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Third-largest hole ever opens in ozone layer

NASA

NASA

A body of experts have revealed the earth’s largest ozone hole gaped to near-record size in the past month.

The UN’s World Meteorological Organisation said the puncture was measured at an average of 26.9 million square kilometres over the 30 day period, covering an area larger than all of North America, just shy of records set in 2000 and 2006.

It peaked at 28.2 million square kilometres on October 2, according to measurements from space agency NASA.

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“This is the third largest observed after the record-breaking ozone holes in 2000 and 2006,” the UN’s climate and weather agency said in a statement.

The ozone layer, which helps protect the Earth from potentially dangerous ultraviolet rays that can cause skin cancer, began developing holes on an annual basis starting in the 1980s due to widespread use of chlorofluorocarbons, or CFCs.

“In 2015, the hole started slowly but then quickly expanded to cover a large area,” NASA said in a statement.

“In 2015, ozone concentrations also plunged lower than in recent years. On October 4, ozone reached an annual minimum concentration of 101 Dobson Units [the threshold is 220 Dobson Units].”

In reality though it is not a ‘hole’ as we would define it, but rather a drop in the concentration of ozone seasonally formed when extremely cold temperatures mix with the returning sunlight to release chlorine radicals that destroy ozone.

WMO scientist Geir Braathen said despite the record-breaking size, “there is no reason for undue alarm”.

“This shows that the ozone hole problem is still with us and we need to remain vigilant,” WMO scientist Geir Braathen said in the statement.

He added large holes were expected in the ozone until at least 2025 due to current weather conditions and lingering ozone-depleting chemicals.

Once commonly used in refrigerators and aerosol cans, CFCs are now almost non-existent thanks to an international treaty signed in Montreal in 1987, amid global concern over widening holes in the ozone layer.

In 2014, WMO predicted the ozone layer would recover mid-century, although the hole over Antarctica was expected to take longer to repair.

-with AAP

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