Technical modeling for policy making: Integrated modeling of a large environmental system

Abstract

Increasingly, models of technical and environmental systems are being developed to support decisions related to the setting of public policy. These efforts are aimed at providing tools which can be used in a variety of roles, such as: for assessment - to test alternative assumptions about the form or parameters of a model or the impact of a proposed action; for research management - to identify and rank model components or parameters in terms of sensitivities or uncertainties according to their influence on predicted behavior; or for education and program integration - to explore how factors in complex systems interact and relate to one another. From the earliest planning stages, the design and implementation of these models must reflect their intended use and the manner in which the results will be incorporated into the policy making process. The modeling of large, integrated environmental systems for policy making creates additional constraints which require the consideration and trading off of many other factors. The model developer must reflect an understanding of who will be using the model, how they prefer to operate, what questions they are likely to want to address, how detailed or aggregated they will want information to be, and the immediacy with which they will require model results. These considerations, which can be unique for each new application of the model, are more difficult to define and constrain in the context of policy analysis than for traditional technical modeling. However, these are central to developing models with a greater probability of being used effectively in support of policy making. These considerations also carry implications with regard to selections of appropriate software and hardware systems; choice of a modeling structure; the adequacy of user interfaces; and the design of model input and output formats. An integrated modeling framework developed by the authors for the National Acid Deposition Assessment Program to simulate the linked set of physical, chemical, and biological processes associated with the environmental problem of acid deposition is examined from the perspective of assessing the intended uses and users of the model and the trade-offs inherent in planning and developing a scientifically credible model for policy analysis and synthesis.