The ecosphere is already saturated with water. You may have noticed those miles deep thingies called oceans covering 3/4 of the earth’s surface.
It is debatable whether increasing CO2 by 10% or 20% by burning hydrocarbons will make a difference in the earth’s temperature. It is not debatable that adding water vapor will NOT make a difference.
When there is room for more water vapor in the air, liquid water evaporates to provide it.
Sorry, no debate-increasing the amount of CO2 by 20 % will have zero impact
CO2 is about 400 parts per million of the atmosphere.
That is less than 1/2 of a unit per 1000
If a yard stick was a chunk of atmosphere, CO2 would take up 1/32 of an inch.
20 % of diddly squat = diddly squat.
“The ecosphere is already saturated with water”
So, you are walking around in a dense fog right now? As is everyone else on earth?
Average Global Relative humidity at the surface is 78%. At higher altitudes it drops, being 37% at 30,000’.