Where does 90% of the CO2 forcing come from? Where does 90% of water vapor forcing come from? Where does 90% of the latent come from? 90% of the energy cooking my dinner came from the ground some where. My meatballs only care how much of that energy they are experiencing due to me turning on the burner. How hot is the burner, how far away is the heat, how conductive is the pot and what is the mass of the meatballs? 90% is meaningless without a reference, often several.
50% of the energy is where in the atmosphere? 50% of the energy due to CO2 is where in the atmosphere. How much will changing that 50% to 51% change the where 50% of the energy in the atmosphere is? How much will that change, change the surface temperature? How much will that surface temperature change impact the cooking time of my meatballs?
Why don't people ask the right questions?
Just for a though experiment, let's say the molecule for molecule, water vapor is just as potent a greenhouse gas as CO2. It's not, but this is my thought experiment. Then CO2 and H2O would have the same impact when they both had the same concentration. Where it that point in the atmosphere?
Okay, you don't like my thought experiment. So where is the impact of H2O equal to the impact of CO2? You pick the number.
Is that at the surface? 100 meters? 1000 meters? Does that make a difference? In thermodynamics it does. The change in forcing with respect to the surface needs to be considered if you what the answer at the surface.
Since water vapor impact is expected to change, where will it change with respect to the surface?