Integrating physical and social modelling - the example of climate change

Climate change brings into sharp relief the most difficult problems in addressing the interaction between science and policy. Instead of trying to solve an existing environmental problem one tries to prevent a problem that scientists expect to come. Results from model simulations have an unprecedented role in shaping the public debate. Forecasts of climate change and potential impacts are basic for any risk assessment. Economic models that compare costs and benefits of different measures provide important arguments for discussing response strategies. Modelling approaches in climate and economics draw their legitimisation largely from their being based on a body of theory that is well accepted in the scientific community. However, the information available for policy makers is plagued by large inherent uncertainties. Reality is complex and the prediction of future developments is beyond our capacities now and for the foreseeable future. In situations where decision stakes are high and uncertainty looms large the role of scientific arguments in general and of model simulations in particular may have to change ( Pahl-Wostl et al 1998, Funtowicz and Ravetz 1996). We note little effort in the community of economists to take complexity and its implications into account. We argue therefore that another tradition of modelling, social simulation, is more appropriate in dealing with the complex environmental problems we face today.