Coordinated effects monitoring and modelling for developing and supportinginternational air pollution control agreements

For 20 years the Convention on Long-range Transboundary Air Pollution has w orked to control air pollutant emissions in Europe and North America. Its W orking Group on Effects (WGE) has been responsible for much of the underpin ning science. The WGE's six International Cooperative Programmes (ICPs) on Waters, Natural Vegetation and Crops, Forests, Materials and Cultural Herit age, Integrated Monitoring, and Modelling and Mapping, together with a Join t Task Force on Human Health with WHO, quantify air pollution effects on th e environment through monitoring, modelling and scientific review. Early wo rk found evidence to support the need for decreases in emissions of sulphur and nitrogen pollutants. More recently, monitoring results and models have provided the scientific basis, e.g. critical loads and levels, for effects -based Protocols and for evaluating their effectiveness. ICP studies on tre nds show recovery from acidification effects in keeping with the fall in su lphur emissions. Steady-state models provide an indication of long-term imp rovements. Recent increased emphasis on developing dynamic models will enab le better links between recovery rates and abatement strategies. The scient ific network of the ICPs and the monitoring and modelling results have been key to the development of the Convention and are an essential component fo r its success in the future.