The preponderance of evidence in the scientific community supports the premise that global climate is changing.  The precise impacts of climate change on natural and man-made systems remain less certain.  Estimation of climate change impacts on river flows, water supply reliability, and ecosystem responses requires the careful application of a variety of models including global or regional circulation models, decision scaling of this information, hydrologic models, and ecosystem response models.  This presentation addresses all stages of this process, but focusses primarily on the need to characterize our current uncertainty about use of climate information in advising large-scale, public decision making.  The presentation will begin with a brief description of forecasted impacts of climate change on the US.  Next, techniques that attempt to appropriately translate these broad climate shifts to the watershed scale in a fashion useful for decision making are described.  Our focus then turns to how best to frame this information for decision makers.

The presentation concludes with examples of how outputs from general circulation models have been used in past water resources studies, both on the east and west coasts.  The examples highlight how the engagement of stakeholders in the evaluation of the potential impacts of climate change significantly improves the level of understanding of the uncertainty of the
information and greatly increases the likelihood that the results will be used in “real” decision making.  The presentation concludes with a discussion of current limits of these techniques and suggests how these limitations may be overcome by the next generation of future engineers and scientists.