It was mentioned in the part you left out, and in the link to CO2 at the top of that page. Your dishonesty knows no bounds."As the temperature of the atmosphere rises, more water is evaporated from ground storage (rivers, oceans, reservoirs, soil). Because the air is warmer, the absolute humidity can be higher (in essence, the air is able to 'hold' more water when it's warmer), leading to more water vapor in the atmosphere. As a greenhouse gas, the higher concentration of water vapor is then able to absorb more thermal IR energy radiated from the Earth, thus further warming the atmosphere. The warmer atmosphere can then hold more water vapor and so on and so on. This is referred to as a 'positive feedback loop'"
You will notice,... not once was CO2 mentioned.
They precisely measured the warming it produced.Precisely measured the effects of .1 % of .04% of a gas in the atmosphere has on the whole planets temperature
I note that your link that you quoted from, in the text you omitted, went on to say the levels and effects is CO2 are better measured and better understood that water vapor.
(Maybe you missed it because they spelled CO2 out in full instead of using the abbreviation "CO2")