Ozone hole

In the early 1980s, it was discovered that the ozone layer was in decline. Ozone is a highly reactive gas, produced when high-energy ultraviolent light strikes a normal oxygen molecule. A normal oxygen molecule is two atoms of oxygen, while ozone is three. Ozone helps to filter ultraviolent by absorbing incoming UV light and splitting into 1 O2 and 1 O, which then combine to form ozone again.

Chloroflourohydrocarbons (CFCs), used in refrigerator coolants and aerosol propellants, are extremely stable long-chain molecules. They are so stable that they don’t react under normal circumstances, and in one famous commercial, a researcher even drank a beaker of CFCs.

Since they are so stable, though, they don’t break down until they reach the upper atmosphere. Here, under bombardment from high-energy UV, the normally-stable CFCs dissociate into fluorine and chlorine, and here the problem arises.

Ozone molecules will rapidly react with chlorine and fluorine, and one molecule of these radicals can dissociate 100,000 molecules of ozone.

ozone layer diagram

Ozone depletion has been seen in two related phenomenon. There is the overall global ozone depletion that has been recorded since the 1970s, at a rate of about 4% per decade. Then there are the holes discovered over the Antarctic and Arctic region in the 1980s. In winter, vortex winds isolate the polar stratosphere, and ozone depletion occurs rapidly. This creates the infamous hole.

CFCs have been largely banned since the discovery of the ozone holes, and in the last few years the ozone layer is showing signs of recovery. It will still be a long time before it recovers completely, but it is headed in the right direction. Global use of CFCs had declined 96% by 1996.

Canadian government cuts world-renowned ozone science group

The Antarctic polar hole is showing strong signs of recovery as well, and this may actually create another problem. The theory is that the hole in the ozone has actually been providing a shield to protect the Antarctic from climate change. High-energy winds, possibly boosted by UV infall, whip up ocean spray and carry the sea salt particles high into the atmosphere, where they reflect incoming sunlight back into space, shielding the continent below. With healing of the hole in the ozone, this aerosol shield may fail, allowing more sunlight, and heat to reach the ground.

Weather and climate effects are very complex and dynamic, and difficult to predict. Progress in one area is marred by the real possibility of a significant setback in another. However, it also shows that problems can be solved, and that there is hope yet for a green Earth.

Colin Dunn was born and raised in Northern Alberta. Growing up in the boreal forest gave him an appreciation for nature, an appreciation that was enhanced by the works of his artist mother, Svala Dunn, who captured the landscapes and wildlife of the north in her oils and watercolors. He holds a Degree in Geography from the University of Alberta, with a concentration in Urban Studies. He has since found career in information technology, but still pursues his first interests in geography and the environment. He lives and works in southern Vancouver Island, with his wife and three children.


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