The main deleterious effect of ozone depletion is that the stratosphere will allow an increased level of solar ultraviolet (UV) radiation to reach the earth. The most biologically damaging radiation wavelength occurs within the 290 to 320 nm band referred to as TJV-B. According to uncertain projections from mathematical models, depletion of the ozone shield would result in 5-20% more UV radiation reaching populated areas within the next 40 years (most of it in the UV-B form).
UV-B radiation can decrease photosynthesis, water use efficiency and yield of plants. The marine environment will also suffer drastic damage.
The harmfulness of UV-B stems from the high energy of these light rays, which allows them to penetrate deeply into water, leaves, and skin. Because of this, increased UV-B radiation can harm the metabolism of cells and even damage genetic material.
Although living organisms have always been exposed to some UV-B, cellular repair mechanisms evolved to protect against its damaging effects. The problem with increased UV-B is that it causes more damage than the natural protection can cope with. Increased UV-B radiation leads to increased incidence of such problems as skin cancer, eye damage and cataracts, and possible inhibition of immune system function in humans as well as other animals. Plants also suffer under increased UV-B, and their vulnerability could result in reduced crop yields, damage to forest ecosystems, and decreased populations of phytoplankton in the world’s oceans.
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Ozone Depletion versus Global Warming
Ozone depletion and global warming are separate problems, though some agents contribute to both. CFCs are the principal cause of ozone depletion, but they also happen to be potent heat- trapping gases.
Still, CFCs are responsible for less than 10% of total atmospheric warming, far less than the 63% contribution of carbon dioxide. Thus, attention paid to CFCs has been on their ozone-depletion role.
This will change as CFCs are phased out and replaced by hydro chlorofluorocarbons (HCFCs) or hydro fluorocarbons (HFCs). These chemicals have little or no effect on the ozone layer but are strong heat-trapping gases.
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As their concentration in the atmosphere is already rising, the likely net effect in the future is that reductions in the CFC- related contribution to global warming will be offset by the presence of HCFCs and HFCs.