[jdsteel]

Not really. CO2 is completely soluble in the other gases of the atmosphere and doesn’t settle in lower lyers.

Being soluable doesn’t negate gravity. Fill a balloon with helium. See what happens. Fill a balloon with CO2. See what happens.

[Moseley]

But this is the fatal flaw.

No one wants to remember that we are talking about GASES which MOVE and circulate.

So even if CO2 molecules are heavier than other atmospheric gases, the turbulence of the atmosphere exceeds the difference in mass.

Otherwise, if CO2 settled out as a layer near the Earth’s surface, all animal life including people would suffocate with only CO2 to breathe.