Monday, September 27, 2010

Expository Thoughts about the Ozone Layer

The ozone layer has become a greatly discussed topic over the past several years, in both scientific and non scientific communities. It is important for one to realize exactly what ozone and the ozone layer are, and to understand the issues relating to them. If not for the ozone layer, life would not exist on the surface of the earth.

The ozone layer is important to everyone that lives on the earth. A cloud of invisible gas encompassing the planet, the ozone layer acts as a “global security blanket” for the earth, blocking out harmful ultraviolet rays, while letting other rays from the sun reach the earth (Fisher 13). Ultraviolet rays are damaging to life on earth, killing plant life and causing cancer in humans. This is the reason that sunblock has become so important in recent years.

The sun is the greatest source of energy for the earth. The temperature of the sun is about 6000 degrees centigrade, and it gives off great magnitudes of radiant energy (Schneider 13). This radiant energy spreads out from the sun and eventually reaches the earth. Some of this energy is reflected from earth’s atmosphere back into space. Some more of the sun’s radiant energy is reflected back into space from the surface of earth. But about 25% of the suns radiant energy is absorbed into the earth’s atmosphere (Schneider 14). The ozone layer is what determines exactly what is absorbed and what is reflected from the sun’s energy. Letting in wavelengths other than ultraviolet, the ozone layer allows enough radiation in to keep the earth warm and provide light (Fisher 13). The 25% of the radiant energy that is absorbed by the atmosphere is absorbed through greenhouse gases in the stratosphere, and the heat that results is enough to sustain life on earth. This is known as the “greenhouse effect,” and is called so because it is similar to the way a greenhouse works. The ozone layer holds in greenhouse gases in the stratosphere of the earth, just as glass panels of a greenhouse hold in heat. As the sun’s radiant energy beats down on the earth, the ozone layer allows some energy through to the greenhouse gases. These gases heat up and send their heat down to the atmosphere and the surface of the earth. According to Stephen Schneider, a Climatologist with the National Center for Atmospheric Research, “If it weren’t for the greenhouse effect, temperatures at the earth’s surface today would be some 33 degrees C colder than they are, and life as we know it would not exist” (13). This is a valid statement and agreed upon by most scientists. It is the ozone and stratospheric gases that hold in the heat from the sun to make earth habitable.

In order for one to understand the implications of the ozone layer, one must first understand what the ozone layer is. The oxygen breathed by humans is comprised of two atoms of oxygen, and it is written O2. Ozone, however, is also a molecule comprised of oxygen. But ozone is of a different nature. Ozone is comprised of three atoms of oxygen, and is written O3. Oxygen is needed for life and is found abundantly in the biosphere. Ozone in the biosphere, however, is a poison, and cannot be breathed by animals (Fisher 17). Ozone is found mainly only in the high stratosphere, about 12 to 20 miles above the surface of the earth, and it is here that the oxygen absorbs ultraviolet radiation form the sun and is turned into ozone (Fisher 18). There is one other place besides the stratosphere that ozone can be found. This is as a pollutant at ground level. Ozone at ground level results from oxides of nitrogen chemically reacting with volatile organic compounds in the sunlight (“Chief Causes for Concern”). So basically, ozone at the surface of the earth is from the sun reacting with pollution on earth. It is for this reason that ozone is a major constituent of smog. Automobile exhaust, industry emissions, gasoline vapors, and chemical solvents all react with sunlight to produce ozone in the biosphere (“Chief Causes for Concern”). This ozone at ground level is the worst during the hotter months of the year, when smog is most prevalent. Another problem with ozone at ground level is that it can be transported very far, even hundreds of miles away (“Chief Causes for Concern”). This pollutant is a poison both to plants and animals as well as humans, meaning that disease and sickness may occur as a result of exposure to ozone. Other possible results of ozone pollution in the biosphere could be the damaging of natural ecosystems and plant life within range of the ozone pollution.

While ozone in the biosphere is a bad thing, life on earth would not be possible without ozone in the stratosphere. The radiant energy emitted by the sun reaches the earth at all different wavelengths. As stated earlier, some wavelengths are allowed to pass through the ozone layer, and these are the longer wavelengths, and these provide heat and light for the earth. However, ultraviolet radiation from the sun also reaches the earth, and the wavelength of this radiant energy is extremely short, and “the shorter the wavelength, the higher its energy, or radiation, content and the more dangerous it is to life on earth” (Fisher 18). Ultraviolet radiation is harmful in varying degrees. UV-A is the longest wavelength ultraviolet radiation, and it is generally not considered harmful (Fisher 18). UV-B is the middle wavelength and it is destructive to life when it leaks through the ozone layer, causing cancer and other problems (Fisher 18). UV-C is the shortest wavelength ultraviolet ray and “would be an instant death ray were any of it to get through the ozone” (Fisher 18). UV-A rays escape through the ozone layer to the surface of the earth quite frequently, and they have something to do with the tanning of humans when they are out in the sun. UV-B rays escape much less frequently through the ozone layer, but are also much more powerful. These rays cause sunburn when humans are out in the sun, and they are also the major contributor to skin cancer. Sunscreen and sunblock have become much more popular in the recent years that the implications of these UV rays have been made known. UV-C rays are not allowed through the ozone layer into the lower atmosphere whatsoever.

There are more implications to ozone than it being a pollutant or blocking out UV rays, however. There is much controversy surrounding some issues dealing with the ozone layer. One such issue is that of ozone depletion. Research has shown that there is a possibility that the ozone layer is slowly being eroded away. The scientists in favor of this idea believe that the release of chlorofluorocarbons (CFCs) or other ozone-depleting substances are slowly eroding the ozone layer as they make their way up into the stratosphere (“Ozone Depletion”). If this suggestion is true, the repercussions could be very grave. If the ozone layer erodes, more UV rays will escape through the ozone into the biosphere, damaging plant and animal life and increasing the chances for humans to get skin cancer. The opposing idea to the erosion of the ozone layer is that the ozone layer is not really eroding at all, just going through periodic cycles of thinning. Regardless, the ozone layer is important to human life and health on earth.

A final controversy regarding the ozone layer is the idea of global warming. Global warming is the idea that the levels of carbon dioxide are rapidly increasing with human activity (such as the burning of fossil fuels), and that these increased levels will allow the atmosphere to absorb more of the sun’s radiant energy. Simultaneously, the erosion of the ozone layer will allow more radiant energy to escape to the atmospheric gases, such as carbon dioxide. According to this theory, this event will heat up the earth to an extent that life will no longer be able to exist. This theory has been under much speculation over the past several years, and it still remains an unproved theory. The opposite view to this theory is that there really is no global warming at all. Some people believe that global warming is an unscientific hoax, just to attract the media and scare people into being more environmentally-minded. Whether one believes in global warming or not is for one to decide, but it is apparent that the ozone layer is an important issue facing the world today.

The ozone layer is important to life and health for humans here on earth. While it is present as a pollutant here on the surface of earth, its presence in the stratosphere preserves life here on earth. Controversy surrounds the ozone layer in several ways, and it is for each person to decide their own views on the subject. The implications of the ozone layer are important no matter what one decides, however.

Works Cited
Chief Causes for Concern. U.S. Environmental Protection Agency. 03 Oct. 2005 .
Fisher, Marshall. The Ozone Layer. New York: Chelsea House Publishers, 1992.
Ozone Depletion. U.S. Environmental Protection Agency. 03 Oct. 2005 .
Schneider, Stephen H. Global Warming. San Francisco: Sierra Books Club, 1989.

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