The United Nations declared the 16^th of September as the International Day for the Protection of the Ozone Layer to commemorate the 16^th of September 1987, the date when the Montreal Protocol was first signed. The Protocol controls the production and use of anthropogenic species which since the early 1970s have destroyed about 10% of the earth’s ozone shield which protects life from the harmful solar ultraviolet radiation. The Protocol is an example of selfless cooperation between the developed and developing countries and provides an excellent paradigm to the international community for cooperation in complex environmental issues of global importance.

Today people believe that the Montreal Protocol has solved the problem and that the issue of the protection of the ozone layer has been settled. Unfortunately, as it has been confirmed by the recent international ozone assessment (WMO, 1999), as well as from results presented during the Sapporo 2000 Quadrennial Ozone Symposium, held last July, global ground-based and satellite measurements show that ozone continues to decline.

The decline in the Northern middle and higher latitudes is larger (5-6% per decade since 1979) during the winter-spring season compared to the summer time (2-3% per decade since 1979), The largest negative deviations have been observed over the Arctic and the Antarctic, where, in the spring, the ozone destruction exceeded 50% in the lower stratosphere for short time-periods over the Arctic, while over the Antarctica the ozone loss in the lower stratosphere exceed 95% for a few weeks in the period from September through October. Last winter-spring (1999-2000) the stratosphere in the northern hemisphere was colder compared to most of the previous winters of the 1990s and this resulted to the continuation of significant ozone destruction over the northern polar latitudes. In the past few weeks the lower stratosphere temperatures, below minus 86^oC, that facilitate ozone destruction have already led to a large depletion of the ozone layer over Antarctica.

The ozone values measured at the few Antarctic stations in August have reached the record low for that month. The size of the area with ozone values less than 220 matm-cm, which is commonly called the "ozone hole", exceeded 13 million km² for the last ten days of August, which is much stronger than the previously largest averages of about 9 and 8 million km² at the end of August 1996 and 1998 respectively. The average sunlit area of the "ozone hole" during the first ten days of September, as determined by satellite observations, has grown to an unprecedented 23 million km² (in single days exceeding 27 million km²) i.e. far greater than twice the size of Europe. This average area is 35% larger, when compared with the average of the previous two austral springs. This year the ozone hole was well established and exceeded 20 million km², about two weeks earlier, as compared to its evolution in the austral springs of the previous decade. However variations in the size of the severely depleted area from year to year are not unexpected, since it strongly depends on the strength and position of the polar stratospheric vortex.

Also the strength of the ozone loss in the beginning of this austral spring is unprecedented. During August 2000, poleward of 60^oS, the Ozone Mass Deficiency (O₃MD) from the pre-1976 averages was about 25% stronger than in the previously strongest ozone deficient August of 1996. In the first ten days of September the ozone values poleward of 55⁰S were down to about 225 matm-cm or about 30% less than the pre-1976 average. These values occurred about 10 days earlier than during most of the 90’s.

It should be noted that over the 35-50⁰S mid-latitude belt the total ozone in August was very close to the values of early 1980s and in the first ten days of September the ozone there continued its annual course and has increased to above 350 matm-cm.

All countries at mid- and high latitudes in both hemispheres are vulnerable to solar UV radiation increase due to declining ozone levels. People that live in mid- and high latitudes of both hemispheres have experienced increases in erythemal (skin reddening) UV radiation at rates up to 10% (Christos is it not up to 10% as in most publications ???) per decade, especially pronounced in the southern hemisphere.

This month, between 25-28 September 2000, in Palermo Italy, an International Science Meeting will take place, which is jointly organised by the European Union and NASA. In this Meeting European and American Scientists will present results from the joint SOLVE-THESEO field campaign, which took place last winter and aimed to examine the processes, which control polar and mid-latitude stratospheric ozone levels. The results are expected to elucidate the complex chemical, dynamical and radiative mechanisms involved in polar and mid-latitude ozone loss.

Based on the recent international assessment of ozone depletion published by WMO in 1999, record low ozone values are possible during the next 10 -15 years, depending on the meteorological conditions (e.g. stratospheric temperatures, vortex strength). According to modelling predictions it is expected that the ozone layer will not recover to pre-ozone hole levels before 2050. The recovery could take longer due to greenhouse gas-induced cooling of the stratosphere, or to the possible occurrence of major volcanic eruptions, such as the Mt Pinatubo (Philippines) eruption in 1991.

The International Ozone Commission (IO₃C) of IAMAS-IUGG urges all national and international Agencies, which support scientific research and monitoring of ozone and related parameters to continue supporting these activities. The IO₃C is ready to collaborate and make significant scientific contributions, as has been done in the preparations of the Ozone Assessments in the past decades.