A NASA satellite has found powerful new evidence that chemicals and not natural forces are causing the global thinning of the protective ozone layer, including the ozone hole over the South Pole.

NASA scientists announced Monday that the Upper Atmosphere Research Satellite has detected hydrogen fluoride, a chemical that is not made by nature, in the stratosphere where the ozone layer is being eroded.Mark Scherberl, project scientist for the satellite, said the amount of hydrogen fluoride measured by the satellite corresponds directly to the amount of chlorofluorocarbons in the atmosphere.

He said hydrogen fluoride is associated with the same chemical reaction that creates chlorine from chlorofluorocarbons. The presence and the amount of hydrogen fluoride, said Scherberl, proves that the chlorine, which actually destroys the ozone, is not from volcanoes or from other natural sources.

"We have this thing nailed," said Anne Douglas, deputy project director. "There is no other possibility. It all adds up."

Atmospheric scientist Dave Hofmann said the new data from the National Aeronautics and Space Administration "puts another nail in the coffin" on an earlier belief that the erosion of ozone in the stratosphere could be a natural phenomenon.

"I know of no scientist active in the field who still believes that the ozone loss is not related to man-made chemicals," said Hofmann, of the National Oceanic and Atmospheric Administration.

Chlorofluorocarbons, or CFCs, are industrial chemicals used for refrigeration and cleaning. Since the early 1980s, many scientists have theorized that CFCs trigger chemical reactions in the stratosphere that cause a thinning of the ozone layer. This happens when sunlight breaks down the CFCs, freeing chlorine, which then reacts with the ozone.

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