Ozone

What is it?

Ozone is found throughout the atmosphere, but most of it is in the higher atmosphere about 15 to 50km above earth. It acts like a giant shield against the sun’s harmful radiation. Ultraviolet radiation (UVR) is made up of three parts: UVA, UVB and UVC. It is known to cause sunburn, skin cancer and eye disease and can affect the body’s immune system. Ozone and other gases absorb all of the UVC and most of the UVB radiation. The UVA is not greatly affected by ozone.

What’s happening to the ozone layer?

Prior to the onset of the ozone depletion (around the early 80s) there was a balance between the processes that make ozone and those that destroy it. We now know that human-made chemicals are increasing the rate at which ozone is destroyed. This has upset the natural balance, and ozone is being destroyed faster than it can be produced. The chemicals involved have been widely used for about 60 years. They are chlorofluorocarbons (CFCs), which are used in freezers, refrigerators and air conditioners and halons, which are used in some fire extinguishers. There are also other less common chemicals involved. Steps are being taken world-wide to phase out use of these chemicals.

Where is the ozone hole?

In the mid 1980s concern about the ozone layer led scientists to discover it had been thinning over Antarctica for many years. This thinning is often called the ozone hole. During the long, dark winter, polar ice clouds are formed, which lock up the chlorine in the CFCs. With spring the sun’s energy causes the chlorine to start destroying the ozone. Scientists have found the hole is growing larger. It is well to the south of New Zealand.

Can the ozone layer be repaired?

Halons and CFCs can have a lifespan of between 40 and 130 years. This means they will be damaging the ozone for a long time before they eventually break down. There are now international controls on the most harmful of these. As ozone-destroying chemicals are phased out the ozone layer will eventually repair itself. The earliest full recovery won’t occur till the middle of the current century. However, this could be delayed through interactions with greenhouse gases.