During the Indian Ocean Experiment (INDOEX) Ackerman et al. [2000> found that black carbon (BC) aerosols can reduce cloud cover and liquid water path (semi-direct aerosol effect). Absorption of solar radiation by BC leads to a heating of the air which can result in an evaporation of cloud droplets. This warming can partially offset the cooling due to the indirect aerosol effect. We use the ECHAM4 general circulation model to investigate whether this effect is discernible on a global scale. The results of this sensitivity study, where the absorption of BC only takes place in clear air and interstitially, indicate that the zonal mean reduction in cloud cover and liquid water path in highly polluted regions of the Northern Hemisphere can amount to 4% and 10 g m-2, respectively. However, the indirect aerosol effects of increasing cloud lifetime and cloud albedo dominate. ¿ 2001 American Geophysical Union