© redOrbit
Check the fine print on many cans of hairspray or shaving cream these days, and you'll probably find a reassurance that the product you are holding contains "No CFCs or chemicals known to harm the ozone layer." Located in the stratosphere, the ozone layer protects life on Earth from the harmful effects of ultraviolet radiation. To stop ozone destruction, chemical manufacturers phased out the production of CFCs (short for chlorofluorocarbons) over the past two decades.
So why is it that this past spring, scientists observed the largest, most severe ozone destruction ever witnessed in the Arctic since records began in 1978? In part, it's because CFCs stick around in the atmosphere for a very long time. But the maps above reveal the main reason this winter's Arctic ozone loss was so much worse than it normally is: unusually persistent cold temperatures.
From January through March 2011, monthly average temperatures in the Arctic stratosphere were colder than usual. Places where temperatures were up to 9 degrees Celsius warmer than the long-term average (1979-2009) are red, while places where temperatures were up to 16 degrees cooler than average are blue. Colder-than-usual temperatures dominated the stratosphere all three months, especially in March.
What does the cold have to do with the ozone hole? Extreme cold allows clouds to form in the stratosphere, even though the air there is extremely dry. The clouds make rare chemical reactions possible. Normally, when CFCs break down, the chlorine they release gets incorporated into very stable molecules that don't react with ozone. But on the surface of particles in these unusual ice clouds, the stable molecules are converted into forms of chlorine that are much more reactive.
