For something like CFC concentrations in atmosphere, I would expect exactly the kind of curve the real data shows: initially a slow decline, followed by a middle period of relatively rapid decline...and that would be followed by "diminishing returns". This is how every chemical reaction works.
...but econazis go right to "Someone is making CFC-11!" Because they are idiots, they talk about an "uptick" in the gases rather than a reduction in the decline.
There is not more CFC-11 in the atmosphere; the concentration is merely declining at a lower speed.
And notice please what kind of magnitude we're talking about: parts per trillion. Okay, to find a gram of CFC-11 you need to filter it out of 4,400 metric tons of air, which is 3.55 million cubic meters of air.
*sigh*
I'm not even going to reiterate what I've said over and over and over again about how the ozone "hole" is a big nothing--discovered and explained in 1956, the magnitude of the decline in ozone has never changed significantly and it has recovered every year.