Very bad assuption, H2O has a far greater effect. In fact GW theory relies on a small increase in C02 causing a large increase in H20 vapor. It is the H2O increase that drive temperatures up, not the CO2 according to the GW theorists.
PS no increase in H2O vaper has been documented even in high CO2 zones.
There’s 30 times as many H2O molecules as CO2. Is the per molecule effect of H2O greater or less than CO2?