The atmospheric ozone layer, the causes and consequences of its antropogenic regional destruction has converted many unaware citizens in the industrialized world during the 1980s and 1990s.
Heavy industrial emissions of volatile compounds containing halogens are thought to destroy the ozone layer, dimishing its UV absorptive effect. A good review on the matter was published by Prof. Solomon showing for exmple, that the ozone concentration above Antartica drastically declined during the 1970 / 80s to a value of less than half its plateau level in the 1960.
Many researchers have provided evidence (sometime rather early on) for a link between increases in biological damage (such as skin cancer occurance) and increase of UV radiation dose, due to reduction of the UV protective effect of the ozone layer. Public awareness was fear heightened and urgency to amend the matter.
So what's up 20 years after the Montreal protocol came into force? Climate is still a buzz word in the media but ozone is not a daily staple anymore.
Is the story over?
Not quite, but there may be some good hope. A comprehensive report was published by the UN in 2006 to summarize the status quo. According to that, the general opinion is, that ozone depletion is slowing down virually to a halt.
Nevertheless, there is no strong increase yet. Recovery to pre 1990s levels (let alone pre 1960s levels...) may not be seen until 2050. Given the usual temporal asymmetry between geophysical events and human life span, this is rather fast. More recent evidence do in fact suggest a turnaround in athmospheric ozone depletion from frightening max. -7% pa to overall positive trends (depending on which altitude you look at).
Thus, we have bucked the trend. Can we do this also with notorious green house gases such as CO2? Unfortunately, that would be too easy. Our globalized system is built on fossile resources not only in regards to energy but also as building blocks for everything from plastics to pharmaceuticals. Also, CO2 is a very stable molecule whereas ozone is unstable and, in this case is catalytically depleted by CFCs and NO species. On top of it, ozone is effective in ppt concentrations. It needs much more CO2 to keep us warm (>150 ppm), but too warm (such as 400- 500 ppm) is not good, plus that it will be hard to get CO2 out of the athmosphere again.
Maybe we need another spray can frenzy...