GENEVA—The Antarctic ozone hole has swelled this month to one of its biggest sizes on record, U.N. and U.S. scientists say.
They insist the Earth-shielding ozone layer remains on track to long-term recovery but residents of the southern hemisphere should be on watch for high UV levels in the weeks ahead.
The World Meteorological Organization, in a regular bulletin released yesterday, said the Antarctic ozone hole often faces seasonal and year-to-year variations.
But it noted the expansion this year shows “we need to remain vigilant.”
The Geneva-based U.N. agency pointed to NASA data on Oct. 2 showing the hole had reached 28.2 million square km—larger than the size of Russia and Canada put together.
It was the largest recorded on that date, and the hole has remained at a record size on the dates since, WMO said.
According to NASA, the record largest ozone hole dates to Sept. 9, 2000, when it was 29.9 million square km.
Paul Newman, chief scientist for earth sciences at NASA’s Goddard Space Flight Center in Greenbelt, Md., said prolonged wintertime conditions in the Antarctic region were persisting longer than usual.
Unusually weak vertical energy flows also were among major contributors to the exceptionally large hole.
The stratospheric ozone layer, which sits some 25 km high and protects against harmful UV rays, is different from the ground level ozone that is a harmful pollutant.