| Title |
OZONE LAYER
PROTECTION (MONTREAL PROTOCOL) |
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Date-wise Events |
- September 16: This special
day is held on September 16th to mark the day back in
1987 when the Montreal Protocol was signed.
- January 01, 1989: The Montreal Protocol on Substances That Deplete the Ozone Layer
came into force on this day.
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Description |
- The ozone layer contains less than 10 parts per million
of ozone, while the average ozone concentration in Earth's
atmosphere as a whole is only about 0.3 parts per million.
- The ozone layer is mainly found in the lower portion of
the stratosphere, from approximately 20 to 30 kilometres (12
to 19 mi) above Earth, though the thickness varies
seasonally and geographically.
- The ozone layer was discovered in 1913 by the French
physicists Charles Fabry and Henri Buisson.
- The properties of the ozone layer were explored in
detail by the British meteorologist G. M. B. Dobson, who
developed a simple spectrophotometer (the Dobsonmeter) that
could be used to measure stratospheric ozone from the
ground. Between 1928 and 1958, Dobson established a
worldwide network of ozone monitoring stations, which
continue to operate to this day. The "Dobson unit", a
convenient measure of the amount of ozone overhead, is named
in his honour.
- The ozone layer absorbs 97–99% of the Sun's
medium-frequency ultraviolet light (from about 200 nm to 315
nm wavelength), which otherwise would potentially damage
exposed life forms near the surface.
- The United Nations General Assembly has designated
September 16 as the
International
Day for the Preservation of the Ozone Layer (a.k.a. World
Ozone Day).
- Venus also has a thin ozone layer at an altitude of 100
kilometers from the planet's surface.
- The ozone layer can be depleted by free radical
catalysts, including nitric oxide (NO), nitrous oxide (N2O),
hydroxyl (OH), atomic chlorine (Cl), and atomic bromine
(Br).
- While there are natural sources for all of these
species, the concentrations of chlorine and bromine
increased markedly in recent decades due to the release of
large quantities of man-made organohalogen compounds,
especially chlorofluorocarbons (CFCs) and
bromofluorocarbons.
- In 1978, the United States, Canada and Norway enacted
bans on CFC-containing aerosol sprays that damage the ozone
layer.
- After negotiation of an international treaty (the
Montreal Protocol), CFC production was capped at 1986 levels
with commitments to long-term reductions.
- Since that time, the treaty was amended to ban CFC
production after 1995 in the developed countries, and later
in developing countries. Today, all of the world's 197
countries have signed the treaty.
- Beginning January 1, 1996, only recycled and stockpiled
CFCs were available for use in developed countries like the
US.
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