Remember when the Montreal protocol was allegedly a "huge triumph" in solving the alleged ozone problem? Never mind

Arctic ozone hole breaks all records - environment - 02 October 2011 - New Scientist

In the first three months of this year, something unprecedented happened in the skies over the Arctic. A large hole appeared in the ozone layer, far bigger than any seen there before.
...
Between 18 and 20 kilometres up, over 80 per cent of the existing ozone was destroyed. "The loss in 2011 was twice that in the two previous record-setting Arctic winters, 1996 and 2005," says Nathaniel Livesey of the Jet Propulsion Laboratory in Pasadena, California.

The hole was similar in size to those seen in Antarctica in the 1980s. The Antarctic hole has continued to grow since then, and is far larger today.

Flashback: Copenhagen climate deal: Spectacular failure - or a few important steps? | Environment | The Guardian

Gavin Schmidt, climate scientist at Nasa and co-founder of RealClimate.org

Look at the history of environment negotiations – take the ozone ones as the best example. People start off negotiating very hard and the first agreement does nothing but moderate the problem.

While the Montreal protocol was ultimately a huge triumph, it made an infinitesimally small difference at first. It took them four amendments to get from reduction to a ban [on CFCs], a process of 20 years after science identified the problem.