Holes in the Ozone Layer
The gas from the Ozone layer consists of a special from of Oxygen. High up in the stratosphere is where it is found in its greatest quantities.
The Ozone layer is continuously formed and destroyed because of the constant bombardment of rays from the sun, and especially ultraviolet (UV) radiation. It is the ozone layer’s reaction to UV rays that prevent a dangerous form of radiation – known as UVB radiation – from reaching the surface of the Earth. It is UVB radiation that causes skin cancer as well as other diseases. And studies have shown that UVB can penetrate the ocean down to 20 meters, where most marine life lives.
In the early 1970’s scientists warned that CFC’s (chlorofluorocarbons) could damage the ozone layer. About that time some countries, including the USA and those in the European Community, reduced production as a precaution – for instance, ending CFC use in many aerosols. But the news of the formation of an Antarctic ozone hold prompted for more action.
Scientists noticed thinning ozone over Antarctica in the early 1980’s. Every spring, about 60 per cent of the ozone layer disappeared, leaving a ‘hole’ in the layer. Research planes discovered that the cause was a build up of chemicals in the stratosphere. There chemicals included chlorofluorocarbons (CFC’s) – invented in the 1920’s, and widely used in refrigerators, aerosols, and air-conditioning systems.
On their escape, these chemicals accumulated in the cold air above Antarctica each winter. Then, each spring, the sun provided energy for ozone-destroying reactions to take place. Scientists also noticed that the entire ozone layer was thinning. And, beginning in about 1990, a hole began to emerge each spring over the Arctic, where the air is almost as cold as over the Antarctica. Sometimes this hole stretches south, opening over parts of Europe during February.
Fortunately, nature can repair the holes in a few weeks as the temperature rises, but they still open up again at the same time each year.
From the first time the ozone hold was measured back in 1976, the largest measured hole was 24 million km2. This was measured in September 2009.
If the world stopped using all ozone-eating substances tomorrow, it would still take until the middle of the 21st century before the ozone layer begins to recover to the levels of the mid 1970’s – before the first hole was formed.