One of the largest ozone holes yet seen opened up above Antarctica this autumn. Yet the loss of ozone that causes the hole to open up continues to slow and should revert to normal in the coming decades, said the World Meteorological Organisation.
It issued an assessment of the current state of ozone loss this afternoon.
It based this on data about ozone over the Antarctic and the size of the ozone hole accumulated by the US National Aeronautics and Space Administration.
On October 2nd, the hole reached its maximum extent this year with an area of 28.2 million square kilometres, the largest yet for this date.
If averaged over 30 days the hole was 26.9 million square kilometres, the third largest after the record-breaking holes that appeared in 2000 and 2006.
This showed that “the ozone hole problem is still with us”, said Geir Braathen of the organisation.
The loss of ozone has serious implications for human health and also wider ecosystems because of its role in reducing the amount of ultraviolet light that reaches the Earth’s surface.
Too much ultraviolet light can damage the skin to cause cancers and can also cause DNA damage to other land and marine organisms.
Significant loss of ozone, a form of oxygen, occurred over a 50-year period up to the 1980s, caused by the release of gases used for refrigeration and as propellants in spray cans.
Chlorine in these gases began breaking down the ozone, causing a gradual decline in the ozone layer 25km above the Earth.
In 1987 the Montreal Protocol was signed, a deal whereby countries agreed to phase out use of the ozone-depleting gases, called CFCs. This has gradually brought down CFC levels and with it ozone damage.
Ozone loss occurs during the Antarctic winter months and also during winter months over the Arctic.
Both poles experience ozone loss during these months, with losses greater over the Antarctic. Between these times ozone reforms and the holes slowly reduce.
Full recovery of the layer may not be achieved until the next century, the organisation said.
