Diagnosing Biases in Tropical Atlantic-Pacific Multi-Decadal Teleconnections Across CMIP6 and E3SM Models

Abstract: Decadal-scale interactions between the tropical Atlantic and Pacific Oceans play a crucial role in global climate variability through bidirectional teleconnections. Current climate models show persistent biases in representing these basin interactions, particularly in simulating the Atlantic's influence on Pacific climate. Using historical simulations from 27 CMIP6 models and two configurations of the Energy Exascale Earth System Model (E3SM) during 1950-2015, we systematically evaluate tropical Atlantic-Pacific teleconnections through both Walker circulation and extratropical wave responses. Most models exhibit Pacific-dominated teleconnections, contradicting observational evidence of Atlantic control on Pacific variability during the past 40 years. By developing a performance metric that combines tropical circulation patterns and extratropical wave propagation, we identify two distinct model behaviors: high-skill models capture the bidirectional Atlantic-Pacific teleconnections with a secondary symptom of systematic 20-degree westward shifts in convective centers, while low-skill models display amplified Pacific dominance through reversed Walker circulation responses warming in both tropical basins. Comparative analysis between standard E3SMv2 and its multi-scale modeling framework configuration demonstrates that implementing more sophisticated cloud-scale processes alone, with limited model tuning, cannot resolve these teleconnection biases. Our results identify four CMIP6 models and E3SMv2 that effectively reproduce observed teleconnection pathways, offering a comprehensive diagnostic framework for evaluating decadal Atlantic-Pacific interactions in climate models.