Earth’s protective ozone layer above the Arctic was pierced by a hole of unprecedented size last winter and spring caused by a long cold period in the stratosphere, according to new research led by scientists at NASA’s Jet Propulsion Laboratory in Pasadena and published Oct. 3 in the journal Nature. The hole covered 772,204 square miles (two million square kilometers)—about the size of Mexico—and allowed high levels of harmful ultraviolet radiation to strike northern Canada, Europe and Russia this spring, the report finds. The stratospheric ozone layer, extending from about 10 to 20 miles (15 to 35 kilometers) above the surface, protects life on Earth from the Sun’s ultraviolet rays. Intense cold in the upper atmosphere of the Arctic last winter activated ozone-depleting chemicals and produced the first significant ozone hole ever recorded over the high northern regions.
The international community agreed to phase out ozone-depleting chlorinated fluorocarbons (CFCs) in the Montreal Protocol of 1989, four years after the Antarctic ozone hole was discovered. CFC levels above Antarctica peaked in the early 1990s, but are not expected to return to their safe 1980 levels until around 2080. Until that happens, existing CFCs will continue to waft from the troposphere up into the stratosphere each year, where a fraction of them will be destroyed by sunlight and turned into a chemical form that depletes the ozone layer. (ENS, NYT, WP’s Wonkblog, Oct. 3)