Fully Coupled Chemistry–Climate Model Simulations: Evaluation with Observations and Future Evolution of the Ozone Layer in a Changing Climate

Abstract

The use of Chemistry-Climate Model (CCM) simulation results is an important contribution assessing the future evolution of the stratospheric ozone layer in a changing climate. In the run-up to such prediction studies the CCMs have to be evaluated in detail with respective measurements. This is one foundation determining the quality of the model systems, for instance regarding their ability to reproduce short- and long-term variability including recent trends. As an example, this evaluation procedure is shortly described as carried out with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. Two investigations are introduced showing how to use the hierarchy of model simulations for scientific investigations, starting with a specified dynamics simulation, serving as the basis for evaluation studies and beyond that using free-running hindcast simulations (representing the past) and projection simulations (until year 2100) to assess the temporal evolution of the ozone layer. In the second part of this presentation an overview of the complete set of CCM results are discussed, which have been prepared and analyzed in a joint effort for the current UNEP/WMO Scientific Assessment of Ozone Depletion: 2018. These activities have been coordinated within the IGAC/SPARC Chemistry-Climate Model Initiative (CCMI), among others defining and investigating the scenario and sensitivity studies with the CCMs.