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 The experts were trying to pinpoint industrial sources of tiny
traces of the new gases, perhaps used in making pesticides or
refrigerants, that were found in Greenland's ice and in air samples
in Tasmania, Australia.
The ozone layer shields the planet from damaging ultra-violet rays,
which can cause skin cancer and eye cataracts, and has been
recovering after a phase-out of damaging chemicals under the U.N.'s
1987 Montreal Protocol.
"The concentrations are not yet a threat to the ozone layer," lead
author Johannes Laube of the University of East Anglia in England
told Reuters of the three types of CFCs (chlorofluorocarbon) and one
HCFC (hydrochlorofluorocarbon).
In total, the scientists estimated more than 74,000 metric tons of
the four had been released to the atmosphere. None was present
before the 1960s in Greenland's ice cores, according to the study in
the journal Nature Geoscience.
That is only a small fraction of the million metric tons of CFCs
produced every year at a 1980s peak, according to the team of
scientists in Britain, Germany, Australia, France, the Netherlands
and Switzerland.
LOOPHOLES
Laube said it was unknown if the emissions of the new gases were
illegal, since the Montreal Protocol has some exemptions. "We hope
to tighten the loopholes," he said.
A hole in the ozone layer was found in the 1980s over Antarctica but
bans on damaging chemicals, for instance used in hairsprays, foams
and refrigerants, means it is on target to recover in the next 50
years.
HCFCs have often been used to replace more damaging CFCs.
One of the newly discovered CFCs was worrying since concentrations
were rising fast, Laube said. Such emission increases had not been
spotted for other CFCs since the 1990s.
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The gases were detected earlier in Greenland than Tasmania,
indicating they were produced in the northern hemisphere and then
blown south. Research planes, taking air samples around the world,
may be able to find the sources, Laube said.
"While these newly discovered gases can, in theory, cause some
damage to the ozone layer, their combined abundance is over 500
times smaller than that of the main ozone-destroying compounds in
the 1990s," said Martyn Chipperfield, a professor of atmospheric
chemistry at the University of Leeds.
"These new observations do not present concern at the moment,
although the fact that these gases are in the atmosphere and some
are increasing needs investigation," he said.
Laube said the gases are also likely to be powerful greenhouse
gases, albeit in tiny amounts. CFCs are often thousands of times
more powerful than carbon dioxide at trapping heat in the
atmosphere. (Reporting by Alister Doyle;
editing by Mike Collett-White)
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