The Antarctic ozone hole has become larger this year than it was in 2007, though it is still somewhat smaller than in 2006.
Revealing this, the World Meteorological Organisation (WMO) has cautioned that the changes in the atmosphere observed recently indicate a further delay in the expected recovery of the ozone layer. This has grave implications for global warming and human health.
The ozone layer is a protective band in the earth's upper-middle atmosphere (stratosphere) which has a high concentration of ozone gas that prevents over 90 per cent of the sun's harmful ultra violet (UV) radiation from hitting the earth. The increased exposure to the UV rays could cause skin cancer and other diseases in humans and damage plant life on earth.
The depletion of ozone gas in the ozone layer over the Antarctic region to as low as less than 33 per cent of the pre-1975 value had resulted in the creation of the ozone hole which has been causing concern about its adverse effect on the earth's habitation and climate. This has spurred global action in reducing the emission of ozone-depleting greenhouse gases (GHGs) which are also responsible for global warming.
According to the latest ozone bulletin issued by the WMO, the meteorological conditions observed so far indicate that the 2008 ozone hole would be larger than in 2007 though it may be smaller than that in 2006. The hole has been growing rapidly in the past weeks and has already outgrown the maximum size attained in 2007.
“Since the ozone hole is still growing, it is too early to determine how large this year's ozone hole will be”, the WMO has said.
On September 13, the ozone hole covered an area of 27 million sq kms. The maximum area reached in 2007 was 25 million sq kms, the global meteorological body has pointed out. In 2006, the hole had grown to around 29 million sq kms.
Scientists are now aware of the links between ozone depletion and climate change. Higher atmospheric concentration of the GHGs will lead to warmer temperatures on the earth’s surface.
Already, the amount of water vapours in the atmosphere has been rising at the rate of about one per cent a year. This, coupled with its interplay with temperature, could lead to more severe ozone loss in both polar zones, the WMO has warned.
The collaborative global effort to phase out the use of ozone-depleting substances like chlorofluorocarbons (CFCs) – used in refrigerators and other cooling equipment – had begun after signing of the Vienna Convention in 1985 and the Montreal Protocol 2 years later.
These treaties have since been modified and updated to phase out even the hydro-chlorofluorocarbons (HCFCs), which had earlier begun to replace the CFCs in these equipments as these were believed to be relatively safer. But now even these are viewed with apprehensions and are, therefore, being replaced with safer alternatives.
These efforts had boosted the hopes of recovery of the ozone layer and consequent disappearance of the ozone hole. However, the recently noticed changes in the atmosphere could delay the expected recovery of the ozone layer, the WMO feels.
Such fears were expressed also by United Nations (UN) secretary-general Ban Ki-moon in his statement issued on September 16, which is observed every year as the 'international day for the preservation of ozone layer'.
He said: “After decades of chemical attack, it may take another 50 years or so for the ozone layer to recover fully." When we degrade our environment too far, nursing it back to health tends to be a long journey, not a quick fix, he added.
The global bodies have appealed to the funding agencies to continue to support research on atmospheric ozone and harmful UV radiation to improve the understanding of the processes that take place in the polar regions.
