The author of that link claims to made calculations that show the absurd conclusion that CO2 works " like a coolant, not a warmer of the atmosphere and the surface". He says one hell a lot of made-up crap, consisting of complete made-up gibberish pretending to be scientific by designed to sound vaguely sciencey such as "...mean free path length of the quantum/waves through those gases", which is just completely made up crap rather than real physics.
And, if his calculations really DID show this, and I have looked at them and they appear not to because is maths formulations appear strange and warped and laughable and don't make a whole lot of sense (and if you deny this, I challenge you to clearly explain in your own words only the exact maths reasoning that went into each and every one of those equations! ), then it would be big news and headline news all over the world. But it isn't headline news all over the world and that tells us that other physicists that look at his calculations must see they are flawed and probably extremely badly flawed at that, being just made up crap rather than completely correctly expressed and correctly applied physics equations. Thus our only rational conclusion is that CO2 has a greenhouse effect, exactly like basic physics says it should.
He vaguely says something about his conclusion of CO2 having a cooling effect is something to do with atmospheric water vapor and CO2 having overlapping IR spectrum bands, which makes no sense as an explanation because;
1, Overlapping IR spectrum bands won't cause cooling. Why should it? Why would that overlap mean more CO2 means LESS total IR absorbed and thus less warming? It wouldn't.
2, Much of the IR absorbed from CO2 isn't absorbed by water vapor and much of the IR absorbed from water vapor isn't absorbed by CO2, so that overlap is only PARTIAL. So, regardless of IR absortion overlap, why would there be no warming effect from that IR part absorbed by CO2 which is NOT absorbed by water vapor?
In short, the author makes obviously false claims that make no sense and is obviously just a nut like you and no doubt he would be dismissed as much by the scientific community.
And, with all else being equal, more CO2 means more climate warming, exactly like basic physics says it should and just as confirmed by the empirical evidence.