In 1985, scientists reported a change in the atmosphere, a hole or thinning of ozone（臭氧） over Antarctica. Scientists were not sure what was causing.
Most scientists believe that man-made chemicals are destroying the ozone. They also have found signs of ozone loss in other parts of the atmosphere.
Ozone is found both in the air we breathe and in the upper atmosphere. Near the earth, ozone in the air is a danger to life. It is a waste product. But ozone found 10 to 50 kilometres up in the atmosphere protects life on earth. Ozone forms in the atmosphere through the action of solar radiation（太阳辐射）. Once formed, the ozone blocks harmful radiation from reaching the earth. Scientists say a reduction in ozone and an increase in the harmful radiation will cause many more cases of skin cancer and will harm crops, animals and fishes.
The report said it is about 8 degrees colder 15 kilometres above earth than it was in 1979. Scientists think the first loss of ozone reduces the amount of solar energy the atmosphere can take in. This cools the atmosphere, increases ice cloud production and leads to more ozone loss.
Scientists found signs the ozone problem has spread. The study shows that the loss of ozone over the areas with larger population in North America and Europe was at least three times greater than scientists had thought. The ozone levels reduced much more seriously during winter months than in warmer months. This is not surprising because the amount of ozone in the atmosphere changes with the temperature.
An international effort is being made to stop the loss of ozone in the atmosphere. But many experts fear that the effort will not produce results fast enough to prevent harm to life on the earth.
