Understanding Models' Global Sea Surface Temperature Bias in Mean State: From CMIP5 to CMIP6

This paper evaluates sea surface temperature (SST) biases of coupled models participating in Coupled Model Intercomparison Project Phase 5 (CMIP5) and CMIP6. Overall, CMIP6 perform better than CMIP5 ones reproducing SST climatology, with lower multi-model ensemble mean (MME) globally averaged absolute bias (1.17 vs. 1.31 K). MME global annual shifts from cooling (−0.09 ± 0.52 K) to warming (0.23 0.60 Regionally, over the Northwest Pacific North Atlantic are reduced by 20% 18%, while Northeast Pacific, Southeast Southern Ocean increased 25%, 16% 107% respectively. These changes mainly attributed combined effects aggravated positive (or alleviated negative) clear-sky downward longwave radiation, negative cloud radiative effect, partially enhanced shortwave radiation.