Black-carbon reduction of snow albedo

Climate models indicate that the reduction of surface albedo caused by black-carbon contamination of snow contributes to global warming and near-worldwide melting of ice(1,2). In this study, we generated and characterized pure and black-carbon-laden snow in the laboratory and verified that black-carbon contamination appreciably reduces snow albedo at levels that have been found in natural settingsa(1,3,4). Increasing the size of snow grains in our experiments decreased snow albedo and amplified the radiative perturbation of black carbon, which justifies the aging-related positive feedbacks that are included in climate models. Moreover, our data provide an extensive verification of the Snow, Ice and Aerosol Radiation model(1), which will be included in the next assessment of the Intergovernmental Panel on Climate Change(5).