The atmosphere has been a subject of interest and concern throughout history. In the form of clouds, winds, and storms, it affects the lives of people in fundamental, obvious ways. In ways of which we are less conscious, it provides protective and stabilizing functions; for example, the ozone filters out ultra-violet radiation, which, in the present evolutionary state of the human species, would do serious harm to our health. In addition, the earth's radiation balance is affected by the composition of the atmosphere. Consequently, with our consumptive practices and increasing abilities to intrude upon its natural condition, the possibilities of long-term, accumulated harmful effects are in evidence.