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The Global Environment-II:
The Ozone Layer
Alok B Guha
The
Global Environment Facility (GEF) supports the Small Grants
Programme to initiate small grassroots activities in various
developing countries. Development Alternatives is the National Host
Institution and houses the small secretariat which processes and
assists NGOs to develop project proposals. The thematic areas
include climate change, ozone layer depletion, biodiversity
conservation and international waters’ protection. For the benefit
of grassroots NGOs, we are serialising five short articles on what
these thematic areas imply to help NGOs develop valid ideas for
projects. This is the second article in the series and draws from
material prepared by GEF, UNDP and the United Nations Environment
Programme (UNEP).
The
ozone layer, comprising a protective layer of gas some 10 to 50 kms
above the earth’s surface, is responsible for absorbing most of the
solar ultraviolet radiation and preventing it from reaching the
earth’s surface. The ozone in the stratosphere is continuously
formed and destroyed by chemical reactions triggered by sunlight.
However, release of ozone depleting chemicals - mainly Chloro Fluoro
Carbons (CFCs) and halons - is eroding the ozone layer, thereby
increasing the amount of ultra-violet radiation reaching the earth’s
surface. In effect, CFCs are raising the global temperature and
augmenting the detrimental impact of ultra-violet rays on human
health.
It is
well established that ultra-violet rays cause skin cancers and other
diseases. Besides permitting more ultra-violet radiation into the
earth’s atmosphere, these chemicals prevent infra-red radiation from
escaping the earth’s atmosphere, thereby trapping the heat being
radiated out of the atmosphere. Actually, these are highly effective
greenhouse gases complementing the build up of carbon dioxide in
raising the temperature of the earth and accounting for an estimated
20 to 25 per cent share in the cause for global warming.
CFCs
and halons are being produced at record levels even though their
deleterious effects were recognised some 15 to 20 years ago. These
chemicals are used in aerosol spray cans, for artificial cooling
(refrigeration, air-conditioning), manufacturing soft seat cushions
and foam-insulation.
In the
1930s, when CFCs were first used as refrigerants in the cooling
cycle of refrigerators, nobody imagined that these chemicals could
damage the ozone layer. The fact that solar radiation breaks down
CFCs, releasing chlorine radicals which in turn disintegrate the
ozone molecule, was discovered only during 1970s and 1980s.
Depletion of ozone levels increases the amount of ultra-violet
radiation reaching the earth’s surface. One form of this radiation,
UV-B, causes eye cataract, melanoma and non-melanoma skin cancers,
suppression of the immune systems in humans, interferes with natural
growth rates in ecosystems and degrades some kinds of plastics.
CFCs, (used in refrigeration, as aerosol propellants, as cleaning
fluids and in the blowing of plastic foams), are the main cause of
ozone depletion but many other chemicals are also implicated,
including carbon tetrachloride used in dry-cleaning, methyl
chloroform used as a solvent, halons used in fire extinguishers and
methyl bromide used in fumigating the soil and crops against pests.
Even
though, initially, just a few countries took the threat seriously,
there was sufficient concern to enact the Vienna Convention on the
Protection of the Ozone Layer in 1985. Only a few months later, the
British confirmed that severe ozone layer depletion was occurring
over the Antarctica during the spring every year. The evidence
pointed to ozone depleting substances (ODS) as a cause of this ozone
hole. This was followed by the Montreal Protocol (1987) and then a
series of ever stricter adjustments and amendments made to it at
various international meetings. The ODS originally planned to be
controlled under the Montreal Protocol included 5 CFCs and 3 halons.1
The
London amendment (1990) added methyl chloroform, carbon
tetrachloride and some other range of CFCs to be phased out, while
the Copenhagen Amendment (1992) added Hydro Chloro Fluoro Carbons (HCFCs),
Hydro Bromo FluoroCarbons (HBFCs) and methyl bromide. The developed
countries were required to phase out the production and consumption
of halons by 1994, and of CFCs, carbon tetrachloride, methyl
chloroform and HBFCs by 1996. Methyl bromide is to be phased out
by 2005 and HCFCs by 2030.
The
developing countries have a longer phase-out period. They phased out
the HBFCs in 1996. The developing countries are required to take
the first step in eliminating ODS by freezing the production of CFCs
at average 1995-97 levels on July 1, 1999. Some developing
countries are already well ahead of their commitments under the
Montreal Protocol, having effectively reduced CFC production and
consumption even before the Montreal deadlines. Prospects of
attaining the ‘1999 Freeze’ are good for other developing
countries.
Without the Montreal Protocol, ozone depletion would have become a
substantial environmental hazard to the well being of humankind.
Without the phase-out of ODS substances, it is estimated that in the
United States and North West Europe alone, an additional 1.5 million
and 5,50,000 people, respectively, would have become victims of skin
cancer. The Montreal Protocol does reduce these figures to
4,40,000 and 1,70,000, respectively. While with the Copenhagen
amendments, it is now likely to result in only 8,000 more cases of
skin cancer in the United States and 4,000 more in North West Europe
by 2100.
On the
negative side, statistics show that CFC use is still increasing in
many developing countries and more attention needs to be paid to
small and medium sized enterprises and to countries that consume
only very low volumes of ODS. Growth of illegal trade in CFCs is
also a problem, with the Institutional Trade Information Service
estimating that as much as one quarter of global CFC production in
1996 was produced for illegal export to developed countries.
While
action to reduce release of ODS in the atmosphere has been
impressive, it has produced very little difference to the ozone
layer itself due to the long life of already released CFCs. Ozone
levels will return to normal only after all the CFCs have
disappeared from the atmosphere, a process expected to take upto
2050. Nothing can change the fact that the average lifetime of a
CFC-11 molecule in the atmosphere is 50 years and that of a CFC-12
molecule is 100 years. Thus globally, average ozone levels continue
to fall by about 5 per cent a decade over mid-latitudes.
Thus,
in the Antarctic spring of 1997, total ozone levels were about 33
per cent less than in the late 1970s - similar to previous
record-lows in 1993 and 1996. In the 12-20 km layer, ozone was
almost completely annihilated for more than 40 continuous days. The
hole extended to more than 20 million square kms, reaching well
within the southern tip of South America.
Substantial depletion has also been observed in the northern
hemisphere, with ozone levels being reduced to 64 per cent of their
normal values in some places in the winter of 1996-97. Record-highs
have recently been discovered in both ozone destruction and UV-B
radiation levels over populated areas at middle and high latitudes
in the Northern hemisphere during the winter and early spring.
While levels of chlorine in the atmosphere are still increasing, the
annual rate of increase is now much slower. Chlorine concentrations
are now expected to peak about 2000 parts per billion by volume and
then decline slowly.
This
article is based on a previous article by the author and published
in the Deccan Herald some time ago. It also draws on material
published by the United Nations Environment Programme titled “Where
We Stand: A State of the Environment Overview of the Global
Environment Facility”, which is essentially a report from the Global
Environment Outlook Programme.
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