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Ozone Layer body

Layers of the atmosphere (not to scale)

Figure A: Ozone Layer Within Stratosphere Contains Highest Concentration of Ozone

The ozone layer is defined by meteorologists as an area/region of concentrated ozone just above the troposphere/lower layer of the stratosphere. It is important to note that ozone is not only confined to the stratosphere (about 90% of the atmosphere’s ozone is in the stratosphere), but across the whole atmosphere. In big cities during the summertime, air quality at the surface can be an issue when ozone and other gases increase to dangerous levels.

Ozone gas is like a double edged sword. When ozone is at the earth’s surface, it can be dangerous as it is corrosive and harmful to breathe in. However, when it is concentrated in the lower stratosphere, it actually protects us from the sun’s harmful UV rays. Without ozone in the atmosphere, it would be too dangerous to walk outside without having to wear some sort of special suit. 

Note: Figure A not drawn to scale...the troposphere and stratosphere make up an extremely small layer above the earth's surface

Ozone "hole" over the South Pole

Figure B: Ozone Hole
Image from NASA

During the mid 1980s, concerns grew over what appeared to be a ‘hole’ in the ozone layer over Antarctica in spring. Scientists determined that the ‘hole’ was caused by humans due to man-made chemicals such as CFCs (chlorofluorocarbons). The CFCs and other chemicals were interacting with the ozone and destroying the layer over Antarctica. A smaller hole was also seen over the Northern Hemisphere.  Initially, it seemed impossible that CFCs could reach the stratosphere as they were heavier than air. However, weather phenomena like thunderstorms can produce updrafts and carry air (and other) particles to the top of the troposphere and even into the parts of the stratosphere. In 1987, the Montreal Protocol was put together by several nations with the goal of reducing and completely stopping the production of CFCs. While CFCs are still being produced today by smaller nations, the ozone ‘hole’ has begun to fill in, although it may be decades before it completely recovers.

Last modified date: Friday, August 10, 2012 - 12:23pm