Figure 4.

The Earth's entropy budget. White arrows denote fluxes of solar radiation, black arrows terrestrial radiation, grey arrows fluxes of heat, and thin lines material cycling. The boxes describe irreversible processes. The symbols are: F, flux of energy or heat (in W m⁻²); Ω, solid angle (in radians); T, temperature (in K); and σ, entropy production (in W m⁻² s⁻¹). (Adapted from Kleidon (2009b).)