water also can act as a greenhouse gas. Reducing its concentration would reduce its participation in warming from the greenhouse effect. However, when a gas condenses (like in cloud formation), energy from the gas is imparted to whatever the "droplet" condenses on causing a net heating of the atmosphere. For example, the evaporation of sweat cools one off while the condensation of steam on one's skin burns (proportional to the amount and the latent heat of vaporization for water).
As far as the temperature of the atmosphere goes, these effects work in opposition to one another. Reduction of the greenhouse effect would prevent warming while condensation would cause warming. It is not immediately clear to me which effect would "win."
The CO2 levels would not likely be affected to a measurable degree. A miniscule amount would dissolve in the condensed phase of water but would be released back into the atmosphere upon dissipation of the clouds or evaporation of any resulting rain. Some may be sequestered to an insignificant degree.