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Montevideo, September 21st 2018 - 00:28 UTC
A report sponsored by the UN Environment Program finds that over the past decade, global ozone levels, and ozone levels in the Arctic and Antarctic regions are at a turnaround point -- no longer decreasing but not yet increasing. Read full article
For public consumption it is usually stated that the Ozone hole was first discovered in 1985, by British scientists Joseph Farman, Brian Gardiner, and Jonathan Shanklin of the British Antarctic Survey, although NASA stake a claim for two years earlier.
However on the BAS website it states that they have been monitoring ozone in the Antarctic since 1956. One wonders why, in all that time, they found no problem, when CFC’s had been in use for refrigeration since the 1930’s.
”Atmospheric ozone is measured in Dobson Units, (DU), during the International Geophysical Year of 1956 there was a significant increase in the number of these devices in use around the globe and the Halley Bay (Antarctica) anomaly was discovered.”
The BAS web site has data for 2009-10 and reports that:
“Ozone values dropped, to reach a minimum of around 125 DU (60% depletion) in late September, (Antarctic spring). The lowest daily value measured was 107 DU on October 1. This minimum value is similar to those recorded each October since the early 1990s.”
It is also similar to those in the spring of 1958 at the French Antarctic Observatory at Dumont d'Urville [opposite side of the South Pole from Halley Bay], when Rigaud and Leroy [quoted in Annales Geophysicae (November, 1990)] reported atmospheric ozone levels as low as 110 DU.
Volcanoes produce a variety of halocarbons, including CFCs. Other natural sources of CFCs include sponges, other marine animals, bacteria (both marine & terrestrial), fungi (both marine & terrestrial), plants (both marine & terrestrial), lichen and insects. In 2007, the British Antarctic Survey found large quantities of ozone-depleting halogens produced by the action of sunlight on sea water. The ozone thinning is an annual event, it is a natural cycle.
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