UV and the ozone layer
When I was in school, the hole in the ozone layer was a big deal. You don’t hear about it very much these days. So what’s going on?
Ozone is a gas molecule composed of three oxygen atoms. You don’t want to breathe it, as that could lead to a variety of health problems including respiratory tract irritation, breathing difficulty, asthma exacerbation, and chest pain. Not good! Luckily for us, ozone forms a layer high up in the atmosphere. It forms in the upper stratosphere, about 30-50 km above Earth’s surface. So A) it’s not really where people are breathing (phew!), but also B) it actually absorbs UV radiation from the Sun, thereby protecting us. UV radiation is high energy radiation, and is responsible for getting us sunburnt, as well as leading to skin cancers and DNA mutations.
Unfortunately, man-made chemicals like freons and chlorofluorocarbons (CFCs) that have been used in aerosol sprays, cooling systems in refrigerators, etc., make their way up into the atmosphere where they are decomposed by light to produce chlorine. The chlorine then reacts with and decomposes ozone. The consequent reduction of the ozone layer allows more high energy UV radiation into the Earth system.
This is bad. It got so bad that for many years there was a hole in the ozone layer, largely over Antarctica. By ‘hole’, we really mean a ‘depletion of’ - it was never an actual hole with no ozone present. Anyhoo, this was A) bad, but also B) good, in that it actually got the world to act together and agree on a solution. It led to what is surely one of the best examples of the world coming together and saying you know what, enough is enough. The outcome was the Montreal Protocol, which came into effect on 1st January 1989. This was an international agreement regulating the production of ozone depleting gases such as CFCs.
The result of the Montreal Protocol is that the ozone layer has been healing, with the hole shrinking in size. Admittedly, it still covers an area of about 16.4 million square kilometres, but that’s 4 million square kilometres less than it was in 2000. Scientists think that if countries continue to stick to the Montreal Protocol, the ozone layer should be fully ‘healed’ by about 2070. By healed, we’re talking akin to what it was pre-1980.
So, good on you world, for coming together back in the late 80s and actually solving, or putting in motion a plan to solve, a global threat. Now, if only the same could be said about climate change...