Above Antarctica, the hole in the ozone layer has reached its largest and deepest level in fifteen years. Every year the hole grows above the South Pole in August, at the beginning of the Antarctic spring. The gap is always at its greatest in October. One of the causes may be global warming. The abundance of sunlight and the remarkably low temperatures at the South Pole also played a role.
Researchers are studying the hole in the ozone layer over Antarctica on a daily basis. Last year it was exceptionally small, mainly due to special weather conditions. This year, however, the ozone hole is much larger than during the October months than in previous years. There is talk of a record size that has not been equaled in 15 years. That reports the American broadcaster CNN.
Sunlight and low temperatures
The enlargement of the ozone layer is partly a seasonal phenomenon. This has to do with the end of winter in the southern hemisphere. Two important elements cause ozone depletion: sunlight and very low temperatures.
These conditions happen at the end of winter, just after the long polar night. Then the sun will reappear at the South Pole, but the temperatures are still very low.
The ozone layer actually forms a protective blanket in the stratosphere, some 10 to 50 kilometers above the ground. The blanket protects the earth against ultraviolet radiation from the sun. However, the ozone layer is damaged by chemicals such as chlorine and bromine.
Climate warming and chemicals
The emissions of harmful chemicals have been greatly reduced since the 1990s through international cooperation, but the gases remain in the atmosphere for a very long time. This causes the concentration to drop very slowly. The ozone layer will therefore take many decades to restore.
Global warming can also further promote ozone depletion. Greenhouse gases such as CO2 and methane accumulate in the lower part of the atmosphere. As a result, it slowly gets warmer. The ozone layer is located above this warming air layer, where heat from the earth is less able to penetrate. That is why it cools down. That also causes ozone depletion.