History of the hole in the Ozone Layer
A teaching example of integrating science in narrative
Students are often unaware of the links between the sciences and humanities, which is the result of the separation of these subjects in the school curriculum. In an interdisciplinary course like environmental history, the story of the hole in the ozone layer provides an illustration of how to integrating science into a narrative. The science and the historical perspectives are not separated but presented as integral parts of the historical events that make up the ozone story. Below is the text plus some of the images images used as slides in the lecture about the history of the ozone layer problem that is used to demonstrate how science can be integrated into narrative.
Thomas Midgley
[A: Personal story; B: History of Science]
The story of the hole in the sky started in 1928. It was then that Thomas Midgley invented CFC (Chloroflourocarbons), a gas that was perfectly suitable for refrigerating and in spray cans. Midgley is an interesting man and historian John McNeill remarked that Midgley "had more impact on the atmosphere than any other single organism in earth history." Not only invented he CFCs but also discovered that adding lead to fuel makes engines run better. However, in 1940, he contracted polio, which left him severely disabled. This led him to devise an elaborate system of strings and pulleys to lift him out of bed. This system was the eventual cause of his death when he was accidentally entangled in the ropes of this device and died of strangulation. Midgley died before the effect of CFCs upon the ozone layer became widely known. One cold argue that Midgley's inventions symbolize how humankind, by developing technology is supposedly killing itself. However this view is too simplistic since it was thought that CFCs were perfectly harmless; you can inhale or swallow it without any consequences as Midgley demonstrated himself. In addition the gas is incredibly stable: is does not react with any other gas or substance. Their remarkable chemical stability (they do not react with other substances) made people confident that there would be few environmental side effects, so they were embraced by industry.
[C. Economic and industrial history]
Fluorocarbons (CFCs and HFCs) were found to be very useful for refrigeration, making styrofoam, as propellants in spraycans, and in air conditioning units. By 1975 spraycans alone were flinging 500,000 tonnes of this gas into the atmosphere, and by 1985 global use of the main types of CFCs stood at 1,800,000 tonnes. It was their stability, however, that was a key factor in the damage they caused, for they lasted a very long time in the atmosphere.
[D. Discovery of harmful effects of CFCs]
Ozone can be regarded as the earth's sunscreen. It is formed when two-atom oxygen 'Normal oxygen" is split uneder the influence of UV radiation. In this process normal Oxygen is able to block ultraviolet (UV) radiation that comes in wavelengths shorter than 0.28 microns, but ozone, which foms from the atoms split off from two-atom oxygen, can block UV wavelengths between 0.28 and 0.32 microns. It shields us from around 95 per cent of harmful UV radiation reaching Earth. Without ozone's very high sun-protection factor, ultraviolet radiation would kill fast, by tearing apart DNA and breaking other chemical bonds within cells. The destruction of the ozone layer began long before anyone was aware of it.
Destruction of ozone under influence of UV radiation
What damage does CFC's cause?
CFCs evaporate easily, but it takes about five years for air currents to waft them into the stratosphere, where UV radiation slowly breaks them down, causing the release of their chlorine atom. It is the chlorine in CFCs that is so destructive to ozone-just one atom can destroy 100,000 ozone molecules-and its destructive capacities are maximised at very low temperatures. This is why the ozone hole first emerged over the South Pole, where the stratosphere is a frigid -62 degrees Celcisus.
This was only discovered after decades of CFCs released into the atmosphere. In 1974 two scientists, M.J.Molina and F.S.Rowland, published a laboratory study demonstrating the ability of CFC's to breakdown Ozone. Further studies estimated that the ozone layer would be depleted by CFC's by about 7% within 60 years.
Hole in the ozone layer,
Antarctica Sept. 2006.
A large shock was needed to motivate the world to get serious about phasing out CFC's and that shock came in a 1985 field study by Farman, Gardinar and Shanklin. Published in Nature in May 1985, the study summarized data that had been collected by the British Antarctic Survey showing that ozone levels had dropped to 10% below normal January levels for Antarctica. The authors had been somewhat hesitant about publishing because Nimbus-7 satellite data had shown no such drop during the Antarctic spring. But NASA soon discovered that the spring-time ''ozone hole'' had been covered up by a computer-program designed to discard sudden, large drops in ozone concentrations as ''errors''. The Nimbus-7 data was rerun without the filter-program and evidence of the Ozone-hole was seen as far back as 1976. Numerous studies since then have confirmed both the Antarctic hole, as well as an overall global decrease in ozone.
[E. Impacts on society] [F. The political, corporate and popular response]
Such were the implications of ozone depletion, however, that colour images of the ozone hole shown on television screens around the world convinced the general public that action needed to be taken, even if only as a precaution. Politicians were bombarded with letters requesting the chemicals be banned. DuPont was the company responsible for most of their manufacture, and in retaliation they and other producers launched a massive public relations campaign aimed at discrediting the link between their products and the problem-and they had a point, for science was still unable to provide conclusive proof of CFCs' damaging impact. Yet public feeling on this issue would not be appeased and, despite the howls of protest from industry about cost, representatives of twenty countries met in Vienna in 1985 and signed the Vienna Convention.
This was followed two years later by the so called Montreal Protocol, a UN sponsored agreement to phase out all CFCs. This protocol laid out a schedule for the phase-out of CFC's and related halocarbons by the year 2030. A additional impact of the protocol was to mandate the sharing of technology between countries in order to speed the replacement and recycling of CFC's.
However, some countries went further. In 1988, Sweden was the first country to legislate the complete phase-out of CFC's, with a scheduled phase-out of CFC's in all new goods by 1994. In March 1989 environmental ministers of the EU announced a total phase-out of CFC's by the year 2000. The US also put a total ban on CFCs.
At present, there are still so much CFCs in the lower atmosphere, it take years for the gas to reach higher levels, that it will take decades before the situation will improve. In fact, the situation will first get worse before it will get better. Nevertheless we have been lucky that the negative consequences of CFCs were recognised before it was really too late.
It shows again that much of the changes in the atmosphere, and the planet as a whole are totally unforeseen. Human kind has taken the driver seat of the planet but does not have the operating instructions ...
Issues explored
- Personal story: Midgely. This is the human face behind the development of CFCs
- History of Science: invention of CFCs
- Economic and industrial history: the success and wide application of CFCs in industrial products
- Discovery of harmful effects of CFCs: History of science & the science principles that explains why it has harmful effects à story of the mechanisms that are at work these include:
- The workings of the protective ozone layer.
- The chemical processes involved by the destruction of ozone by CFCs
- The damage that UV can cause to live on the planet
- Impacts on society: the relationship between human culture and the environment
- The political, corporate and popular response: Social, economic and social history.
Conclusion: Science is not operating in a vacuum of formulas, mathematics and chemical symbols but is affecting human society and many aspects of our personal lives everyday. It is an integral part of historical, social and political studies. It is this interface that combines the science with typical humanities subjects such as history. Note that the ozone story is not considered from different points of view, i.e. from different disciplinary perspectives. In this respect environmental history and any other cross-disciplinary sub-discipline is not interdisciplinary but integrative in nature.
More examples
Other examples used in the course include:
- Little Ice age: changes in weather patterns and position of pressure systems over north atlantic and impact on societies in Scandinavia, Scotland Iceland and Greenland. This included an intorduction into some basic meteorolgy.
- Ice Age cycles: to understand the history of the past 10,000 years it is important to understand the causes and consequences of the the end of the Last Ice Age. Introduction of the Milankovitch cycle of the Earth orbital movements, the position of the earth axis and the relation to the energy received fromt he Sun.
- Pandemics in history : examination of the ways in which we have shaped the diseases which have afflicted us and the way in which health and disease have shaped our ways of life and our beliefs. Introduction to basics of disease ecology.
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