The hole in the ozone layer was first spotted 33 years ago, and when I was in secondary school (11-16 years old), it was one of the biggest scientific news stories we addressed. However, researchers have found that the hole has decreased after unprecedented international action. So what is the ozone layer, why do we need it, and what could this healing mean for nature?
With plastic pollution, and global warming at the forefront of issues to be combated, it seems a very long time since someone talked about the hole in the ozone layer. What is the ozone layer and why do we need it? The ozone (O3) layer lies between ~9.3 – 18.6 miles above Earth’s surface (in the stratosphere) and works to block most of the sun’s high-frequency UV-B rays. UV rays are known to cause skin cancer amongst humans and harm the reproductive processes of some animals, including frogs and fish. When oxygen (O2) is present high in the Earth’s atmosphere, sunlight will break this into two free oxygen atoms. If one of these free atoms interacts with an O2 molecule, they can bond and form O3: ozone.
O3 is unstable, meaning it can be broken apart relatively easily. In the 1920’s CFCs (chlorofluorocarbons) were invented and used in fridges to remove heat (i.e. keeping our food cold) and in aerosols (i.e. the gas used to pushed the product out), amongst other processes. However, CFCs escaped into the atmosphere and are very stable in the lower atmosphere, staying there for years/decades unchanged. Due to this long lifetime, some CFCs were able to reach the stratosphere where UV light can break the bonds holding onto the chlorine (Cl) atoms. This produces a chlorine radical which can go on to break apart (react with) ozone, as shown in the below diagram. The chlorine radical is actually regenerated during the process, ready to destroy more ozone.
Levels of ozone have been reported to be decreasing since the 1980’s. The “hole” is not actually a hole, just a largely depleted region which is above the antarctic. The hole continued to widen and finally peaked in 2000 at 15 million square miles, remaining relatively constant until 2015. Over the cold, dark winter months, stockpiles of CFCs can build up over the South pole and then every spring (October), when the sun returns to the antarctic, UV rays can react with CFCs, freeing chlorine and subsequently depleting ozone levels by up to 65%. In 2016, modelling conducted by researchers at the University of Leeds and MIT showed the ozone layer was actually beginning to heal. Their work found that the hole has been shrinking by 1.7 million square miles each year since 2016. How did this happen?
The huge “hole” in the ozone layer was a large news story in the late 90’s and early 2000’s, but has since diminished after the drastic reduction and subsequent banning of CFC use. In 1987 Montreal Protocol was brought into force, whereby every member of the United Nations would ban the use of CFCs in the hope of restoring the ozone layer. An atmospheric physicist from NASA, Paul Newman, stated that if we had continued down the path of CFC use, there was a real chance the “hole” could have extended across the planet. Such Global drastic action demonstrates that countries can come together with a common goal and achieve real change (let’s hope they do something similar for plastic pollution soon).
What does this mean for the Antarctic? Surely it’s a good thing? Some scientists suggest that due to the continuing increase in Global warming, a repaired ozone may not be ideal over the antarctic and could actually boost the effects of global warming over this part of the world. The “hole” in the ozone layer leads to stronger winds around the antarctic which in turn, push more sea spray into the atmosphere, creating brighter clouds which can reflect the sun’s rays back into space and thus, have a cooling effect. The study conducted at the University of Leeds found that repairing the “hole” could lead to an overall increase in temperature in the Southern hemisphere.
With the “hole” on track for full repair by 2060, the united nations have succeeded in their initial goal to reverse the effects of CFC use. However, should more research be conducted into the potential this repair has to actually speed up global warming? Either way, there is a lot of work to be done. With global warming in the news most days, governments need to sit up and listen to such research groups, put differences aside, and come together again for impactful global change to conserve this planet we call home.