NEW DELHI: The protective ozone layer that started depleting heavily in the 1980's is on a recovery mode according to a new assessment by 300 scientists across the world released on Thursday. "Assessment for Decision-Makers"-- a summary document of the Scientific Assessment of Ozone Depletion 2014 published by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) indicates that the ozone layer is expected to recover to 1980 levels before the middle of this century in many parts.
But the news for India is grim. Tropical countries were not significantly affected by the above ozone depletion problem. But, along with severe climate change impacts, India and other tropical regions may face an ozone depletion problem towards the end of the century. Gufran Beig, project director at System of Air Quality Weather Forecasting and Research (SAFAR) of IITM, Pune and only Indian scientist in the international expert review team has flagged off certain ozone concerns for India. Climate change is inducing a change in circulation patterns in the upper layers of the atmosphere that will influence ozone concentration adversely, he has said in his submission.
This undated image provided by NASA shows the ozone layer over the years, Sept. 17, 1979, top left, Oct. 7, 1989, top right, Oct. 9, 2006, lower left, and Oct. 1, 2010, lower right. The fragile ozone layer is finally starting to rebound, says a United Nations panel of scientists. (AP photo)
These changes in the tropical circulation of winds (called Hadley Cell Circulation) will be as a result of climate change and can deplete the ozone layer in future as per the model projections because they tend to shift air in these layers, said Beig. He shared the document he sent to UNEP/WMO with TOI where he adds that concentration of aerosols--suspension of fine liquid droplets in the atmosphere, often particulate air pollution, can negatively impact the ozone layer over the tropics because of their chemical properties. "It has been the opinion of scientists that increasing greenhouse gas emissions and consequent change in the weather system will impact the ozone layer adversely. There has to be immediate measures to cut down on GHG emissions," he added. Beig has also highlighted that emissions from fossil fuel, bio-fuels, industries and power sector, troposphere or ground-level ozone, a toxic gas is increasing in India which also a problem.
Due to successful implementation of the Montreal protocol across the world that mandated phasing out ozone depleting substances such as chloroflurocarbons (CFCs) used in refrigerators, air conditioners and solvents, the ozone problem has been tackled unto larger extent. But now there is also a problem with the new alternatives. Hydrofluorocarbons (HFCs) which are now widely used (replacing CFCs) do not harm the ozone layer but many of them are potent greenhouse gases and have very high global warming potential. Their emissions are growing at a rate of about 7 % per year. Left unabated, they can be expected to contribute very significantly to climate change in the next decades. We have to avoid them" Beig added., Replacements of the current mix of High GWPs (Global Warming potential) HFCs with alternative compounds with low GWPs would limit this potential problem.
The ozone layer was expected to recover towards its 1980 level by mid-century, or slightly later for Antarctica, where it gets dangerously thin every year between mid-August and November or December.
"The development you saw during the 1990s that the ozone hole got bigger from year to year — that development has stopped, so it has levelled off," said Braathen.
"We think in about 2025 or thereabouts we'll be able to say with certainty that the ozone hole is getting smaller," he added.
Progress could be sped up by as much as 11 years if existing stocks of ozone-depleting substances — many of them stored up in old fridges and fire-extinguishers — were destroyed.
The largest ozone hole on record was about 30 million square km in 2006. The hole now covers about 20 million square km — big enough for the moon to pass through — but may not have peaked this season.
The size of the hole varies from year to year, partly due to temperature in the upper atmosphere.
The reduction of ozone-damaging chemicals would also help the environment, the report said, as many of the substances were also greenhouses gases blamed for global warming.
But the rising levels of other greenhouses gases in the atmosphere had "the potential to undermine these gains," said the report.
One of the ozone-depleting substances that was supposed to have been phased out - carbon tetrachloride, a solvent - was still being released into the atmosphere suggesting, the report said, illicit production and usage over the past decade.
