Frequency changes in tropical cyclones under a warmer climate state are discussed in this study. A high-resolution (~ 40km) atmospheric general circulation model is used to determine the frequency of tropical cyclones in the Pacific with global warming. The 20C3M and A1B scenarios for boundary conditions of the global model are utilized in order to simulate the current and the warmed climate, respectively. A significant shift is found in the location of tropical cyclones from the western to central Pacific. The shift to more tropical cyclones in the central and less in the western Pacific is not attributable to a change in atmospheric static stability, but to a change in variance of tropical perturbations associated with a change in the background vertical wind shear and boundary layer divergence.