Heat Budget of the Earth

By : Neha Dhyani

Updated : Feb 9, 2023, 17:50

The concept of Heat Budget of Earth refers to the perfect balance of the heat that the Earth is absorbing and the heat escaping from the Earth. This process takes place in the form of radiation. The Heat Budget of Earth is calculated by the heat balance equation and is expressed as gram calories of heat per centimetre square of the lake surface.

Through this concept, the Earth's constant temperature can be explained despite the massive transfer of heat. Find out more about the heat budget of the earth and its significance here.

What is Heat Budget of the Earth?

The heat budget of the atmosphere is the amount of heat that is required to raise the temperature of the water lakes to a maximum level in the summers. The heat budget of the atmosphere is a combination of the following:

  • 34% of radiations from the outgoing long-wave terrestrial, 
  • 48% of the solar radiation, and 
  • 14% of the radiations emerge from the shortwaves that enter the solar radiations.

How does the Heat Budget of Earth Work?

Here, we have explained how the heat budget of Earth works:

  • About 30% of all solar energy that reaches Earth is reflected back into space by Earth's atmosphere, clouds, and surface. The other 23% of energy is absorbed by water vapour, clouds, and dust in the atmosphere, which is converted into heat.
  • Solar radiation is assimilated by ocean and land, and the Earth's surface gets heated with this energy. The atmosphere receives energy absorbed by the Earth through three processes: radiation, conduction, and latent heat.
  • To understand how the heat budget of Earth works, consider that we receive hundred per cent of isolation at the topmost layer of the atmosphere. Some energy is reflected, some absorbed, and some scattered. Only a part of this energy reaches the Earth.
  • Roughly the amount of energy reflected back to space is 35 units; 27 units of energy are reflected from the clouds, and areas that are covered with ice of the Earth reflect two units. This amount of reflected radiation is defined as the Albedo of the Earth.
  • 48 units are being absorbed by the atmosphere, and a part of it is also radiated back to space. Hence, the total amount of radiation that returns from the Earth is around 65 units. The perfect balance of both incoming and outgoing heat forms the stable Heat Budget of Earth.

Heat Budget of Earth and its Connection to Earth's Energy 

To understand the heat budget, it is important to know the basics of the earth's energy flow. Despite the enormous transfer of energy in and out of the Earth, the Earth maintains its constant temperature because, as a whole, there is no net gain or loss. This is because the Earth emits the same amount of energy as it receives. This crucial mechanism forms the foundation of the Heat Budget of Earth.

Heat Budget of Earth - Incoming Solar Energy

  • The total amount of energy received on Earth per second at the top of the Earth's atmosphere is called Incoming solar energy. 
  • This is added to the total value of the heat budget. It is also called short-wave radiation. It is measured in watts. 
  • The Earth's sphere shape receives the approximate amount of 340 watts per square meter. Also, the amount of energy absorbed varies with location.
  • Out of this 340 watts per meter square, 77 watts per metre square is reflected back to space by clouds and the surface of the Earth, and the rest 240-metre square is added to Earth's solar energy budget. This amount is called absorbed solar radiation.

Outgoing Solar Energy and its Impact on the Heat Budget of Earth

  • The total amount of energy leaving the Earth is called outgoing solar energy. It is also called longwave radiation. 
  • Energy absorbed is converted into different forms of heat energy, and some of it is emitted out of space in the form of OLR (outgoing longwave radiation). This energy is subtracted from the total energy value in the heat budget of the earth.
  • We can say that Earth receives a certain amount of insolation in the form of short waves and gives back heat in the form of longwave radiations, and through this, the Earth can maintain its temperature and, consequently, a constant Heat Budget of Earth.
  • Earth's energy is governed by the first law of Thermodynamics, which states that energy cannot be created nor destroyed.

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FAQs on Heat Budget of Earth

Q.1. What is the Heat Budget of Earth?

The heat budget of Earth is the equilibrium between the isolating radiations and the terrestrial radiations. In simpler words, the heat budget is an ideal balance of the head radiations absorbed by the Earth and the heat radiation escaping from the Earth’s atmosphere.

Q.2. Which factors can disturb the heat budget of the Earth?

There are certain factors that can greatly influence the heat budget of Earth by changing the composition of the atmosphere. Factors that can disturb the Heat Budget of Earth are as follows:

  • Atmospheric aerosols
  • Clouds
  • Vegetation
  • Land use methods
  • Greenhouse gases

Q.3. Which three processes take place during the Heat Budget of Earth?

Three different processes take place during the Heat Budget of Earth. These processes are:

  • Conduction
  • Radiation
  • Convection

Q4. Is Heat Balance and Heat Budget the same?

The heat balance and the heat budget can be the same only if the amount of heat received (isolation) is equal to the amount of heat lost (terrestrial radiation). If the balance is disturbed, the Earth will either get cooler or warmer as time passes. Hence, the heat budget is only the loss and gain of heat on Earth.