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 Global Outgoing Longwave Heat Radiation

The orange-red areas of this image show heat being emitted from relatively cloud-free bands north and south of the equator. On the other hand, the dark blue areas over Amazonia, North America, tropical Africa, Indonesia, and Asia show where less heat is being emitted—in these areas, the earth’s heat is being trapped by thick, high clouds. Clouds tend to form over warm areas (like tropical landmasses) as heat rises. The heated air cools as it rises, and the water vapor it contains condenses to form clouds.

NASA’s Terra satellite system measures the infrared radiation emitted by the earth, showing where the atmosphere allows heat to escape back into space. This picture offers a way of seeing the greenhouse effect in action. The amounts of greenhouse gases in the atmosphere partly determine the strength of the atmosphere’s ability to keep the planet warm: Increases in global carbon dioxide concentrations, for example, trap more heat near the planet’s surface.

 glossary glossary terms  

Click for definitions of words used on this page:

electromagnetic radiation
energy budget
greenhouse effect
greening hypothesis

View the full, printable version of the glossary.

Global Outgoing Longwave Heat Radiation

Global Outgoing Longwave Heat Radiation - Longwave (infrared) radiation, which we feel as heat, is energy with longer wavelengths than visible light. This satellite image shows heat emitted by the earth’s surface. Red and orange areas indicate where more heat is emitted; blue and white areas indicate less heat emission. This picture was constructed from images gathered over a one-month period during March 2000. Source:CERES instrument team

 questions about the data  

question Why is carbon dioxide such an important greenhouse gas? Don’t other gases exist in the atmosphere in much higher concentrations?

email Email your own questions about this data set. 

 research connection  

Researchers often look for areas where different kinds of data support each other. For example, compare this image to the Global Reflected Shortwave Solar Radiation map in this section. These two maps are mirror images: Bright areas in one image are dark in the other. That’s because high clouds reflect the sun’s heat into space and prevent the earth’s heat from escaping—so these areas are dark and cold in the heat image on this page, and bright white on the other page, indicating reflected sunlight.

 related sites  

NASA’s Global Hydrology and Climate Center - Information on the role of water vapor in the earth’s climate.

Earth Observatory - Changes in the earth’s heat emission over time.

NASA’s Visible Earth - Satellite images of the earth’s atmosphere in action.

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