The flux process on Earth made inevitable by the fact that more heat is incipient on and absorbed at low than high latitudes and that the Earth is surrounded by a fluid envelope. This excess heat then moves from the tropics to the poles in both hemispheres, i.e. down the gradient, via the atmosphere and the oceans. The partitioning of this flux between the atmosphere and the oceans is as yet not well estimated. If there were no fluid envelope on the Earth, then the tropics would be much warmer and the poles much colder.