The ozone hole over the south pole this past winter grew to be four
times as large as the United States, the biggest it has ever been.
Since 1970, the south-pole ozone hole has opened up each year between
August and December, then closed up again as sunlight created a new
supply of ozone, leaving Earth's entire ozone supply slightly more
diminished each passing year.
The source of the problem is industrial chemicals (CFCs, halons and
others containing chlorine and bromine), which waft upward into the sky
where they break into smaller molecules. These smaller molecules remain
in the stratosphere, nine to 18 miles above the earth, until they
encounter frozen clouds. Frozen clouds break down the small molecules
further, releasing pure chlorine and bromine which then begin to devour
nearby ozone molecules that ordinarily protect Earth from deadly
ultraviolet radiation, which is constantly streaming in from the sun.
According to NASA [National Aeronautics and Space Administration] a
one-percent reduction in the ozone shield produces a 2% increase in
ultraviolet radiation on the ground.
In early February this year, NASA announced that conditions were ripe
for development of a huge ozone hole over the NORTH pole for the first
time. In the northernmost region of the stratosphere, NASA scientists
had measured chlorine monoxide levels higher than previously seen
anywhere in the stratosphere. When chlorine monoxide encounters a
frozen cloud, chlorine is released and ozone destruction begins
immediately. At a hastily-called press conference February 3rd NASA
scientists said this spring the north pole ozone hole might get big
enough to cover most of Canada, northern New England, and northern
Europe. This would place large human populations beneath an ozone hole
for the first time. NASA said in February ozone losses up to 30% might
occur this spring over Toronto and Boston. This would be a significant
reduction indeed. Environment Canada, the Canadian equivalent of EPA
(U.S. Environmental Protection Agency) immediately recommended that
children under 18 be kept indoors throughout the spring. But within a
week, this alarming and unrealistic recommendation had changed into
"normal prudence should be used," whatever that might mean.
Fortunately, almost immediately after NASA's announcement, a warming
trend melted the frozen clouds over the arctic and this year's ozone-
depletion-season ended after ozone loss of only 10%. NASA called the
10% loss "quite significant" but said it should not be called a "hole."
Ozone loss inside the south-pole ozone hole each year now routinely
reaches 50% or more but relatively few humans are affected.
NASA says it now knows that ozone destruction depends on two main
factors: the total amount of chlorine and bromine atoms in the
stratosphere, and the length of the cold season when stratospheric
temperatures dip below -78 Centigrade (-108 Fahrenheit), forming frozen
clouds that release chlorine and bromine.
As soon as the cold season ends, pure chlorine and bromine change back
into a less-destructive form, and sunlight proceeds to create a new
batch of ozone at the rate of 350,000 tons per day, partially
replenishing Earth's acutely depleted supply. But nature produces the
same amount of new ozone each year whereas humans destroy MORE of the
Earth's ozone each year, so Earth's total (average) ozone supply is
being diminished, allowing slightly more ultraviolet light to reach
Earth's surface each year.
Therefore the ozone problem has two parts: large short-term "holes"
that can allow large amounts of ultraviolat light to strike the earth
during spring and early summer (August-December over the south pole,
February-June over the north). And the long-term depletion of ozone,
producing smaller increases of ultraviolet light over much larger areas
Despite the reprieve from NASA's worst fears about a northern ozone
hole, 1992 was not a good year for Earth's ozone shield:
** During January, February, and March, NASA's TOMS [Total Ozone
Monitoring Spectrometer] satellite measured average ozone over the
northern hemisphere lower than any previous year in the satellite's 13-
** Over the north pole, ozone normally reaches a peak during late
winter, but this year the late-winter peak was 10 to 15% lower than any
peak previously measured.
**The threat of a northern "hole" will be with us for several decades.
In 1991/92, frozen clouds in the north lasted only 39 days, saving us
from a severe ozone hole over populous regions. But the average winter
has 68 days of frozen clouds. In a cold year, frozen clouds can last
considerably longer; for example, in 1988/89 frozen clouds lasted 79
days. Thus NASA says it expects large ozone holes over northern
latitudes during many years in the next two decades.
** One major source of the problem, chlorine monoxide (derived from
CFCs and a few other chemicals like carbon tetrachloride), is
increasing in the stratosphere at about 5% per year, NASA said in
** Even if the Montreal ozone treaty of 1987 and its June, 1990,
amendments are accepted world-wide, it will be 80 years before Earth's
ozone returns to normal.
The bad news of 1992 followed close on the heels of a series of
unwelcome revelations in late 1991.
Daniel Albritton, directory of the Aeronomy Laboratory for NOAA
[National Oceanic and Atmospheric Administration] testified before
Congress November 15, 1991, giving a litany of trouble:
(a) During the period 1970 through the mid-'80s, ozone depletion got
worse one year then better the next; every other year brought some
relief. But in the late '80s through today, the situation has steadily
worsened every year. Scientists are not sure why the pattern has
changed, but it apparently has, Albritton said.
(b) In the 1970-1991 period total ozone depletion over northern mid-
latitudes (where the U.S. population resides) ozone depletion occurred
at the rate of 2.7 percent per decade. But during the later part of
this period, 1979-1991, ozone depletion accelerated to 4.7% per decade.
Thus total ozone destruction is accelerating. Albritton's picture of
accelerating ozone loss was confirmed by new analyses announced in
SCIENCE magazine April 17.3
(c) In the 1970s and early '80s, ozone loss was restricted to winter
time. However in recent years, ozone depletion has also been observed
during summer. Over northern mid-latitudes during the period 1979-1991,
summer ozone losses averaged 3.3%
NASA doesn't talk much about what ozone depletion means. For one thing,
information is scarce. This scarcity did not occur by chance. Of all
the money spent worrying about the ozone hole(s) during the past 20
years, less than 1% has been spent measuring effects of ultraviolet
light on living things like plankton, peas, polar bears, and people.
Over 99% of the money has been spent outfitting airplanes with special
equipment, building satellites with special eyes for seeing ozone, and
As a result, effects of modest ozone loss are poorly understood.
However, effects of severe ozone loss were studied in 1975 by the
National Academy of Sciences (NAS) as part of an effort to understand
the consequences of nuclear war. The Arms Control and Disarmament
Agency in 1978 used the NAS study to assess effects of nuclear
conflict. According to the Agency, a 50% reduction in Earth's ozone
shield over mid-latitudes "would cause blistering after one hour of
exposure. This leads to the conclusion that outside daytime work in the
northern hemisphere would require complete covering by protective
clothing.... It would be very difficult to grow many (if any) food
crops, and livestock would have to graze at dusk, if there were any
grass to eat." [Quoted in reference 4.]
Besides severe blistering, ultraviolet light harms the immune systems
of humans and animals (regardless of skin pigmentation); reduces crop
yields; reduces the growth of phytoplankton (which form the basis of
all oceanic food chains); and causes eye cataracts in humans and
animals, leading to blindness.
Ozone losses less than 50% might cause blindness in domestic animals,
thus disrupting agriculture in much of Asia which depends heavily on
beasts of burden. Other complex, far-reaching negative effects are
The Institute for Energy and Environmental Research (IEER), a private
organization, has developed a practical plan for rapid phase-out of all
ozone-destroying chemicals, but the Bush administration has shown no
real interest. After the NASA press conference in February, Mr. Bush
speeded up the U.S. timetable for phasing out ozone-killing chemicals,
but only by one year. In Washington, it's business as usual.
 "Press Briefing; End of Mission Statement; Second Airborne Arctic
Stratospheric Expedition AASE-II." Washington, DC: National Aeronautics
and Space Administration, April 30, 1992. The increased ultraviolat
radiation may not all reach the ground because other pollution (for
example, urban smog) may absorb it, but where the air is clear, a 1%
reduction of stratospheric ozone will cause a 2% increase in
ultraviolet on the ground, NASA says.
 Daniel L. Albritton, Director, Aeronomy Laboratory [in Boulder,
Colorado], National Oceanic and Atmospheric Adminstration, U.S.
Department of Commerce, "Testimony... before the Committee on Commerce,
Science and Transportation, United States Senate, November 15, 1991."
 Richard Stolarski and others. "Measured Trends in Stratospheric
Ozone." SCIENCE Vol. 256 (April 17, 1992), pgs. [342-349.]342-349.
 Arjun Makhijani, Kevin Gurney and Annie Makhijani, SAVING OUR
SKINS; THE CAUSES AND CONSEQUENCES OF OZONE LAYER DEPLETION AND
POLICIES FOR ITS RESTORATION AND PROTECTION. Takoma Park, MD: Institute
for Energy and Environmental Research [6935 Laurel Ave., Takoma Park,
MD 20912; phone (301) [270-3029],] February, 1992. $10.00 and worth it.
Descriptor terms: ozone; nasa; south pole; ozone hole; ozone depletion;
national academy of sciences; ieer;