The uncertainty of the ensemble mean should decrease with the square root of the number of independent time steps. There are large inter-model differences. This remains true for other variables: Net Surface Heat flux, PR, Sea Surface Height, SST regressed on SSH, SST, Taux, Taux regressed on SST, Tauy
project: CMIP6
experiment: historical
epoch lengths: 30, 45, 60, 75, 90, 105, 120, 135, 150-year
regions: Niño4 (5N-5S, 160E-150W), Niño3.4 (5N-5S, 120-170W), Niño3 (5N-5S, 90-150W)
variable: NHF regressed on SST (seasonal cycle removed)
statistics: correlation, slope
Computed using equation (9) from Planton et al. (preprint)