World Meteorological Organization (WMO)

The ozone hole of 2008 is larger than in 2007

“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”, said Ban Ki-moon, Secretary-General of the United Nations, on the occasion of the International Day for the Preservation of Ozone Layer today. According to the World Meteorological Organization (WMO), the 2008 Antarctic ozone hole will be larger than the one of 2007. The observed changes in the stratosphere could delay the expected recovery of the ozone layer. It is therefore vital that all Member States with stratospheric measurement programmes continue to support and enhance these measurements.

Routine ozone measurements in all parts of the world using surface-based spectrophotometers, balloon-borne sensors, aircraft and satellites have been made by the National Meteorological and Hydrological Services of WMO Members and partners worldwide since the 1950s. Thirty years later, comprehensive measurements started under coordination of the WMO Global Atmosphere Watch (GAW). These measurements have been critical to the series of Scientific Assessments of Ozone Depletion published since the mid-1980s by WMO and the Ozone Secretariat of the United Nations Environment Programme documenting progress made under the Vienna Convention for the Protection of the Ozone Layer. The most recent of these assessments came out in the spring of 2007. The work on the next ozone science assessment will begin in the middle of 2009.

In 1985, the Vienna Convention was signed by 22 countries. Two years later, the Montreal Protocol was signed on 16 September, a day which has since been designated by the United Nations as International Day for the Preservation of the Ozone Layer. The theme for 2008 is 'Montreal Protocol - Global partnership for global benefits'.

The Montreal Protocol on Substances that Deplete the Ozone Layer underpins our efforts to combat depletion of the Earth’s fragile protective shield. It also contributes to combating climate change, since many of the chemicals controlled under the treaty also contribute to global warming. By phasing out chlorofluorocarbons (CFCs) – once common in products such as refrigerators – and now deciding to accelerate a freeze and phase-out of hydrochlorofluorocarbons (HCFCs), the treaty has provided two benefits at once. The UN Secretary-General expressed the hope that “Governments will look at such results and feel empowered to act across a wide range of environmental challenges, and not only in prosperous times.”

At the end of August 2008, WMO released its first of the 2008-series bi-weekly Antarctic Ozone Bulletin on the current state of stratospheric ozone in the Antarctic. These bulletins use provisional data from the WMO/GAW stations operated within or near the Antarctic, where the most regular and dramatic decreases in ozone occur.

According to the latest bulletin, the vortex is presently more circular than at the same time last year. This has led to an onset of ozone depletion that is close to the 1979-2007 average and somewhat later than last year, when the vortex was more elongated and more exposed to sunlight. The meteorological conditions observed so far could indicate that the 2008 ozone hole will be smaller than that of 2006 hole but larger than that of 2007.

Usually, the Antarctic ozone hole reaches its maximum intensity in late September/early October. In 2008, the ozone hole appeared relatively late. However, during the last couple of weeks it has grown rapidly and has now passed 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. On 13 September 2008 the ozone hole covered an area of 27 million square kilometers. The maximum area reached in 2007 was 25 million square kilometers. WMO and the scientific community will use ozone observations from the ground, from balloons and from satellites together with meteorological data, to keep a close eye on the development during the coming weeks and months.

Scientists are increasingly aware of the possible links between ozone depletion and climate change. Increased atmospheric concentrations of greenhouse gases (GHGs) will lead to warmer temperatures in the troposphere and at the Earth’s surface. 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. 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.

These observed changes in the stratosphere could delay the expected recovery of the ozone layer. It is therefore vital that funding agencies continue to support research on stratospheric ozone and harmful ultra violet radiation and that all nations with stratospheric measurement programmes continue to enhance these measurements.

Together with the International Council for Science (ICSU), WMO is coordinating the International Polar Year 2007-08. Thousands of scientists are collaborating to increase our understanding of processes that take place in polar regions, including those of stratospheric ozone and ultra violet radiation. On 25 February 2009, WMO and ICSU will celebrate the closure of the International Polar year in Geneva, and release WMO’s Status of Polar Research.

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