Attribution and prediction of global and regional warming requires a better understanding of the magnitude and spatial characteristics of internal global-mean surface air temperature (GMST) variability. We examine interdecadal GMST variability in Coupled Modeling Intercomparison Projects Phase 3, 5, and 6 (CMIP3, CMIP5, CMIP6) pre-industrial control (piControl), last millennium, and historical simulations and in observational data. We find that several CMIP6 simulations show more GMST interdecadal variability than the previous generations of model simulations. Nonetheless, when we compare 100-year trends in CMIP6 piControl simulations to observed global warming trends, we find that GMST trends in unforced simulations never exceed the maximum observed warming. Furthermore, interdecadal GMST variability in the unforced piControl simulations is associated with regional variability in the high latitudes and the east Pacific, whereas interdecadal GMST variability in historical simulations with external forcing and in instrumental data is more globally coherent and is associated with variability in tropical deep convective regions.