Geoscience Reference
In-Depth Information
refrigerators and air-conditioning systems possible, and were later utilised in
industrial solvents, insulated packaging and as propellants in aerosol cans for
deodorants, hairsprays, paints, furniture polishes, and numerous other household
products. Up until the 1920s, most natural refrigerants had been extremely haz-
ardous, such as ammonia (both a
ammable and toxic gas). Freon and other CFCs
were stable, non
ammable, nontoxic, and inexpensive to produce. Chemically, they
were stable and unreactive until they reached the stratosphere, a slow journey that
took several years, where UV radiation broke them down and released the ozone
depleting substance chlorine. However, because demand for CFCs was modest
before the Second World War, and the process of ozone depletion was slow, it was
not until the 1970s that concerns about the thinning of the ozone layer emerged.
58
As late as 1950, emissions of CFC compounds were still moderate at around
20,000 tons per annum. But by the 1970s, as DuPont
'
s original patents expired and
the market became crowded with new producers
—
and consumers, as demand for
refrigerators and air-conditioning units rose
CFC emissions increased sharply to
some 750,000 tons annually.
59
During the same decade, scienti
—
c studies of CFCs
in the stratosphere indicated that they had the potential to seriously deplete the
ozone layer. In 1985, the depletion of the Earth
'
s protective ozone layer was
nally
con
rmed by scientists with the British Antarctic Survey, and was soon made
'
'
'
s
Nimbus-7 satellite. Numerous studies since then have revealed a global decrease in
what is sometimes called
visible
to the public by the processing and dissemination of data from NASA
'
good ozone
'
. Inert at ambient temperatures, human-made
chloro
uorocarbons reacted very aggressively with ozone in the extreme cold of the
polar stratosphere in the months of early spring, when sunlight returned. The
destruction of ozone by the chlorine in CFCs resulted in
appearing
over both the Antarctic and Arctic regions (the latter being less pronounced). The
ozone layer also thinned signi
'
ozone holes
'
cantly above Australia and Chile, and slightly above
much of the Northern Hemisphere (but not over the tropics). The increase in
exposure to ultraviolet radiation can cause skin cancer and eye disorders (especially
cataracts and
'
snow blindness
'
) in humans, as well as impairing photosynthesis in
plants and reproduction in
adversely affecting terrestrial
and aquatic ecosystems.
60
The threats to human health and the environment were
clear and attracted considerable media attention, which led to widespread public
support for action to combat ozone depletion.
Governments lost no time in responding to the threat posed by CFCs, in no small
part because competitively priced substitutes were easy to manufacture, such as
hydro
sh and phytoplankton
—
uorocarbons (HFCs) which contain no ozone-depleting chlorine. In 1985,
the United Nations Environment Programme organised the Vienna Convention for
Protection of the Ozone Layer, which encouraged international cooperation on
research into ozone depletion and its effects. It was followed in 1987 by the
58
Jacobson (
2002
) and McNeill (
2000
).
59
Ackermann (
2002
) and McNeill (
2000
).
60
Lambright (
2005
), Davis (
2002
), McMichael (
2001
) and McNeill (
2000
).
