Negligible Unforced Historical Pattern Effect on Climate Feedback Strength Found in HadISST-Based AMIP Simulations

Abstract Recently it has been suggested that natural variability in sea surface temperature (SST) patterns over the historical period causes a low bias estimates of climate sensitivity based on instrumental records, addition to by time variation feedback parameter atmospheric general circulation models (GCMs) coupled dynamic oceans. This excess, unforced, “pattern effect” (the effect evolving strength) found simulations performed using GCMs driven AMIPII SST and ice changes (amipPiForcing). Here we show, both amipPiForcing experiments with one GCM Green’s functions derived from another GCM, whether such an unforced pattern is depends underlying dataset used. When replacing usual SSTs those HadISST1 experiments, unaltered, first indicates effects are indistinguishable forced corresponding GCM. Diagnosis second supports this result for five out six non-AMIPII reconstruction datasets. Moreover, internal rarely sufficient account even one-quarter strength previously reported. The presented evidence that, if have as small record our findings suggest, they unlikely significantly long-term observations obtained GCMs.