This relates to water vapor "feedback" due to CO2's alleged "radiative forcing." See below for further comments from Richard Linzen, Brian Valentine, Lord Monkton, Fred Singer, David Deming & Ben Herman
From A Simple Method to Measure the Dew Point Temperature
by R. L. Snyder, Biometeorology Specialist
Gaseous water molecules consist of one oxygen and two hydrogen atoms. When in a liquid state, the water molecules form strong hydrogen bonds between the molecules. In order to evaporate water, heat must be supplied to break the hydrogen bonds and allow individual molecules to break off as a gas.