By Richard Black
Environment correspondent, BBC news website
Faster progress is needed to safeguard the ozone layer, according to one of the scientists who discovered the "ozone hole" over Antarctica.
The Antarctic "ozone hole" should repair in about half a century
Writing on the BBC News website, Joe Farman calls for faster phase-out of some ozone-destroying chemicals, and for the destruction of stockpiles.
The Montreal Protocol regulating these substances is 20 years old this week.
Some of Dr Farman's arguments have been echoed by senior figures in the UN, and by European and US politicians.
He is critical of the agreement that allows developing countries to keep on using some ozone-depleting chemicals until 2040.
"Frequent reviews rescued the Montreal Protocol from deficiencies in the original draft, and another comprehensive re-examination is clearly needed," he writes in the BBC's Green Room series.
Joe Farman was one of three British Antarctic Survey scientists who reported signs of severe damage to the ozone layer over Antarctic - the "ozone hole" - in 1985.
Member countries of the Montreal Protocol are meeting this week, again in Montreal, to review progress.
Faster, sooner, cheaper
The 1987 Montreal Protocol was designed to phase out chemicals such as chlorofluorocarbons which were found to be depleting the ozone layer in the Earth's stratosphere, the higher portion of the atmosphere.
The ozone layer blocks ultraviolet-B radiation from the Sun, which can cause skin cancers and other medical conditions, as well as harming wildlife.
Industrialised nations phased out almost all CFC production in 1995, with developing countries having a deadline of 2010.
Many of the substances, used in applications such as refrigeration, aerosols and fire-fighting, could be replaced relatively easily with related families of chemicals including hydrochlorofluorocarbons (HCFCs).
Ozone-depleting chemicals are still used by some fire-fighting forces
These cause much less damage to the ozone layer; but production in the developing world is now increasing so fast that there is renewed concern about their impact.
Current regulations mean that in 2015, developing countries will have to freeze their HCFC use at or below the level it is then, phasing out entirely by 2040.
"The rate of HCFC use is skyrocketing," noted Clare Perry, senior ozone campaigner with the Environmental Investigation Agency (EIA).
"So it's actually going to cost less to phase it out sooner when investment in plant and equipment is at a lower level."
French Environment Minister Nathalie Kosciusko-Morizet said the EU would be pushing for a faster phase-out at this week's ozone treaty meeting.
"The schedule for eliminating HCFCs must be pushed up by 10 years - that will be the benchmark for deciding if the negotiations are succesful," she said.
Accelerating the phase-out would require new funds from the industralised world, as well as changes to the current funding regulations.
Joe Farman also wants cash set aside to combat leakage of ozone-depleting chemicals, such as the fire retardant halon 1301, from developing world installations.
"There is some production in developing countries," he writes, "but the main source is now through leaks from existing installations, and during recycling. It is surely time to consider collecting the existing stockpile, and destroying it."
HCFCs also contribute to climate change. They are much more potent, molecule for molecule, than carbon dioxide; one byproduct of HCFC manufacture, HFC23, is 11,700 times more powerful.
Reducing HCFC use "offers the international community the chance to make rapid gains both concerning the ozone layer and global climate change," said UN Environment Programme (Unep) executive director Achim Steiner in the run-up to this week's summit.
Joe Farman discovered major Antarctic ozone depletion in the 1980s
And President Bush's chief environmental advisor James Connaughton said that accelerating HCFC phase-out by 10 years would "produce at least twice the reduction (in greenhouse gas emissions) of the Kyoto Protocol".
However, some environmentalists believe there is an element of political spin here intended to divert attention from carbon dioxide, which is much more important overall as a greenhouse gas.
There is also concern that the Kyoto Protocol may be creating a "perverse incentive" for companies to boost HCFC use.
The protocol's Clean Development Mechanism (CDM) funds the reduction of greenhouse gas emissions in developing countries. It can be used to pay for equipment to trap and burn HFC23.
"In 2005, the destruction of HFC23 accounted for 64% of the value of all CDM projects, and 51% in 2006," Dr Farman writes.
"There is currently much debate on whether carbon trading based so heavily on burning HFC23 constitutes sustainable development."