According to a United Nations report, the annual dose of harmful ultraviolet radiation striking the northern hemisphere rose by 5 percent during the past decade.
During the past 40 years, the world has seen an alarming increase in the incidence of malignant skin cancer; the rate today is tenfold higher than in the 1950s.
In this season of new beginnings, the hole in the ozone layer reforms, allowing lethal ultraviolet radiation to stream through Earth's atmosphere.
The hole lasts for only two months, but its timing could not be worse.
Years of study on the ground, in aircraft, and from satellites has conclusively identified the source of the chlorine: human-made chemicals called chlorofluorocarbons (CFCs) that have been used in spray cans, foam packaging, and refrigeration materials.
Ozone is a relatively simple molecule, consisting of three oxygen atoms bound together.Because it reacts strongly with other molecules, large concentrations of ozone near the ground prove toxic to living things.At higher altitudes, where 90 percent of our planet's ozone resides, it does a remarkable job of absorbing ultraviolet radiation.Just as sunlight awakens activity in dormant plants and animals, it also delivers a dose of harmful ultraviolet radiation.After eight weeks, the hole leaves Antarctica, only to pass over more populated areas, including New Zealand and Australia.Yet it has dramatically different effects depending upon its location.Near Earth's surface, where ozone comes into direct contact with life forms, it primarily displays a destructive side.All of the compounds detected possessed an even number of electrons, a characteristic which typically gives chemical stability.Other less common compounds with an odd number of electrons—known as free radicals—readily undergo chemical reactions and do not survive for long.In the absence of this gaseous shield in the stratosphere, the harmful radiation has a perfect portal through which to strike Earth.Although a combination of weather conditions and CFC chemistry conspire to create the thinnest ozone levels in the sky above the South Pole, CFCs are mainly released at northern latitudes—mostly from Europe, Russia, Japan, and North America—and play a leading role in lowering ozone concentrations around the globe.