A Dynamical Model of the Tropical Pacific Zonal SST Gradient Change Under Global Warming

Abstract How the tropical Pacific mean‐state sea surface temperature (SST) responds to global warming is an ongoing heated debate, as climate models are flawed and their projections are opposite to the observed zonal gradient strengthening. Here, we build a dynamical tropical Pacific air–sea coupled model that incorporates three key mechanisms of the forced response, the differential evaporative damping, the Pacific Walker circulation (PWC) weakening, and the ocean thermostat, to better understand how the long‐term zonal SST gradient responds to global warming. By choosing suitable parameters, this model can reproduce the long‐term zonal SST gradient weakening seen in climate models, demonstrating its ability to serve as an emulator. We find the sign and magnitude of the zonal SST gradient change depend strongly on the weakening rate of the PWC and the magnitude of the eastern Pacific subsurface warming, providing physical insights into understanding the diversity of the zonal SST gradient change across climate models.