GENEVA: Ozone depletion over the Arctic hit a “record level” in March, the biggest since 2011, but the hole has now closed, the UN World Meteorological Organisation (WMO) said on Friday.

The springtime phenomenon in the northern hemisphere was driven by ozone-depleting substances still in the atmosphere and a very cold winter in the stratosphere, WMO spokeswoman Clare Nullis told a UN briefing in Geneva.

“These two factors combined to give a very high level of depletion which was worse than we saw in 2011. It’s now back to normal again ... the ozone hole has closed,” she said.

Nullis, asked whether less pollution during the pandemic had played a role, said: “It was completely unrelated to Covid.”

The UN meteorological agency said depletion of the ozone layer, which protects the Earth from harmful levels of ultraviolet radiation, briefly reached an unprecedented level over large swaths of the Arctic in March.

The World Meteorological Organisation reported that the spike stemmed from the lingering presence of man-made ozone-depleting substances in the atmosphere and very cold temperatures in the stratosphere that prevented ozone from reaching the northern region.

WMO spokeswoman Clare Nullis said conditions were back to normal again in April, describing the temporary depletion as not a cause for exceptional concern.

Nullis credited an international accord known as the Montreal Protocol, which has sharply curtailed production of substances like chlorofluorocarbons, or CFCs, that harm the ozone layer, for helping to limit the springtime depletion this year.

The World Meteorological Organisation said that sunlight, wind fields, harmful chemicals and temperatures below -80 degrees Celsius (-112 F) drive the formation of ozone holes. Most ozone depletion in the Arctic occurs in the polar vortex, a region of fast-blowing circular winds, it said.

Arctic ozone loss tends to be far less severe than in the Antarctic.

Published in Dawn, May 2nd, 2020