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by Nomad
This is an anniversary of something gone missing – which is somewhat odd. And then consider that what’s gone missing doesn’t really form a hole sensu strictu but resembles more a patch of thinning fabric. Worn down, threadbare fabric, but fabric nonetheless. Still, we talk of the Ozone Hole. And although it’ll be around for a few more anniversaries, it doesn’t look like it’ll be deepening.
In 1984, Joe Farman and his colleagues of the British Antarctic Survey measured for the second year in a row a significant thinning of the atmospheric ozone across Antarctica, and published these results in Science. They brought incontrovertible evidence to the table in a discussion between scientists that was already over 15 years old, and that had been mostly academic to that point: the role of chlorofluorocarbon (CFCs or freons) released to the earth’s atmosphere.
The evolutionary cycle of ozone (O3) had drawn scientific interest since the 1930s. By the 1970s , the role of ultraviolet light in the creation of ozone had become clear, but it remained unclear at that time what mechanisms acted to break down ozone. The Dutch chemist Paul Crutzen showed in a publication in 1970 that it was NOx that acted as catalyst in breaking down ozone. But what's more: the publication also influenced thinking whether other substances could play a similar role. And if there were, what were they? One of those substances people were already worrying about were CFCs. James Lovelock (yes, he of Gaia) sailed out in 1971 aboard the ship “Shackleton” to the South Pole to make measurements of the atmosphere. His aim: to find out what would happen with CFCs released to the atmosphere. He then found those CFCs in the air at the South Pole too, and thus showed that atmospheric CFCs were mixing very well and had spread all around the globe. In his Nature publication in 1973 he added blithely that the measured CFC concentrations could pose “no conceivable hazard”. Which was a bit of a mistake, in hindsight. However, Lovelock's article did form the next step that led to the final scientific breakthrough: Rowland and Molina’s research to the ultimate fate of the CFCs. They discovered that CFCs would finally reach the stratosphere where the chloride bit would act, like NOx as Crutzen had showed, as a catalyst in breaking down atmospheric ozone. Nature published their article in 1974, and Crutzen, Rowland and Molina were awarded the Nobel price for their work on atmospheric chemistry in 1995. But during the 70s no immediate counter measures to stem or stop CFC production were undertaken after these publications, not even after the risks of increased skin cancer when losing the ozone layer had become part of widespread public concern. It took until 1984, when the ozone layer was already significantly starting to fade, that the momentum began to gather for real action. The initiative of the 1986 Montreal protocol is remarkable in two ways: in the alertness of the USA, and in the celerity of developing the protocol. (And the protocol did not even get real teeth until 1992, in Kyoto.) Not too much flattery, however, can go to European nations in this story, who weren’t too accommodating to the Montreal protocol at first. Remarkable little attention had been given to ozone by European scientists in general. The European CFC-producing companies, such as ICI, Atochem and Akzo, initially didn’t show the same willingness of their American counterparts (such as the Du Pont company) to switch to CFC replacements – which existed by that time. Only when it was shown by scientists that also the ozone layer above Europe was thinning, European companies joined the ranks and began working on an accelerated phase-out. The inflicted damage lingers. 25 years on, and the Ozone Hole is still there. However, the maximum size of the “hole” and the minimal thickness of the layer of ozone stabilized since about 1995, and roughly forms a linear trend since.
Estimates vary on when we’ll first can expect a recovery, and on when recovery is complete. 2060 is an oft quoted estimate – although increased stratospheric cooling (because of increasing stratospheric CO2) may lengthen this period. Add that as another reason to limit humanity’s CO2 output. The Montreal protocol could have stood model for an approach to limit CO2 output, were it not that the matter for finding a proper replacement for liquid carbon-based fuels is a far tougher nut to crack compared to replacing one nefarious chemical element.
More information about the ozone hole available at: |
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The Ozone Hole turns 25 | 6 comments (6 topical, 0 editorial, 0 hidden)
The Ozone Hole turns 25 | 6 comments (6 topical, 0 editorial, 0 hidden)
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