In article ,
Lawrence Jenkins writes:
snip
Could it be that 80ppm that humans have put into the atmosphere
has reached a saturation point where it no longer has any effect
on catastrophic warming.

I think that the short answer is: no, it couldn't.
--
John Hall "He crams with cans of poisoned meat
The subjects of the King,
And when they die by thousands G.K.Chesterton:
Why, he laughs like anything." from "Song Against Grocers"