This award provides funds to support a Workshop entitled Making Sense of the multi-model decadal prediction experiments from the Coupled Model Intercomparison Project (CMIP5). This Workshop will bring together researchers, primarily from the high-end climate modeling centers, with an objective to devise an analysis and evaluation methodology for the suite of decadal simulations. The Aspen Global Change Institute will also document the entire proceedings (e.g. power point presentations, background papers and supplementary references) at its website Methodologies essential for quantifying the reliability and credibility of decadal simulations will be developed, thus the intellectual merit is high. The Workshop will facilitate collaboration and analysis of the decadal prediction model output produced thus far and scientific results will be synthesized in a timely manner for inclusion in the IPCC AR5. One of the deliverables from this Workshop will be a peer-reviewed journal article that will be assessed as part of the forthcoming report of the Intergovernmental Panel for Climate Change (IPCC AR5). Thus the broader impacts of the activity is also high.

Project Report

In June 2011, the Aspen Global Change Institute hosted thirty-two scientists representing major climate modeling centers in the U.S. and abroad to participate in a workshop entitled, "Making Sense of the multi-model decadal prediction experiments from CMIP5." Decadal prediction, or near term climate prediction, has elicited a lot of interest in both the climate science and policy communities. However, decadal prediction is a new area of climate science and in recognition of this fact, a seminal 2008 AGCI session formulated a first-ever experimental design to address the science issues involved with decadal prediction that became incorporated in the Coupled Model Intercomparison Project phase 5 (CMIP5). Following this design phase, modeling groups from around the world began a set of CMIP5 experiments with the intention that they would be assessed as part of the IPCC AR5. A summary statement from the workshop participants described the challenge: "The rapidly evolving field of decadal climate prediction, using initialized climate models to produce time-evolving predictions of regional climate, is producing some of the first results for predictions, predictability, initialization, and evaluation." Most of the decadal experiments for CMIP5 are hindcasts designed to quantify expected skill of the predictions. These are 10-year hindcasts for initial states starting in 1960 and performed every five years, and two 30-year hindcasts for initial states of 1960 and 1980. There are two predictions for the initial state of 2005, one for 10 years and another for 30 years. There are a number of other optional experiments that some modeling groups may also perform. As the modeling groups begin to make the outputs of these decadal hindcasts/predictions available for analysis in late 2010 and early 2011, there have been produced a bewildering array of results that have to be synthesized in some way prior to their inclusion in the IPCC AR5. Early results indicate greater prediction skill out a few years with the benefit of incorporating initial conditions and after about 8 years as external forcing begins to dominate over internal variability. The AGCI session was designed to help make sense of the decadal hindcasts/predictions in terms of evaluation metrics, skill quantification, and summary figures that communicate the synthesis of the multi-model results. The product of the session is a forthcoming journal article that can then be assessed as part of the AR5. This AGCI workshop was the first time a synthesis of results was attempted of a multi-model dataset of decadal hindcasts/predictions and served as a vital contribution to the IPCC AR5. Videos and other proceedings of the workshop are available via the AGCI website:

National Science Foundation (NSF)
Division of Atmospheric and Geospace Sciences (AGS)
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Anjuli S. Bamzai
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Aspen Global Change Institute
United States
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