Perhaps this should be a chemistry question, but it seems to have physics attributes. There's a perennial ozone "hole" around the south pole created by destruction from Cl based chemicals like CFCs. Given that most CFC emissions originated in the northern hemisphere, why isn't there a significantly similar effect around the north pole?
From the Wikipedia article:(My emphasis)
Some people thought that the ozone hole should be above the sources of CFCs. However, CFCs are well mixed globally in the troposphere and the stratosphere. The reason for occurrence of the ozone hole above Antarctica is not because there are more CFCs concentrated but because the low temperatures help form polar stratospheric clouds. In fact, there are findings of significant and localized "ozone holes" above other parts of the earth.
The chemical processes are complicated and involve UV-dissociation of the CFCs to release chlorine which then destroys the ozone. However:
The Cl-catalyzed ozone depletion can take place in the gas phase, but it is dramatically enhanced in the presence of polar stratospheric clouds (PSCs).
The first quote states that the conditions over the Antarctic are more favorable for the chemical process of ozone depletion to occur.
A critical DuPont manufacturing patent for Freon was set to expire in 1979 ... The United States banned the use of CFCs in aerosol cans in 1978...
Dr. Mostafa Tolba, former head of the UN Environment Programme, who was quoted in the 30 June 1990 edition of The New Scientist, '...the chemical industry supported the Montreal Protocol in 1987 because it set up a worldwide schedule for phasing out CFCs, which [were] no longer protected by patents. This provided companies with an equal opportunity to market new, more profitable compounds.'"
Simply put: without regulation = small business due to the low manufacturing price; with regulation = new protected compounds and big business, as usual;
The subject was born, grew up in a short time and bore fruits (a regulation and a Nobel). It is now almost dead and buried.
Now back to physics speculation:
I wonder: Would have been ruled out other possible explanations for the phenomenon? For example: variation of the Earth magnetic axis, some characteristic of the solar cycle, cosmic rays, a mix of causes, etc...
As protons and electrons are differently attracted to North and South magnetic Poles a distinct pattern could arise and explain your question in a different way.