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A new NASA study takes a closer look at a group of

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chemicals once thought to be harmless to Earth's ozone layer.

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Hydrofluorocarbons, or HFCs, are synthetic chemicals found in common

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household items like refrigerators and air conditioners. They were

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created to replace chlorofluorocarbons, a group of ozone-depleting

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chemicals found to cause the ozone hole over Antarctica.

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But NASA scientists now reveal that HFCs also contribute

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to ozone depletion. HFCs were thought to be "ozone-friendly"

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because they don"t contain chlorine atoms, which destroy ozone molecules.

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Our study is the first to show that as HFC levels

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increase, they'll have a weak but measurable effect on the ozone layer.

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HFCs trap heat in the atmosphere, raising temperatures.

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In the stratosphere, which contains the protective ozone layer,

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this warming speeds up chemical reactions that deplete ozone.

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Atmospheric concentrations of these chemicals are currently growing around 7

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percent a year and are projected to be over 17 times higher by 2050.

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Using a NASA computer model, the scientists simulated

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the impact of HFCs on the ozone layer. They found

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that HFCs will reduce global ozone levels by 0.035%

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by the year 2050. The ozone

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depletion that we calculated was small, but about 100 times larger than

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a previous estimate. Studies show an increase in HFC levels

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will affect more than the ozone layer. HFCs are strong greenhouse gases

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that contribute to the warming of the planet. By the year 2050,

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their contribution to global warming could be as large as

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20 percent that of carbon dioxide. Now that we better understand

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the impacts of these particular greenhouse gases on the ozone layer, our