Annual mean atmospheric temperature (left) and water vapor (right) vertical profiles of atmospheres with different total surface pressure (solid black: 1 bar; dashed, dark red: 0.1 bar; dotted red: 0.01 bar). The composition of all three atmospheres is N₂ with 376 ppm of CO₂ and a variable amount of water vapor. The profiles are shown at the substellar point, but horizontal variations are fairly small above the 0.1 mbar level due to an efficient transport. Decreasing the surface pressure increases the water vapor ratio in the upper atmosphere drastically.