The holes in the ozone layer that appeared at both poles during each of their springtimes was one of the most cataclysmic environmental disasters in recent human history. The safety and future of humanity was once again put into question by human-induced climate change, as was the survival of millions of organisms and ecosystems across the globe.
However, in the past few years, the ozonosphere has made headlines as news organizations have claimed that it has made a recovery. So, how valid are these claims and what does the future hold for the ozone layer?
Ozone Holes and Depletion
Unfortunately, in the past 4 or 5 decades, the ozone layer has been significantly damaged by human activities. Before humans emitted harmful chemicals into the atmosphere, a balance in the ozone layer was maintained between the sunlight, which created ozone, and the natural chemical reactions that destroyed it. However, humans have drastically hastened the rate of these chemical reactions by emitting chlorofluorocarbons (CFCs) and other halocarbons into the atmosphere.
Ozone levels vary naturally from season to season, as ozone most readily forms on warm, sunny days with more direct sunlight, while its formation is inhibited by turbulent weather. Nevertheless, the trend in ozone levels that was observed in the late-19th century was not a natural occurrence, but rather one for which humans were at fault. This ozone depletion was most severe at the poles, where large swaths of Earth lacked sufficient protection from the harmful radiation of the sun. These areas are known as ozone holes. They appear at the poles because circulating air currents transport CFCs and other damaging gasses to both Antarctica and the Arctic. The low temperatures of polar regions also spur the formation of polar stratospheric clouds, which foster reactions that harm the ozone layer.
Photo Credit: NASA Ozone Watch
Left: The Antarctic Ozone Hole at its deepest extent in September of 1994, Right: The Artic Ozone Hole in October of 2005
CFCs are harmful to ozone because they begin as pollutants in the lower atmosphere, but are relatively unreactive, meaning they are able to drift upwards into the stratosphere. Energy from sunlight then splits CFC molecules, causing a chlorine atom to be released. This chlorine atom reacts with ozone to form chlorine monoxide (ClO) and oxygen gas. Subsequently, scientists have recorded increased levels of chlorine monoxide as ozone levels decreased. This process of ozone depletion can also occur with other halocarbons, which can release different halogens, such as bromine, that also destroy ozone.
CFCs were incredibly common in various household products after the 1930s, and they would often be utilized in AC and refrigeration units, insulation materials, and aerosol cans. This meant it would be quite difficult to prevent the use of CFCs internationally and would require an unprecedented amount of global cooperation.
Dichlorodifuoromethane, the most common CFC molecule
Scientists began to publish their findings that ozone levels were dropping dangerously fast during the mid-1980s, which alerted the world to an environmental crisis. In 1985, several meteorologists and other scientists published the first paper that detailed seasonal depletions in ozone over the Antarctic. Soon after, NASA began compiling data from satellites that reinforced these claims. In the late ‘80s, the scientific community made the connection that CFCs were the driving force behind ozone depletion, and international demand for regulation of ozone-harming chemicals soon followed.
The Recovery
In 1987, in one of the greatest examples of international collaboration to combat a problem that threatened all of humanity, the Montreal Protocol on Substances that Deplete the Ozone Layer was held and signed by 30 countries. The Protocol laid out plans to completely phase out the usage of CFCs and other harmful substances to the ozone layer in all commercial products. Many other meetings after 1987 saw the regulation of many other harmful substances as well, such as hydrobromofluorocarbons (HBFCs), carbon tetrachloride (CCl4), and hydrofluorocarbons (HFCs).
In the coming years, many more countries would ratify the Protocol as well, and currently a total of 197 countries have signed it. That includes not only every single UN member state, but the Cook Islands, Niue, and the Vatican City as well. Even North Korea has ratified the agreement. This level of cooperation is unparalleled across modern human history.
Not only was the scale of the Montreal Protocol so impressive, the efficiency and speed surrounding its ratification were astounding as well. The ozone hole had only been definitively discovered two years prior to the Protocol in 1985. Moreover, in 1990, the Protocol was enhanced such that the usage of CFCs was completely banned in all industrialized nations by 2000, and in all developed nations by 2010.
Photo Credit: cmosarchives.ca
The Canadian delegation at the Montreal Protocol on September 16, 1987
Because the cutdown in chemicals such as CFCs was so effective worldwide, scientists began to see results in less than three decades. By 2014, slight increases in levels of stratospheric ozone were recorded, and in 2016, a study was released that proved the validity of ozone recovery. This study detailed a steady rise in stratospheric ozone levels and a reduction in the size of the Antarctic Ozone Hole by more than 1.5 million square miles. A total replenishment of the ozone layer was predicted within the next half century.
Concerns and Controversy
While it is unilaterally agreed upon in the scientific community that ozone depletion is an immense threat to all of humanity, not all scientists agree that the ozone is on its way to recovery globally.
In addition, there have been some seemingly discouraging data points recently. For instance, the Antarctic Ozone Hole in October of 2021 was the 13th largest since 1979, and the Hole appeared to increase in size since 2019.
Photo Credit: NASA Ozone Watch
A comparison in the size of the Antarctic Ozone Hole between September of 2019, September of 2020, and September of 2021
However, these facts alone are somewhat misleading, as they do not indicate a roadblock in the ozone’s recovery, but rather are the product of an abnormally cold Antarctic winter in both 2020 and 2021, which inhibited the creation of ozone. According to Paul Newman, a climatologist and Chief Scientist in Earth Sciences at the Goddard Space Flight Center, “… without a Montreal Protocol, [the hole] would have been much larger”. Furthermore, the 2021 Hole was still much smaller than the holes that appeared in Antarctica in the late ‘90s and early 2000s.
The real concerning news comes from certain scientists who claim that new ozone holes have been found. For example, a Canadian scientist named Qing-Bing Lu from the University of Waterloo claimed that a tropical ozone hole that affects nearly half of the world’s population had been found. Lu also proposed that this hole had been around for 40 years, and proposed an immense, existential threat to those who had been impacted. While this is a frightening possibility, Lu’s claims are widely condemned by the scientific community, and many meteorologists and climate scientists believe they are invalid. Paul Young of Lancaster University said that Lu was mistaken and his assertions were inaccurate because he had looked at ozone percentage changes rather than absolute changes.
Despite all the controversy surrounding the study, scientists who are well-versed in atmospheric physics and chemistry are calling for more research. Lu’s claims are unsubstantiated by other scientists’ studies, and, as the University of Leeds professor Martyn Chipperfield puts it, “Science should never depend on just one study and this new work needs careful verification before it can be accepted as fact”. Lu’s findings will not be accepted by the scientific community unless follow-up studies are able to support them.
How the Media Affects Popular Perception of the Ozone Layer
The news and social media undoubtedly play major roles in shaping public opinions in the modern world. However, being vigilant of the media that we consume can give us a better understanding of the topics that we read about and can prevent us from being misled.
Read more about how media affects popular perception of the ozone here: https://www.cleanwestchester.org/articles/mediaimpactonozonelayer
Read about the history and science behind the ozone here: https://www.cleanwestchester.org/articles/sciencebehindozonelayer
Sources:
https://www.cbsnews.com/news/arctic-ozone-hole-largest-closed/
https://www.britannica.com/story/is-the-ozone-layer-finally-healing-itself
https://ozonewatch.gsfc.nasa.gov/monthly/monthly_2020-09_SH.html
https://ozonewatch.gsfc.nasa.gov/facts/history_SH.html
https://www.britannica.com/print/article/437240
https://www.uvfab.com/uv-spectrum-and-applications/
https://commons.wikimedia.org/wiki/File:Sauerstoffgehalt-1000mj2.png
https://eartharchives.org/articles/life-on-land-made-possible-by-ozone-layer/index.html
https://ozonewatch.gsfc.nasa.gov/facts/SH.html
https://globalnews.ca/news/8970778/ozone-layer-hole-tropics/