Climate forcing by stratospheric ozone depletion calculated from observed temperature trends

The radiative forcing of the surface‐troposphere system caused by stratospheric ozone depletion in the 1980s is calculated using observed values of change in ozone, from TOMS data, and temperature, from MSU data. The seasonal variation of the ozone and temperature trends produces strong seasonal and latitudinal variations in radiative forcing. The balance between peak positive solar forcing and maximum negative longwave forcing shifts the peak negative forcing at the South Pole from November to October. The time difference between peak ozone loss and maximum temperature decrease results in net positive values in Southern Hemisphere mid‐latitudes in August and September. Positive values also occur at low latitudes in both hemispheres. The globally and annually averaged net radiative forcing is about −0.025 Wm −2 between 1979 and 1990, much less than that previously reported using fixed dynamical heating model temperature changes, although inclusion of the ozone 14 µm band would somewhat narrow this gap. Ozone radiative forcing is very sensitive to the vertical profile of temperature change.