Radiative forcing calculations of changes in tropospheric ozone in the period 1980 to 1996 are performed. The tropospheric ozone changes used in this study are from a chemistry transport model [Karlsdóttir et al., this issue]. For the radiative transfer calculations, schemes for thermal infrared radiation and shortwave radiation are used. Effects of reduced stratospheric ozone and emissions of tropospheric ozone precursors on the changes in tropospheric ozone are taken into account. Large positive radiative forcing is estimated over Southeast Asia, due to emissions of ozone precursors. Effects of decreased stratospheric ozone have reduced the radiative forcing due to change in tropospheric ozone from 1980 to 1996, particularly at high latitudes where the radiative forcing is negative.