In this study we compare simulations of climate in two general circulation models: a coupled GCM in which the atmosphere and ocean interact dynamically and a slab GCM in which the ocean is represented by a static layer. W. L. Gates and G. L. Potter carried out multiyear simulations of global climate with these two models at the Lawrence Livermore National Laboratory. These simulations have no imposed conditions on the nature of the interannual variability. We present results showing that the slab model generates the signal of the Southern Oscillation in atmospheric pressure during the northern spring season but the signal is not propagated to other seasons. The coupled model manifests the Southern Oscillation in other seasons and in several climatic variables in which it is found in nature.