February 28, 2007
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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 5, NUMBER 3, MARCH 1992
DISCOURAGING OZONE NEWS
At a February 3, 1992, press conference,
NASA scientists presented results from this winter's Airborne Arctic
Stratospheric Expedition and from NASA's Upper Atmosphere Research Satellite,
launched last September. They concluded that an ozone hole is likely to form
over populated regions of the Northern Hemisphere sometime within the next
decade. Chlorine monoxide (ClO), the substance most effective in ozone
destruction, was found over northern New England and Canada at levels higher
than ever observed, even in the Ant-arctic ozone hole. Similarly high levels
persisted over northern Europe for a period in January. Such high levels of ClO,
which were found in the Arctic stratospheric vortex, can lead to ozone
destruction of 1 to 2 percent per day, but only in the presence of sunlight. The
formation of an Arctic ozone hole depends on persistence of the vortex into
March, which would permit sunlight to act on the high levels of ClO it contains.
Scientists feel it is only a matter of time before this happens.
There were other surprises. Two different chemical reactions known to
inhibit the destructive action of ClO were found to be less effective than
expected, and thin sheets of air high in ClO were observed as far south as the
latitude of Cuba.
The high levels of ClO are thought to be partly a result of the recent
abundance of stratospheric aerosol particles, which provide surfaces for
reactions that generate ClO and which are in unusually good supply following the
June eruption of Mount Pinatubo. (See Prof. Pubs./Mt. Pinatubo ERuption, this
GLOBAL CLIMATE CHANGE DIGEST issue--Mar. 1992.) Levels of ClO are likely
to keep rising through the next decade, regardless of any modifications that
might be made to the Montreal Protocol.
See Science, pp. 797-798, Feb. 14, 1992; Sci. News, p. 84,
Feb. 8; Intl. Environ. Rptr., pp. 59-60, Feb. 12; Global Environ.
Change Rep., pp. 1-3, Feb. 14.
An interim report issued in early February from the European Arctic
Stratospheric Experiment stated that ozone amounts are lower than expected based
on measurements in previous years, and could drop to record low levels later in
the winter. (New Scientist, p. 16, Feb. 8.)
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