The discovery of a hole in the sky (Part:1)
“The work is going well, but it looks like the end of the world.”
Tracking Atmospheric CFCs
In 1971, the British research ship Shackleton embarked on a scientific expedition to Antarctica. This voyage was part of a broader effort to understand the Earth's climate and atmospheric conditions, especially in remote and extreme environments like Antarctica. Onboard was James Lovelock, the British scientist, known for his Gaia Hypothesis, a thought-provoking theory which suggested that life is not merely a passive inhabitant of a fortuitously habitable planet, but has played an active role in regulating the planetary environment throughout geological history.
Lovelock had a successful career inventing chemical instruments, including, most famously, the electron capture detector (ECD). The ECD, with its high sensitivity, could detect even the smallest traces of harmful chemicals. Its effectiveness has led to its widespread adoption by government agencies, such as the US Food and Drug Administration, and provided the hard data that allowed Rachel Carson to write her book Silent Spring, a book that helped to transform the conservation movement into a more comprehensive and ecologically informed environmentalism. Silent Spring had such a profound impact, that Chinese author Cixin Liu included it as a historical element in his book, The Three-Body Problem. In the story, Silent Spring serves as the catalyst that made Ye Wenjie, an astrophysicist who became disillusioned with humanity due to the environmental degradation she witnessed, come into contact with an advanced extraterrestrial civilisation, the Trisolarians, with catastrophic consequences.
During a holiday in southwest Ireland in the summer of 1970, Lovelock measured atmospheric concentrations of sulphur hexafluoride and trichlorofluoromethane (commonly known as Freon-11), a chlorofluorocarbon (CFC). CFCs, human-made synthetic chemical compounds developed in the early 1930s, were once considered among the greatest human achievements. Because of their unique properties, such as inflammability and non-toxicity to humans, they were produced and consumed on a massive scale, particularly in developed countries, as refrigerants for refrigerators, propellants for aerosol sprays, and also in automobiles and air conditioners, among other applications.
Curious about the presence of CFCs in the Atlantic, Lovelock sought to find out whether they had accumulated in the atmosphere. After his grant application to conduct these measurements aboard the Shackleton on its way to Antarctica was denied, he self-funded the trip and joined the Shackleton in 1972. His measurements showed that chlorofluorocarbons (CFCs) had indeed spread throughout the atmosphere of both the northern and southern hemispheres. Upon his return, Lovelock published his findings in the scientific journal Nature.
A Hole in the Sky
In 1973, Mario Molina joined the laboratory of Professor F. Sherwood (Sherry) Rowland at the University of California, Irvine, as a postdoctoral fellow. At the time, CFCs were considered harmless and inert compounds, but Rowland was intrigued by Lovelock’s findings and wondered about the potential consequences of releasing them into the atmosphere. He suggested that Molina investigate their environmental impacts.
Soon, Molina’s computer models started to build up a worrying picture. According to his calculations, CFCs are inert, and they would remain in the atmosphere for a long time—somewhere between 40 and 150 years—before eventually reach the stratosphere. There, ultraviolet radiation (UV) from the sun, breaks the chemical bonds of the CFC molecules, causing them to release significant amounts of chlorine atoms. These chlorine atoms react with ozone molecules, leading to the destruction of the ozone atmospheric layer.
Chlorofluoromethanes are being added to the environment in steadily increasing amounts. These compounds are chemically inert and may remain in the atmosphere for 40–150 years, and concentrations can be expected to reach 10–30 times present levels. Photodissociation of the chlorofluoromethanes in the stratosphere produces significant amounts of chlorine atoms and leads to the destruction of atmospheric ozone.”— F. Sherwood Rowland and Mario J. Molina, Nature, 1974
The Confusing Molecule
Ozone is a confusing molecule. It is a powerful oxidizing agent, and its reactions can be complex. At ground level, ozone is a pollutant and a component of photochemical smog. Also known as "Los Angeles smog," this is a type of air pollution, that results from the interaction of sunlight with nitrogen oxides (NOx) and volatile organic compounds (VOCs). [1] The photochemical smog is characterised by a brownish or yellow haze, and it’s common in urban areas with heavy traffic and industrial activity. Prolonged exposure can cause respiratory problems, such as asthma and other lung diseases, and can damage, crops, forests, and other vegetation, leading to reduced agricultural yields.
However, in the stratosphere, the region of the atmosphere from 6 to 31 miles, ozone absorbs most of the sun's harmful UV radiation, protecting living organisms on Earth. As the Royal Swedish Academy of Sciences put it in its announcement of the 1995 Nobel Prize in Chemistry: “Even though ozone occurs in such small quantities, it plays an exceptionally fundamental part in life on earth. This is because ozone, together with ordinary molecular oxygen (O2 ), is able to absorb the major part of the sun’s ultraviolet radiation and therefore prevent this dangerous radiation from reaching the surface. Without a protective ozone layer in the atmosphere, animals and plants could not exist, at least not upon land.”
If CFCs could destroy ozone in the stratosphere, the world would be in serious trouble within a few decades. Molina and Rowland initially thought they had made some big mistake in their calculations, but they couldn't find any. They then realised that their research, which started as an interesting scientific exercise, had turned into a global environmental problem. (Molina & Rowland, 1974) In their book, "One With Nineveh: Politics, Consumption, and the Human Future," Paul R. Ehrlich and Anne H. Ehrlich, share an anecdote where Rowland, after arriving home one evening and being asked about the work by his wife, sombrely replied, “The work is going well, but it looks like the end of the world.”
Following their short Nature paper, Molina and Rowland presented their findings to the September 1974 meeting of the American Chemical Society (ACS) and recommended a complete ban on the future release of CFCs into the environment. While the paper in Nature had passed almost unnoticed, a press conference organised by the ACS brought extensive attention to the chlorofluorocarbon-ozone problem and triggered a response by the government, the public, and environmental organisations. The first governmental hearing on the CFC-ozone depletion theory took place in December 1974, conducted by the U.S. House of Representatives Subcommittee on the Environment. Both Sherwood Rowland and Mario Molina testified and highlighted the dangers of CFCs to the ozone layer.
The chemical industry argued that the data on CFCs and stratospheric ozone were inconclusive and didn’t warrant drastic action. This stance was rooted in concerns over the economic implications of phasing out CFCs. They stressed the need for more comprehensive studies to conclusively determine the extent of the environmental risk before implementing any sweeping policy measures.
Not all of them, though. In June 1975, the household cleaning products manufacturing company, SC Johnson, made a groundbreaking environmental decision by becoming the first major company to eliminate CFCs from its aerosol products. This move was led by the then-CEO, Sam Johnson, who was convinced by the mounting scientific evidence that CFCs were detrimental to the ozone layer. As he said at the time “Our own company scientists confirm that as a scientific hypothesis, [the idea that fluorocarbon propellants in some aerosol containers might be causing ozone depletion] may be possible. Effective today, our company has removed all fluorocarbon propellants from our production lines.”
As it turned out, removing CFCs was not only the right thing to do but also good for business. in September 1976, The National Academy of Sciences released its report verifying the Rowland-Molina findings, leading to the Food and Drug Administration and the Environmental Protection Agency initiating a phase-out of CFCs in aerosols. In 1978, after numerous congressional hearings and testimonies, the U.S. banned the use of CFCs in aerosol sprays. SC Johnson’s scientists had already found that propane and isobutane, among the cheapest gases, offered an excellent substitute for CFCs. The company ultimately saved millions of dollars in aerosol production and was well-established in CFC-free products by the time competitors caught up. Twenty years later, the scientific research Sam relied on to make the decision won the 1995 Nobel Prize.
From Concorde to Controversy: The Environmental Impact of Supersonic Transport
However, this was not the first time that ozone depletion became an environmental issue. In the late 1950s, the United Kingdom, France, the United States and the Soviet Union were all exploring supersonic aviation design. The Anglo-French Concorde became the iconic symbol of supersonic travel (SST), perhaps the only known and the only one to have successfully established a long-term civil supersonic service. In contrast, the Soviet Tupolev TU-144 had a brief and troubled history, marred by two catastrophic crashes—one at the Paris Air Show in 1973 and another in the USSR in 1978 – resulting in its civilian transport service being discontinued after just one year.
After the crash on July 25, 2000, which resulted in the deaths of all 109 passengers and crew onboard along with four individuals on the ground, and following the aviation industry's downturn after September 11, 2001, high costs, and concerns about noise pollution, particularly the sonic boom produced by supersonic flights [2] both British Airways and Air France decided to retire their fleets. The last commercial flight took place in October 2003, marking the end of an era of supersonic civil travel.
The SST development program in the United States began in 1963 with proposals from Boeing and Lockheed. However, by the spring of 1971, the U.S. House of Representatives voted to terminate the program due to high costs and concerns about noise pollution. Interestingly, noise pollution wasn't the only concern; the main issue was the effects of supersonic aircraft emissions on the stratospheric ozone layer.
In 1968, while US astronauts prepared for the first trip to the Moon, Paul Crutzen was awarded his PhD. His research was centred on the photochemistry of ozone (the reactions triggered by the absorption of different types of radiation) in the stratosphere, a field then deemed pure science, and unrelated to human activities. Crutzen was the first scientist to demonstrate that certain chemical reactions involving nitrogen oxides (NO and NO2) regulate ozone levels in the middle stratosphere. This discovery eventually earned him the Nobel Prize in Chemistry in 1995, together with Mario J. Molina and F. Sherwood Rowland, "for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone."
In the late 1960s, there was no formal program for monitoring the ozone layer, but a few scientists were actively engaged in debates and studies about environmental issues related to atmospheric chemistry. One of these scientists was the physicist James Edward McDonald from the University of Arizona, who investigated the environmental consequences of supersonic aircraft on the ozone layer. In 1971, McDonald testified before Congress, arguing that emissions from supersonic transport could deplete the ozone layer through reactions with water vapour and suggested that ozone depletion could cause skin cancer. However, McDonald's credibility was questioned due to his research on unidentified flying objects (UFOs) and related phenomena, which made his testimony vulnerable to criticism.
However, McDonald was not the only scientist who conducted research in this field. Harold S. Johnson, a physicist at the University of California, Berkeley, also suggested that exhaust from aircraft flying in the stratosphere could deplete the ozone layer. In 1971, he published a paper in Science magazine highlighting the possible effects of nitrogen oxides emitted by supersonic transport aircraft on the ozone layer. (Johnston, 1971) This was yet another early warning that human activities could transform the entire planet within a relatively brief span of time.
Supersonic Flights Comeback: Balancing Ozone Reduction and Climate Impact
While supersonic flights seem poised to make a comeback, there are still obstacles to overcome. (Fox, 2021) Sonic booms aren’t the only disadvantage of supersonic aircraft. A 2022 study assessed the environmental impacts of deploying the anticipated fleet of supersonic aircraft powered by the current generation engine technology and fossil-fuel-based kerosene fuel and found that it would cause a 0.046% reduction in global column ozone. However, this slight reduction in global ozone levels comes with a trade-off. Using zero-sulphur fuel might cut the overall ozone depletion in half, but it would simultaneously increase the non-CO2 forcing, that is the impact of emissions from aviation that go beyond carbon dioxide, such as water vapour, aerosols and nitrogen oxides, on climate due to the loss of the cooling effect provided by sulphate aerosols. Therefore, when considering the re-introduction of supersonic aviation, policymakers must take into account the increased climate impacts. (Eastham, Fritz , & et, 2022)
But we're still in the late 1970s. While governments were discussing phasing out the production of substances responsible for ozone depletion, an unexpected discovery would change everything. The ozone hole above Antarctica will revolutionise science and help establish one of the most successful global environmental policies of the twentieth century. This will be the subject of the next article.
Sources and References:
Bach, W., Pankrath, J., & Kellogg, W. (1979). Man's Impact on Climate : Proceedings of an International Conference held in Berlin, June 14-16,1978. Berlin : ELSEVIER SCIENTIFIC PUBLISHING COMPANY.
Bonolis, L. (n.d.). F. Sherwood Rowland . Retrieved from Lindau Nobal Laureate Meetings: https://mediatheque.lindau-nobel.org/laureates/rowland/research-profile
Chlorofluorocarbons and Ozone Depletion. (n.d.). Retrieved from American Chemical Society : https://www.bing.com/ck/a?!&&p=ce036cf6b776e2e5JmltdHM9MTcxODU4MjQwMCZpZ3VpZD0yNGU3NGZhMi0xYjQ3LTY3YmQtMTVkNC01YjMzMWFmZTY2ZmImaW5zaWQ9NTI1MQ&ptn=3&ver=2&hsh=3&fclid=24e74fa2-1b47-67bd-15d4-5b331afe66fb&psq=Rowland%2c+F.+S.+(1989).+Chlorofluorocarbons+and
Eastham, S. D., Fritz , T., & et, a. (2022, February 14). Impacts of a near-future supersonic aircraft fleet on atmospheric composition and climate. Environ. Sci.: Atmos, 2, 300-403. doi:https://doi.org/10.1039/D1EA00081K
Fox, C. (2021, June 5). United plans supersonic passenger flights by 2029. doi:https://www.bbc.co.uk/news/technology-57361193
Johnston, H. (1971). Catalytic Reduction of Stratospheric Ozone by Nitrogen Oxides. Retrieved from Retrieved from https://escholarship.org/uc/item/2z96r6kx
Lambright, H. (2005). Ozone Depletion (Monographs in Aerospace History No. 38 ed., Vols. SP-2005-4538). NASA. doi:https://www.nasa.gov/wp-content/uploads/2023/04/sp-4538.pdf
Lovelock , J. E., Maggs, R., & Wade, R. (1973). Halogenated Hydrocarbons in and over the Atlantic. Nature(241), 194-196. doi:https://doi.org/10.1038/241194a0
Lovelock, J. (1971, April 9). Atmospheric Fluorine Compounds as Indicators of Air Movements. Nature, 379. doi:https://doi.org/10.1038/230379a0
Molina, M. J., & Rowland, F. S. (1974). Stratospheric sink for chlorofluoromethanes: chlorine atom-catalysed destruction of ozone. Nature, 249(5460), 810-812.
Molina, M. J., & Rowland, F. S. (1974, June 28). Stratospheric Sink for Chrolofluoromethanes: Chlorine Atom-catalyzed Destruction of Ozone. Nature, 249, 810-12.
Paul J. Crutzen: The engineer and the ozone hole. (2007, May 29). Retrieved from ESA: https://www.esa.int/About_Us/ESA_history/Paul_J._Crutzen_The_engineer_and_the_ozone_hole
Taking CFCs Out of Aerosols How Sam Johnson Led SC Johnson to Environmental Activism. (n.d.). Retrieved from scjohnson: https://www.scjohnson.com/en/about-us/the-johnson-family/sam-johnson/taking-cfcs-out-of-aerosols-how-sam-johnson-led-sc-johnson-to-environmental-activism
This Week's Citation Classics. (1987, December 7). (49). doi:https://garfield.library.upenn.edu/classics1987/A1987K930400001.pdf
Footnotes:
[1] Volatile organic compounds (VOCs) are organic chemical substances found in various products. They can easily transition from a liquid or solid state to a gas, emitting vapours into the environment. They have increased mobility, and they are resistant to degradation, being able to be transported long distances to the environment.
They are responsible for the odours in perfumes and play an important role in communication between animals and plants. They serve as attractants for pollinators and help animals to be protected from predators. While some VOCs are harmless, others can be dangerous to human health and cause harm to the environment.
VOCs are present in different household products and some of them are toxic and carcinogenic. The most common VOCs are aromatic hydrocarbons, such as benzene, toluene, xylene and ethyl benzene, and halogenated hydrocarbons, such as chloroethylene and trichloroethylene. They can cause short-term effects like headaches and coughing and long-term effects, affect organs like the lungs, kidneys and liver.
[2] Sonic booms are shock waves created when an aircraft or another object travels through the air faster than the speed of sound. To the human ear, sonic booms sound similar to an explosion t a thunderclap