ARCHIVE: e-Digest Statistics about: Ozone Depletion
Understanding Stratospheric Ozone Depletion
There is unequivocal evidence that stratospheric ozone depletion is being caused by man-made emissions of chlorine and bromine-containing substances such as CFCs and halons, emitted as a result of their use in a variety of applications such as spray can propellants, refrigerants, foam-blowing agents and in fire extinguishers, and HCFCs, which are similar to CFCs but have a lower potential for depleting ozone and can be used as transitional replacements in many sectors. Emissions of methyl chloroform, carbon tetrachloride and methyl bromide also contribute to the depletion of ozone.
Ozone is continually created and destroyed in the stratosphere by a cycle of chemical reactions. Depletion of the ozone layer is caused when halogenated compounds are broken down in the stratosphere by sunlight to release chlorine and bromine atoms which then catalyse the reactions that destroy ozone. This process is enhanced by the presence of polar stratospheric clouds (PSCs), which form at very low temperatures in the stratosphere and enable normally inert compounds to take part in reactions that produce ozone destroying free radicals such as chlorine atoms.
In polar regions, ozone depletion is particularly rapid during the winter and spring but slows when the atmosphere warms up enough to prevent the formation of PSCs. As the rate of ozone destruction slows down the reactions that form ozone, and the influx of ozone-rich air from other latitudes help to replenish the ozone lost during the previous months.
Chemically-initiated ozone depletion in the Antarctic occurs each winter and spring and in recent years the ozone hole has covered an area equivalent to the United States of America. The approximate maximum areas covered by the annual ozone holes since 1979 are given in Table 8 (also Figure 10) and illustrate the increasing loss of ozone which has occurred during the 1980s.
A variety of observations have now provided clear evidence of significant and widespread ozone losses in the Arctic in winter, with features similar to the beginnings of the Antarctic ozone hole being seen. Temperatures in the Arctic lower stratosphere in recent winters have been low which has promoted the formation of PSCs and subsequent rapid ozone depletion in the Arctic vortex [17].
In Detail:
- Stratospheric Ozone Depletion and Possible Impacts of Ozone Depletion in the UK
- Agreements to limit Ozone Depleting Substances
Further Information:
- Key Facts:
- Column ozone in the UK
- Atmospheric concentrations of ozone depletors
- World and UK consumption of CFCs
Data Tables:
| Table
No. |
Title | Download
file type |
| 8 | Approximate maximum area of the Antarctic ozone hole: 1979-2006 | |
| Fig 10 | Maximum area of the Antarctic ozone hole: 1979-2006 |
- References, further reading and links to other resources:
- [17] Department of the Environment, (1996). Stratospheric Ozone, 1996. United Kingdom Stratospheric Ozone Review Group
- [18] Scientific Assessment Panel of the Montreal Protocol, (2002). Executive Summary of UNEP/WMO Scientific Assessment of Ozone Depletion: 2002. WMO/UNEP
- Internet Links:
- British Atmospheric Data Centre (BADC)
NASA Total Ozone Mapping Spectrometer site
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Page last modified: 6 November 2007
Page published: 10 September 2003