Stratospheric Ozone Depletion

Ozone is both beneficial and harmful to us. Near the ground, ozone forming as a result of chemical reactions involving traffic pollution and sunlight may cause a number of respiratory problems, particularly for young children. However, high up in the atmosphere in a region known as the stratosphere, ozone filters out incoming radiation from the Sun in the cell-damaging ultraviolet (UV) part of the spectrum. Without this ozone layer, life on earth would not have evolved in the way it has.

The stratosphere is the second major layer of the atmosphere and lies above the troposphere, the lowest layer. It occupies the region of atmosphere from about 12 to 50 km above the Earth's surface, although its lower boundary tends to be higher nearer the equator and lower nearer the poles.

Concentrations of ozone in the stratosphere fluctuate naturally in response to variations in weather conditions and amounts of energy being released from the Sun, and to major volcanic eruptions.

Nevertheless, during the 1970s it was realised that man-made emissions of CFCs and other chemicals used in refrigeration, aerosols and cleansing agents may cause a significant destruction of ozone in the stratosphere, thereby letting through more of the harmful ultraviolet radiation.

Then in 1985, evidence of a large "ozone hole" was discovered above the continent of Antarctica during the springtime. This has reappeared annually, generally growing larger and deeper each year. More recently, fears have emerged about significant ozone depletion over the Arctic, closer to the more populous regions of the Northern Hemisphere.

Download Twenty Questions and Answers about the Ozone layer (PDF 2.10 MB).

Ozone is regularly monitored above the UK to determine the level of ozone loss. For more information visit the Ozone Hole Tour Web site.

Impact of low stratospheric ozone on the natural environment.

Increases in Ultra Violet (UVB) radiation caused by reductions in stratospheric ozone concentrations are associated with effects on Biogeochemical cycles - balance between production and destruction of organic matter. Effect on natural emissions of CO and CO2 and mineral nutrient cycling. Air quality - increases in the amount of chemical activity in lower atmosphere and the rate of removal of primary pollutants from the atmosphere. Ecosystems - aquatic foodweb - UVB has negative impact on growth, photosynthesis, protien content and reproduction of phytoplankton. Terrestrial organisms and altered patterns of gene activity.