Constraints on the Projected Tropical Pacific Sea Surface Temperature Warming Pattern by the Tropical North Atlantic Cold SST Bias in CMIP6 Models

Abstract

Reliable projections of the tropical Pacific sea surface temperature (SST) warming (TPSW) patterns are critically important for exploring the future climate change. However, climate models suffer from long-standing common biases in simulating the present-day climate, raising doubts about the model projected TPSW patterns. Here by using outputs from 30 CMIP6 models, we find the projected TPSW patterns are significantly correlated with the simulated present-day SST in the tropical North Atlantic (TNA), with higher present-day TNA SSTs tending to project more weakened zonal SST gradients by producing more present-day low-level clouds and the resultant positive cloud–shortwave–SST feedbacks over the eastern equatorial Pacific. An emergent constraint using observed TNA SST reveals a consistent El Niño-like warming pattern in all models with more weakened zonal SST gradient than before in most models, together with a reduction of the inter-model uncertainty in the zonal SST gradient change by more than 20%.