Geneva: The depleting ozone layer is well on track to recovery in the next few decades because of "concerted international action", according to an assessment report by UN Enviornment Programme and World Meterological Organisation.
Ozone layer, a fragile shield of gas, protects the Earth from harmful ultra-violet rays of the sun.
The Scientific Assessement of Ozone Depletion 2014, a study done by 300 scientist across the globe, says the actions taken under the Montreal Protocol on subtances that deplete the ozone layer are "enabling the return of the ozone layer to benchmark 1980 levels".
"Compliance of the report have led to decreases in the atmospheric abundance of gases, such as CFCs (chlorofluorocarbons) and halons, once used in products such as refrigerators, spray cans, insulation foam and fire suppression.
"Total column ozone declined over most of the globe during the 1980s and early 1990s. It has remained relatively unchanged since 2000, but there are recent indications of its future recovery," the report said.
The treaty was designed to decrease the production and consumption of ozone depleting substances -- many of these are also potent greenhouse gases -- in order to reduce their abundance in the atmosphere, and protect the layer.
The report stated: "In 1987, ozone depleting substances contributed about 10 gigatonnes CO2-equivalent emissions per year. The Montreal Protocol has reduced these emissions by 90 per cent. This decrease is about five times larger than the annual emissions reduction target for the first commitment period (2008?2012) of the Kyoto Protocol on climate change."
UN Under-Secretary-General and UNEP Executive Director Achim Steiner said: "There are positive indications that the ozone layer is on track to recovery towards the middle of the century. The Montreal Protocol, one of the world's most successful environmental treaties, has protected the stratospheric ozone layer and avoided enhanced UV radiation reaching the earth's surface.
"Without the Montreal Protocol and associated agreements, atmospheric levels of ozone depleting substances could have increased ten-fold by 2050."
According to global models, the Protocol will have prevented 2 million cases of skin cancer annually by 2030, averted damage to human eyes and immune systems, and protected wildlife and agriculture.
However, the assessment report cautions that the rapid increase in certain substitutes, which are themselves also potent greenhouse gases, has the potential to undermine these gains.
Another finding of the report was that the Antarctic ozone hole, which continues to occur each spring, is expected to continue occurring for the better part of this century as the ozone depleting substances persist in the atmosphere, even though their emissions have ceased.
Also, the Arctic stratosphere in winter or spring 2011 was particularly ozone depletion as expected under these conditions.
The WMO too came out in praise in the success of the Montreal Protocol.
"International action on the ozone layer is a major environmental success story," said WMO Secretary-General Michel Jarraud.
"This should encourage us to display the same level of urgency and unity to tackle the even greater challenge of climate change. This latest assessment provides solid science to policy-makers about the intricate relationship between ozone and climate and the need for mutually-supportive measures to protect life on earth for future generations," Jarraud said.
The assessment also notes that there are possible approaches to avoiding the harmful climate effects of these substitutes.
"Hydrofluorocarbons (HFCs) do not harm the ozone layer but many of them are potent greenhouse gases. They currently contribute about 0.5 gigatonnes of CO2-equivalent emissions per year. These emissions are growing at a rate of about 7 per cent per year. Left unabated, they can be expected the next decades.
"Replacements of the current mix of high-GWP HFCs with alternative compounds with low GWPs or not-in-kind technologies would limit this potential problem," the report said.
The report added that Carbon dioxide, Nitrous Oxide and Methane will have an increasing influence on the ozone layer in the second half of the 21st century.
"What happens to the ozone layer in the second half of the 21st century will largely depend on concentrations of CO2, methane and nitrous oxide ? the three main long-lived greenhouse gases in the atmosphere.
"Overall, CO2 and methane tend to increase global ozone levels. By contrast, nitrous oxide, a by-product of food production, is both a powerful greenhouse gas and an ozone depleting future ozone depletion," the report said.
