The global recognition of CFCs’ destructive potential led to the 1989 Montreal Protocol banning the production of ozone-depleting chemicals. Scientists estimate that about 80% of the chlorine (and bromine, which has a similar ozone-depleting effect) in the stratosphere over Antarctica today is from human, not natural, sources.
Models suggest that the concentration of chlorine and other ozone-depleting substances in the stratosphere will not return to pre-1980 levels until the middle decades of this century. These same models predict that the Antarctic ozone layer will recover around 2040. On the other hand, because of the impact of greenhouse gas warming, the ozone layer over the tropics and mid-southern latitudes may not recover for more than a century, and perhaps not ever.
The slide show linked here shows the ozone hole’s growth and stabilisation, but not reduction. (Blue and purple means thin ozone, ie bad; red means lots of ozone ie good.)
Antarctic Ozone Hole
The stratospheric ozone layer protects life on Earth by absorbing ultraviolet light, which damages DNA in plants and animals (including humans) and leads to skin cancer. Prior to 1979, scientists had not observed concentrations below 220 Dobson Units. But in the early 1980s, through a combination of ground-based and satellite measurements, scientists began to realize that Earth’s natural sunscreen was thinning dramatically over the South Pole each spring. This large, thin spot in the ozone layer came to be known as the ozone hole.
This series of images shows the size and shape of the ozone hole each year from 1979 through 2008 (no data are available for 1995). The measurements were made by NASA’s Total Ozone Mapping Spectrometer (TOMS) instruments from 1979–2003 and by the Royal Netherlands Meteorological Institute (KNMI) Ozone Monitoring Instrument (OMI) from 2004–present. Purple and dark blue areas are part of the ozone hole.
Earth Observatory article here.
Also Satellite Measurements Help Reveal Ozone Damage to Important Crops