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

• Published in: Geophysical Research Letters
• Main Authors: Qibei Zhang, Bo Liu, Shuanglin Li, Tianjun Zhou
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: global SST bias; CMIP; coupled climate models; Geophysics. Cosmic physics; QC801-809; North Atlantic; Southern Ocean
• Online Access: https://doi.org/10.1029/2022GL100888; https://doaj.org/article/b85408bdba4543aba6dadb575729892b

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