The PIAM approach to modular integrated assessment modelling

The next generation of integrated assessment modelling is envisaged as being organised as a modular process, in which modules encapsulating knowledge from different scientific disciplines are independently developed at distributed institutions and coupled afterwards in accordance with the question raised by the decision maker. Such a modular approach needs to respect several stages of the model development process, approaching modularisation and integration on a conceptual, numerical, and technical level. The paper discusses the challenges at each level and presents partial solutions developed by the PIAM (Potsdam Integrated Assessment Modules) project at the Potsdam Institute for Climate Impact Research (PIK). The challenges at each level differ greatly in character and in the work done addressing them. At the conceptual level, the notion of conceptual consistency of modular integrated models is discussed. At the numerical level, it is shown how an adequate modularisation of a problem from climate–economy leads to a modular configuration into which independently developed climate and economic modules can be plugged. At the technical level, a software tool is presented which provides a simple consistent interface for data transfer between modules running on distributed and heterogeneous computer platforms.