THE ozone layer that shields much of the earth from cancer-causing ultraviolet rays is showing signs of thickening after years of depletion, according to a recent study by the United Nations. According to the report, titled Scientific Assessment of Ozone Depletion 2014, published on September 10, “actions taken under the Montreal Protocol have led to decreases in the atmospheric abundance of controlled ozone-depleting substances (ODSs), and are enabling the return of the ozone layer toward 1980 levels.”
A pale blue gas with a distinctively pungent smell, the ozone absorbs 97 to 99 percent of the Sun’s medium-frequency ultraviolet light, which otherwise would potentially damage exposed life forms near the surface of the earth.
“Total column ozone declined over most of the globe during the 1980s and early 1990s by about 2.5 percent averaged over 60°S to 60°N [which corresponds roughly over the area covering Antarctica],” the UN report said.
But it added that “it has remained relatively unchanged since 2000, with indications of a small increase in total column ozone in recent years, as expected.”
Published by the World Meteorological Organization (WMO) under the United Nations Environment Programme, the report noted that “in the upper stratosphere there is a clear recent ozone increase, which climate models suggest can be explained by comparable contributions from declining ODS abundances and upper stratospheric cooling caused by carbon dioxide increases.”
The report also said the ozone hole that appears annually over Antarctica has also stopped growing bigger every year, but cautioned that “it will take a decade before the hole starts to shrink,” citing assessments by scientists that the recovery is entirely due to political determination to phase out the man-made chlorofluorocarbon (CFC) gases destroying ozone.
“International action on the ozone layer is a major environmental success story. [This] should encourage us to display the same level of urgency and unity to tackle the even greater challenge of tackling climate change,” WMO Secretary-General Michel Jarraud was quoted as saying.
Notwithstanding the good news on ozone is the atmospheric greenhouse gases that fuel climate change had reached a record high, WMO said in a separate announcement.
Ozone-eating depleting chemicals—including CFCs once widely used in refrigerators and spray cans—have known substitutes, but preventing the use of gas like carbon dioxide, which is a direct by-product of coal burning used to produce energy or electricity, is a different story. To recall, the 1987 Montreal Protocol banned or phased out ozone-depleting chemicals, including CFCs, have prevented would-be skin cancers victims estimated to reach 2 million annually by 2030.
It included potential damage to wildlife and agriculture, the UN said.
According to the WMO, the ozone should recover toward its 1980 level by midcentury, or slightly later for Antarctica, where it gets dangerously thin every year between mid-August and November or December.
It added that the snail-paced progress could be accelerated by as much as 11 years if existing stocks of ozone-depleting substances stored up in old and unused refrigerators and fire-extinguishers were destroyed.
After the Montreal Protocol came into effect in 1989, countries began phasing out manufacture and use of ozone-destroying substances. A side benefit of CFC reduction is that it may be helping to blunt the progress of global warming, since CFCs are also powerful greenhouse gases.
The assessment estimates that in 2010, lowered emissions of ozone depleters equated to keeping around 10 metric gigatons of CO2 out of the atmosphere, “which is about five times larger than the annual emissions reduction target” for 2008-2012 under the Kyoto Protocol climate treaty.
The report also warns on the use of compounds being swapped in for ozone-eaters, such as hydrofluorocarbons (HFCs) which are also strong greenhouse gases. If their use increases as predicted, they will contribute quite a lot to surface temperature rises, the UN said.
HFCs are mainly used as substitutes for CFCs and some of its uses are as refrigerants in refrigeration and air conditioning equipment and as agents for plastic thermal insulation foams for refrigerated vehicle insulation.
Minor uses include metered dose inhalers for asthma, blowing one component foam for building work and as a propellant for industrial and technical aerosols.
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