A new analytic method for finding policy-relevant scenarios

Scenarios play a prominent role in policy debates over climate change, but questions continue about how best to use them. We describe a new analytic method, based on robust decision making, for suggesting narrative scenarios that emerge naturally from a decision analytic framework. We identify key scenarios as those most important to the choices facing decision makers and find such cases with statistical analysis of datasets created by multiple runs of computer simulation models. The resulting scenarios can communicate quantitative judgments about uncertainty as well as support a well-defined decision process without many drawbacks of current approaches. We describe an application to long-term water planning in California.