Page "Insolation" Paragraph 17

The theory for the distribution of solar radiation at the top of the atmosphere concerns how the solar irradiance ( the power of solar radiation per unit area ) at the top of the atmosphere is determined by the sphericity and orbital parameters of Earth.

The theory could be applied to any monodirectional beam of radiation incident onto a rotating sphere, but is most usually applied to sunlight, and in particular for application in numerical weather prediction, and theory for the seasons and the ice ages.

The last application is known as Milankovitch cycles.