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North Atlantic influence reconciling model-observation discrepancy in the tropical Pacific warming pattern
Yueh-Chi Lin1, Masahiro Watanabe2
1Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan. yueh-chi@aori.u-tokyo.ac.jp.
Nature Communications
|May 28, 2026
Summary
Climate models struggle to replicate tropical Pacific sea surface temperature (SST) trends. A bias in simulating the Atlantic Multidecadal Variability (AMV) teleconnection is identified as a key factor, affecting Pacific zonal SST contrast.
Area of Science:
- Climate Science
- Oceanography
- Atmospheric Science
Background:
- Observed tropical Pacific sea surface temperature (SST) zonal contrast has strengthened over the past four decades.
- Climate model simulations predominantly show a weakening of this SST zonal contrast, indicating a model-observation discrepancy.
- Internal variability of the Pacific Ocean alone does not explain this divergence.
Purpose of the Study:
- To investigate the source of model errors in simulating tropical Pacific SST trends.
- To identify the role of the Atlantic Multidecadal Variability (AMV) in the model-observation discrepancy.
- To assess whether correcting AMV-related biases can reconcile climate model simulations with observations.
Main Methods:
- Analysis of observational data and a large ensemble of historical climate model simulations.
- Identification and evaluation of the simulated SST pattern associated with the Atlantic Multidecadal Variability (AMV).
- Comparison of observed and simulated teleconnection between AMV and Pacific zonal SST contrast.
Main Results:
- Climate models exhibit a bias in the tropical Pacific SST pattern linked to the AMV, despite accurately reproducing AMV's temporal evolution.
- Observations show a positive AMV increases Pacific zonal SST contrast, while the model incorrectly simulates a weakening effect.
- This AMV-related bias is a common feature across multiple climate models.
Conclusions:
- The biased simulation of the AMV teleconnection in the tropical Pacific is a significant contributor to the model-observation discrepancy in SST zonal contrast.
- Correcting this externally forced AMV-related SST pattern bias offers a pathway to partially reconcile climate model simulations with observed trends.
- Further research into externally forced responses is crucial for improving climate model fidelity.
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