Action Against the Ozone “Hole” Provides Hope
Ozone layer is an important part of the Earth’s atmosphere.
On September 16, we celebrate the International Day for the Preservation of the Ozone Layer. The ozone layer is vital to human life, but in 1985 the British Antarctic Survey identified a hole in the ozone layer, leading to the Montreal Protocol in 1987: the first treaty ever to be ratified by every country on Earth. But what exactly are the ozone layer and ozone hole, and how does the Montreal Protocol help fight the triple planetary crisis of climate change, biodiversity loss, and pollution?
What is the Ozone Layer?
Ozone (O3), is a molecule consisting of three oxygen atoms. In comparison, oxygen molecules that we need to breathe consist of two oxygen atoms (O2). Made up of these O3 molecules, the ozone layer is part of the stratosphere: the second of five layers that make up the Earth’s atmosphere. It helps to absorb the ultraviolet (UV) radiation from the Sun, notably UVB, reducing the amount that reaches the Earth’s surface. There are three main types of UV radiation: UVA, UVB, and UVC; which while important for health can also cause sunburn, cancer, and other conditions in humans.
What is the Ozone “Hole”?
The term “ozone hole” is a misnomer: there are not actual holes in the ozone layer, but instead areas where the ozone layer thins because of ozone-depleting substances. Usually, O3 molecules are in a cycle of breaking and reforming while in the stratosphere. However, when chlorine and bromine atoms interact with O3 in the stratosphere, it alters this cycle, with more O3 being broken than O3 being reformed, thereby causing O3 depletion. In the presence of large amounts of UV radiation in the stratosphere, certain compounds release chlorine and bromine. Such compounds are known as ozone-depleting substances and include chlorofluorocarbons (CFC’s) and halons.
“The latest view of total ozone over the Antarctic pole. The purple and blue colors are where there is the least ozone, and the yellows and reds are where there is more ozone.” Source: NASA
The most significant ozone “hole” was identified above Antarctica and reoccurs during the Southern Hemisphere’s spring (August - October) each year. Chlorine from ozone-depleting substances is stable under normal atmospheric conditions. However, during winter months in Antarctica the atmospheric conditions change and enable reactions that otherwise wouldn’t otherwise occur. This results in chlorine reservoirs becoming more active. When there is increased UV radiation from the sunlight in spring, the more active chlorine then undergoes a chain reaction, alongside bromine, increasing the breakdown of O3, and causing ozone depletion. Once normal atmospheric conditions above Antarctica resume, the chlorine becomes less active and more stable, and the ozone layer returns to normal until the next spring.
While this is an annual cycle, in 1985 the British Antarctic Survey identified that the ozone layer above Antarctica was not reverting to completely normal after each spring and was instead thinning due to the increased use of ozone-depleting substances. As a result of the increasing ozone depletion and its implications on human health, the Montreal Protocol was introduced, implementing a worldwide step-by-step reduction of the use of ozone-depleting substances.
Since then, it has been identified that such substances have, in part, been replaced by hydrofluorocarbons (HFC’s). While HFC’s do not cause ozone depletion, they are greenhouse gases and are thought to be between 140 and 11,700 times more potent than carbon dioxide. Therefore, as of 2019, the Kigali Amendment to the Montreal Protocol came into action with the hope that by reducing HFC use, we will transition to both ozone-preserving and environmentally-friendly alternatives.
A Message of Hope
The Montreal Protocol has proven to be one of the most successful pieces of environmental legislation ever. Approximately 99% of ozone-depleting substances are no longer used globally, the ozone “hole” above Antarctica is predicted to normalize by the 2060s, and other areas of ozone depletion are predicted to normalize sooner.
However, it is a symbol of so much more. The Montreal Protocol provides hope for the future: that through international cooperation, it is possible for us to make positive change when tackling a planetary crisis.
