Pacific tropics are warmer than Atlantic tropics. This can be seen immediately from a world’s sea surface temperature atlas, but readings from it of the latitudinal bandwidths between 80 F isotherms in the open waters of both oceans make this result very clear. Explanations are offered by introducing what has already been proposed for the large-scale surface circulations of the Pacific and incorporating conjectures for the circulation of the upper layer of the South Atlantic.