Effect of Chlorofluoromethane Infrared Radiation on Zonal Atmospheric Temperatures

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Abstract
A GCM sensitivity experiment has been carried out to estimate the change of atmospheric climate due to the radiative effects of 10 ppb of chlorofluoromethanes (CFM's). This was done with NCAR's old 12-layer stratosphere GCM and with an appropriate specified change of ocean temperature. Two maxima in zonal average temperature change were found, both in the tropics, one in the upper troposphere and one centered at the tropopause. In these regions the temperature change exceeds the surface temperature change by greater than a factor of 2. If this temperature change is scaled down to correspond approximately to that inferred for indefinite continuation of the 1975 CFM emission, the model calculation indicates that the temperature of the tropical tropopause would still increase by about 2 K. If stratospheric water vapor concentrations are controlled by the saturation vapor pressure at the trapopause, an increase of tropical tropopause temperature would imply an increase in stratospheric water vapor concentrations. An increase of water vapor would modify the perturbation of ozone due to the CFM's alone. with a 60% increase of water vapor, corresponding to a 2.5 K increase of tropical tropopause temperature and ignoring temperature changes due to the O3 change as well as the effect of temperature changes on reaction rate constants, the calculated O3 column decrease due to 1975 CFM emission rates would be an additional 4% of the natural O3 column.

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