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Issue: Stratospheric ozone - General stratospheric ozone

This is an issue under the Atmosphere theme of the Data Reporting System.

Why we need to know about this issue

Ozone is an important constituent of the atmosphere because it absorbs most of the harmful ultraviolet B (UV-B) radiation that emanates from the sun, preventing it from reaching the earth’s surface. UV-B radiation can adversely affect animals and plants including crop yields and cause changes in species composition of phytoplankton and zooplankton that affect marine food webs. UV-B also causes several human health problems, some life threatening, and includes damage to the eyes, the immune system and the skin.

Ozone is continuously being produced and destroyed by several chemical and photolytic processes. Net ozone depletion occurs when ozone loss exceeds ozone production.

Indicators

• A-10 stratospheric chlorine from the major ozone-depleting substances 
  Chlorine released from the earth’s surface, breaks down in the stratosphere, releasing chlorine species that can cause ozone destruction.
  The chlorine species of interest are atmospheric concentrations of chlorofluorocarbons (CFCs), chlorinated solvents (methyl chloroform and carbon tetrachloride), methyl chloride (CH₃Cl), methyl bromide (CH₃Br), halons and hydro-chlorofluorocarbons (HCFCs). Their combined concentrations can be expressed as ‘equivalent effective stratospheric chlorine’, or simply ‘total stratospheric chlorine’, which is a way of representing their ability to destroy stratospheric ozone. Total stratospheric ozone is a direct indicator for this issue.
• A-11 Summer mean total ozone column 
  This measures the total amount of ozone in a column of air from the earth’s surface to the top of the atmosphere and thus is a measure if ozone levels are sufficient to protect us from harmful radiation.
• A-12 Trend in the area of the ozone hole 
  The largest ozone depletions have occurred over Antarctica. The hole is the region, the so-called ‘ozone hole’ is defined where total ozone levels are less than 220 Dobson units. The cause of ozone depletion from the 1980s has been the steady accumulation of stratospheric chlorine and bromine compounds. This is particularly the case over Antarctica in spring because of the presence of ice nuclei (polar stratospheric clouds) and weak Antarctica sunlight, which provide a very efficient mechanism for ozone depletion. Trends in the size of the ozone hole is a direct measure of this pressure.
• A-13 Surface ultraviolet radiation in Australia 
  This indicator shows the intensity of ultraviolet radiation reaching the surface of the planet which may be affected by ozone depletion.
• A-14 Consumption of ozone-depleting substances - Australian consumption of ozone-depleting substances 
  The ozone layer occurs in the upper atmosphere (the stratosphere) 15-30 km above the surface of the earth, and protects life on earth by absorbing harmful ultraviolet (UV) radiation from the sun. The ozone layer is also an important part of the global atmosphere-climate system. Any significant change to this layer can have far-reaching consequences for human and animal health.
  The Montreal Protocol on Substances that Deplete the Ozone Layer is an international agreement that sets out a mandatory timetable for the phase out of ozone depleting substances. In Australia, the production of many ozone-depleting substances has ceased and local consumption is limited to some imports. Hence, the level of consumption of ozone depleting substances is based on the level of imports less any substances destroyed by the National Halon Bank. Changes in consumption of ozone depleting substances in Australia is a direct indicator of the effectiveness of Australia’s response to the threat of ozone depletion.
• A-15 Skin melanoma rates 
  One of the harmful effects of less ozone in the stratosphere is an increase in the incidence of melanoma rates. This indicator measures to what extent these harmful effects are impacting on human health.

Related issues

• Land - Contributions and pressures between the land and the atmosphere - Ozone depletion 
• Coasts and Oceans - Contributions and pressures between the coasts and oceans and the atmosphere - Ozone depletion