Comparing the decision-relevance and utility of alternative ensembles of climate projections in water management and other applications

Abstract:

Decisions to manage the risks of climate change hinge, among many other things, on deeply uncertain and imperfect climate projections. Improving the decision relevance and utility of climate projections requires navigating a trade-off between increasing the physical realism of the model (often by improving the spatial resolution) and increasing the representation of decision-relevant uncertainties. This talk will examine the decision-relevance and utility of alternative ensembles of climate information by comparing two decision support applications, in water management and biodiversity perseveration, both in California. The climate ensembles will consist of different combinations of high and medium resolution projections from NARCCAP (North American Regional Climate Assessment Program) as well as low resolution, but more numerous, projections from the CMIP3 and CMIP5 ensembles. The decision support applications will use the same ensembles of climate projections in different contexts. Workshops with decision makers examine the extent to which the different ensembles lead to different decisions, the extent to which considering a wider range of uncertainty affects decisions, the extent to which decision makers' confidence in the projections and the decisions based on them will be sensitive to the resolution at which they are communicated and the resolution dependent skill, and how the answers to these questions varies with the water management and biodiversity contexts. This study aims to provide empirical evidence to support judgments on how best to use uncertainty climate information in water management and other decision support applications.