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Collins, M., and CMIP Modeling Groups, 2005: El Niño- or La Niña-like climate change? Clim. Dynam., 24, 89-104, doi:10.1007/s00382-004-0478-x.
The potential for the mean climate of the tropical Pacific to shift to more El Niòo-like conditions as a result of human induced climate change is subject to a considerable degree of uncertainty. The complexity of the feedback processes, the wide range of responses of different atmosphere-ocean global circulation models (AOGCMs) and difficulties with model simulation of present day El Niòo southern oscillation (ENSO), all complicate the picture. By examining the components of the climate-change response that projects onto the model pattern of ENSO variability in 20 AOGCMs submitted to the coupled model inter-comparison project (CMIP), it is shown that large-scale coupled atmosphere-ocean feedbacks associated with the present day ENSO also operate on longer climate-change time scales. By linking the realism of the simulation of present day ENSO variability in the models to their patterns of future mean El Niòo-like or La Niòa-like climate change, it is found that those models that have the largest ENSO-like climate change also have the poorest simulation of ENSO variability. The most likely scenario (p=0.59) in a model-skill-weighted histogram of CMIP models is for no trend towards either mean El Niòo-like or La Niòa-like conditions. However, there remains a small probability (p=0.16) for a change to El Niòo-like conditions of the order of one standard El Niòo per century in the 1% per year CO2 increase scenario.
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