Statement on the State of the Ozone Layer

The International Ozone Commission (IOC) of the International Association for Meteorology and Atmospheric Physics (IUGG/ICSU), at the conclusion of the Quadrennial Ozone Symposium-88 (August 8-13, 1988) held at the University of Göttingen, Federal Republic of Germany and attended by nearly 500 scientists, briefly summarized the predominant views on the state of the ozone layer in the following statement.

1. IOC confirms the analysis of revised ground-based Dobson spectrophotometer data over the northern hemisphere for the period 1965-1986 by the NASA/WMO International Ozone Trends Panel 1988 which indicates that, after allowing for the known natural variability (e.g. solar cycle, quasi-biennial oscillation), ozone has decreased since 1970 by about 4% in the winter months and about 1% in the summer months over the latitudinal band 30 to 64°N. The winter trends become more negative with increasing latitude and also differ between geographical regions.
2. Meanwhile, the observed increase in tropospheric ozone at the same latitudes of about 1% per year infers that the stratospheric ozone decreases determined from the total ozone column measurements must have been greater.
3. The model calculations are broadly consistent with the observed change in column ozone, except that the mean values of the observed decreases in winter are larger than models had predicted. However, current model calculations do not include the effects of heterogeneous chemistry which might results in an underestimation of the impact of CFCs on ozone. The ozone satellite data from the last nine years are in concurrence with the conclusions deduced from ground-based observations.
4. The IOC also confirms that substantial decreases of total ozone which started in in the late 1970's are now occurring every spring over Antarctica, although with variable strength. The main ozone depletion during this season is observed between 12 and 24 km. Scientific research shows that the decreases are strongly linked with the specific circumpolar circulational conditions accompanied by extremely low stratospheric temperatures (favoring generation of polar stratospheric clouds) and greatly enhanced abundance of active chlorine released from substances produced by industries elsewhere in the world.
5. In the absence of other changes, the Antarctic ozone hole will continue to appear each astral spring until stratospheric chlorine levels fall to those of the mid-1970's. Even if no more man-made chlorine were to be released into the atmosphere, the Antarctic ozone recovery would take many decades.
6. The rapid and frequent meridional exchange of air into the Arctic lower stratospheric levels precludes the possibility of a strong closed circumpolar vortex with extremely low stratospheric temperatures, which is typical over the Antarctic region during the polar night. This could at least partly explain why the available observations do not indicate over the Arrctic the existence of an extensive ozone reduction similar by scale and magnitude to the one observed over Antarctica since the late 1970's. Also, recent observations indicate a somewhat perturbed state of the chemical composition in the lower stratosphere during the Arctic winter.
7. The IOC wishes it to be noted that, after many years of monitoring and research, there is now clear evidence of mankind having affected the whole global ozone layer. This is a significant point as it is the first firm evidence in history that humans have very noticeably and harmfully altered the atmosphere on a global scale.
8. There is an added climatological effect of the complex of increasing CFC's and changing ozone on the temperatures. The CFCs have a strong greenhouse effect, and at current concentrations they contribute by 10% to 15% to the total surface warming calculated by various modes. The increasing tropospheric ozone also has a similar effect. On the other hand, the decreasing stratospheric ozone amounts would result in a local temperature decrease in the middle stratosphere.
9. Scientific understanding of the processes which control ozone has improved since the last Ozone Symposium-84. However, may more atmosphere measurements and laboratory and modeling studies are needed to test and refine this. The IOC members are ready to play a significant part in the continuing investigation of ozone and other related environmental problems expecting that there will be national and international firm commitments to long-term funding for programs of instrument development, deployment and calibrations, of analysis of the data obtained, and of studies of processes relevant to their interpretation.
10. The IOC urges all national and international agencies such as the World Meteorological Organization (WMO), the Commission of European Communities (CEC), which support scientific research and monitoring of ozone and associated atmospheric parameters, and such as the United Nations Environment Programme (UNEP) which handles studies of impacts and related public policy, to continue support of these activities. The IOC is ready to collaborate in all these fields, as has been done in the past decades.
11. The IOC supports the need for regular scientific assessment of the ozone problem at an international level under the auspices of the World Meteorological Organization and the United Nations Environment Programme, such as are conducted as part of the Montreal Protocol on Substances that Deplete the Ozone Layer. The IOC anticipates participating in these reviews both as an independent Commission of scientists and as individual scientists.