Explanation:
Higher latitudes receive less light intensity from the sun than lower latitudes. This is due to the way the sun rays differentially 'hit' the earth's surface at the different latitudes as a result of the spherical nature of the earth. The higher the latitudes, the sun rays 'hit' the earth at a more oblique angle and cover a larger surface area (hence lower density). This is why the equatorial regions are the warmest because the sun rays 'hit' more or less at right angle and therefore more sun rays hit per surface area (high density).
