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[1] The history of the global sulfur cycle has been simulated using an emission inventory of SO2 for 1990 and previously published historical trends in emission on a per country basis. The global- annual-mean radiative forcings due to sulfate aerosols increase (in absolute values) from near-zero and −0.17 Wm−2 up to −0.4 and −1 Wm−2 between 1850 and 1990, for the direct and indirect effects, respectively. The forcing efficiency (defined as the ratio of the radiative forcing to the anthropogenic sulfate burden) is fairly constant for the direct effect at −150 W(g sulfate)−1 but decreases significantly for the indirect effect with increasing sulfate burden. The model results are compared with long-term observations for the period 1980 to 1998 in the U.S. and Europe.