CFC ban has helped heal hole in ozone layer, say Nasa scientists

THE hole in the ozone layer has shrunk, thanks to the ban on CFCS, Nasa has said, after finding that chlorine levels are rapidly falling in the stratosphere.

Last year, satellite images showed that the hole had begun to close and could be completely healed by 2060.

But it was not certain if the fall was a direct result of the Montreal Protocol, signed by all countries in 1985, phasing out CFCS (chlorofluorocarbons).

Long-term satellite observations by Nasa has shown a 20 per cent decrease in levels of chlorine in Earth’s atmosphere since 2005, suggesting for the first time that the global 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 Center 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. Nasa has been permanently monitoring the hole in the ozone layer with its Aura satellite since 2005.

Past studies have used statistical analyses of changes 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.

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 co-author. “As far as the ozone hole being gone, we’re looking at 2060 or 2080. And even then, there might still be a small hole.”

The research was published in the journal Geophysical Research Letters.