Hole in the ozone layer shows signs of healing. Or doesn't.

A report has come out this week stating that international co-operation to manage a global environmental issue is showing signs of success: the hole in the ozone layer over the Antarctic is decreasing. First identified as an issue by British Antarctic scientists in the early 1980's, the concern over the thinning of the ozone layer above the southern polar region resulted in one of the first international agreements to tackle a global issue. The Montreal Protocol was signed in 1987 by most of the word's governments with agreement to phase out use by industry of chlorofluorocarbons (CFCs) that were thought to be responsible for the issue. This week's report suggests that, nearly thirty years on, signs of success are being measured. However, in a typical geographical topic of dissenting views, some say that the effect is to be welcomed - but the reason is a greater cause for concern.

The layer of ozone high in the earth's atmosphere absorbs considerable UV radiation incoming from the sun. An increase in chlorine in the upper atmosphere destroys molecules of ozone and allows more UV radiation to penetrate to ground level. The effects of this include faster skin damage in sunlight, greater likelihood of skin cancer, eye damage and debilitated plant growth. The source of much atmospheric CFCs was from leaking coolant in fridges and freezers and gases uses to vaporise the contents of aerosol sprays, such as hair and deodorant sprays. Alternatives were switched to relatively rapidly after the 1987 agreement, but as chlorine can reside in the atmosphere for upward of 50 years, it has taken time for signs of the ozone hole to start to recover.

However, before the back-slapping self-congratulation breaks out, there may be another, more worrying cause of the hole reduction. The ozone hole was always more noticeable over the Antarctic because cold upper atmosphere temperatures speed the reaction with chlorine molecules. As temperatures rise, the reactions slow down and less ozone is destroyed. There are some suggestions that the closing of the hole - which isn't disputed - may be a result of not only banning CFCs, but of rising atmospheric temperatures over the Antarctic. If the latter is a major component, it indicates that the warming planet is extending its impact to the most extreme reaches and coldest parts of the planet, and has implications for the rate of climate change over more populated continents. Before the world fully congratulates itself on sewing up the ozone hole, it may need to make sure the spirit of international co-operation extends to the far more challenging task of reducing carbon emissions and slowing the rate of global warming.

A recent article on the improving situation with the ozone hole from BBC News can be read here.

A 2014 report on the improving situation over the Antarctic by NASA can be read here, and summarized by their video clip here: