The Earth energy-balance Term Paper Example | Topics and Well Written Essays - 2000 words

The Earth energy-balance - Term Paper Example This phenomenon is known as earth energy budget or earth energy balance. There are many factors that can deteriorate this balance and can contribute to significant changes in the climate of the earth. Earth Atmosphere: To understand how energy is received and returned to maintain energy balance it is important to understand what constitutes the atmosphere. There are five layers that surrounds the earth; exosphere, thermosphere, mesosphere, stratosphere and troposphere. Exosphere is the most outer space with particles so far apart that they do not affect the pathway of radiations from sun. Troposphere is the innermost layer that span from the earth surface to about 10 kilometers above. This layer is important as it provides the maximum reflection of radiation as discussed below. The following diagram (fig 1) demonstrates the inner three layers of earth atmosphere. Fig 1. Inner three layers of earth’s atmosphere Incoming radiation: Radiations from sun experience no interference as they travel undisturbed in space to reach the earth’s atmosphere. In the atmosphere, there are different layers with variable densities of gases and other molecules. When these radiations collide with these molecules they are deflected in many directions, a phenomenon known as scattering. An important concept to remember here is that these radiations that reach the earth have very small wavelength and not all but a small selective proportion of electromagnetic radiations can be scattered by molecular collision. (Ahrens, 2012). The rest of energy is absorbed by the earth system in various forms. Most of the energy is absorbed by the solid earth that increases the core and surface temperature. Part of the energy is absorbed by clouds, water vapors and other molecules present in the earth atmosphere. The following diagram (fig 2) represents the overall exchange budget of earth’s energy. Figure 2. Earth’s energy balance It is evident from the diagram that the tot al incoming energy absorbed by the earth system almost equals to the energy returned back to space thus maintaining energy balance. Outgoing radiations: The radiations received from sun can be returned back to space by two basic mechanisms as explained below. Reflection: Some of the energy that enters the atmosphere is reflected back as same short wavelength radiations identical to what was received from sun. Different component of earth’s atmosphere have variable ability to reflect these radiations and this property is known as ‘albedo’. Therefore, various surfaces have variable albedo. For example, deserts have high albedo because they are able to reflect about 40% of the radiations that reach them back into the space. On the other hand, ocean surfaces and rainforests have low albedo as they are able to reflect only a small proportion of radiations. (Ahrens, 2012). It is important to understand that those surfaces that have lower albedo tend to retain heat more than those with higher reflection abilities. By looking at fig 2, it can be observed that only a part of the radiations, about 30%, are reflected back into the space by earth surface, clouds and scattering process. There should be another way of returning the remaining 70% of the radiations which were absorbed by the atmosphere and the earth. Emission: Thermic emission is the most