Without the Sun's light and heat, the Earth's surface would be dead and lifeless. But the Sun's radiation isn't all good news. If the Earth moved too close to the Sun, we'd get too hot! If it moved away, we'd get too cold. If the Earth were to tilt too far on its axis, climate changes would be extreme.

Give or take the odd Ice-age, we don't have to worry about these factors. However we do have to worry about what's happening to the Earth's Atmosphere. This works like a combination of sun-glasses and sun-tan lotion to shield the Earth's surface from excessive and harmful radiation from the Sun. The atmosphere is a vast chemical and optical filter.

What's the Ozone Layer?
The Ozone Layer is a global sun-filter that is formed when the Sun’s ultra-violet radiation hits the upper atmosphere. At high altitude the Sun’s intense ultra violet radiation converts oxygen into ozone, as this conversion takes place most of the Sun’s harmful ultra violet energy is absorbed. The Ozone Layer is about 15 miles (24 kilometres) above the Earth’s surface and protects life on Earth from most of the Sun's ultra-violet radiation.

What's the problem with Ultra Violet Radiation?
Too much of the wrong kind of UV radiation may cause burning, skin-cancer, cataracts and blindness. It can also kill crops and damage wild-life and vegetation. Some still reaches the surface of the Earth but life has evolved to cope. We can go sun-bathing as long as we don't stay out in the Sun for too long or we use sun-protective creams and clothes. Outdoor workers develop harder, thicker skin. Tropical people have evolved sun-resisting skin pigments, clothing and life-styles that enable them to cope. Even so, sun-burn and skin cancer is still a problem. It would be a hundred times worse if it were not for the Ozone Layer.

What's all the fuss about?
Our cars and factories are polluting the atmosphere and breaking up the Ozone Layer. It is becoming a less-effective filter. Over the poles, in Spring and Summer, the Ozone Layer is breaking down completely. Elsewhere, it is thinning. More harmful ultra-violet radiation is breaking through the atmosphere and causing medical and ecological damage. If this goes on, the incidence of skin-cancer, certain eye-diseases and other conditions will increase very significantly. International agreements are being made to try to limit the use of ozone-depleting chemicals. The problem is that more and more of us want to drive cars and enjoy a consumer life-style. The downside of world economic development is its effect upon the natural world.

Can I see it happening?
Click Here for an Ozone Layer Animation

This shows and explains a computer simulation based on satellite photos.

For more information on this subject:

USA EPA - Ozone Depletion
http://www.epa.gov/spdpublc/index.html

Cambridge University - Ozone Hole Tour
http://www.atm.ch.cam.ac.uk/tour/
This attractive site provides videos and graphics with text suitable for 15+ school projects and offers a complete overview of the science.