The Future of Environmental Modeling


Background on the Environmental Model Guidance Document
and on the
Environmental Model Knowledge Base

In January 2004, the U.S. EPA released two products to improve EPA's use of environmental models (Draft Guidance on the Development, Evaluation, and Application of Regulatory Environmental Models and the Models Knowledge Base). The Agency frequently relies on a wide range of models to support regulatory decisions. These include models to simulate the fate of pollutants, to estimate pollution's impacts on human health and the environment, and to evaluate the costs and benefits of alternative policies for environmental protection. In the past, parties impacted by EPA's policies have sometimes questioned the credibility of these models.

These two complementary products work in tandem to describe and document good modeling practices. The guidance recommends best practices to help determine when a model, despite its uncertainties, can be appropriately used to inform a decision. The Knowledge Base is, a web-accessible database of information on some of EPA's most frequently used models, is intended to be a living demonstration of the recommendations from the Guidance for Environmental Models. The former recommends what information about models to document, while the latter serves as a repository where this information is documented. Currently, the Models Knowledge Base contains about 100 models. Both products are available from EPA's Council for Regulatory Environmental Modeling (CREM) Internet site at

By providing access to our tools and methods, the EPA increases transparency and can improve the public's understanding of how sound science is used to make environmental decisions. In short, these products help to foster a culture of building the black box, as models are sometimes referred to, out of plexiglass.