The vast hole in the ozone layer above Antarctica appears to be healing, scientists say, putting the world on track to eventually remedy one of the biggest environmental concerns of the 1980s and 90s.
Research by US and UK scientists shows that the size of the ozone void has shrunk, on average, by around 4m sq km since 2000. The measurements were taken from the month of September in each year, when the ozone hole starts to open up each year.
The study, published in Science, states that the phase-out of chlorofluorocarbon (CFC) chemicals means that the ozone layer is “expected to recover in response, albeit very slowly.” CFCs, once commonly found in aerosols and refrigeration, can linger in the atmosphere for more than 50 years, meaning that the ozone hole will not be considered healed until 2050 or 2060.
The Montreal protocol, a 1987 international treaty ratified by all UN members, successfully spurred nations to eradicate the use of CFCs in products.
The agreement followed fears that ozone depletion could cause serious health and environmental harm through the ultraviolet light that would reach the surface of the Earth through the ozone barrier. The UN estimates that2m cases of skin cancer a year have been avoided through the phase-out of CFCs.
The ozone hole opened up over the Antarctic due to the vast amounts of cloud that forms over the coldest continent on Earth. This cloud helps the CFC chemicals linger, causing the ozone layer to be eaten away. The void is at its greatest during the southern hemisphere’s spring.
Volcanic activity can also spur greater ozone depletion, as scientists discovered last year when, to their alarm, the largest ever ozone hole opened up in October, measuring more than 20m sq km.
This is thought to be a blip, however, caused by volcanic activity in Chile. When scientists looked at data from September, compared to the same month over the past decade, they found a consistent shrinkage, with the opening up of the ozone hole occurring later each year.
“When volcanoes team up with man-made chlorine, it’s a toxic mix and Antarctica is particularly vulnerable,” said study co-author Susan Solomon, of the Massachusetts Institute of Technology.
Source: The Guardian UK