Explain the latitudinal heat balance.

Although the earth as a whole maintains a balance between the incoming and outgoing radiation, its distribution on the surface of the earth is not uniform.
This is primarily due to the spherical shape of the earth and the revolution of the earth around the sun on its inclined axis. The amount of insolation gradually decreases from the equator towards the poles. Similarly the amount of terrestrial radiation also varies. At latitudes below 40 degrees or more the solar radiation received than is lost to space by the earth. Beyond the 40° latitudes more heat is lost than received.

Latitudinal Heat Balance
The area between 40° north and south latitudes should have been getting progressively hotter and the area from 40° latitude to the poles getting cooler progressively. But this is not so.
The atmosphere and ocean act against thermal energy that transfer heat from the tropics towards the poles. Due to imbalance of heat, winds and ocean currents are produced. This transfer of heat energy from the surplus zones to deficit zones maintains an overall balance over earth's surface.