- This study makes use of calendar month averages of surface temperature taken from the long control runs of 13 coupled atmosphere/ocean general circulation models (GCMs) as well as from the record of observational surface temperature measurements. After aggregating the data into global averages, we examine the mean seasonal cycle as well as the anomaly statistics. We find a large range of different results for the models in the seasonal cycle of anomaly statistics. There appears to be an "empirical" relationship between the published sensitivity of the models to CO2 doubling and the seasonal cycle of the anomaly statistics. We draw an inference about the sensitivity of the real climate based upon this relationship, The relationship appears to be plausible based upon simple considerations of the land-sea distribution and the wintertime variance of climatic noise forcing. This inference leads us to estimate the sensitivity of climate to a doubling of CO2 to be about 2.7C with the 95% confidence interval (2.3C, 3.1C).