. Normal oxygen, which we breathe has two oxygen atoms and is odorless. Ozone is much less common than normal oxygen. The ozone layer absorbs a portion of the radiation from the sun, preventing it from reaching the planet’s surface. Most importantly, it absorbs the portion of ultraviolet light called UVB. UVB has been linked to many harmful effects including various types of skin cancer, cataracts, and harm to some crops, certain materials, and some forms of marine life. At any given time, ozone molecules are constantly formed and destroyed in the stratosphere. The total amount, however, remains relatively stable. The concentration of the ozone layer can be thought of as a stream’s depth at a particular location. While ozone concentrations vary naturally with sunspots, the seasons, and latitude, these process are well understood and predictable. Records have been established spanning several decades that detail normal ozone levels during these natural cycles. Each natural reduction in ozone levels is followed by a recovery. Recently, however, convincing scientific evidence has shown that the ozone layer shield is being depleted well beyond changes due to natural processes. Thinning of the ozone layer has been caused by a variety of ozone destroying chemicals released by human activities. More than half the damage has been caused by chlorofluorocarbons. For over 50 years, chlorofluorocarbons,(CFCs), were thought of as miracle substances. They are stable, nonflammable, low in toxicity, and inexpensive to produce. Over time, CFCs found uses as refrigerants, solvents, foam blowing agents, and in smaller applications. CFCs and other compounds have atmospheric life times long enough to allow them to be transported by winds into the stratosphere. Because they release chlorine and bromine when they breakdown, they damage the protective ozone layer. In the early 1970’s, researchers began to investigate the effects of various chemicals on the ozone layer, particularly CFCs, which contain chlorine. Potential impacts of other chlorine sources were examined also. Chlorine from pools, for example, do not reach the stratosphere. Those chlorine compounds readily combine with water and repeated measurements show that they rain out of the troposphere very quickly. In contrast, CFCs are so stable that they do not dissolve in rain. There are no natural processes that will remove the CFCs from the lower atmosphere. Over time, the CFCs are driven into the stratosphere by winds. It typically takes seven to ten years for CFC molecules to rise through the lower atmosphere and reach the stratosphere.. The CFCs are stable that only exposure to strong UV radiation can break them down. When that happens, the CFC molecule releases atomic chlorine. One chlorine molecule can destroy over 100,000 ozone molecules. Some two billion pounds of CFCs are manufactured every year. Gaseous emissions of CFCs, both during manufacturing processes and later, from finished products have caused atmospheric levels of chlorine to dramatically increase. Scientists estimate that before 1900 chlorine comprised 0.6 parts per billion (pp.) of the stratosphere. Today, the chlorine level is about 3.5 pp., and growing by more than 1.0 pp. per decade. The net effect is to destroy ozone faster than it is naturally created. Scientists are finding that under this assault the protective ozone layer in the stratosphere is thinning. In some regions it vanishes almost entirely for a few weeks every year. Although CFC use has been greatly reduced in recent years, CFC molecules already released in the lower atmosphere will be making their way into the stratosphere and further ozone depletion is expected. As a result, experts anticipate an increase in skin cancers, more cataracts, and reduced yields of some crops. The initial concern about the ozone layer in the 1970’s led to a ban on the use of CFCs as aerosol propellants in several countries, including the United States. However, prod

Some topics in this essay:
UVB UVB, Orbiting Earth, Doyle April, Ozone Layer, ozone layer, Hydrochlorofluorocarbons HCFCs, Research Satellite, Montreal Protocol, Vienna Convention, lower atmosphere, depletion ozone layer, depletion ozone, research paper, ozone molecules, layer stratosphere, atomic chlorine, oxygen atoms, cfcs stable, cfc molecules, Upper Atmosphere, Atmosphere Research, ozone layer 1970’s, protective ozone layer, affects ozone layer, chlorine molecule destroy,