Aerosols are known to influence global climate by reflecting or absorbing solar radiation (direct effect) and by changing cloud properties and precipitation (indirect effect). In spite of their importance, the current scientific understanding of aerosols is still low. The prediction of atmospheric evolution and the climate effects of aerosols in many global models are mainly done by using simplified aerosol modules often ignoring the size distributions of aerosols. To better understand the role of aerosols in the climate system, an interactive aerosol-climate model has been developed by incorporating a chemistry and size-dependent aerosol model into the National Center for Atmospheric Research Community Atmospheric Model, version 3 (CAM3). For the present study four different aerosol species of black carbon (BC), organic carbon (OC), sulfate (SO4), and mixed aerosols are included in the model as six aerosol modes (3 for sulfate aerosols). The aerosol model thus provides prognostic number and mass concentrations of various modes of aerosols by including emissions, transport, dry/wet deposition, and aerosol chemical and physical processes in the model. The global radiative forcings of various aerosols are then examined using predicted information of aerosol size distributions. The modeled aerosol distributions are compared with satellite and surface observations and discrepancies between modeled and observed results have been analyzed. The impact of modeled aerosols evolution on their radiative forcings will be discussed.