This paper triggered a large interest, because it is a follow-up of the first journal publication (Varotsos C., ESPR, 9: 375-376, 2002), which suggested and documented an unprecedented event that occurred in the Southern Hemisphere in September 2002, notably: a major, stratospheric sudden warming (SSW) that had never been observed before in the Southern Hemisphere. It was the causal effect for the smaller-sized ozone hole which appeared over Antarctica in 2002 and its splitting into two separate holes.

The thematic topic of this paper may be considered as a new discovery because it was thought, prior to September 2002, that a major SSW could happen only in the Northern Hemisphere. In addition, it is suggested that the major SSW did not allow the heterogeneous chemical reactions, which are substantially active at very low temperatures, to lead to a considerable chemical ozone loss.

Therefore, this first-ever observed event of these extremely high temperatures in the polar stratosphere led to the explanation of the drastic reduction of the size and intensity of the Antarctic ozone hole in 2002, which does not promise a recovery of the ozone layer.

Polar ozone loss is linked to the perturbations of the polar vortices, which are prominent features of the winter stratosphere in both hemispheres.

Although the zonal-mean temperature normally decreases towards the winter pole in the stratosphere, sometimes the polar stratospheric temperatures increase rapidly with time (stratospheric sudden warming). If the poleward increase of temperature is strong, then a reversal of zonal-mean winds from westerly to easterly direction is observed. Such an event is often called major SSW.

From a dynamical point of view, SSW is a transient phenomenon observed in the middle atmosphere, where during some winters the upward-propagating planetary waves from the troposphere cause a sudden breakdown of the stratospheric polar vortex. Therefore quite strong planetary waves cause major SSW.

It was previously considered that planetary activity is much weaker in the Southern Hemisphere due to various reasons (e.g., the reduced mountainous land cover, weaker longitudinal land-sea contrast, and the presence of the cold, elevated Antarctic continent at the pole). Therefore, since the beginning of Antarctic temperature records dating back to 1940, a growing body of evidence had accumulated against a possible occurrence of a major SSW and split of the Antarctic vortex. In particular, according to the available record of observations, the major SSWs only occurred in one or two northern winters, and they had not been observed in the Southern Hemisphere before September of 2002.

On September 24^th and 25^th in 2002, the diminutive Antarctic ozone hole split into two parts. It was attributed to the puzzling occurrence of a major, sudden stratospheric warming (SSW) in Antarctica—an event which appeared for the first time in that region. Processes based on the nonlinear nature of atmospheric dynamics could probably address the question, "What caused the southern hemisphere to exhibit very strong planetary waves in 2002?" that is now of main interest.

Since 1980 we have been performing various atmospheric measurements utilizing ground-based and balloon-borne instrumentation. Simultaneously, we analyze satellite observations in order to explore both the temporal and spatial variability of the atmosphere.

In recent years we have studied aspects of the non-linear nature of atmospheric phenomena. Among these is a focus on the study of atmospheric ozone variability through the employment of new analytical techniques. Although we have already reached promising results, problems such as a complete understanding of the intrinsic properties of the atmospheric variables remain far from being solved.

In 1970 Professor Dr. Paul J. Crutzen pioneered in the discussion of adverse impacts on the ozone layer of nitrogen oxides from fertilizers and from supersonic aircraft. In 1974 Professors F. Sherwood Rowland and Mario J. Molina identified CFCs (chlorofluorocarbons) as ozone destroyers, which has been confirmed by subsequent studies. In recognition of their pioneering work, these three scientists were awarded the Nobel Prize for Chemistry in 1995.

The ongoing depletion of the ozone layer due to anthropogenic impacts results in the enhancement of surface ultraviolet radiation, which may lead to dangerous consequences for man and the biosphere. The implications of this ozone depletion would be horrendous, including nearly an additional 19 million cases more of non-melanoma skin cancer up to the year 2060 and three million more cases up to the year 2030. The number of eye cataracts would increase also by about 130 million cases by the year 2060 and approximately 50% of these cases would occur in developing countries.

There are many unquantifiable effects such as the loss of immunity, the adverse impact on animals, the lower productivity of crops, damage to aquatic ecosystems, and others. However, as stated above, the driving mechanism for the diminutive ozone hole over Antarctica in 2002 was of a dynamical nature and it cannot be considered as a recovery of the ozone layer.

Knowledge of the present status of ozone depletion in the stratosphere is a crucial component of the scientific input provided to the United Nations Montreal Protocol on the ozone layer and the deliberations of the countries which are parties to the Protocol on matters related to the protection of the ozone layer are of major importance.