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The ozone layer

Children often get the greenhouse effect and ozone depletion muddled. The two are not actually linked. Here is what is known about the causes and results of ozone depletion.

What is the hole in the ozone layer?

In 1984, it was found that the amount of ozone in the atmosphere above Antarctica was much less than expected. Since then, ozone 'holes' have been found over other parts of the world, including Europe. This general loss of ozone in the stratosphere, which is found 15 - 50km above the Earth's surface, is called ozone depletion and is not concentrated in 'holes'.

Why does it matter?

The ozone layer absorbs most of the ultraviolet light coming from the sun. This far ultraviolet light, called UV-B, is harmful to plants and animals. It causes cancers and eye damage in animals, and reduces the growth rate of some plants, including the microscopic plants called plankton living in the oceans, which are an important source of food for animals.

How is it caused?

When we release certain gases into the atmosphere, some complicated chemical processes occur in the upper atmosphere, and ozone is destroyed. The main ozone depleting gases are called CFCs (chlorofluorocarbons), which are found in aerosols, in fridges, in car air conditioning systems and in the process of making plastics. Other ozone depleting gases are halons, which are used in fire extinguishers.

How can we stop ozone depletion?

By cutting down our production of CFCs and halons. In 1987 the major industrial countries agreed to cut their production of CFCs and halons by 50% by 1991, and in 1990 they agreed to phase out all of these chemicals by 2000.

Some difficult problems remain. CFCs are the cheapest gases that are used to make fridges work. Several countries in hot parts of the world have not agreed to stop using them, because of the great assistance refrigeration can be in feeding their people.

The dangers of ozone depletion have to be balanced against improved health in poor countries.

Does ozone depletion have anything to do with global warming?

No, the two processes are different: ozone depletion does not directly cause temperature rise.

The only link between ozone depletion and global warming is that CFCs are a cause in both processes. Global warming happens when we release greenhouse gases such as carbon dioxide and methane into the atmosphere. This causes sunlight energy to be trapped and the temperature rises. CFCs are greenhouse gases.

Other common misconceptions

  • 'Holes' in the ozone layer allow more 'heat rays' to reach the earth, causing global warming
  • Increase of carbon dioxide in the atmosphere causes ozone depletion
  • The sun 'burns' holes in the ozone layer