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  • Wang, M., J. E. Overland, V. Kattsov, J. E. Walsh, X. Zhang, and T. Pavlova, 2007: Intrinsic Versus Forced Variation in Coupled Climate Model Simulations over the Arctic during the 20th Century. J. Climate, 20, 1093-1107, 10.1175/JCLI4043.1.

There were two major multi-year, Arctic-wide (60-90N) warm anomalies (> 0.7C) in land surface air temperature (LSAT) during the 20th century, between 1920-1950 and again at the end of the century (after 1979). Reproducing this decadal variability in coupled General Circulation Models (GCMs) is a critical test for understanding processes in the Arctic climate system and increasing the confidence in the IPCC model projections. Our study evaluated 63 realizations generated by 20 coupled GCMs made available for the IPCC 4th Assessment for their 20th century simulations (20C3M) and corresponding control runs (PIcntrl). Warm anomalies in the Arctic during the last two decades are reproduced by all ensemble members, but with considerable variability in magnitude among models. Eight models generated warm anomalies at least 2/3 of the observed mid-century warm event in at least one realization but not their timing. However, the durations of the early warm event in all the models are shorter than the observed. Large region-to-region, year-to-year, ensemble to ensemble, and model to model variability are seen in the simulations. These results suggest that the observed mid-century warm period is consistent with intrinsic climate variability, and one should not expect each ensemble member to have a year-to-year correspondence to the observed time series. Further, the variance of the control runs in nine models was comparable with the variance in the observations. Five models compare favorably to Arctic observations in matching both the variance in their control runs and representing the decadal mean temperature anomaly magnitude in their 20C3M simulation. Seven additional models could be given further consideration. Our results support selecting a subset of GCMs when making predictions for future climate by using performance criteria based on comparison with retrospective data.

Last Updated: 2009-07-09

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