In this study, a set of reconstructed black carbon (BC) data is used to analyze the relationship between BC over southern China (SC) and the South China Sea (SCS) summer monsoon (SCSSM) on the interannual time scale.An abrupt change of the relationship appears at around 2000.Before 2000, there is a negative correlation between them, namely larger BC concentration corresponding to weaker SCSSM, while positive correlation begins in 2000.By means of composite and contrast analyses, it is found that a major climate effect of BC over SC is attributed to the indirect radiative forcing during the first period (1988-1999):Namely, the reduced cloud particle radiuses related to BC over SC suppress the spring precipitation, yet increase the cloud lifetime, which decreases the amount of solar radiation, thus leading to a cooling at the surface and in the lower atmosphere.The negative air temperature anomalies excite an anomalous anticyclone with easterly anomalies over the SCS.In summer, the anomalous easterlies weaken the SCSSM and decrease the precipitation over the SCS.During the second period (2000-2010), the main BC climate effect is direct radiative forcing:The warmer atmosphere associated with the larger BC concentration enhances the spring precipitation, while decreasing the number of rain days, which in turn increases the amount of solar radiation, thus leading to a greater warming at the surface and in the lower atmosphere.The positive air temperature anomalies excite an anomalous cyclone with westerly anomalies over the SCS.In summer, the anomalous westerlies enhance the SCSSM and the precipitation over the SCS.