  Radiative power balance of a planet in the solar system is delineated. The
terrestrial powers are transformed to average global flux in an effective
atmospheric column (EAC) approximation, its components are delineated. The
estimated and measured secular changes of the average global flux are compared
to the fluxes derived from the Stefan-Boltzmann law using the observed global
annual temperatures in the decades between 1880 and 2010. The conclusion of
this procedure is that the radiative contribution of the greenhouse gas ${\rm
CO}_2$ is some $21\pm 7$~\% to the observed global warming from the end of the
XIXth century excluding the feedback mechanisms playing determining role in the
climate system. Stationary radiative flux transfer is treated in an air column
as a function of the column density of the absorbent. Upper and lower limit of
radiative forcing is given by assuming true absorption and coherent scatter of
the monochromatic radiation. An integral formula is given for the outgoing long
wave radiation (OLR) as a function of column density of the components of
greenhouse gases.
