Could a Paris agreement on climate change be like the Montreal Protocol on CFCs?

I am puzzled, once again, by the sudden rise in the area of thinned ozone from 1980. What evidence do we have of its size before that time? There is one reference I can find (in the article by the British scientists), and that suggests that there is an annual fluctuation in the amount of ozone in the stratosphere that was pretty similar from 1957 to 1980. Yes, it was declining over time, too. But what seems to be the case is that new instrumentation from the early 1980s has provided data that are not, at least to my eye, strictly comparable with the earlier data. In short, we don’t know, and no one says we do.

The comments below the WUWT article are really worth reading, and you will get some interesting suggestions about the whole issue, ideas that are not to be found in the Wikipedia article. For example, and I should have thought of this myself, who defines what ‘thinning’ or a ‘hole’ is? The answer is that it is quite arbitrary, and in part a function of how you define things (rather like ‘climate’ being the average of 30 years of ‘weather’, a definition based on convention).

Or perhaps Antarctica never had much of an ozone layer anyway (argued on the basis of physics, and sensible given my limited knowledge). Or that it is natural factors, not CFC’s, that determine the annual cycle. Or that it is concentrations, rather than actual emissions, that are important — which might explain the second diagram in this essay.

All in all, my old feeling that the Montreal Protocol was a good thing and has had a good outcome, is somewhat shaken.  Observations don’t seem to support the whole argument very well. Maybe they will in another fifty years, which is what NASA says, on the basis of models, but I won’t be around then.