Three long-term climate simulations have been performed with an atmospheric general circulation model using monthly global SSTs. EOF analysis is used to study the ensemble-mean results for seasonal-mean fields as a means of evaluating the capability to simulate interannual variability. The analysis reveals a strong ENSO-related signal in the major fields of mean sea level pressure, rainfall, cloud cover, and zonal winds. The EOF for surface pressure closely resembles the Southern Oscillation pattern but, although significantly correlated with the Southern Oscillation index, cannot explain a large proportion of the observed variance. Furthermore, there are a number of differences between the model rainfall pattern and known ENSO-related rainfall anomaly patterns and between model zonal winds and observed zonal-wind stresses in the tropical Pacific.