The hole in the ozone layer over Antarctica will be wider in 2008 than reported in 2007, a new U.N. study has said.
Img: Ozone hole in Sept. 2006. Credit: NASA
The U.N.'s World Meteorological Organisation (WMO) has advised that the observed changes in the stratospheric measurements will delay the repair of the ozone hole and called on its member states to continue to support observations and prevent further damage.
Speaking at the International Day for the Preservation of the Ozone Layer on September 16, U.N. Secretary-General Ban Ki-moon said it would take many years before the ozone layer fully recovers from damage caused by chemicals such as chlorofluorocarbons (CFCs).
“After decades of chemical attack, it may take another 50 years or so for the ozone layer to recover fully. As the Montreal Protocol has taught us, when we degrade our environment too far, nursing it back to health tends to be a long journey, not a quick fix,” he said.
The 1987 Montreal Protocol was signed amongst member nations to phase out substances harmful to the ozone layer. Among these were CFCs and HCFCs (hydrochloroflourocarbons).
According to the most recent measurements taken by the WMO, the ozone hole, though appearing later in the year than usual, will exceed the size reached in 2007 as it reaches its peak towards the end of September and early October.
Using ground observations, measurements from balloons and satellites, and accompanying meteorological information, WMO scientists found that the hole covered an area of 27 million square kilometers on September 13 of this year. The maximum area reached in 2007 was 25 million square kilometers.
The scientists say they are aware of the effect climate change is having on the ozone hole. According to a statement released by the WMO, an excess of greenhouse gases, while causing a warming effect in the troposphere and on the Earth's surface, results in a cooling effect in the stratosphere, accelerating the ozone damage.
"Increased atmospheric concentrations of greenhouse gases (GHGs) will lead to warmer temperatures in the troposphere and at the Earth’s surface," the statement said.
"In the stratosphere, at altitudes where we find the ozone layer, there will be a cooling effect. A cooling of the stratosphere in winter over the last decades has indeed been observed, both in the Arctic and in the Antarctic. Lower temperatures enhance the chemical reactions that destroy ozone," it added.
"At the same time, the amount of water vapour in the stratosphere has been increasing at the rate of about one per cent per year. A wetter and colder stratosphere means more polar stratospheric clouds, which is likely to lead to more severe ozone loss in both polar regions."
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