This series of images shows the Antarctic ozone hole on the day of its maximum depletion in 1979, 1987, 2006, and 2010; that is, the days with the thinnest ozone layer.
NASA satellites have observed the Antarctic ozone hole since the late 1970s—before and after nations agreed to stop producing chemicals that destroy the ozone layer.
Does a smaller hole mean that Antarctic ozone is recovering? Not yet, say NASA scientists. A deeper look at the ozone hole shows that for now weather still has a bigger influence on the size of the ozone hole than policies that limited emissions of ozone-destroying chemicals.
In 1979, Antarctic ozone levels dropped below 200 Dobson Units for the first time on record. This threshold became the standard for defining the ozone hole. In 2008, minimum ozone levels dropped to 100 Dobson Units on October 4.