The Earth’s energy budget describes the balance between the radiant energy that reaches the Earth from the Sun and the energy that leaves the Earth back into space. The atmosphere absorbs a large amount of energy and radiates it into space, as well as back to the surface of the planet. In fact, the atmosphere emits almost twice as much radiation as direct sunlight on the Earth’s surface. This is due to the fact that the sun heats the surface only during the day, whereas the warm atmosphere is there all day. The difference between incoming sunlight and outgoing infrared is due to the accumulation of greenhouse gases in the atmosphere, such as carbon dioxide. These gases are transparent to visible light, but opaque to infrared rays, absorbing and emitting back a large number of infrared photons. To restore the balance between incoming and outgoing radiation, the temperature of the Earth’s surface must rise, which is the cause of global warming.
Reference
South Central Climate Adaptation Center. (2016). 1.1.2 Earth’s energy budget [Video]. YouTube. Web.