| Ozone Depletion |
| In 1979, an experimental American satellite
recorded atmospheric ozone concentrations over Antarctica that were so
low that the measurements were dismissed as an instrument error. Only
when British scientists recorded similar levels using weather balloons
were the satellite measurements taken seriously. Atmospheric conditions
over Antarctica conspire to destroy ozone in the stratosphere, 20-25km
(12-15 miles) above the Earth's surface. In the spring months, levels
are usually 40% lower than in the 1960s. On some days, ozone is too scarce
to be detected at all.
Stratospheric ozone concentration over Antarctica measured by the Nimbus 7 environmental satellite (red represents high values, blue is low). The ozone layer is important because it shields us from the Sun's ultraviolet radiation, which is damaging to all forms of life. The situation observed over Antarctica is just an extreme example of a global depletion of ozone caused by man-made chemicals such as chloroflourocarbons (CFCs), used in industrial processes and products, such as aerosol sprays and refrigerator coolants. Once they escape into the atmosphere, they are extremely long-lived and have a strong effect on ozone: a single chlorine atom released from a CFC molecule is able to destroy 100,000 ozone molecules. Although CFC production has been phased out in the leading industrial nations, the CFCs already released will persist for most of this century. Prolonged exposure to ultraviolet leads to increased incidence of skin cancer and eye cataracts. 800,000 additional cancer deaths are estimated to result from damage to the ozone layer. |
