Outgoing radiation

The Earth then radiates away the energy it has absorbed. The diagram summarizes the global energy budget. The numbers in the drawing refer to the percentages of the total energy budget. Those with a plus sign represent incoming solar energy and those with a minus sign represent outgoing terrestrial radiation. Other numbers indicate the movement of

Outgoing radiation

energy between the Earth and atmosphere. The table shows the budget in more detail.

The surface of land and sea receive 51 percent of the solar constant—the amount of solar energy that reaches the topmost layer of the atmosphere—25 percent as direct radiation and 26 percent as indirect radiation that has been scattered during its passage through the atmosphere. The surface reflects 4 percent of the incoming radiation directly back into space and emits 5 percent as long-wave (infrared) radiation, also directly into space. Infrared radiation from the surface also transfers 13 percent of the total to atmospheric water vapor, carbon dioxide, and cloud droplets, and the surface loses 24 percent as latent heat and 5 percent as sensible heat. The total outgoing radiation amounts to 51 percent of the solar constant.

Radiation budget. The numbers refer to the percentage of the total at each stage. Numbers that carry a + or — sign represent energy that reaches the Earth from the Sun (+) and that leaves as terrestrial radiation ( — ). The arrows indicate the direction of energy flow.

Terrestrial Radiation

ENERGY BUDGET (EARTH AND ATMOSPHERE)

Incoming

Percent of the total

Absorbed by ozone

3

Absorbed by water vapor and aerosols

13

Absorbed by clouds

2

Reflected by clouds

24

Reflected by air and aerosols

7

Reflected by surface

4

Subtotal

53

Absorbed by surface from the Sun

25

Absorbed by surface from air and clouds

22

Subtotal

47

Total incoming

100

Outgoing

Shortwave from water vapor, carbon dioxide, and clouds

31

Shortwave from surface

4

Subtotal

35

Long-wave from surface

5

Long-wave from water vapor, carbon dioxide, and clouds

60

Subtotal

65

Total outgoing

100

The stability of the global climate depends on maintaining the balance between incoming and outgoing radiation. From time to time that balance has shifted and the shifts have brought major climatic changes. The onset and ending of ice ages are the most extreme changes, of course, but there have been many less dramatic periods of increased warmth and cold (see "Edward Walter Maunder and the Unreliable Sun," "The Medieval Optimum," and "The Little Ice Age" on pages 70-78, 79-86, and 87-93 respectively).

Siting the thermometer

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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