This image shows the ozone levels in the Arctic in March 2010 (left) and after a drop of about 50 percent in 2011 (right).
Unusual weather ripped a sizable hole in the ozone layer above the Arctic last winter, exposing people in northern Russia, parts of Greenland and Norway to high levels of UV radiation. Human activity did not cause the hole’s sudden appearance, scientists said in a report released Monday. But the abnormal weather did enable ozone-eating chemicals already present in the atmosphere to cause the damage.
Exposure to high levels of the sun’s ultraviolet radiation can cause skin cancer and cataracts. The rift in the ozone layer is an annual event, but this one was the largest on record in the Northern Hemisphere, and scientists say the trend of expansion could continue. —ARK
During extreme events, up to 70% of the ozone layer can be destroyed, before it recovers months later. The hole above the Arctic was always much smaller – until March this year, when a combination of powerful wind patterns and intense cold temperatures high up in the atmosphere created the right conditions for already-present, ozone-eating chlorine chemicals to damage the layer.
... Normally, atmospheric conditions high above the Arctic do not trigger a large-scale plunge in ozone levels. But during the 2010/11 winter, a high-altitude wind pattern called the polar vortex was unusually strong, leading to very cold conditions in the stratosphere that also lasted for several months. This created the right conditions for the ozone-destroying forms of chlorine to slash ozone levels over a long period.