Natural Environment Blog

The Earth radiation budget represents the balance between incoming energy from the sun and outgoing (reflected) energy from the Earth.

The term ‘budget’ can be likened to an individual’s budget or company budget - income versus expenses.

The earth radiation budget is determined by calculating all of the incoming sunlight minus all of the reflected sunlight and emitted heat.

If the radiation budget is in balance, Earth’s temperature will remain constant. If the budget is out of balance, the earth will either heat up or cool down.

Currently, the global radiation budget is in balance. This means that the amount of energy coming in is the same that is leaving. Having said this, different parts of Earth are completely out of balance. But as a whole, the earth’s radiation budget is in balance.

Many things can (and do) happen to sunlight on its way to Earth. It can be reflected back into space before or even after it reaches Earth. It can also be absorbed into many of the Earth’s surfaces.

There are 3 ways that the Earth radiation budget can tip out of balance:

• the amount of incoming solar radiation changes
• the amount of greenhouse gases in the Earth’s atmosphere changes
• the amount of Earth’s reflective features changes (clouds, ice, aerosols etc). Bright white surfaces reflect more sunlight than they absorb. The opposite is true for darker objects.

Since 1978, NASA scientists have been studying the earth’s radiation budget closely. When they launched the Nimbus-7 satellite, it carried a new instrument they called the Earth Radiation Budget Experiment (ERBE). ERBE was designed to measure all the energy through the top of the Earth’s atmosphere.

Since then, NASA has launched many more projects and satellites in order to study this area.