Assessment of CMIP6 Models' Performance for South America: Multilevel Perspective

The selection of global climate models (GCMs) that represent the main features of the present climate is crucial for reducing uncertainties when assessing climate trends or driving regional climate models. Based on this premise, the main goal of this study is to assess the skill of 17 GCMs from the Coupled Model Intercomparison Project - Phase 6 (CMIP6) in representing basic features of the present climate (1979-2014). As the analyses are performed for different atmospheric variables and vertical levels, the study is considered multilevel. Different statistical metrics are used to compare the simulations with ERA5 reanalysis focusing on 5 subdomains of South America (SA): northern Amazon Basin (NAMZ), southern Amazon Basin (SAMZ), Northeast region of Brazil (NEB), South American Monsoon (SAM) and La Plata Basin (LPB). The statistics are summarized through a comprehensive rating index, which is described in detail in this study, in order to provide the models' ranking in terms of performance. Among the results, model performance varies across regions and variables. Models such as CNRM-CM6-1, GFDL-ESM4, MPI-ESM1-2-HR, and NorESM2-MM stand out for their superior performance across multiple variables and regions, whereas INM-CM4-8, KIOST, and NESM3 show limitations, particularly in simulating upper-level circulation and precipitation processes. Therefore, the main conclusion is that models should be chosen based on their performance in the region of interest.