"Ozone Hole Remains Size of North America, NASA Data Shows"

"Antarctic hole in protective layer of gas stands around same level as 2010, 2012 and 2013, but scientists say recovery is on track"

"The Antarctic ozone hole, which was expected to reduce in size swiftly when manmade chlorine emissions were outlawed 27 years ago, is stubbornly remaining the size of North America, new data from Nasa suggests.

The hole in the thin layer of gas, which helps shield life on Earth from potentially harmful ultraviolet solar radiation that can cause skin cancers, grows and contracts throughout the year but reached its maximum extent on 9 September when monitors at the south pole showed it to cover 24.1m square km (9.3m sq miles). This is about 9% below the record maximum in 2000 but almost the same as in 2010, 2012 and 2013.

But scientists remain unsure why the hole has not reduced more since the Montreal Protocol agreement was signed by countries in 1987."

John Vidal reports for the Guardian October 31, 2014.