Aerosols and climate: Anthropogenic emissions and trends for 50 years

A global inventory has been prepared for anthropogenic particulate emissions into the troposphere that covers the period 1990-2040. The inventory provides estimates for both primary particulate emissions and secondary contributions from atmospheric chemical reactions, particularly of SO2. Using a conventional method, total worldwide anthropogenic emissions of particles <10 mu m diameter are estimated at 345 Tg/yr, excluding secondary NO3(-) and organics. Approximately 35% of the particles entering the troposphere is airborne sulfate from oxidation of SO2 emissions. Emissions worldwide are dominated by fossil fuel combustion, particularly coal, and biomass burning. These emissions are projected to grow by 1.5 2.1 times in 2040, largely from fossil fuel combustion. Growth is expected to be greatest in the developing countries, especially India and China. Present anthropogenic emissions appear to be a small fraction of emissions from natural sources. However, the man-derived component could become comparable to natural emissions by 2040. Increased haziness may enhance negative climate forcing both directly by increased radiative scattering and indirectly by modifying cloud albedo and cover. The forcing will be spatially non-uniform, superimposed on the forcing derived from greenhouse gases.