Earth’s protective ozone layer is slowly but noticeably healing at a pace that would fully mend the hole over Antarctica in about 43 years, a new United Nations report says.

More than 35 years after every nation in the world agreed to stop producing chemicals that “chomp” on the layer of ozone in Earth’s atmosphere that shields the planet from harmful radiation linked to skin cancer, cataracts and crop damage, the scientific assessment found recovery was progressing.

“In the upper stratosphere and in the ozone hole, we see things getting better,” co-chair of the scientific assessment Paul Newman said.

The progress is slow, according to the report presented on Monday at the American Meteorological Society convention. However, the global average amount of ozone 30 kilometres high in the atmosphere will not be back to 1980 pre-thinning levels until about 2040, the report said, and it will not return to normal in the Arctic until 2045.

Antarctica, where it’s so thin there’s an annual giant gaping hole in the layer, will not be fully fixed until 2066, the report forecast. Scientists and environmental advocates across the world have long hailed efforts to heal the ozone hole as one of the biggest ecological victories for humanity.

This is off the back of the Montreal Protocol in 1987, which banned a class of chemicals — hydrochlorofluorocarbons (HCFCs) and chlorofluorocarbons (CFCs) — which were often used in refrigerants and aerosols.

“Ozone action sets a precedent for climate action,”  World Meteorological Organization secretary-general Petteri Taalas said.

 
The purple and blue regions are where there is the least ozone, and the yellows and reds are where there is more ozone. Images from September 2000, left, and September 2018. (NASA via AP)

Signs of healing were reported four years ago but were slight and more preliminary.

“Those numbers of recovery have solidified a lot,” Dr Newman said. He said the two chief chemicals that munch away at ozone are in lower levels in the atmosphere.

Chlorine levels are down 11.5 per cent since they peaked in 1993 and bromine, which is more efficient at eating ozone but is at lower levels in the air, dropped 14.5 per cent since its 1999 peak, the report said.

Dr Newman said the fact that bromine and chlorine levels “stopped growing and [are] coming down is a real testament to the effectiveness of the Montreal Protocol”.

“There has been a sea change in the way our society deals with ozone depleting substances,” scientific panel co-chair David W Fahey said.

Decades ago, people could go into a store and buy a can of refrigerants that would eat away at the ozone, punch a hole in it and pollute the atmosphere, Dr Fahey said. Now, not only are the substances banned but they are no longer much in people’s homes or cars, replaced by cleaner chemicals.

Natural weather patterns in the Antarctic also affect ozone hole levels, which peak in the fall.
Dr Newman said this had caused the hole to be bigger in the past couple of years but the overall trend was one of healing.

United Nations environment program director Inger Andersen said the trend of ozone layer healing was “saving two million people every year from skin cancer”.

The report also warned that efforts to artificially cool the planet by putting aerosols into the atmosphere to reflect the sunlight would thin the ozone layer by as much as 20 per cent in Antarctica.

Article from: ABC NEWS (Australia)