Because of the long period of time between the release of CFCs at the ground and when they reach the ozone layer, and because there is not enough data to establish the magnitude of the natural variations in the ozone concentration over long periods of time, it is difficult to assess whether or not any significant ozone depletion is occurring at this moment. However, the rapid deepening of the Ozone Hole over the South Pole during the last several years is probably our first solid evidence that ozone depletion is occurring or can occur from CFC emissions (that and the analysis of gases in the area that had carbon atoms, chlorine atoms, and fluorine atoms in roughly the same proportions as they appear in a common type of CFC molecule).

During the South Polar Winter (June-September), the sun is below the horizon or very low on the horizon all day long. The lack of sunlight allows stratospheric ozone to build up to high concentrations (on the order of 350-450 DU). The lack of sunlight also creates extremely cold temperatures in this region. The pool of cold air circulates around the pole in a tight pattern and prevents the diffusion of gases in or out of the circulation pattern (the circumpolar vortex). When the sun begins to illuminate the South Polar stratosphere around the beginning of Spring in the Southern Hemisphere (mid-September), the sunlight goes to work on the air inside the vortex. Observations show that there is a large amount of Cl₂ (diatomic chlorine, a stable molecule that is relatively harmless to ozone) that has formed out of the atomic chlorine confined to the vortex region at the beginning of the previous winter months. The sunlight photodissociates the Cl₂ into two atoms of chlorine and this sudden flood of atomic chlorine starts destroying ozone within the vortex. This occurs rapidly (a week or so, with no ozone from higher latitudes able to diffuse toward the pole and mitigate the ozone loss, because the vortex does not allow cross-latitude mixing. The confined region of ozone loss (concentration as low as 150 DU) appears as a "hole" in the ozone layer directly above the South Pole. After a few weeks, the vortex region warms and the circulation collapses. Ozone from higher latitudes mixes in and erases the ozone hole.

The Ozone Hole of September 2000 pictured here looks larger in area than usual (normally, it's confined to a region directly over Antarctica, but this time it appears to extend all the way to the tip of South America), but it's not as "deep" as in previous years. The vortex that confines the "hole" is wider and the air is warmer than before, so the "hole" is more of a wide, shallow pool.