North Atlantic influence reconciling model-observation discrepancy in the tropical Pacific warming pattern.

Over the past four decades, zonal contrast in the tropical Pacific sea surface temperature (SST) has strengthened in observations but weakened in majority of climate model simulations. This model-observation discrepancy cannot be explained by internal mode of interdecadal climate variability in the Pacific alone, and the source of possible model errors remains unclear. Here, using observations and a large ensemble of historical simulations by a climate model, we identified that the simulated SST pattern associated with the Atlantic Multidecadal Variability (AMV) is biased in the tropical Pacific despite the time evolution of the AMV being reproduced well. Observations suggest that the positive AMV acts to increase the Pacific zonal SST contrast whereas this teleconnection process falsely weakens it in the model, which is a common feature in other climate models, and correcting the AMV-related SST pattern, which is likely an externally forced response, partly reconciles the model-observation discrepancy.