Uncertainties in integrated assessment modelling of abatement strategies: illustrations with the ASAM model

Following the signing of the Second Sulphur Protocol in 1994 under the 1979 Convention on Long-range Transboundary Air Pollution, preparations are now underway for a new multi-pollutant multi-effects protocol, under the auspices of the United Nations Economic Commission for Europe (UN ECE). A number of scientific models have been used to provide policy makers involved in these preparations with sound scientific information. These include the Abatement Strategies Assessment Model (ASAM). ASAM has recently been extended to cover abatement strategies for NH₃ and NOx as well as SO₂, in order to address the amelioration of acidification and eutrophication in the ECE region. It is important to be able to demonstrate that the scientific information provided to policy makers is robust to uncertainties, and hence there is a need for a thorough sensitivity analysis. In this study ASAM is used to demonstrate a large degree of robustness of derived abatement strategies to uncertainties in critical loads, meteorological data and cost information. This is based on a comparison of strategies at the same overall abatement cost. Systematic changes in data are shown to influence model results more profoundly than random changes.