I'm have armchair interest in greenhouse gases. One of the interesting points is the amount of greenhouse effect that CO2 has versus water vapor. I go to this page http://www.climate4you.com/GreenhouseGasses.htm and find that the relative percentage of atmospheric humidity is 45%. I suppose that is the best guess average of measurements taken throughout the atmosphere of planet earth. Does that mean 45% of the atmosphere is made of water vapor? Then on the other hand we have CO2 which makes up .0390 percent of the earths atmosphere. When we measure the greenhouse effect of each I know we are not comparing apples to oranges. I have read a thread on this forum talking about saturation effect of CO2. Meaning the more you have the less of a greenhouse effect it creates. Can the same thing be said of water vapor? How much of the greenhouse effect is from water vapor and how much is from CO2 at current levels?