The hole in the ozone layer above Antarctica is 30 percent smaller than it was a year ago. But experts see no reason to sound the all-clear.
No all-clear: Experts attribute the shrinkage to natural factors Image: dpa
The hole in the ozone layer protecting against UV rays is currently 30 percent smaller over the South Pole than a year ago. This is reported by the European Space Agency ESA on its website. The ozone layer at the South Pole is built up and depleted in an annual rhythm and is always thinnest at this time of year. The measured ozone loss in 2007 peaked at 27.7 million tons, the European Space Agency ESA reports on its website. Last year, a record loss of 40 million tons was measured. According to the ESA, the ozone hole this year is about the size of North America, at 24.7 million square kilometers.
Experts attribute the improvement to natural factors and therefore do not give the all-clear. Because the ozone hole was less centered around the South Pole, the air inside it mixed with warmer air, slowing the process of ozone loss. Ozone is only depleted at particularly cold temperatures. In addition to the extent in the area, the height of the zone with ozone loss is also crucial.
Over the past decade, the ozone layer in the stratosphere as a whole has decreased globally by about 0.3 percent annually. As a result, more carcinogenic ultraviolet radiation is reaching the Earth’s surface. The damage to the ozone layer is attributed to the industrial use of chemicals such as chlorofluorocarbons (CFCs), which can persist in the atmosphere for decades.
The Montreal Protocol laid the foundation for a ban on ozone-depleting substances 20 years ago. ESA considers an ozone hole to be areas where the strength of the ozone layer is particularly low – below 220 Dobson units.