The aerosol-cloud interactions due to black carbon (BC) aerosols, as well as the implied climate responses, are examined using an aerosol module in the coupled atmosphere-ocean general circulation model MPI-ESM. BC is simulated to enhance cloud droplet number concentration (CDNC) by 10-15% in the BC emission source regions, especially in the Tropics and mid-latitudes. Higher CDNC and reduced auto-conversion from cloud water to rain water explains the increased cloud water path over the tropical regions (30 degrees S-30 degrees N) in the model. In the global mean, the cloud water-as well as precipitation changes are negligibly small. The global-mean effective radiative forcing due to aerosol-cloud interactions for BC is estimated at -0.13 +/- 0.1 Wm(-2), which is attributable to the increase in CDNC burden and (regionally) cloud water in the model. Global mean temperature and rainfall response were found to be -0.16 +/- 0.04 K and -0.004 +/- 0.004 mm day(-1), respectively, with significantly larger regional changes mainly in the downwind regions from BC sources.