Whatever happened to that ozone hole thing? I never hear about it any more.
Ozone depletion
The danger is that ozone-destroying chemicals are long-lasting and take time to travel up to the stratosphere. Chemicals released years ago are still present in the atmosphere and are contributing to today's peak concentrations.
Meanwhile, global climate change is thought to be slowing the ozone layer's healing process. The warming of the atmosphere near the ground causes the stratosphere to become even colder. Cold stratospheric temperatures, particularly during the early Antarctic spring, catalyze the chemical processes that destroy ozone molecules (UNEP, 2000).
The results of the WMO/UNEP scientific assessment of ozone depletion, released in 1998, confirmed the effectiveness of the Montreal Protocol on Substances that Deplete the Ozone Layer (WMO/UNEP, 1998). A full recovery of the Earth's protective ozone shield could occur by the middle of the 21st century if the Protocol is fully implemented. However, even though the Protocol is working well to reduce the use and release of ozone-depleting substances, the life of chemicals already released in the atmosphere will keep the depletion going for years to come.
The combined total abundance of ozone-depleting compounds in the troposphere (the lowest part of the atmosphere) peaked in 1994 and is now slowly declining. However, total concentrations of bromine are still increasing. In the northern polar latitudes, in six out of the last nine boreal winter-spring seasons, ozone has declined during some months by 25 % to 30 % below the 1960s average. In the Antarctic, the appearance of the ozone hole during the austral springs has continued unabated, with ozone column losses usually exceeding 50 % during the months of September and October. Only over the middle latitudes in both the northern and southern hemispheres has the ozone decline slowed in comparison with the previous scientific assessment in 1994. If measures had not been taken in accordance with the Montreal Protocol and its Amendments and Adjustments, the ozone decline would have been much stronger and would have continued for many more decades. Ozone losses in the stratosphere may have caused part of the observed cooling of the lower stratosphere in the polar and upper middle latitudes (about 0.6 degrees centigrade per decade since 1979). The increase of ozone in the troposphere since pre-industrial times is estimated to have contributed 10 % to 20 % of the warming due to the increase in long-lived greenhouse gases during the same period. The abundance of ozone-depleting substances in the stratosphere is expected to peak by the year 2000. However, when changing atmospheric conditions are combined with natural ozone variability, detecting the start of the ozone layer recovery may not be possible for perhaps another 20 years
