Global Ozone Change and Possible Climate Implications
A review of the current state of the ozone layer is presented based on the results of more than 37 years of continuous observations by the WMO Global Ozone Observing System (GO3OS) of the Global Atmosphere Watch. It shows a significant decline in the stratosphere and some increase in the troposphere, the hemispheric differences due to macrocirculational patterns and the non-uniform vertical ozone distribution are also highlighted. Then the role of ozone as a greenhouse gas having an essential role in determining the temperature profile of the stratosphere and possible implications of the observed ozone changes on the climate system is discussed.
The stratospheric ozone decrease, which started in the 1970s is continuing (except over the 20°S-20°N) and is twice as strong in the winter-spring (>6% per decade) than during the summer season. The integrated ozone loss outside of the tropics for the last 25 years is close to 10 per cent.
Tropospheric ozone has more than doubled in the northern mid-latitudes since preindustrial times. Models and deducations from observations suggest this has caused a positive radiative forcing of ~0.5W m−2. The increase of the tropospheric ozone from 1971–1980 to 1981–1990, from measurements over Hohenpeissenberg (Germany), is estimated to have caused positive radiative forcing of about half of the forcing of all other greenhouse gases changes during the same time periods. Due to rather uneven ozone distribution both in horizontal and vertical planes the observed ozone changes cause a more complicated climate forcing than the other principal greenhouse gases having longer lifetimes and uniform global distribution.
The information is up-dated to include the extremely low ozone values observed in January-March 1995 over the northern middle latitudes and on the 1995 Antarcticspring ozone hole event which turned out to be the longest lasting phenomenon observed so far. Greater ozone losses at polar and mid-latitudes are expected in the next ten years or as long as the atmospheric chlorine loading continues to be greater than 3 ppbv; the ozone destruction will not end until the chlorine loading falls back to its pre-ozone-hole values of ~2 ppbv expected to occur after the middle of the 21st century — providing that all countries strictly adhere to the Montreal Protocol and its Amendments.
KeywordsTotal Ozone Tropospheric Ozone World Meteorological Organization Quasi Biennial Oscillation Ozone Hole
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