Thanks for bringing up this very important issue. I don't know what category this belongs in, but it seems to me that there should be one for direct reductions in short-lived greenhouse gases. In the developing world, providing sustainable alternatives to fuels such as dung and scrap wood for cookstoves would have a tremendous climate effect and perhaps even more profound impacts on quality of life for those who now use these fuels. In the developed world, much of black carbon comes from non-point sources such as diesel vehicles. I'd be very supportive of a proposal to address these issues!