Aerosols play the important role as scatter or absorb solar radiation, which consequently modies the radiative balance of the atmosphere. Aerosol and its eects, especially its indirect eects, on climate have drawn increasing attention in recent years. Understanding of interactions of aerosols and climate is important to better prediction of future climate change. In this study, the direct and indirect effect of fossil fuel organic carbon aerosol (OC) and its impacts on the climate during the period of the early of 20th century (1901~1920) and the end of 20th century (1986~2005) were investigated. we examine changes in aerosol emission during 20th century. Using HadGEM2-AO (Hadley Centre Global Environmental Model version 2, Atmosphere and Ocean), historical experiments are carried out with and without anthropogenic aerosol emissions (HIST, FIXA) from 1860 to 2005. Fossil fuel organic carbon aerosol (OCFF) emission xed at 1860 is added. Due to the large emission of OC, thick optical depth of the OC appears over Asia, western Europe and eastern north America. e direct eect due to increasing OC influences negative radiative effect at the surface, which leads to a cooling effect on the surface. The OC shows direct eect and indirect eect as well. e variation of total amount of clouds are aected by the OC aerosols emission.