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Abstract

Abstract Sources of uncertainty (i.e., internal variability, model and scenario) in Atlantic Niño variability projections were quantified in 49 models participating in the Coupled Model Intercomparison Phases 5 (CMIP5) and 6 (CMIP6). By the end of the twenty-first century, the ensemble mean change in Atlantic Niño variability is ?0.07 ± 0.10?C, with 80% of CMIP models projecting a decrease, and representing a 16% reduction relative to the 1981?2005 ensemble mean. Models' projections depict a large spread, with variability changes ranging from 0.23?C to ?0.50?C. Internal variability is the main source of uncertainty until 2045 but model uncertainty dominates thereafter, eventually explaining up to 80% of the total uncertainty. The scenario uncertainty remains low (<1%) throughout the twenty-first century. The total uncertainty on Atlantic Niño variability projections is not improved when considering only CMIP models with a realistic zonal equatorial Atlantic sea surface temperature gradient.