Ozone depletion -- blamed for higher
ultraviolet radiation that causes skin cancers and cataracts and damages
agriculture -- will continue for decades as several key damaging substances
stay in the atmosphere for a long time after emissions end.
While many cooling agents or other
compounds harmful to the ozone are no longer being produced or emitted, some of
their industrial replacements are greenhouses gases that contribute much more
to global warming, the report said.
"The ozone has bottomed out. It is
no longer really decreasing. But there is also no real sign yet of an increase
in ozone," Geir Braathen, senior scientific officer at the World
Meteorological Organization (WMO), told a news briefing.
"We still believe that the ozone
layer, at least in mid-latitudes, will be repaired by around 2050," he
said.
The ozone hole which forms over the
Antarctic every springtime is only expected to return to the pre-1980 benchmark
values in the late 21st century, the report said. High levels of ultraviolet
rays are detected when it is large.
However, the current Antarctic ozone
hole is smaller than in the past two years, according to Braathen.
While chlorofluorocarbons (CFCs) once
used in refrigerators, spray cans and other appliances have been phased out,
demand for substitutes such as hydrochlorofluorocarbons (HCFCs) and
hydrofluorocarbons (HFCs) has risen, according to the study by the WMO and the
UN Environment Program (UNEP).
Many are also potent greenhouse gases,
blamed for causing climate change that unleashes extreme weather such as
droughts, wildfires, heat waves, floods, mudslides and rising sea levels.
The report by 300 scientists credited
the 1987 Montreal Protocol signed by some 200 countries with stopping
additional ozone loss and helping to mitigate the greenhouse effect.
Through tight controls, the pact avoided
an equivalent of 10 gigatons per year of carbon dioxide being emitted, it said.
This was five times more than the Kyoto Protocol's targets for reducing
greenhouse gases from 2008-2012.
Current annual emissions of CO2 from
burning fossil fuels and cement production amount to 30 gigatons, Braathen
said.
HCFCs, ozone-depleting substances
covered by the Montreal Protocol, are due to be capped in 2015 and phased out
by 2040. As HFCs are not ozone-depleting, they are not covered, but developing
countries are pushing for them to be brought under the Kyoto protocol.
"The replacements are in some cases
greenhouse gases but there are replacements that have low greenhouse warming
potential," said Len Barrie, WMO research director. "So there's room
technologically to play here. And that's the point."
Up to 20 million cases of skin cancer
and 130 million cases of cataracts have been averted due to the Montreal
Protocol, according to the report being published in full in early 2011.
