Greenhouse gases hold heat in the atmosphere.  CO2 holds a small fraction of the amount that H2O in its gaseous form holds.  The devil is in how they define how much that small fraction is in terms of heat retention.  That a gas (CO2) that's less than 1% by volume vs H2O could be a bigger influence on warming is absurd.

I repeat, CO2 was chosen to demonize because it allowed spending on the AGW agenda under the Clean Air and Water Act by classifying a clean, harmless gas, CO2, as a "pollutant," when no life on Earth can exist without it.

Billions of dollars in grant money has been doled out for research papers supporting the agenda; nothing for research that doesn't.  Many of those papers are prefaced with statements that basically say, "This is what you're paying me to rationalize, but it's not necessarily what I believe to be true.  You won't pay me for that."