A steep decline in stratospheric ozone was measured during the winter of
1994-1995 by government scientists (NOAA) operating from the top of Mauna
Loa volcano in Hawaii. Ozone values dropped below 200 Dobson Units (DU)
for the first time since measurements began at this site began thirty years
The report, which appeared in the June 1, 1996 issue of Geophysical
Research Letters, stated: "Total ozone levels this low have not previously
occurred over populated areas except on rare occasions when the edges of
the springtime Antarctic ozone hole temporarily pass over the southern tip
The article was received for publication by GRL November 27, 1995.
reviewed and listed as accepted on January 10, 1996. It was not, however
updated to reflect the record breaking low levels of ozone over England (a
50 percent decline) and Northwestern Europe from January to March of this
year. (See Coastal Post , April 1996).
Of the 29 articles published in the current issue, 27 were revised before
publication, so it would not be unusual to update and the measurements for
January 1996 which were publicly available on the Internet in mid March.
For January 1995, the monthly average for the Ozone layer over Hawaii was
216 Dobson Units or about 14 percent below the norm established for the
period 1965-1981. Levels of the powerful, shorter wavelengths of
ultraviolet radiation, ultraviolet -B, which can be deadly to living
things, tripled in intensity during clear periods of low stratospheric
What these increased levels of ultraviolet-B radiation meant for living
things on the ground could not be determined from the article, since
measurements were not made continuously-even though such measurements can
be easily and inexpensively made. Many health conscious resort hotels have
their own ultraviolet monitors to alert sunbathers of the times when UV is
Mauna Loa is three and a half kilometers above sea level where ultraviolet
levels are much higher than at sea level. However, even taking scattering
by clouds and air pollution, UV levels at the surface should have been
What is worrisome about the recent announcement (at least to the Coastal
Post) is that this is the first official admission that stratospheric ozone
has thinned in the sub-tropics where normal backround levels of ultraviolet
are naturally intense. Previously, all scientific consensus statements have
indicated no decline between 20 degrees north and 20 degrees south of the
As an example, when the springtime ozone hole passes over the Southern tip
of Argentina at 55 degrees south, the suns rays are weak and the weather is
usually cold, windy and cloudy. Hawaii is 19.5 degrees north of the
equator and although it is often cloudy, the much stronger rays of the sun
have the potential for affecting people engaged in a number of outdoor
activities. And of course plants and animals are always out there.
Whether the low ozone is the result of dynamic changes in atmospheric
circulation or chemical reactions from industrial waste chemicals, or some
combination of both, is not clear. Whatever the reasons they are irrelevant
from a public health point of view, since damage to human skin from
ultraviolet-B radiation is clearly linked to the two most common forms of
skin cancer which number almost a million cases each year in the U.S.
The relationship between UVB and the most dangerous form of skin cancer,
melanoma, is less clear. Intense exposure as an adult is not linked,
however people who move closer to the equator as a child clearly acquire an
increased risk of malignant melanoma.
The authors are not unaware of the public health implications for Hawaii
(and presumably other areas at the same latitude across the globe) since
they mention, "This analysis provides an accurate method of forecasting
low-ozone, high-UV winters in Hawaii." They do not, however, give any
measurements which might help authorities determine if there is any need to
consider forecasting "high UV-winters". This is possibly a case of
messengers not wanting to be punished for bringing bad news.
On the other hand there was wide dissemination of the welcomed news of the
success of the Montreal Protocol which limited and banned the worst of
substances which depleted the ozone layer . A paper published in Science
reported that the concentration of Chlorofluorocarbons (CFCs) had peaked in
the troposphere and, all things being equal, after they had worked their
way up into the stratosphere and were eventually destroyed, after four or
five years, the ozone layer would begin to return to levels of the 1980s.
There Antarctic ozone hole, where there is no chamber of commerce and no
tourist industry to speak of , is forecast to heal halfway through the next
Of course, if the stratosphere continues to cool as it has been doing, then
ozone destruction will continue, and if sulfur emissions from fossil fuel
are ever reduced, then level of ultraviolet radiation in the northern
Hemisphere will increase.
Incidentally, New Scientist Magazine, the only important publication to
mention the low ozone levels over the Northern Hemisphere this March,
recently used the term, "springtime Arctic ozone hole"-this is the mention
seen by the Coastal Post.
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