Why does the Ozone Hole only occur over Antarctica?
The chemical reactions that lead to the formation of the Antarctic Ozone Hole take place on the surface of Polar Stratospheric Clouds (PSCs), which can only form in very cold conditions (-78C). Because of differences in the geography of the northern and southern hemispheres, the temperature over Antarctica in winter is somewhat colder than over the Arctic, resulting in PSCs being able to form over a much greater area and for a longer duration. This is the main reason why ozone depletion in the Arctic, while significant, does not result in a sustained ozone hole forming.
