Graphic depicting the greenhouse effect. Some of the sun's solar radiation is reflected by the earth and atmosphere but most of it is absorbed by the earth's surface. Infrared radiation is emitted from the earth's surface. Some of the infrared radiation passes through the earth's atmosphere and some of it is absorbed and re-emitted by greenhouse gas molecules, causing the earth's surface and lower atmosphere to warm.
Source: EPA 2008q
Larger view of illustration.

Greenhouse Gas: Any gas that absorbs heat in the atmosphere (e.g., CO2)

Greenhouse Effect: Trapping and buildup of heat in the atmosphere near the Earth’s surface caused in part by increased levels of greenhouse gases

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Climate Change 101:

What Is the Greenhouse Effect?

Sunlight passes through the atmosphere and warms the Earth’s surface. Some of this solar radiation is reflected by the Earth and the atmosphere. Greenhouse gases in the atmosphere, such as carbon dioxide (CO2), absorb heat and further warm the surface of the Earth. This is called the greenhouse effect.

As more greenhouse gases are emitted into the atmosphere, heat that would normally be radiated into space is trapped within the Earth’s atmosphere, causing the Earth’s temperature to increase.

Graphic Reference:
EPA. 2008q. Climate Change Web site. Climate Change—Science. accessed August 31, 2009.

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Section 4 of 50