Lessons learned from ozone thematic session 2016 Short presentations: Augustin Colette: Current scientific knowledge and understanding about past and predicted future ozone trends Frank Dentener: Contributions of the hemispheric transport of air pollution to ozone levels as well as local peaks Marie-Eve Heroux: Impacts of ozone on health – indicator to be used in impact assessments Harry Harmens: Impacts of ozone on ecosystems – indicator to be used in impact assessments Isaura Rabago: Ozone issues specific to the Mediterranean in the current and future climate Xavier Querol: The origin of the highest ozone episodes in Spain Discussion: Ideas & priorities for future research agenda (2018- 2019) to support policy response to Assessment Report and upcoming mid-term review of the Long Term Strategy

Priorities for the future (1) Long-term (>20 years), good quality ozone data required to assess trends Understanding trends is necessary to understand LRT contributions - and the anthropogenic part of it. Determine main driving forces for changes in ozone profile and trends (e.g. 1960 – 2000: Emission changes only explain 30-50 % of ozone changes at baseline stations ) Determine trends and projections (including climate dependent receptor scenarios) in ozone exposure proxies and impacts Europe: analyse changes of ozone concentration frequencies due to regional and extra-regional emission perturbations (HTAP 2) Apply new regional tools to global models to gain new insights and learn from regional differences (e.g. TOAR data: present to CLRTAP) Test if Ox (O3+NO2) can facilitate understanding of trends & attribution

Priorities for the future (2) Vegetation: flux-based approach (allows incorporation CC & N interactions): Identification of crops, ecosystems and regions/areas globally most vulnerable to ozone pollution and climate change (including extreme events); impacts on biodiversity Collate evidence; need for experiments with current O3 profile; Inform agricultural community (primarily interested in soil moisture and N impacts) of ozone impacts on crop yield Mediterranean: apply Med.-specific flux-effects relationships and model parameterisation in risk assessments (e.g. EMEP model) Effect soil moisture important EMEP/WGE working group to assess feasibility and scope Health: New indicator required for chronic ozone impacts: SOMO10 or continue with SOMO35? Evidence needed to support indicator.

Additional comments Can we do more in Europe to mitigate ozone concentrations and impacts? Yes, but comes at a cost What can we learn more from past data to improve predictions in the future (e.g. Eurodelta trend analysis)? Translate concentration/deposition trends into impacts, and for both assess % contribution from local pollution and from baseline/LRT. Imbalance in progress made with LRT modelling and data we have for impacts for current ozone profile (many impacts data from 1980s/90s which high ozone peaks, not enough data on impacts of rising baseline concentration). Don’t forget: ozone impacts on vegetation feed back to the climate and surface ozone concentrations