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Assessing Stratospheric Ozone
| Article
# : |
13471 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
9 / 1987 |
2,412 Words |
| Author
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S. Fred Singer
S. Fred Singer, Visiting Eminent Scholar at George Mason
University and former director of the U.S. Weather Satellite
Program, is a pioneer in unmanned space science. His early
work included study of primary cosmic radiation and the
discovery of the equatorial "elctrojet" current in the Earth's
ionosphere. He also proposed to NASA the manned mission to
Phobos and Deimos now referred to as the Ph-D Project. |
The discovery in 1985 of a "hole" in the atmospheric ozone layer near the South Pole has focused worldwide interest on what is happening to ozone, a small yet vitally important constituent of the earth's atmosphere. It has also raised concern about possible health effects, particularly an increase in the skin cancer rate.
A question dating back to the 1970 controversy about the effects of supersonic transport aircraft has resurfaced: To what extent are human activities producing ozone changes? Over the last fifteen years, the focus of investigation has shifted from one probable cause to another. Today, the emission of chlorofluorocarbons (CFCs) into the atmosphere has raised fears of their effect on the ozone layer and has led to demands that the production of these extremely useful chemicals be curtailed or even abolished.
Of course, the "hole" isn't really a hole at all, but a temporary thinning in the ozone layer between 10 and 25 kilometers above sea level. This phenomenon takes place for a few weeks each year, around October, in the region of the Antarctic. Research so far has discovered no long-term changes in ozone elsewhere, although the evidence is not conclusive.
The ozone hole was discovered by scientists of the British Antarctic Survey operating an observation station on the Antarctic continent. After they reported their findings in 1985, NASA scientists searching their records of satellite data confirmed the effect. Indeed, the hole has been around since the mid-1970s, and getting larger every year, reaching a depletion of about 50 percent. Concern has centered both on the extent of the hole and on our inability to explain the reasons for its geographic and cyclic occurrence.
This was the situation in the summer of 1986, as a large scientific expedition set off to investigate the mystery. The National Ozone Expedition, which took measurements of the Antarctic stratosphere from July through October, found that the effect was present in October 1986, but was not as large as in 1985 - the first indication that the hole may not continue to grow. Also, by tackling the problem simultaneously with ground observations, satellite observations, and balloon experiments, scientists for the first time had enough data to at least eliminate the theory that the hole was related to the 11-year solar cycle.
Ozone Theory
Ozone is a
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