Impact of Radiatively Active Trace Gases on Long-Term Changes in the Middle Atmosphere

We conduct model simulations to examine how changes in concentration of radiatively active trace gases affect long-term changes in the middle atmosphere. We focus our model study on the impact of increases in carbon dioxide and methane, and decreases in ozone, between 1983 and 2003. The increase of carbon dioxide can cool the middle atmosphere through infrared emission at 15 microns, ozone depletion can cause cooling in the stratosphere and mesosphere through reduced solar heating, whereas the enhancement of methane, which increases water vapor, can introduce a cooling through reduced chemical heating or a warming through increased solar heating. We investigate the effect of each gas separately as well as the combined effect, using the National Center for Atmospheric Research (NCAR) Whole Atmosphere Community Climate Model (WACCM).