Review of long-term trends in the upper mesosphere, thermosphere and ionosphere

A review of the recent publications on long-term variations (trends) in the temperature and composition of the mesosphere and thermosphere is given. It is shown that there is a large group of experimental data, which demonstrate that the upper mesosphere cooling theoretically predicted as a consequence of increased carbon dioxide amount really exists, though the amplitude of the effect is different according to different authors. The observed trends of the electron concentration and ion composition in the E region may be related to the same initial reason-the systematic changes of the temperature between the mesopause and turbopause. There are also several indications of the trends existing in the F region parameters, however currently one can not yet definitely say which thermospheric parameter is the cause. (C) 1998 COSPAR. Published by Elsevier Science Ltd.