Earth's energy budget

Earth's Energy Budget refers to the balance between the energy that Earth receives from the Sun, and the energy the Earth radiates back into outer space after having been distributed throughout the five components of Earth's climate system and having thus powered the so-called "earth heat engine". This system is made up of Earth's water, ice, atmosphere, rocky crust, and all living things.

Radiation

The Earth receives energy from the Sun in the form of radiation. This incoming solar radiation, or insolation, is absorbed, reflected, or transmitted by the Earth's atmosphere. The amount of insolation absorbed by the Earth is known as the albedo of the Earth, which is approximately 30%.

Absorption and Reflection

The Earth's surface absorbs the majority of the insolation, while the rest is reflected back into space. The absorbed energy is then used to heat the Earth's surface and atmosphere, drive weather and ocean currents, and sustain life through photosynthesis.

Re-radiation

The Earth's surface and atmosphere re-radiate some of the absorbed energy as heat, or infrared radiation, back into space. This process is known as terrestrial radiation.

Greenhouse Effect

Some of the re-radiated energy is trapped by the Earth's atmosphere in a process known as the greenhouse effect. Greenhouse gases, such as carbon dioxide and methane, absorb and emit infrared radiation, which warms the Earth's surface and lower atmosphere.

Balance

The balance between the incoming and outgoing energy is the Earth's energy budget. If the balance is positive, with more energy coming in than going out, the Earth warms. If the balance is negative, with more energy going out than coming in, the Earth cools.

See Also

• Climate system
• Solar radiation
• Greenhouse effect
• Albedo
• Insolation