The ozone layer (located 9-22 miles above the earths surface) is made up of a large concentration of 3 bonded oxygen atoms (O3), and was originally formed over 1 billion years ago when oxygen atoms (molecules consisting of 2 bonded oxygen atoms "O2"-of which we breathe) found high above the earths surface were split apart due to ultraviolet light produced from the sun; and reconnected with other oxygen atoms into groups of 3 to form the ozone molecules that make up the layer.
These ozone molecules are effective absorbers of ultraviolet radiation, which can cause cancer-forming mutations in living organisms, cataracts, crop damage as well as other serious problems, and therefore the layer acts as a much needed protective blanket around our planet. Which is why when scientists discovered that this protective blanket was under threat, it was very unwelcome news.
Holes:
In the 1920's, a man called Thomas Midgley invented CFC's (chloro-fluorocarbons), which is a chemical consisting of chlorine, fluoride and carbon. This chemical went on to be widely used in aerosol sprays, refrigerators, foams, and for cleaning electrical equipment, all over the world. However this chemical also had a huge impact on the planet in ways that were less useful, and more catastrophic. CFC's do not degrade quickly, and therefore were able to reach the stratosphere high above the earths surface and react with/damage the ozone layer. This damage occurred when the CFC chemical got broken apart by ultraviolet light, and went on to absorb oxygen atoms from the ozone layer, turning the sunlight-absorbing O3 molecular properties, into the much less effective O2 properties. This not only caused the ozone layer to degrade, creating holes in its structure, but it also allowed higher quantities of ultraviolet light to enter the planet.
The need to act:
Once the true effects of CFC's on the planet were discovered, a ban was put into action in 1978 in Norway, the USA, and Canada, on CFC containing aerosol sprays, although other parts of the world such as Europe did not follow their example straight away. After years of negotiations, and the creation of an international treaty that lead to a cap on the chemical at 1986 levels (Montreal protocol), an outright ban was put into place in 1995 for developed countries, and later on for undeveloped countries.
Years after the cap was put into place, it was discovered in 2003 that the degradation of the ozone layer was dramatically slowing down, and although the CFC's will continue to persist in the atmosphere for decades to come due to its slow break-down rate, scientists are now saying the ozone layer will recover to the much more protective, and structurally sound state it once was in the 1980's.
-Thomas Glen
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