July 22, 2020 zoe Peres

Our Ozone Layer and The Montreal Protocol

By Eloise Callaghan

The largest hole ever recorded in our ozone layer was approximately 28.3 million square kilometres on September 3rd, 2000.[1] To try and visualize what that number means, Canada’s entire landmass is 9.98 million square kilometres, meaning the hole was almost three times the size of the entire landmass of Canada.

What does this hole mean for us?

To understand what this massive hole in our ozone layer means for us as humans we are going to start by going over the basics of the ozone layer. Ozone is a molecule that is made up of three oxygen atoms. These molecules make up the ozone layer which forms in the stratosphere level of our atmosphere. The ozone layer absorbs some of the ultraviolet (UV) rays from the sun, which prevents it from reaching the earth’s surface. There are two major types of UV rays, UVB and UVA. UVB rays are the ones that cause sunburns and play the greatest role in causing skin cancer. UVA rays were historically thought of as less harmful because they did not cause burns, but we now know they are in fact more harmful than UVB rays. UVA rays penetrate deeper into our skin and play a role in skin cancer formation as well as causing premature skin ageing.

What is causing the hole?

There is no true “hole” in the ozone layer, rather it is thinning out to the point where there are not enough ozone molecules to effectively block the UV rays. This thinning is due to chemicals called chlorofluorocarbons (CFCs). A CFC is a molecule that contains the elements carbon, chlorine and fluorine. When CFCs are released in the atmosphere they drift up to the stratosphere and are broken up by the UV radiation: this releases chlorine atoms that are able to destroy the ozone molecules. CFCs are non-toxic, non-flammable and inexpensive so they have been a molecule commonly used in refrigeration, fire suppression, foam insulation and aerosol sprays.

What did we do about it?

A global agreement was set in a place called The Montreal Protocol. This called to phase out the production and consumption of ozone-deleting substances. The protocol was finalized in 1987 and signed by 197 countries, making it the first treaty in the history of the United Nations to achieve universal ratification.[2]

Unfortunately, the projected path of recovery has not gone as originally projected, and there have been setbacks along the way. Since the global ban, there has been a decrease in the number of CFCs in our atmosphere, but new studies are showing a significant slowdown in that decline. Studies are showing that the use of CFC-11 has been increasing significantly in recent years which caused the rate of decline of CFCs to slow down by about 50% after 2012. The emissions of CFC-11 have been traced back to eastern China and are equivalent to about 35 million tonnes of CO2 being emitted into our atmosphere every year. Since this discovery, the Chinese have started to clamp down and investigate these producers.

Even with the unexpected presence of CFC-11 in our atmosphere, our ozone layer is on its way to recovery. In September and October of 2019, the hole in our ozone layer was the smallest that had ever been recorded, at 10 million square kilometres.[3]

What The Montreal Protocol showed us

While the hole in the ozone layer does not lead to climate change, it is a stratospheric problem of global concern, and CFCs are greenhouse gasses (atmospheric build-up of greenhouse gases lead to climate change). The Montreal Protocol was the first time we came together globally to address a collective concern affecting the health of our earth. If it was not for The Montreal Protocol in the US alone, we would have seen an additional 280 million cases of skin cancer, 1.5 million skin cancer deaths, 45 million cataracts and the world would be at least 25 percent hotter.[4] The Montreal Protocol shows us that change is possible.

Sadly, The Montreal Protocol was so far the first and last time that we were able to come together in this way to address climate change. We have yet to meet that level of collaboration and agree upon significant enough actions to address the problem. That being said, let’s not make this the last major global action we took towards climate change. We must continue to educate ourselves and others and demand better from our governments and corporations.


[1] https://visibleearth.nasa.gov/images/54991/largest-ever-ozone-hole-over-antarctica#:~:text=A%20NASA%20instrument%20has%20detected,largest%20such%20area%20ever%20observed.

[2] https://www.epa.gov/ozone-layer-protection/international-actions-montreal-protocol-substances-deplete-ozone-layer

[3] https://www.nasa.gov/feature/goddard/2019/2019-ozone-hole-is-the-smallest-on-record-since-its-discovery

[4] https://www.nationalgeographic.com/environment/global-warming/ozone-depletion/