Different parts of Earth's surface receive different amounts of sunlight (Figure below). The Sun's rays strike Earth's surface most directly at the Equator. This focuses the rays on a small area. Near the poles, the Sun's rays strike the surface at a slant.
Many factors, both natural and human, can cause changes in Earth's energy balance, including:
Variations in the sun's energy reaching Earth.
Changes in the reflectivity of Earth's atmosphere and surface.
Changes in the greenhouse effect, which affects the amount of heat retained by Earth's atmosphere.
