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05 What is the Antarctic ozone hole?




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This article is from the Ozone Depletion: The Antarctic Ozone Hole FAQ, by Robert Parson rparson@spot.colorado.edu with numerous contributions by others.

05 What is the Antarctic ozone hole?

For the past decade or so, ozone levels over Antarctica have fallen
to abnormally low values between August and late November. At
the beginning of this period, ozone levels are already low, about
300 Dobson units (DU), but instead of slowly increasing as the
light comes back in the spring, they drop to 150 DU and below. In
the lower stratosphere, between 15 and 20 km, about 95% of the
ozone is destroyed. Above 25 km the decreases are small and the net
result is a thinning of the ozone layer by about 50%. In the late
spring ozone levels return to more normal values, as warm,
ozone-rich air rushes in from lower latitudes. The precise duration
varies considerably from year to year; in 1990 the hole lasted well
into December.

In some of the popular newsmedia, as well as many books, the
term "ozone hole" is being used far too loosely. It seems that
any episode of ozone depletion, no matter how minor, now gets
called an ozone hole (e.g. 'ozone hole over Hamburg - but only for
one day'). This sloppy language trivializes the problem and blurs
the important scientific distinction between the massive ozone
losses in polar regions and the much smaller, but nonetheless
significant, ozone losses in middle latitudes. It is akin to
using "gridlock" to describe a routine traffic jam.

 

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