The Synthesis Report of the Intergovernmental Panel on Climate Change (IPCC) Third Assessment concluded that one of the key uncertainties regarding regional climate change was "relating regional trends to anthropogenic climate change". Recent studies have shown that an anthropogenic climate change signal can be detected in surface temperature changes at continental scales. This project will use methods from detection and attribution of climate change to estimate the fraction of the observed temperature changes at regional scales in the United States (US) that can be attributed to anthropogenic forcing and other climate forcing factors. These methods will be applied to mean, minimum and maximum temperatures for both annual and seasonal averages, as well as to temperature extremes. Optimal fingerprint analysis of the temperature changes over the last 100 years will be used to constrain estimates of future global and regional temperature changes from a number of different climate models and to develop probability distributions of the regional temperature changes. Through collaboration with the climateprediction.net group in England, their very large perturbed parameterization ensemble of transient climate change simulations will be used to better estimate the uncertainties in current and future regional climate change projections for the US.
Many aspects of the research are innovative. The regional attribution of climate change and the scaling of modeled signals of anthropogenic climate change have not been undertaken previously, but are extensions from recent studies. A novel approach to enhancing the anthropogenic temperature change signal relative to natural variability by removing the rainfall related temperature variations will be applied in the US region, with preliminary results indicating that it is likely to enhance the signal-to-noise ratio. The application of the climateprediction.net ensemble simulations to regional climate change projections is an extension of their earlier work.
Broader Impacts: This project directly addresses two of the five goals of the Strategic Plan of the US Climate Change Science Program (CCSP) through quantification of the contribution of different factors to observed climate change in the US and estimation of probability distributions for projections of future climate change in the US. The expected outcomes of this research are likely to have significant impact internationally and in the US. Quantifying the contribution to regional climate change due to greenhouse forcing will assist policymakers in reaching decisions about policies on greenhouse gas emission reductions or adaptation to greenhouse climate change. The probability distributions of different regional climate changes due to greenhouse forcing will be very useful in better quantifying the possible impacts of regional climate change and estimating the costs or benefits of regional climate change. These probability distributions of regional climate changes can be used as improved inputs to economic models, ecosystem models, or agricultural models. The results will be provided as inputs to the relevant CCSP synthesis products and to the next IPCC assessment.
In addition to the scientific outcomes and inputs to scientific assessments, there will be important training outcomes from this project. Both the graduate student and research fellow employed on this project will gain valuable training and experience in climate change science, which will allow them to contribute better to future research and development in climate change and its impacts in the US.
