Environment: Ozone Loss Over Arctic At Record Level
Ozone loss over the Arctic this year was so severe that for the first time it could be called an "ozone hole" like the Antarctic one, scientists report.
About 20km (13 miles) above the ground, 80% of the ozone was lost, they say.
The cause was an unusually long spell of cold weather at altitude. In cold conditions, the chlorine chemicals that destroy ozone are at their most active.