ABSTRACT
One of the most important functions of the atmosphere is to provide the surface of the earth with protection from solar radiation. This may seem contradictory at first sight, since solar radiation provides the energy which allows the entire earth/atmosphere system to function. As with most essentials, however, there are optimum levels beyond which a normally beneficial input becomes harmful. This is particularly so with the radiation at the ultraviolet end of the spectrum (see Table 6.1). At normal levels, for example, it is an important germicide, and is essential for the synthesis of Vitamin D in humans. At elevated levels it can cause skin cancer, and produce changes in the genetic make-up of organisms. In addition, since ultraviolet radiation is an integral part of the earth’s energy budget, changes in ultraviolet levels have the potential to contribute to climatic change.
