OSLO - Curbs on chemicals that damage the ozone layer could have a side-effect of reducing far more greenhouse gases than the main U.N. plan for confronting climate change, the U.N. Environment Programme (UNEP) said on Thursday.

About 191 governments will meet in Montreal from Sept. 17 to 21 to seek ways to speed up freezing on production and phasing out ozone-depleting HCFC gases, widely used in fridges and air conditioners, that also trap heat in the atmosphere.

"If governments accept accelerated action on HCFCs, we can look forward to not only a faster recovery of the ozone layer, but a further important contribution to the climate change challenge," Achim Steiner, head of UNEP, said in a statement.

A new study indicates a cumulative 38 billion tonnes of carbon dioxide, also the main heat-trapping gas released by burning fossil fuels, could be avoided in the coming decades if tight new curbs were imposed on HCFCs, UNEP said.

That is up from 18-25 billion tonnes previously forecast and far more than the some 2 billion tonnes a year the U.N.'s Kyoto Protocol is intended to eliminate in a first 2008-12 phase as the main plan for fighting global warming, UNEP said.

"If a full freeze and phaseout is achieved this might well do more for the climate than the existing Kyoto Protocol," UNEP spokesman Nick Nuttall said.

The ozone layer has been recovering after governments agreed in 1987 to cut gases, found in everything from hairsprays to refrigerants, that were thinning the ozone that shields the planet from ultra-violet rays.


CANCERS

Benefits of phasing out the chemicals include a reduction in skin cancers, cataracts and harm to the human immune system, UNEP said. UNEP reckons the ozone layer is on track to recover its pre-1980 thickness by 2050-75.

To reach the maximum effect of phasing out HCFCs, UNEP said measures would have to include proper recovery and destruction of old equipment -- like air conditioners now dumped and left to rust and leak -- and improvements in energy efficiency.

HCFCs, or hydrochlorofluorocarbons, were introduced as a less ozone-depleting alternative to other gases known as CFCs. But they have been found to be stoking climate change that could bring more floods, droughts, heatwaves and rising seas.

Chemical maker DuPont, which makes less damaging alternatives to HCFCs, favours a faster phaseout. "Additional actions need to be taken globally by governments and industry," Linda Fisher, a DuPont vice president, said in a statement.

DuPont estimates that 60 million of 110 million households in the United States alone have central air conditioning and that many of those systems still use HCFCs.

Any accord in Montreal to phase out HCFCs could be brandished as a step towards reining in climate change at a high-level U.N. meeting in New York on Sept. 24 called by U.N. Secretary-General Ban Ki-moon.