The limitations of integrated assessment modelling in developing air pollution control policies

Integrated assessment models such as the IIASA RAINS model have been used in developing pollution control policies in Europe over recent years. Large uncertainties occur in all subunits of such models, especially in energy scenarios, abatement costs, emission-deposition-transport relationships, and the definition of the environmental targets. The effects of these uncertainties, together with errors in input data, have been investigated for the RAINS 7.2 modelling used in developing the initial EU Acidification Strategy proposals. Changes in input data, well within these uncertainties, can lead to significantly different "optimal" strategies, with large differences in absolute levels of costs and their distribution between countries. It may be concluded that the outputs of integrated assessment models can only be a guide to policymaking, and should not be accepted uncritically. Model output should always be accompanied by a full uncertainty analysis, and the model and data used should be subject to thorough peer review.