Climate change refers to the variation in the Earth's global climate or in regional climates over time. It describes changes in the variability or average state of the atmosphere—or average weather—over time scales ranging from decades to millions of years. These changes may come from processes internal to the Earth, be driven by external forces (e.g. variations in sunlight intensity) or, most recently, be caused by human activities.

Wednesday, August 23, 2006

Ozone-friendly chemicals lead to warming

Cool your home, warm the planet. When more than two dozen countries undertook in 1989 to fix the ozone hole over Antarctica, they began replacing chloroflourocarbons in refrigerators, air conditioners and hair spray.

But they had little idea that using other gases that contain chlorine or fluorine instead also would contribute greatly to global warming.

CFCs destroy ozone, the atmospheric layer that helps protect against the sun's most harmful rays, and trap the earth's heat, contributing to a rise in average surface temperatures.

In theory, the ban should have helped both problems. But the countries that first signed the Montreal Protocol 17 years ago failed to recognize that CFC users would seek out the cheapest available alternative.

The chemicals that replaced CFCs are better for the ozone layer, but do little to help global warming. These chemicals, too, act as a reflective layer in the atmosphere that traps heat like a greenhouse.

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