THE ROLE OF THE STRATOSPHERE IN CLIMATE CHANGE

A variety of climate perturbations have the potential to alter the thermodynamic and dynamical characteristics of the middle atmosphere, which may then affect tropospheric climate. Increased thermal emission from rising stratospheric CO2 levels and scattering of solar radiation from stratospheric volcanic aerosols have a direct impact on surface temperatures, while variations in stratospheric water vapor and ozone can affect tropospheric temperatures. Observations and modeling experiments suggest that these perturbations. as well as solar irradiance variations operating through the stratosphere, may affect tropospheric dynamics, such as planetary wave amplitudes and Hadley cell intensity. In addition, climate changes will probably alter tropospheric/stratospheric exchange. with the potential for modifying trace gas distributions and climate forcing. These issues are reviewed in the light of the incorporation of middle atmosphere studies into IGBP.