Stratosphere, cooling

The different greenhouse gases can have complicated interactions. Carbon dioxide may cool the stratosphere which slows the process that destroys ozone. Stratospheric cooling can also create high altitude clouds which interact with chlorofluorocarbons to destroy ozone. Methane may be produced or destroyed in the lower atmosphere at various rates, which depend on the pollutants that are present. Methane can also affect chemicals that control ozone formation. 

Ramaswamy, V., M. D. Schwarzkopf, and W. J. Randel, Fingerpirnt of Ozone Depletion in the Spatial and Temporal Pattern of Recent Lower-Stratospheric Cooling, Nature, 382, 616-618 (1996). 

Kodera, K., and K. Yamazaki, A possible influence of recent polar stratospheric coolings on the troposphere in the Northern hemisphere winter. Geophys Res Lett 21, 809, 1994. 

Forster, P.M., and K.P. Shine, Stratospheric water vapor changes as a possible contributor to observed stratospheric cooling. Geophys Res Lett 26, 3309, 1999. 

Ramaswamy, V., M.D. Schwarzkopf, and W.J. Randel, Fingerprint of ozone depletion in the spatial and temporal pattern of recent lower-stratospheric cooling. Nature 382, 616, 1996. 

Following this immediate shock the stratosphere cools. The increased CO2 in the stratosphere enhances the thermal emission. Because the stratospheric temperature increases with altitude, this has the effect that the cooling into space is larger than the absorption from layers below. This is in fact the fundamental reason for the COi-induced cooling in the stratosphere. After stratospheric cooling a new radiative equilibrium develops with the new doubled CO, concentration. This reduces the increased downward emission at the tropopause by about 0.2 W in - and the tropopause forcing is adjusted accordingly. 

The possible effects of a decrease in stratospheric ozone concentrations include (1) an increase in skin cancers, (2) an increase in damage to crops and trees, (3) stratospheric cooling leading to large-scale climate changes, and (4) additional production of tropospheric ozone as more and more uv radiation is able to penetrate into the atmosphere closer to Earth. In addition, CFCs themselves, like carbon dioxide and other compounds mentioned in Chapter 11, are greenhouse gases. 

---