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We compute the effective radiative forcing (ERF) of the internally mixed sulfate-black carbon (SBC) aerosol species in the Geophysical Fluid Dynamics Laboratory's (GFDL) Atmospheric Model version 4 (AM4) model using five different formulations. The formulations differ in how they account for the presence of other aerosol species. The global mean ERF of SBC in the GFDL AM4 model ranges from -0.51 +/- 0.1 to -1.06 +/- 0.1 W m-2. The three most realistic configurations of the five, in which the emissions of other aerosol species vary between 1850 and 2010 states, depict a tighter distribution of ERF (-0.51, -0.55, and -0.57 +/- 0.1). The two outlier configurations completely exclude one or more other aerosol species, which is slightly unrealistic but included for completeness. The former three configurations, however, result in substantially different ERFs over the regional hot spots of aerosols, e.g., over the land-mass of East China; the choice of the emission conditions for organic carbon (i.e., present-day or preindustrial) affects the ERF of SBC by similar to 37%. The component of ERF related to aerosol-cloud interactions (ACI) gets principally affected by the presence of other aerosol species. The higher the emissions of other aerosol species, the lesser is the ERF of SBC associated with ACI. This finding suggests that for ERF estimates, the choice of the emission level/concentrations of the other aerosol species significantly affects the estimates of SBC, especially over the aerosol hot spots. The radiative imbalance at the top-of-the-atmosphere caused by the changes in the anthropogenic emissions of aerosols from preindustrial (PI) times to the present-day (PD), with the oceanic conditions held constant, is termed as the effective radiative forcing (ERF) of anthropogenic aerosols on the earth system. In this study, using the Geophysical Fluid Dynamics Laboratory's (GFDL) Atmospheric Model version 4 (AM4) model, we show that the ERF of the individual aerosol species depends upon the prescription of the emission levels of the other aerosol species. For instance, the prescription of emissions or organic carbon aerosol to PI and PD values changes the ERF of sulfate-black carbon (SBC) composite species by 37% over eastern China. This dependence principally arises from the aerosol-cloud interaction, while aerosol-radiation interactions are relatively independent of the emission levels of the other aerosol species. Nevertheless, on a global mean basis, this dependence of ERF of SBC on the emissions of other anthropogenic aerosols is much weak. The effective radiative forcing (ERF) of sulfate-black carbon (SBC) composite species in GFDL AM4 model ranges from -0.51 +/- 0.1 to -1.06 +/- 0.1 W m-2The broad range is attributed to the choice of emissions and the permitted influence of the other aerosol speciesOver East China, the choice of the emission condition for organic carbon (present-day or preindustrial) modulates the ERF of SBC by 37%

来源平台：JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES