NA - Stratospheric ozone depletion and climate change in the Arctic region

Ozone is the third most important greenhouse gas according to IPCC. Its distribution in the stratosphere and the troposphere is affected by human activity and has therefore changed significantly over the last decades. Emission of ozone precursors has lead to ozone increases in the troposphere, while ozone depleting substances, has lead to ozone decreases in the stratosphere. Of particular interest for the planned project are ozone changes and links to atmospheric climate changes, and what effect this has on ozone layer recovery as chlorine levels have started to decrease We have been involved in modeling of ozone changes in the atmosphere for more than two decades and have published a number of articles on the issue in international journals. We have had and have coordinated, and have had key roles in several EU projects (TRADOFF, ACCENT, QUANTIFY, SCENIC, SCOUT-O3) and NFR projects (CHEMCLIM, AerOzClim). In the proposed project we will extend our activity to the modeling of climate-chemistry interaction with particular focus on the high latitude stratosphere by collaboration with experienced climate modeling groups in the US. The NCAR group is a leading climate modeling group, which has experience in stratospheric studies, while we already have collabora tion on tropospheric climate-chemistry modeling with the SUNYA group that will be the basis for the new project. We will contribute to the collaboration with our experience in modeling of chemical changes. Before a collaborative proposal can be submitted, planning of collaboration, the role of the groups in the modeling activities, exchange of personal (PhD, post docs) and financing, has to be planned. The project will contribute to the accepted international IPY activity on polar ozone loss. The project will also contribute to our extensive European collaboration through EU projects: QUANTIFY and SCOUT-O3.It will build on the NFR projects which we coordinate and where we collaborate with NILU.