Ozone is a molecule made up of three oxygen atoms that naturally occur in small amounts.
In the stratosphere, about seven to 25 miles above the Earth's surface, the ozone layer acts as a sunscreen, protecting the planet from potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress the immune system and also damage plants.
It is produced in tropical latitudes and distributed throughout the world.
Closer to the ground, ozone can also be generated by photochemical reactions between the sun and pollution by emissions from cars and other sources, forming harmful smog.
Although warmer than average stratospheric weather conditions have reduced ozone depletion over the past two years, the current ozone area is still large compared to the 1980s, when the depletion of the ozone layer above Antarctica for the first time was discovered.
In the stratosphere, about seven to 25 miles above the Earth's surface, the ozone layer acts as a sunscreen, protecting the planet from potentially harmful ultraviolet radiation
This is because levels of ozone-reducing substances such as chlorine and bromine remain high enough to produce significant ozone losses.
In the 1970s, it was recognized that chemicals called CFC's, for example used in refrigerators and aerosols, contained ozone in the & # 39; destroying a stratosphere.
In 1987, the Montreal Protocol was agreed, leading to the collapse of CFC's and, more recently, the first signs of recovery of the Antarctic ozone layer.
The upper stratosphere at lower latitudes also shows clear signs of recovery, which indicates that the Montreal Protocol is working well.
But the new study, published in Atmospheric Chemistry and Physics, found that it is unlikely to return to latitudes between 60 ° N and 60 ° S (London is at 51 ° N).
The cause is uncertain, but the researchers believe it is possible that climate change is changing the pattern of atmospheric circulation – causing more ozone to be released from the tropics.
They say another possibility is that very short-lived substances (VSLS), which contain juice and bromine, could destroy ozone in the lower stratosphere.
VSLSs include chemicals used as solvents, dye strippers, and as degreasing agents.
One is even used in the production of an ozone-friendly replacement for CFC's.
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