Ozone Depletion

Ozone Depletion

Ozone depletion is the anomalous decrease in "total column ozone" over Earth's surface. This could be caused by variations in sunlight, but its not. It caused by contaminants that are added to the atmosphere in addition to what Nature throws up there. These contaminants include water vapor and chlorofluorocarbons (CFCs). After controlling CFCs, their levels are slowly decreasing. So water vapor, that stuff we spew out the back ends of our jets, and spray into the air from our cooling towers, is the major contaminant we have yet to control.

The ozone hole
What is the ozone hole:
A definition by the The American Heritage® Science DictionaryCopyright © 2002. Published by Houghton Mifflin states that the ozone hole is "A severe depletion of ozone in a region of the ozone layer, particularly over Antarctica and over the Arctic. The depletion is caused by the destruction of ozone by CFCs and by other compounds, such as carbon tetrachloride (CCl4) and carbon tetrafluoride (CF4). The amount of ozone in ozone holes is about 55 to 60 percent of the normal concentration in the ozone layer. Although the full effect of increased ozone depletion is not yet known, the amount of ultraviolet radiation the Earth receives is greatly increased by ozone depletion, creating a heightened risk of skin cancers and likely contributing to global warming. "

An article, “the origin of the ozone hole- Natural or Anthropological” by James A. Marusek, written on 24 February 2005 states that there are 2 theories about what caused the ozone hole
1.Anthropological : the release of man-made material
2.Natural: a weakening of the earth’s magnetic field

Anthropological reasoning:
The depletion of ozone is due to release of man-made chemicals such as chlorofluorocarbon (CFC)compounds and ozone depleting substances such as carbon tetrachloride, methyl bromide and methyl chlorofoam.
As they reach into the stratosphere, ultraviolet raditation causes these sompounds to break apart, releasing chlorine atoms, halons and bromine atoms which would in turn destroy the ozone. (See Free Radical Catalysts)

If this theory were to be correct, then we would expect to see that the ozone hole would appear at the mid- Latitude Nothern Hemisphere zone where the industry and population centers in the U.S, Canada, Europe, India, Asia, Russia, China and Japan. However, as we see it now, the ozone hole appears at the Southern hemisphere, one of the most pristine places left on the planet, Antartica.

Natural theory:
As the earth’s magnetic field weakens, less energetic protons in solar and galactic cosmic rays are now able to enter the stratosphere and thereby producing an increase in the ozone depleting chemical, nitric oxide.

NO + O3 ___>NO2 + O2
O + NO2 ___>NO + O2


On the Earth’s surface, the magnetic field varies from being horizontal and of magnitude ~ 30,000 nanoTesla (nT) near the equator to vertical and ~ 60,000 nT near the poles. Charged particles are deflected by the horizontal component of the Earth’s magnetic field. Therefore the magnetic shielding of charged particles is strongest above the equator and weakest above the poles.

If this theory were to be correct, we would expect the highest concentration of nitric oxide production to occur at the magnetic pole because at this location the field in general has only a vertical component.

Present Situation of Ozone Depletion:
Discovered in 1985 by the British Antarctic Survey (BAS), the south pole has been experiencing a decline of magnetic field of 13 percent during the past century. The antartic ozone hole has reached a maximum size of around 10.5 million square miles.