OK, I'm sorry, I know I play rough with you sometimes. I understand that even basic math isn't necessarily in your wheelhouse but it's always fun to see someone who clearly has no real understanding of the topic make such BOLD declarations as "Bingo, center mass hit!"
Let me explain it to you:
The increase in forcing with increasing CO2 follows a "logarithmic curve", this means that at higher amounts of CO2 (relative to some starting condition) the relative forcing will increase less and less.
It looks like this:
Now this is a "generalized" log curve (NOT specific to CO2 forcing) but it shows what I'm talking about. Note that as X gets bigger and bigger Y doesn't rise as much with each addition to X. It starts to look like it's going to kind of flatten out (not necessarily perfectly flat but you get the point).
Your glee at the logarithmic curve is understandable, most denialists like to point this out. But, sadly, it doesn't really alter the fact that added CO2
will still lead to more warming.. The effect of added CO2 is NOT saturated. Some absorption bands may be close to saturated but not all of them,
and besides, global warming works not by absorbing all IR, but rather increasing the altitude at which absorbed IR is re-emitted back into space.. With increasing CO2 that level gets higher and higher and higher until it is re-emitting from a very sparsely populated zone of the atmosphere which is much less efficient at re-emission.