On Modeling the Upper Atmosphere and Ionosphere Response to Global Change

Abstract

Ice core records indicate that the temperature and composition of the atmosphere can change significantly over geologic times. These changes occur naturally, however, recently the releases of trace gases from human activity have been recognized to have a potential for causing a significant change in the climate of the Earth. Most of the effort in investigating the global response to these trace gases has been directed toward the troposphere and stratosphere. Studies have shown that the troposphere will warm and the stratosphere will cool as trace gas concentrations increase in the 21st century. Studies have also been made that suggest that the mesosphere and thermosphere could also cool and affect the compositional structure of the upper atmosphere and ionosphere. We first review previous studies of the upper atmosphere and ionosphere response to trace gas increases. We then use both a global average model and the NCAR Thermosphere - Ionosphere - Mesosphere - Electrodynamics General Circulation Model (TIME-GCM) to investigate the atmospheric response to various scenarios of trace gas increases and compare the modeling results to the present day upper atmosphere and ionosphere structure. We will also discuss the key aeronomic processes that control the structure of the upper atmosphere as well as the extent to which these processes are known.