Staff at the South Pole release a balloon carrying an instrument up to 20 miles in the atmosphere, measuring ozone levels all along the way. Photo: NOAA

It sounds counterintuitive – one pollution-propelled problem reducing the effects of another – but it’s true.

The ozone hole over Antarctica is the smallest it’s been in more than 20 years, about 8.2 million square miles according to the National Oceanic and Atmospheric Association (NOAA). But don’t start waving the environmental activism victory flag just yet – the cause is a bit nefarious.

It happens like this: Thirty years ago we started poking a hole in the ozone layer with chlorine atoms released from chlorofluorocarbons, air pollutants that result from certain kinds of chemical manufacturing. That chlorine eats away at ozone through what are called polar stratospheric clouds, or PSCs. That particular kind of cloud only forms in extremely cold conditions, which is why the ozone holes form over the Arctic and Antarctic poles. Lately, temperatures have been alarmingly higher at the poles, so the PSCs don’t form or facilitate ozone degeneration.

Now we’re suck with a question of which is the lesser evil: An ozone hole that lets in dangerous UV rays, or warmer temperatures that drive species from their habitats, change the geography of where we can grow certain crops, and potentially alter weather systems.

And don’t forget those intrepid researchers living in Antarctica, who can’t get supplies as easily because their runway is melting. Frankly folks, it’s a mess.