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Ozone Layer Depletion

The Ozone Hole and CFC Hazards Examined

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Ozone Layer Long View

The Ozone Layer Provides Protection from Harmful UV Radiation

NASA GSFC Scientific Visualization Studios
Ozone depletion is a crucial environmental problem on Earth. The growing concern over CFC production and the hole in the ozone layer is causing alarm among scientists and citizens. A battle has ensued to protect Earth's ozone layer.

In the war to save the ozone layer, and you may be at risk. The enemy is far, far away. 93 million miles away to be exact. It is the sun. Each day the Sun is a vicious warrior constantly bombarding and attacking our earth with harmful Ultra Violet radiation (UV). Earth has a shield to protect against this constant bombardment of harmful UV radiation. It is the ozone layer.

The Ozone Layer is Earth's Protector

Ozone is a gas that is constantly formed and reformed in our atmosphere. With the chemical formula O3, it is our defense against the Sun. Without the ozone layer, our Earth would become a barren wasteland on which little to no life could exist. UV radiation causes a host of problems for plants, animals, and humans including dangerous melanoma cancers. Watch a short video clip on the ozone layer as it provides protection to Earth from harmful solar radiation. (27 seconds, MPEG-1, 3 MB)

Ozone Destruction is Not All Bad.

Ozone is supposed to break up in the atmosphere. The reactions taking place high in our atmosphere are a part of a complex cycle. Here, another video clip shows a close-up view of ozone molecules absorbing solar radiation. Notice the incoming radiation breaks apart ozone molecules to form O2. These O2 molecules are later rejoined to form ozone again. (29 seconds, MPEG-1, 3 MB)

Is There Really a Hole in the Ozone?

The ozone layer exists in a layer of the atmosphere known as the stratosphere. The stratosphere is directly above the layer that we live in known as the troposphere. The stratosphere is approximately 10-50 kilometers above the Earth's surface. The diagram below shows a high concentration of ozone particles at about 35-40 km in altitude.

But the ozone layer has a hole in it!…or does it? Although commonly nicknamed a hole, the ozone layer is a gas and cannot technically have a hole in it. Try punching the air in front of you. Does it leave a “hole”? No. But ozone CAN be severely depleted in our atmosphere. The air around the Antarctic is severely depleted of atmospheric ozone. This is said to be the Antarctic Ozone Hole.

How is the Ozone Hole Measured?

The measurement of the ozone hole is made using something called a Dobson Unit. Technically speaking, “One Dobson Unit is the number of molecules of ozone that would be required to create a layer of pure ozone 0.01 millimeters thick at a temperature of 0 degrees Celsius and a pressure of 1 atmosphere”. Lets make some sense of that definition...

Normally, the air has an ozone measurement of 300 Dobson Units. This is equivalent to a layer of ozone 3mm (.12 inches) thick over the entire earth. A good example is the height of two pennies stacked together. The ozone hole is more like the thickness of one dime or 220 Dobson Units! If the level of ozone drops below 220 Dobson Units, it is considered to be a part of the depleted area or “hole”.

Causes for the Ozone Hole

Chlorofluorocarbons or CFCs are used in refrigerants and coolants. CFCs are typically heavier than air, but they can ascend in the atmosphere in a process that takes 2-5 years.

Once in the stratosphere, UV radiation break apart the CFC molecules into dangerous chlorine compounds which are known Ozone Depleting Substances (ODS). The chlorine literally slams into the ozone and breaks it apart. In the atmosphere a single chlorine atom can break apart ozone molecules again and again and again. Watch the video clip showing the break-up of ozone molecules by chlorine atoms.
(55 seconds, MPEG-1, 7 MB)

Have CFCs Been Banned?

The Montreal Protocol in 1987 was an international commitment to reduce and eliminate the use of CFCs. The treaty was later amended to ban CFC production after 1995. As part of Title VI of the Clean Air Act, all Ozone Depleting Substances (ODS) were monitored and conditions were set forth for their use. Initially, the amendments were to phase out ODS production by the year 2000, but it was later decided to accelerate the phase out to 1995.

Will we win the war?

Only time will tell...



References:

OzoneWatch at NASA Goddard Space Flight Center

The Environmental Protection Agency

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