Long-Term Ozone Changes

Kurzfassung

Continuous measurements of ozone have been made for several decades, with the longest record starting in 1926. While the longest records are from ground-based stations, global coverage was only achieved in 1979 with instruments carried on satellites. Together these show the following general features. In polar regions, severe ozone depletion occurs over Antarctica nearly every Austral spring (the Antarctic ozone hole), while large ozone losses have only occasionally appeared over the Arctic in Boreal spring. Smaller long-term decreases are seen over the midlatitudes in both hemispheres, with the larger losses occurring in the Southern Hemisphere. There are only small ozone trends over the tropics. Changes in chemical composition, particularly in chlorine and bromine containing species, and changes in atmospheric dynamics have influenced ozone. It is important to distinguish between these and other factors in order to assess the effect of the international treaty on phasing out of the emissions of ozone depleting substances and the possible influence of climate change on stratospheric ozone and UV radiation.