THE
OZONE layer is showing signs of recovering, thanks to a drop in ozone-depleting
chemicals, but it is unlikely to stabilise at pre-1980 levels, researchers said
on Wednesday.
Depletion
of the earth’s protective ozone layer is caused by the chemical action of
chlorine and bromine released by manmade chlorofluorocarbons (CFCs), which are
used in aerosol sprays and cooling equipment.
Ozone-depleting
chemicals were banned by the 1987 Montreal Protocol which has now been ratified
by 180 nations.
“We now
have some confidence that the ozone layer is responding to the decreases in
chlorine levels in the atmosphere due to the levelling off and decrease of
CFCs,” said Dr. Betsy Weatherhead, of the University of Colorado in Boulder.
“Not only is the ozone layer getting better, we feel it is due to the Montreal
Protocol,” she added in an interview.
The
depletion of the ozone layer, which absorbs most of the harmful effects of the
sun’s ultraviolet radiation, increases the risk of skin cancer and cataracts
in humans and may harm crop yields and sea life.
Despite the
signs of recovery, Weatherhead, who reported the findings in the journal Nature,
said people should still protect themselves from ultraviolet rays.
Weatherhead
and Signe Bech Anderson of the Danish Meteorological Institute in Copenhagen
analysed data from satellites and ground stations and information from 14
modeling studies.
They found
that ozone levels have stabilised or increased slightly in the past 10 years.
But full recovery is still decades away.
The
researchers said depletion has been most severe at the poles and to a lesser
extent at mid-latitudes covering bands of North America, South America and
Europe.
Shifting
temperatures, greenhouse gases, nitrous oxide (N20) and atmospheric dynamics,
which can influence ozone levels, are going to change in the future, they added.
“Therefore we really don’t think ozone is going to stabilise back to its
pre-ozonedepleting-substance levels,” Weatherhead said. Fact file Ozone layer
is improving because of a drop in the ozone-depleting chemicals Depletion has
been caused by the chemical action of chlorine, bromine released by man-made
chlorofluorocarbons (CFCs) These CFCs are used in aerosol sprays and cooling
equipment .
* Source: Times of India, Friday
dated - May 05,2006 *