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Green Corner


 

 

 

An A-Z of the environment & issues

by Peter Hatswell

 

 

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U is for Ultra-Violet

Ultra-violet radiation comes from the sun and, if it were visible, it would appear next to indigo and violet at the bottom of a rainbow. It is essential for humans in that in low doses it helps to produce beneficial vitamin D but in excess causes sunburn and eye damage particularly when close to reflective surfaces such as snow, water and pale sand. Fortunately our hair and clothing plus window glass and clouds provide good protection for any radiation that penetrates the stratosphere (7 to 30 miles up).

Most living organisms can repair the damage done by UV but where the concentration is too high, permanent damage may occur and plant growth rates and flowering times may change, affecting animals that depend on them. Phytoplankton in the sea can also be destroyed, affecting the amount of carbon that they can absorb from the atmosphere and adding to the problem of global warming.

Ozone in the stratosphere is an excellent absorber of UV so it is important that accidental man-made emissions of ozone destroying chemicals such as refrigerants (controlled under the Montreal Protocol) are held to a minimum. Because this danger has been recognised, the ozone layer should return to its original thickness in about 50 years time but there are still some unscrupulous suppliers for whom the lowest cost is more important than lasting damage to the environment.

In Europe during the months of September and October we regularly receive over twice the normal level of UV due to thinning of the ozone layer over the Artic but the effect is worse in cloud-free countries such as S Africa and Australia during their summer in December to February.

Unfortunately both carbon dioxide and methane also destroy stratospheric ozone so the Government’s Climate Bill is a very timely piece of legislation which our politicians should be attempting to augment  rather than diminish. Action now may appear to be expensive but as the Stern Report said, it will be much more expensive and deadly if we continue to procrastinate.

National

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