Integrated OLR for p_surf = 260 bar and T_surf = 1000 K and different H₂O to CO₂ content. Mixing CO₂ into the steam atmosphere mainly acts to cool the upper atmosphere layers toward the CO₂ condensation curve. Only for $x_{{\text{H}}_2\text{O}}<{10}^{-3}$ (that is, $x_{{\text{H}}_2\text{O}}>0.999$) will the overall thermal emission increase again as the steep adiabat of a CO₂- dominated atmosphere extends into the upper thermally emitting part of the atmosphere.