Ozone layer
From RationalWiki
This article is only a brief description of the subject, and is not intended to give a full explanation.
Check out the "see also" or "references" sections, or Wikipedia's article for more detail.
The ozone layer is anywhere between 15 km and 35 km above the surface of the earth. The name is a slight misnomer as the percentage of ozone in the layer is only a few parts per million; however, over ninety percent of the free natural ozone in the atmosphere is found within this layer. It varies in thickness throughout the year and across the globe.
The most notable effect of the ozone layer is to absorb most of the high frequency ultraviolet light from the sun. This light would be very harmful to most terrestrial life if it reached the earth's surface.
Annual fluctuations occur naturally in the position, thickness and density of the layer. However, it has been affected by man-made chemicals transported into the stratosphere by air currents. Chlorofluorocarbons, which are inert and harmless in the lower atmosphere, and were used heavily for refrigeration and as propellants in aerosols, are long lasting pollutants that form radicals that catalyse the breakdown of ozone.
As a result of this, CFCs have been largely phased out of use. This can be seen as one of the greatest successes of the environmental movement, and the ozone layer is repairing because of it.
