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  • Sang-Wook Yeh and B. P. Kirtman, 2007: ENSO amplitude changes due to climate change projections in different coupled models. Journal of climate, 20, 203-217.

Four climate system models are chosen here for an analysis of ENSO amplitude changes in 4xCO2 climate change projections. Despite the large changes in the tropical Pacific mean state, the changes in ENSO amplitude are highly model dependant. In order to investigate why similar mean state changes lead to very different ENSO amplitude changes, we analyze the characteristics of sea surface temperature anomaly (SSTA) variability simulated in two coupled general circulation models (CGCMs): the Meteorological Research Institute (MRI) and Geophysical Fluid Dynamics Laboratory (GFDL) models. The skewed distribution of tropical Pacific SSTA simulated in the MRI model suggests the importance of non-linearities in the ENSO physics, whereas the GFDL model lies in the linear regime. Consistent with these differences in ENSO regime, the GFDL is insensitive to the mean state changes, whereas the MRI model is sensitive to the mean state changes associated with the 4xCO2 scenario. Similarly, the low frequency modulation of ENSO amplitude in the GFDL model is related to atmospheric stochastic forcing, but in the MRI model the amplitude modulation is insensitive to the noise forcing. These results suggest that the understanding of changes in ENSO statistics among various climate change projections is highly dependent on whether the model ENSO is in the linear or non-linear regime.

Last Updated: 2007-02-27

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