The ozone layer over the Arctic is thinner than it has ever been because of harmful chemicals and a cold winter, according to UN world weather experts.

The layer of gases, that protects the Earth from damaging ultraviolet (UV) rays, has been depleting for decades because of chemicals used in the making of refrigerators, air conditioners, fire extinguishers and even hairspray.
A treaty was signed in 1987, after a hole developed over the Antarctic, in order to reduce the use of the chlorofluorocarbons, halons and other chemicals.
However the chemicals stay in the atmosphere for decades and the ozone has continued thinning.
The World Meteorological Organization (WMO) said the area over the Arctic region has suffered a loss of about 40 percent from the start of winter until late March, exceeding the previous seasonal loss of about 30 percent.
The loss was blamed on the continuing presence of harmful chemicals and a cold winter. Despite warmer temperatures at ground level, the upper atmosphere known as the stratosphere has been colder this year. This causes a chemical reaction that depletes the ozone layer.
Scientists blame the cooling of the stratosphere on the same processes that are causing global warming at ground level. Michel Jarraud, WMO secretary-general, said the two factors mean the ozone layer is thinner than it has ever been over the Arctic. This means that more harmful UV rays are getting through in areas of Scandinavia, Greenland and Siberia.
Ozone provides a natural protective filter against harmful ultra-violet rays from the sun, which can cause sunburn, cataracts and skin cancer and damage vegetation.
Areas at risk are advised to keep an eye on UV forecasts, however it will not affect countries at lower latitudes such as Britain. The ozone layer over the Arctic is still not as thin as over the Antarctic, where a hole developed, and health effects were seen in countries like Australia and New Zealand.
Eventually the ozone layer is expected to recover to pre-1980 levels by 2030 to 2040, because of the 196 nation 1987 Montreal Protocol, which has resulted in cutbacks in ozone-damaging chemicals.
(Source: Daily Telegraph)