Improvements and persistent biases in the southeast tropical Atlantic in CMIP models

Abstract State-of-the-art climate models simulate warmer than observed sea surface temperatures (SST) in eastern boundary upwelling systems (EBUS), generating biases with profound implications for the simulation of present-day and its future projections. Amongst all EBUS, bias is largest southeastern tropical Atlantic (SETA). Here, we provide a comprehensive evaluation performance SETA Coupled Model Intercomparison Project phase 6 (CMIP6), including fine resolution (HighResMIP) ocean-forced (OMIP) models. We show that remain large CMIP6 but are reduced HighResMIP, OMIP giving best performance. The analysis suggests that, once local forcing errors have been reduced, major source lies equatorial Atlantic. This study shows finer model has helped reduce origin SST further developments physics schemes will be required to make progress.