Modelling long-term changes of mesospheric temperature and chemistry

Using an interactive, bi-dimensional model of the middle atmosphere, we simulate the long-term changes of temperature and chemistry in the mesosphere during the second half of the twentieth century, taking into account the 11-year solar cycle, the increase of water vapor at the tropopause, and the anthropogenic increases of methane and carbon dioxide. It is found that the long-term increase of water vapor at stratopause levels results in a long-term decrease of mesospheric ozone, hence of solar heating. The long-term mesospheric cooling due to this new mechanism is maximum in the lower mesosphere, and has the same order of magnitude as the cooling due to CO2 increase. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.