Evidence of the impacts of climate change on the middle and upper atmosphere is increasing, making clear the critical need for observational data to monitor and understand trends. For example, a contraction of the stratosphere has been quantified, but we still face significant limitations on the data available to assess it. Past efforts to study trends have focused mainly on the atmospheric levels separately (mesosphere, thermosphere, ionosphere), where cooling and contraction have also been observed. Monitoring these trends and their impacts on satellites and space debris needs a continued effort, providing better data and improved insight into the consequences that increased carbon dioxide has on the middle and upper atmosphere.

This session concerns changes in the structure of the atmosphere through all their dimensions, vertical and horizontal: contractions, heating and cooling, and changes in atmospheric circulation (e.g., related to tropical expansion). Also, the impacts of atmospheric contraction, for example, on the drag of space objects. We especially welcome presentations about existing data, data gaps and measurements to monitor trends in the middle and upper atmosphere. Also, studies evaluating causes, documenting, modelling or projecting changes in these layers.