Publisher Summary This chapter discusses the global radiation. Through a figure it gives a mean curve of global radiation spectral distribution as obtained from averaging over serial observations of a cloudless sky. The solid curve characterizes the diffuse radiation spectral composition of a clear sky. The interrupted curve is characteristic of the relative energy distribution in the spectrum of global radiation. It can be used for the computation of the global radiation spectral distribution in absolute units. It is natural that spectral fluxes of global radiation will also depend first of all on solar height. Because the spectral composition of global radiation is independent of solar height, it becomes clear that the dependence on solar height for a spectral flux of global radiation will be uniform throughout the spectrum. To obtain the value of a spectral radiant flux at a given solar height in absolute units, it is sufficient to multiply the corresponding ordinate of the interrupted curve.