The ozone layer above the Arctic withered by 40% this winter, according to the UN's weather agency, a stark increase from the previous seasonal record of 30%. The loss was driven largely by frigid conditions in the stratosphere—though surface temperatures were actually warmer than normal—and lingering chemicals banned in 1987's Montreal Protocol. "The 2011 ozone loss shows that we have to remain vigilant and keep a close eye on the situation in the Arctic in the coming years," the secretary-general of the World Meteorological Organization says.
Late last month, wind blew the hole over Greenland and Scandinavia, where the WMO asked that people heed national ozone-level alerts. The BBC notes that though the amount of chemical pollution driving ozone loss is falling, the Antarctic ozone hole is expected to persist until 2045 to 2060. Ozone outside the poles is expected to hit pre-1980 levels between 2030 and 2040, reports the AP. (Read more ozone stories.)