Tropical-extratropical climate interaction is studied using a coupled climate model. It is found that the extratropical impact on tropical climate is as strong as the tropical impact on extratropical climate, with the remote SST response being about half the magnitude of the imposed SST change in the forcing region. The extratropical impact on tropical SST is accomplished by both the atmospheric bridge (70%) and the oceanic tunnel (30%). The equatorial SST increase is first driven by the latent heat flux and the poleward surface Ekman transport, and then enhanced by the change of Subtropical cells' strength and the equatorward subduction of warm anomaly. In contrast, the tropical impact on the extratropical climate is accomplished solely by the atmospheric bridge. The extratropical SST change is initiated by the atmospheric radiation forcing, and then enhanced by the positive sea ice ¨C albedo feedback. Sensitivity experiments also explicitly show the dominant role of the Southern Hemisphere (SH) in the global climate change. A warm SST in the SH contributes 30% more than that in the Northern Hemisphere (NH) to the equatorial SST warm because of stronger southern Hadley circulation change. Moreover, the NH climate response to the SH forcing is faster and stronger than the SH climate response to the NH forcing.