[00:09] High above the Earth, NASA shuttle astronauts can look down and see a thin blue ribbon around our planet. This fragile veil is our atmosphere.

[00:17] Without air, life could not exist on Earth's surface. The atmosphere, which controls global temperature, also contains a layer of ozone, a pungent bluish gas that filters deadly ultraviolet, or UV, solar radiation.

[00:32] Ozone is an unstable molecule made up of three oxygen atoms. Its' concentrated at the top of the atmosphere in a region called the stratosphere. It acts as a planetary defense shield against UV rays.

[00:44] In the 1970's, industrial chemicals called CFC's, short for chlorofluorocarbons, were found to add ozone destroying chlorine to the stratosphere. A ban on CFC's in aerosol cans was in force by 1979.

[00:58] By the 1980's with the aid of satellites, scientists observed a vast hole growing in the ozone layer above Antarctica. A hole about twice the size of China.

[01:08] Worldwide use of CFC's grew alongside the ozone hole. Finally, by the late 1980's, people of the world agreed to protect the ozone layer.

[01:16] Because of the long lag time involved, the final recovery of our fragile ozone layer may lie far in the future. In the meantime, it will still remain important to heed warnings about excessive sun exposure caused by reduced ozone protection.