1. LINKAGES AND SYNERGIES OF REGIONAL AND GLOBAL EMISSION CONTROL Workshop of the UN/ECE Task Force on Integrated Assessment Modelling January 27-29, 2003 International Institute for Applied Systems Analysis European Topic Centre on Air and Climate Change Convention on Long-range Transboundary Air Pollution Cooperative programme for monitoring and evaluation of the long-range transmission of air pollutants in Europe

2. Questions What do we know about the linkages between air pollution and climate change? How important are these linkages? Which of these linkages could potentially influence rational policies to control emissions?

3. Sessions 1.Physical linkages through atmospheric chemistry 2.Physical linkages through environmental impacts 3.Concerns of national decision makers 4.Synergistic measures: Sectoral perspectives 5.Strategies to harness synergies 6.Economic instruments 7.Modelling approaches

4. Linkages through atmospheric chemistry Also air pollutants exert climate impacts Radiative forcing (RF) of ozone and PM are different in space and time from that of GHGs Sulphates, nitrates and organic carbon have cooling effect and can reduce precipitation Black carbon has positive forcing Ozone has strong positive RF, better understood than that of aerosols Methane influences RF and ozone CC impacts on meteorology seem less relevant for the next two decades

5. Linkages through environmental impacts Numerous linkages exist, not all of them are yet fully understood. CC might reduce ecosystems sensitivity to acidification Increased N deposition increases C storage Air pollution weakens plant growth, reduces C storage Air pollution and CC affect biodiversity

6. Synergies of multi-objective strategies Simultaneous emission controls result in multiple benefits. Synergies may free resources. Existing trade-offs should be considered. Global CO 2 stabilization will lead to lower SO 2 emissions. Extent depends on how reduction is achieved. Synergies in agricultural sector important. Significant ancillary benefits demonstrated in many case studies

7. Strategic aspects GHG emission trading schemes can have impacts on air pollution: C trading influences air pollution control costs C trading affects regional environmental impacts of air pollution. Ancillary (dis-)benefits should be considered. Effects of C trading are uncertain. This causes a problem for defining an air pollution baseline scenario.

8. Modelling the linkages Modelling requires bridging different temporal and spatial scales. Extension of multi-effect approach? Could offer a systematic tool for choosing multiple targets of different types. Models will have to address sustainable development and structural changes beyond cost-effectiveness. Keep models manageable!

9. The way forward Extension of RAINS towards greenhouse gas cost curves is underway to –Help decision makers maximizing positive synergies and minimizing trade-offs, and –Selecting most cost-effective measures in view of the objectives of both policy areas. Primary focus should be on scientific issues. Improved contacts between air pollution and climate change science communities necessary.