Rethinking the Default Construction of Multimodel Climate Ensembles

Journal Article · Tue Jul 21 00:00:00 EDT 2015 · Bulletin of the American Meteorological Society

DOI:https://doi.org/10.1175/BAMS-D-13-00181.1· OSTI ID:1408078

Rauser, Florian ^[1]; Gleckler, Peter ^[2]; Marotzke, Jochem ^[1]

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1. Max Planck Institute for Meteorology, Hamburg (Germany)
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Here, we discuss the current code of practice in the climate sciences to routinely create climate model ensembles as ensembles of opportunity from the newest phase of the Coupled Model Intercomparison Project (CMIP). We give a two-step argument to rethink this process. First, the differences between generations of ensembles corresponding to different CMIP phases in key climate quantities are not large enough to warrant an automatic separation into generational ensembles for CMIP3 and CMIP5. Second, we suggest that climate model ensembles cannot continue to be mere ensembles of opportunity but should always be based on a transparent scientific decision process. If ensembles can be constrained by observation, then they should be constructed as target ensembles that are specifically tailored to a physical question. If model ensembles cannot be constrained by observation, then they should be constructed as cross-generational ensembles, including all available model data to enhance structural model diversity and to better sample the underlying uncertainties. To facilitate this, CMIP should guide the necessarily ongoing process of updating experimental protocols for the evaluation and documentation of coupled models. Finally, with an emphasis on easy access to model data and facilitating the filtering of climate model data across all CMIP generations and experiments, our community could return to the underlying idea of using model data ensembles to improve uncertainty quantification, evaluation, and cross-institutional exchange.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23). Climate and Environmental Sciences Division
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1408078
• Report Number(s): LLNL-JRNL--662060
• Journal Information: Bulletin of the American Meteorological Society, Journal Name: Bulletin of the American Meteorological Society Journal Issue: 6 Vol. 96; ISSN 0003-0007
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English

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54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES