An ongoing project of the Program is to utilize the Integrated Global System Model (the IGSM) to identify the impacts of global environmental change on energy and economic activities, land productivity, agricultural production, and human health. Assessments of uncertainties in the human-climate interaction, and the associated societal risks, are needed to inform decision-making and policy formulation. We are working to describe uncertainty in quantitative terms, and to assess the extent to which mitigation policies may be able to reduce the risk of extreme climatic change and other dangerous levels of interference in the Earth system.