiation by atmospheric brown clouds leads to dimming at the Earth's surface with important implications for the hydrological cycle, and the deposition of black carbon darkens snow and ice surfaces, which can contribute to melting, in particular of Arctic sea ice. Globally, sources of black carbon emissions include burning of forests and agricultural residues, combustion of fuels for residential energy, brick production, diesel transport and coal-fired thermal power production. In this paper the role of black carbon in climate change and implications for policies directed at reducing short term climate change by targeting BC reductions are discussed.