The temperature of a body is linked to the balance between the amount of radiation absorbed and emitted.
|Rate of absorption||Temperature of the body|
|greater than the rate of emission||increasing|
|equal to the rate of emission||constant|
|less than the rate of emission||decreasing|
The temperature of the Earth depends on many factors including the concentration of greenhouse gases such as water vapour, methane and carbon dioxide.
The Earth’s temperature also depends on the rates at which light radiation and infrared radiation are:
When visible light and high frequency infrared radiation are absorbed by the surface of the Earth, the planet’s internal energy increases and the surface gets hotter. Some of this energy is transferred to the atmosphere by conduction and convection.
The Earth also radiates lower frequency infrared radiation. Some of this infrared radiation is transmitted through the atmosphere back out into space, and some is absorbed by greenhouse gases in the atmosphere. The greenhouse gases emit infrared radiation in all directions - some out into space and some back towards Earth, which is then reabsorbed.
The ‘greenhouse effect’ caused by naturally occurring greenhouse gases, such as water vapour, stabilises the surface temperature of Earth. This allows the planet to support life.
However, human activities such as deforestation and the burning of fossil fuels are releasing additional carbon dioxide. This causes more infrared radiation to be ‘trapped’ and reabsorbed by the Earth’s surface. This enhanced greenhouse effect is causing global temperatures to increase, leading to climate change.