Blackwell Reference Online

Extract

Global warming refers to the belief – now very widely held in the international scientific community – that the earth's climate is undergoing change as a result of inadvertent human actions that have enhanced the “greenhouse effect.” Some people contest this view about the trend toward warming while others have reservations about the proposed explanation for the trend; the public debate around this issue is a vital sociological topic in its own right. But it is important at the start to note that there is little doubt about the greenhouse effect itself. The greenhouse effect is the reason why the earth is considerably warmer than the moon, even though both bodies are the same average distance from the sun. Every square meter of the surface of each body receives about the same amount of heat from the sun, but the heat energy that the moon gets from solar rays is dissipated into space while the atmosphere forms an insulating layer around the earth, leading the diffusion of heat energy to occur more slowly; this insulating action of the atmosphere is the greenhouse effect. Over millions of years both bodies have arrived at an equilibrium temperature, with the average surface temperature on earth around 15° and the moon's around −18°. The “greenhouse” makes us over 30° warmer than we would otherwise be. Various components of the earth's atmosphere are responsible for this greenhouse ... log in or subscribe to read full text