https://www.scientificamerican.com/article/the-mysterious-return-of-ozone-depleting-cfcs/

Avid Everyday Einstein listeners may recall that the depletion and subsequent rebound of the ozone layer is one of my favorite science stories. Scientists were able to identify a problem (the depletion of the ozone layer) and its cause (chlorofluorocarbon gases or CFCs) and within two years, politicians took swift action to reverse course to protect our planet and its inhabitants. The ozone layer has now rebounded and scientists predict that by 2060-2075, the ozone layer will be back to its pre-1950 levels. Science truly can change the world.

Unforutnately, CFCs are making a comeback in the atmosphere and scientists are not sure where they are coming from. Let’s take a look at how we know they have returned and what the leading theories are to suggest why.