As the societal impacts of hazardous weather, air quality, and other environmental pressures grow, the need for integrated predictions which can represent the numerous feedbacks and linkages between sub-systems of our environment is greater than ever. In particular, atmospheric chemistry is playing a key role in driving climate on multiple temporal and spatial scales, while climate, seasonal, and synoptic-scale variability affect variability and trends in atmospheric composition. This session, co-sponsored by the WMO WWRP, GAW, and IGAC/WCRP SPARC CCMI focuses on the understanding of chemistry-climate-weather interactions and how they have shaped past and will shape future changes in both composition and climate/weather in the troposphere and the stratosphere. We invite abstracts on studies using regional to global, free-running and forecasting models and observations with the aim at understanding the complex interactions between composition, radiation, cloud physics and dynamics, as well as providing information on observation and model differences and uncertainties. Topics may include:

- Effects of climate change on tropospheric air pollution via meteorological effects, through to policy implications.
- Two-way interactions between atmospheric pollution/composition and climate variability/change.
- Radiative forcing of tropospheric and stratospheric ozone (and other greenhouse gas or aerosol) changes.
- Effects of ozone depletion and recovery on the Southern hemisphere surface climate and ocean circulation.
- Improved numerical weather prediction (NWP) and chemical weather forecasting (CWF) with short-term feedbacks of aerosols and chemistry on meteorological variables.
- Data assimilation of atmospheric composition.
- Evaluation, validation, and applications of coupled modelling systems.