The radiative effects (both forcing at the tropopause and absorption in the lower troposphere) of standard aerosol models are examined as a function of relative humidity. Several of the models are also modified by the inclusion of additional soot, in line with recent observations. Increasing relative humidity causes many aerosol types to expand and also increases their single-scattering albedo. We have examined the impacts of these changes and also the interaction between aerosol growth and absorption of solar radiation by water vapor. These effects are seen not to be additive, especially in the case of flux divergence due to absorbing aerosols. ¿ 2000 American Geophysical Union