3. Energy Balance of the Earth

The energy transformations on Earth are discussed in this chapter. The Earth’s temperature is determined by the global energy balance between radiative energy coming from the Sun and radiative energy emitted back to space. The atmosphere has a strong additional impact on the global energy balance as it efficiently absorbs infrared radiation coming from the surface of the Earth. As a result of this greenhouse effect, the surface temperature is much higher than in the absence of the atmosphere. Life on Earth has the ability to convert energy received from the Sun into energy-containing chemical components via photosynthesis. The biosphere that is based on this mechanism is capable of changing energy-relevant properties of the Earth and alters the energy balance on a global scale. Also discussed are spatio-temporal variations of the conditions on Earth, which are caused by the movement of Earth around the Sun and its rotation. Finally, selected simple feedback models of the Earth are treated to describe important general aspects of the global climate system.