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International Ozone Commission (IO3C)

September 15th. On the 25th anniversary of the signing of the Montreal Protocol, the global ozone layer has stabilized, but large depletion in the polar regions continues to occur.

The United Nations has declared the 16th of September as the International Day for the Protection of the Ozone Layer to commemorate 16 September 1987, the date when the Montreal Protocol on Substances that Deplete the Ozone Layer (a protocol to the Vienna Convention for the Protection of the Ozone Layer) was signed. The Montreal Protocol controls the production and use of ozone-depleting substances. It is an outstanding example of a successful cooperation between scientists, governments, non-government organizations, and industry, as well as between developed and developing countries. It also provides an excellent paradigm to the international community for cooperation on complex environmental issues of global importance.

The theme of the International Day for the Preservation of the Ozone Layer on 16 September 2012 is: “Protecting our atmosphere for generations to come.”1

The Montreal Protocol has been highly successful in reducing the emissions and atmospheric abundances of ozone-depleting substances. Recent ground-based and space-based measurements show that the stratospheric amounts of chlorine and bromine, the species most harmful to the ozone layer, continue to decline, and that global ozone abundances have stabilized at about 3.5% below 1980 levels in the 60°S-60°N latitude range.

While the ozone layer is recovering from the effects of ozone depleting substances such as chlorofluorocarbons, increased greenhouse gases levels are projected to change the stratosphere. These changes require continued vigilance in monitoring the ozone layer.

Return of the global ozone layer to pre-1980 levels is expected to occur around the middle of the 21st century, as a result of the decrease of ozone-depleting substances regulated by the Montreal Protocol. In Antarctica the return is predicted to occur about two decades later.

At the present time, however, a large Antarctic ozone hole is still a recurrent seasonal feature in the Southern Hemisphere, and record-setting ozone depletion was observed in the Arctic in 2011.

There is a strong interplay between increases in the concentration of greenhouse gases in the atmosphere and stratospheric ozone recovery. In the midlatitudes of both Hemispheres, greenhouse gases are projected to accelerate the return of midlatitude total ozone columns to 1980 values, and to increase ozone towards the end of the 21st century to values higher than in 1980, particularly in the Northern Hemisphere. In the tropics, greenhouse gases are projected to cause a decrease of ozone. Because of these greenhouse gases, the ozone layer will not return to its pre-industrial natural state. Recent research demonstrates that stratospheric ozone changes have had important influences on climate in the stratosphere and also at the ground.

The number of ground stations that observe ozone has continued to decrease in the last decade. In addition, satellite systems that measure ozone-depleting substances are aging, and are likely to fail in the next few years. The loss of ozone-observing capabilities threatens the ability of scientists to report on the state of the ozone layer, and restricts their ability to project future levels of ozone.

The International Ozone Commission (IO3C) of IAMAS-IUGG urges all national and international agencies that support scientific research and monitoring of ozone and related parameters to continue supporting these activities. Without ozone measurements, threats to the ozone layer will not be identified, and scientists will be unable to forewarn future problems. Without observations, the theme of “Protecting our atmosphere for generations to come” cannot be fulfilled.

This text was last reviewed by the IO3C members on September 15th
For more information: Dr. Sophie Godin-Beekmann, Secretary of the International Ozone Commission, Université Pierre et Marie Curie, Laboratoire Atmosphère, Milieux, Observations Spatiales, Centre National de la Recherche Scientifique 75252, Paris, Cedex 05, France, Tel.: +33 1 44 27 47 67, Fax: +33 1 44 27 49 67, mobile: +33 6 77 18 38 64, e-mail:
WMO Northern Hemisphere Ozone Mapping Center
WMO Antarctic Ozone Bulletin
European Ozone Coordinating Unit
World Ozone and Ultraviolet Data Center
Ozone Hole Watch
Assessments on the state of the ozone layer Who is who in the Montreal Protocol:

(1) Please visit the web site of the Ozone Secretariat for the Vienna Convention , where you will find suggestions for worldwide activities on the 2012 International Ozone Day