Nasa confirms ozone hole shrinking due to CFCs ban
The hole in ozone layer has shrunk thanks to the ban of CFCs, Nasa has confirmed, after finding that chlorine levels are rapidly declining in the Earth's stratosphere.
Last year, satellite images showed the hole had begun to close and could be completely healed by 2060.
But it was not clear whether the closure was a direct result of the Montreal Protocol, which was signed by all countries of the world in 1985, phasing out chlorofluorocarbons (CFCs).
Now long-term satellite observations by Nasa have shown a 20pc decrease in levels of chlorine in the Earth's atmosphere since 2005, proving for the first time that the worldwide action is having a dramatic impact on the planet.
"We see very clearly that chlorine from CFCs is going down in the ozone hole, and that less ozone depletion is occurring because of it," said Susan Strahan, an atmospheric scientist from Nasa's Goddard Space Flight Centre in Greenbelt, Maryland.
CFCs, which were used in aerosols, fridges, air conditioning and packing materials, are so harmful because they rise into the stratosphere, where they are broken apart by the Sun's ultraviolet radiation, releasing chlorine atoms that destroy ozone molecules. Ozone protects life by absorbing potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and damage plant life.
Past studies have used statistical analyses of changes in the ozone hole's size to argue that ozone depletion is decreasing.
But the new study is the first to use measurements of the chemical composition inside the ozone hole to confirm that not only is ozone depletion decreasing, but that the decrease is caused by a decline in CFCs.
The ozone layer is expected to recover gradually as CFCs leave the atmosphere, but it will take decades before the hole closes entirely.
"CFCs have lifetimes from 50 to 100 years, so they linger in the atmosphere for a very long time," said Anne Douglass, a fellow atmospheric scientist at Nasa, and the study's co-author.
"As far as the ozone hole being gone, we're looking at 2060 or 2080."
The research was published in 'Geophysical Research Letters'.