In the absence of such aerosols, the spontaneous conversion of water
vapour into liquid water or ice crystals requires conditions with relative humidities much greater than 100 percent, with respect to a flat surface of H2O.
Not exact matches
The process where
liquid water turns
into vapour (e.g. a rain puddle may evaporate
into water vapour when the sun comes out).
Carbon dioxide is fully part of that
water cycle where
water heated by the thermal infrared direct from the Sun evaporates and anyway lighter than air rises in air and takes away heat from the surface — all pure clean rain is carbonic acid, the
water vapour spontaneously joining with carbon dioxide in the atmosphere releases its heat in the colder heights and condenses out back
into liquid water and ice, cooling the Earth from the 67 °C it would be without the
water cycle.
The local pressure reduction pointed to when condensation reduces volume is instantly offset by mass flowing
into the original volume from the surroundings and the energy released is not enough to make the air parcel and the
liquid contents lighter than air containing
water vapour.
What do you think happens to the energy that is released when
water vapour condenses back
into liquid water?