Clim. Past Discuss., 9, 775-835, 2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP.
Using paleo-climate comparisons to constrain future projections in CMIP5
G. A. Schmidt1, J. D. Annan2, P. J. Bartlein3, B. I. Cook1, E. Guilyardi4,5, J. C. Hargreaves2, S. P. Harrison6,7, M. Kageyama8, A. N. LeGrande1, B. Konecky9, S. Lovejoy10, M. E. Mann11, V. Masson-Delmotte8, C. Risi12, D. Thompson13, A. Timmermann14, L.-B. Tremblay10, and P. Yiou8
1NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA
2Research Institute for Global Change, JAMSTEC, Yokohama Institute for Earth Sciences, Yokohama, Japan
3University of Oregon, Eugene, OR 97403, USA
4NCAS-Climate, University of Reading, Whiteknights, P.O. Box 217, Reading, Berkshire, RG6 6AH, UK
5Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques/Institut Pierre Simon Laplace, UMR7617, CNRS-IRD-UPMC, 4 place Jussieu, 75252 Paris Cedex 05, France
6University of Reading, Whiteknights, P.O. Box 217, Reading, Berkshire, RG6 6AH, UK
7Macquarie University, Sydney, NSW 2109, Australia
8Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS-UVSQ/Institut Pierre Simon Laplace), UMR8212, CE Saclay l'Orme des Merisiers, 91191 Gif-sur-Yvette, France
9Brown University, 324 Brook St., P.O. Box 1846, Providence, RI 02912, USA
10McGill University, 805 Sherbrooke Street West, Montreal, Quebec H3A 0B9, Canada
11Pennsylvania State University, University Park, PA 16802, USA
12Laboratoire de Météorologie Dynamique/Institut Pierre Simon Laplace, 4, place Jussieu, 75252 Paris Cedex 05, France
13University of Arizona, Department of Geosciences, Gould-Simpson Building #77, 1040 E 4th St. Tucson, AZ 85721, USA
14University of Hawaii, 2525 Correa Road, Honolulu, HI 96822, USA

Abstract. We present a description of the theoretical framework and "best practice" for using the paleo-climate model component of the Coupled Model Intercomparison Project (Phase 5) (CMIP5) to constrain future projections of climate using the same models. The constraints arise from measures of skill in hindcasting paleo-climate changes from the present over 3 periods: the Last Glacial Maximum (LGM) (21 thousand years before present, ka), the mid-Holocene (MH) (6 ka) and the Last Millennium (LM) (850–1850 CE). The skill measures may be used to validate robust patterns of climate change across scenarios or to distinguish between models that have differing outcomes in future scenarios. We find that the multi-model ensemble of paleo-simulations is adequate for addressing at least some of these issues. For example, selected benchmarks for the LGM and MH are correlated to the rank of future projections of precipitation/temperature or sea ice extent to indicate that models that produce the best agreement with paleoclimate information give demonstrably different future results than the rest of the models. We also find that some comparisons, for instance associated with model variability, are strongly dependent on uncertain forcing timeseries, or show time dependent behaviour, making direct inferences for the future problematic. Overall, we demonstrate that there is a strong potential for the paleo-climate simulations to help inform the future projections and urge all the modeling groups to complete this subset of the CMIP5 runs.

Citation: Schmidt, G. A., Annan, J. D., Bartlein, P. J., Cook, B. I., Guilyardi, E., Hargreaves, J. C., Harrison, S. P., Kageyama, M., LeGrande, A. N., Konecky, B., Lovejoy, S., Mann, M. E., Masson-Delmotte, V., Risi, C., Thompson, D., Timmermann, A., Tremblay, L.-B., and Yiou, P.: Using paleo-climate comparisons to constrain future projections in CMIP5, Clim. Past Discuss., 9, 775-835, doi:10.5194/cpd-9-775-2013, 2013.
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