The soot that is emitted into the atmosphere from activities such as burning of diesel and biomass is making a bigger contribution to global warming than previously thought. This finding puts 'black carbon' second only to carbon dioxide in terms of its warming impact.

Tami Bond at the University of Illinois at Urbana-Champaign and her colleagues analysed data from a ground-based network of aerosol sensors, run by NASA, as well as satellite observations and global-emissions inventories. The authors found that the amount of warming from black carbon — which absorbs solar radiation and heats the atmosphere, as well as melting snow and ice — is roughly double most earlier estimates.

Lowering black-carbon emissions could be a quick way to cool the climate, but the overall effect of atmospheric aerosols on climate is still uncertain, the authors caution.

J. Geophys. Res. http://dx.doi.org/10.1002/jgrd.50171 (2013)