In October, scientists reported that the ozone hole over the South Pole was the largest it has ever been. By November, it had reached the area of Puentas Arenas, Argentina. For the first time, a city was under an area of the sky stripped of ozone.

The hole in the ozone layer has appeared over Antarctica every year since 1978. Ozone absorbs harmful ultra-violet light from the sun. Too much ultra-violet can cause skin cancer, cataracts and suppress the immune system, and will destroy plant life on land and phyloplankton in the oceans, and cause blindness among unprotected animals.

Man-made chemicals started the chemical reactions in the atmosphere that destroyed the ozone and it will take years, scientists say, before preventative measures will show up in a smaller ozone hole. However, it looks like that time may be coming, since an international groups of scientists is predicting that the ozone hole will shrink and close within 50 years, because a ban on the chemicals that thin the ozone layer is showing signs of success. Other scientists believe that this will not happen, because other, thus far unrecognized pollutants are going to replace flurocarbons.

But the experts warn that governments must also reduce greenhouse gas emissions, because the cooling of the lower atmosphere caused by global warming can delay the closing of the ozone hole.

Meanwhile, an international research team has confirmed that cloud particles speed up the destruction of the ozone layer because they activate the man-made chemicals that attack ozone. These observations were made by European scientists who flew a balloon over the Arctic last January, taking samples from different layers of cloud.

Ozone-destroying chemicals are relatively harmless until activated by frozen particles in the clouds, along with sunlight. “The importance of the clouds are that they can activate chlorine molecules which otherwise would not be dangerous to the ozone,” said Konrad Mauersberger of the Max Planck Institute in Germany.

Now NASA reports that the Antarctic ozone hole disappeared completely this year, by November 19. Dissipating earlier than expected, after attaining a record size, seems like a mixed message about whether or not the ozone layer is improving or getting worse. But Dr. Richard McPeters, principal investigator for NASA?s Total Ozone Mapping Spectrometer at Goddard Space Flight Center (GSFC), said that long-term trends cannot be drawn from a single year?s ozone hole because its size and duration depend on that year?s weather. “Just because you see these changes from year to year or because you see an unusually deep (ozone hole) this year, that doesn?t say anything about the long-term prognosis,” he said.

“Any particular year, there?s just too much randomness in the weather to put your finger on an ultimate explanation for why it happened this way,” agrees Dr. Paul Newman, atmospheric physicist at GSFC. “The ozone hole isn?t going to go away for a long time. This is because the lifetimes of CFCs and HCFCs and halons are so long. We might be back to 1979 levels sometime around 2050 or so.”

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