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Press Release No. 863

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WMO UPDATE ON THE INTERNATIONAL DAY FOR THE PRESERVATION OF THE OZONE LAYER

Geneva, 16 September 2009 (WMO) – While the world is celebrating today the International Day for the Preservation of the Ozone layer, the 2009 Antarctic ozone hole, which appeared earlier than usual, is similar in size to those of recent years, according to the World Meteorological Organization (WMO). “This year’s ozone hole confirms earlier WMO statements that we must be prepared for severe ozone holes as long as the atmospheric contents of ozone depleting gases remains high” said Michel Jarraud, WMO Secretary-General. “Now that we are less than 100 days away from the United Nations Climate Change Conference in Copenhagen, it remains vital for all Member Sates with stratospheric measurement programmes to continue supporting and enhancing such measurements.”

Two years after the Vienna Convention, the Montreal Protocol was signed on 16 September 1987, a date that since 1994 has been designated by the United Nations as the International Day for the Preservation of the Ozone Layer. The theme for 2009 is "Universal participation: Ozone protection unifies the world".

WMO and the scientific community use ozone observations from the ground, from balloons and from satellites together with meteorological data, to keep a close eye on the development of the ozone holes. On 21 August 2009, WMO released its first of the 2009-series of Antarctic Ozone Bulletin on the current state of stratospheric ozone in the Antarctic. According to provisional data from the WMO/GAW stations operated within or near the Antarctic, the vortex was in August 2009 less concentric around the South Pole than at the same time last year. This led to an onset of ozone depletion that was earlier than recent years. The last couple of weeks, the development of the ozone hole has been similar to that observed in recent years. The meteorological conditions observed so far could indicate that the 2009 ozone hole will be smaller than those of 2006 and 2008 and close to that of 2007.

Today, observations show that by mid September, the hole has reached an area of about 23-25 million km2, which is an average value for mid September compared to recent years. It is still too early to make a definitive statement on the size and depth of this year’s ozone hole. The hole typically reaches its maximum surface area during the second half of September and the maximum depth during the first half of October. The amount of ozone depleting gases in the Antarctic stratosphere reached a maximum around year 2000 and is now decreasing at a rate of about 1% per year.

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 in the polar regions. At the same time, the amount of water vapour in the stratosphere has been increasing at a 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 ultraviolet radiation and that all nations with stratospheric measurement programmes continue to 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 scientific assessment has begun and the report will be finalised in late 2010, to be published in the spring of 2011.

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.

WMO is the United Nations' authoritative voice on weather, climate and water

For more information please contact WMO Communications and Public Affairs:

Ms Carine Richard-Van Maele, Chief, tel: +41 (0) 22 730 8314/15, E-mail: cvanmaele@wmo.int

Ms Gaëlle Sévenier, Press Officer, Tel. +41 (0) 22 730 8417. E-mail: gsevenier@wmo.int

Website: http://www.wmo.int

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