DHAKA: Researchers say they have found the first clear evidence that the thinning in the ozone layer above Antarctica is starting to heal.
The scientists said that in September 2015 the hole was around 4 million square km smaller than it was in the year 2000 - an area roughly the size of India.
The gains have been credited to the long term phasing out of ozone-destroying chemicals.
The study also sheds new light on the role of volcanoes in making the problem worse.
British scientists first noticed a dramatic thinning of ozone in the stratosphere some 10 kilometres above Antarctica in the mid 1980s.
Ozone is important because it blocks out harmful ultraviolet radiation from the Sun. Its absence increases the chances of skin cancer, cataract damage, and harm to animals and plants.
In 1986, US researcher Susan Solomon showed that ozone was being destroyed by the presence of molecules containing chlorine and bromine that came from chlorofluorocarbons (CFCs). These gases were found in everything from hairsprays to refrigerators to air conditioning units.
The reason the thinning was occurring mainly over Antarctica was because of the extreme cold and large amounts of light. These helped produce what are termed Polar Stratospheric Clouds.
In these chilled-out clouds, the chlorine chemistry occurs that destroys the ozone.
Several studies have shown the declining influence of CFCs, but according to the authors this new study shows the “first fingerprints of healing” and the ozone layer is actively growing again.
Prof Solomon and colleagues carried out detailed measurements of the amount of ozone in the stratosphere between 2000 and 2015.
“We don’t expect to see a complete recovery until about 2050 or 2060 but we are starting to see that in September the ozone hole is not as bad as it used to be.”
“Until we did our recent work no-one realized that the Calbuco eruption in Chile, actually had significantly affected the ozone loss in October of last year.”
"This is the first convincing evidence that the healing of the Antarctic ozone hole has now started," said Dr Markus Rex from the Alfred Wegener Institute for Polar and Marine Research in Germany.
“This was an era in which international co-operation went rather well on some issues. I was inspired by the way the developed and developing countries were able to work together on dealing with the ozone hole,” said Prof Solomon.
BDST: 0914 HRS, JULY 1, 2016
BD
