ABSTRACT
This chapter examines the nature of radiation and its flows and balances in the earth–atmosphere system. Dust from erupting volcanoes has a marked effect. Most space, however will be devoted to the many ways in which humans can and do alter the radiation balance. As an energy source for evaporating water, radiation drives the hydrological cycle of the earth thus providing, through precipitation, a continually renewed source of fresh water for the world's agriculture and life. The question of what is radiation has puzzled scientists at least from the time of Sir Isaac Newton. There is no absolute certainty, but there is a useful conceptual framework that satisfactorily explains most of the radiation-related phenomena that are observed. The actual measurement of the flows of radiation to and from the earth's surface, and within the atmosphere is therefore quite complex. However, calculations and checks on the measurements are made easier by the fact that there is a radiation balance.
