Importance of Sulfate Aerosol in Evaluating the Relative Contributions of Regional Emissions to the Historical Global Temperature Change

During the negotiations of the KyotoProtocol the delegation of Brazil presentedan approach for distributing the burden ofemissions reductions among the Partiesbased on the effect of their cumulativehistorical emissions on the global-averagenear-surface temperature. The Letter tothe Parties does not limit the emissions tobe considered to be only greenhouse gas(GHG) emissions. Thus, in this paper weexplore the importance of anthropogenicSOx emissions that are converted tosulfate aerosol in the atmosphere, togetherwith the cumulative greenhouse gasemissions, in attributing historicaltemperature change. We use historicalemissions and our simple climate model toestimate the relative contributions toglobal warming of the regional emissions byfour Parties: OECD90, Africa and LatinAmerica, Asia, and Eastern Europe and theFormer Soviet Union. Our results show thatfor most Parties the large warmingcontributed by their GHG emissions islargely offset by the correspondingly largecooling by their SOx emissions. Thus,OECD90 has become the dominant contributorto recent global warming following itslarge reduction in SOx emissions after1980.