Ozone Layer
Depletion
The ozone
layer over the U.S. and worldwide has been found to be thinning, which is likely to
have serious health and biological implications (1,5,11,15,21-23). The hole over Antartica
is still growing and reached a high for this time of year in 2003(24,25). The 2003 Antarctic ozone
hole was the second largest ever observed, say scientists from three U.S.
federal agencies. Researchers from the National Oceanic and Atmospheric
Administration (NOAA), the National Aeronautics and Space administration
(NASA), and the Naval Research Laboratory made the observations. The seasonal ozone hole over Antarctica widened sharply in
2005, making
it the biggest hole since
2000 and the third largest on record, according to measurements reported here
on Tuesday by the European Space Agency (ESA). . There has been a resulting increase of
approx. 0.5% per year in ultraviolet radiation(UV) since the mid 1980s, with an
even larger increase of approx. 2% in 1992 (2).
Ozone losses reached record levels
in 1993, with the levels over Canada for the first 4 months about 11 to 17 %
below normal(9).
According to satellite measurements as confirmed by ground measurements
throughout the eastern U.S., the ozone layer losses reached record levels in
the northern hemisphere in 1994(12) again in 1995(7), and in 1999 and
2000(21,22). The ozone layer was 10% below normal over Europe in the winter of
1995, and 15% to 20% below normal over the U.S. in March 1995. The level was 35% below normal in some Arctic
regions. Average ozone measurements in the northern hemisphere by NOAA for Dec
95 to March 96 were 10 to 25% lower than
levels during the base period 1979-1986(19) and the lowest in history in
March 1997. 20 to 25% reductions were
seen in far northern regions of Greenland, Europe, and Siberia(19). The reduction over Alaska was approx. 10% and
over the mainland U.S. was 6%. These
record levels of ozone thinning result in corresponding increases in UV-B increases(11,13,21).
The record low ozone levels over Antarctica in 1993, 1994, and produced
increases in UV-B levels that were 44 % higher than in 1992 for one monitoring site(13). Recent years have again reached even lower levels and the
worst hole on record in 2000(11,23). Since 2000 total chlorine is declining, while
bromine from industrial halons is still increasing,
albeit at a slower rate than was occurring previously(25).
Biologists indicate that the increased ultraviolet radiation due to
ozone declines is already having significant adverse impacts on ocean plankton,
coral reefs, and ocean food chains(11,16). UV-B inhibits growth of plants and
accumulation of biomass, causing serious damage to crops, plants, trees, and plankton(9,10,16).
Controlled studies have found that UV-B retards the growth of freshwater
and ocean algae, and also of the larva and small animals that live on the larvae(10,16). The increased UV-B in the 1990s has caused
failures in reseeding Canadian forests and significant decreases in seedling
growth rate. The increased UV-B levels could also be a factor along with global
warming in dramatic declines in plankton levels in recent years, such as the 80
% decline in zooplankton levels in the Pacific Ocean off the coast of California(18).
A
1% decrease in ozone in the atmosphere has been found to lead to an increase of
over 2 % in UV-B(11,21), and a 2% to 4% increase in
skin cancer and a 0.6 to 0.8% increase in cataracts. Studies have found UV radiation levels to be
a major factor in causing skin cancer- being both a tumor initiator and tumor enhancer(11,15,21).
The number of cases of the most serious type of skin cancer, melanoma,
has risen by over 4% per year over the last decade, and incidence doubled in
the U.S. between 1980 and 1994(4). Other
types of skin cancer are also increasing(4). The northern hemisphere is seeing approx. 3 %
reduction per decade in atmospheric ozone levels, resulting in a 2 to 3%
increase per year in related skin cancer in Europe(21,22).
UV exposure also adversely affects the
immune system, and has been documented to be related to immune system diseases
and genetic or metabolic problems such as herpes simplex, tuberculosis,
leprosy, lupus, etc. Higher doses of
UVB appear to have even more widespread adverse effects on plants, animal, and
ecosystems. Frogs and other
amphibians are declining in numbers drastically all over the world, and
scientists at Oregon State University and the Univ. of California at Santa Cruz
have found increased levels of ultraviolet radiation B along with acidic water
to be a major factor by damaging frog eggs(6). This is also resulting in increases in
insect populations and drops in the number of frog-eating fish and wildlife. Forests have also been found to be adversely
affected. UVB also damages polymers
used in building materials, paints, packaging, etc(4).
The ozone layer has declined globally over 6 % since 1980, and even more
over northern U.S. latitudes(1,11,21). Satellite measurements by Nimbus-7 in 1992,
1993, and 1994 show levels have reached record lows over much of the earth and declined much
more rapidly in 1992 than ever before.
The global decline in 1992 alone was over 2 % and perhaps was aided
somewhat by aerosols from the Mt. Pinatubo eruption(1). An ozone hole has been found to be forming
over the Arctic area similar to the one previously documented over Antarctica(11,21,22).
The formation of polar statospheric clouds act
as catalyst in ozone destroying chemical reactions in the stratoshpere,
especially over Antarctica and the Arctic(11,21-23). While the formation of such clouds in the
Arctic is not as heavy and consitent as in
Antarctica, such formations are increasing and appear to be increased by global
warming. Scientists have also found
concentrations of ozone destroying chlorine monoxide over the U.S. to be much
higher than previously expected.
Chlorine compounds such as chlorofluorocarbons(CFCs)
and other ozone layer destroyers such as nitrous oxide have been found to be rapidly
increasing in the atmosphere in recent years.
Space shuttle measurements of hydrogen chloride(Hcl)
and hydrogen fluoride(HF) levels in the upper stratosphere found an increase in
concentration of 37% and 62% respectively between 1985 and 1992(14). The
program also determined that the main source of the increases in ozone
destroying chemicals in the stratosphere appears to be man-made sources such as
CFCs, HCFCs, and halons. HF levels were growing at
exponential rates of over 5% per year.
NASA has found natural chlorine to account for only 20% of the chlorine
effect on ozone in the stratosphere, while virtually all fluorine, which is
even more harmful to ozone, is from manmade sources(11). Another destroyer of ozone in the
stratosphere for which manmade emissions from power plants, high flying
aircraft, and other sources are increasing is nitrous oxide(N2O). Power plant combustion at lower temperatures
to reduce overall levels of nitrogen oxides can produce higher levels of
nitrous oxide. Conversion of tropical
forests to farm or ranch land can reduce CO2 sequestration while increasing
nitrous oxide emissions by as much as a factor of 3 (11,17).
This decline could have large effects on Florida's sun based tourist
businesses, as well as on increased health costs and crop losses(3). Florida tourism is a multibillion dollar
industry, and insurance cost of skin cancer treatment are
already rapidly increasing. A Florida
Dept. of Commerce official indicated that there appears to have been a significant
decline in beach tourism in the last 5 years due to ultraviolet skin damage
concerns. Tourist related sales in beach
areas amount to over $10 billion per year, not counting large amounts of
uncounted real estate business, so even a decline of 1% would result in reduced
tourism spending in the hundreds of millions of dollars.
Air conditioning and refrigeration systems are a major user of CFCs, and some types of units will be both less efficient
and more expensive in the future due to limits or bans on the use of CFCs. New
cooling technologies that do not use CFCs such as natural gas chillers, natural
gas heat pumps, heat pipe cooling systems, and desiccant cooling systems appear
to be cost effective for many applications and are likely to expand their share
of the cooling market(8).
New technologies for refrigeration
that are much more efficient than conventional compressors are also being
developed. HFCs, which are being used in
some cases to replace CFCs because of their lesser effect on the ozone layer,
have been found to have an average of about 30 times as much greenhouse gas
effect as CO2.
Montreal
Protocol
Countries
reached an agreement in 1987 to phase out CFCs over the next 10 to 15 years(26). The
decline of the ozone layer has been stabilized since 2005 at a little over 3%
less than the 1964-1980 average, and the magnitude of the loss is no
longer increasing. According to new studies(27) based
on monitoring data,the winter ozone hole is expected
to gradually decline and repair over the next 60 years. The hole in the Earth's ozone
layer has shielded Antarctica from the worst effects of global warming until
now, according to the most comprehensive review to date of the state of the
Antarctic climate. But scientists warned that as the hole closes up in the next
few decades, temperatures on the continent could rise by around 3C on average,
with melting ice contributing to a global sea-level increases
of up to 1.4m. The western Antarctic peninsula has
seen rapid ice loss as the world has warmed, but other parts of the continent
have paradoxically been cooling, with a 10% increase in ice in the seas around
the region in recent decades. Many climate change sceptics have used the Antarctic cooling as evidence
against global warming.
But John
Turner of the British Antarctic Survey said scientists are now "very
confident" that the anomaly had caused by the ozone hole above Antarctica.
"We knew that, when we took away this blanket of ozone, we would have more
ultra-violet radiation. But we didn't realise the
extent to which it would change the atmospheric circulation of the
Antarctic."
These changes in weather have
increased winds in the Southern Ocean region and meant that a large part of the
continent has remained relatively cool compared with the western peninsula. But
because the the CFC gasses that caused the ozone hole
now been banned, scientists expect the damage to repair itself within the next
50-60 years. By then the cooling effect will have faded out and Turner said the
Antarctic would face the full effects of global warming. This means an increase
in average air temperatures of around 3C and a reduction in sea ice by around a
third.
The biggest threat to the continent comes from warming seas. Robert Binschadler, a glaciologist at Nasa who monitors Antarctic ice sheets, said: "The heat in the ocean is getting underneath the floating ice shelves, these floating fringes of the ice sheet that are hundreds of metres thick. That warm water is melting the underside of the ice shelf, reducing the buttressing effect." Thinning of the ice shelf at the fringes leads to glaciers moving more quickly. Average sea-level rise will be closer to 1.4m by the end of the century- more than the IPCC estimate which not take changes in the ozone layer over Antarctica into effect.
References
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& "NASA identifies cause of ozone depletion", Science News, Vol
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N.A.S.A., "Ozone Depletion at Northern and Southern Latitudes- 1979 to 1991", Journal
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(2) Kerr et al, Science, Vol 262, 1993, p1022 &
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(3) U.S. EPA, in Science News, 1988.
(4)Science News, 1-22-94, p54 and Vol 151,6-21-97,p383; &
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(24) straight to the
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(25) Bryan Johnson
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2004 & NOAA Scientific
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(26) CFC Phaseout Agreement, Montreal Protocol ,1987
