Atmospheric, dayside and nightside surface temperatures as functions of logarithm of control parameter L_sen. Left: τ_s;L = 0.01 (quasi-transparent). Middle: τ_s;L = 0.1 (small optical thickness). Right: τ_s;L = 1 (Earth-like optical thickness). In all cases, the atmosphere is quasi-transparent in the shortwave (τ_s;S =10⁻⁴), pure absorption is assumed (β_L0 = β_S0 = 1), A_s = 0.2, and F_⋆ = 1366 W m⁻². The atmospheric temperature is designated by the solid black line, the dayside surface temperature by the dashed red line, the nightside surface temperature by the dotted blue line, and the black body equilibrium temperature (Eq. (2)) by the dotted grey line. The value of L_sen for a 1-bar CO₂-dominated atmosphere is indicated by the green triangle.