Direct aerosol radiative effects during a heavy pollution episode that occurred in October 2004 over northern China are explored on the basis of ground-based and satellite-retrieved data. Aerosol loading rapidly built up due to a strong inversion and high relative humidity, with aerosol optical depth (AOD) at 550 nm increasing steadily from about 0.1 on October 1 to more than 1.0 six days later. Reflected irradiances at the top of the atmosphere (TOA) and surface irradiances change dramatically in response to the variation of the AOD. At the peak of the heavy pollution episode, the instantaneous reflected irradiances at the TOA increased by about 50 Wm−2, while the instantaneous irradiances at the surface decreased by about 350 Wm−2, resulting in solar heating of the atmosphere on the order of 300 Wm−2. Solar radiation reflected to the space increased due to the build up of aerosols, indicating an overall cooling effect of the aerosols in the region.