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7.13: Greenhouse Effect

Difficulty Level: Basic Created by: CK-12
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How does the atmosphere resemble a greenhouse?

Farmers use greenhouses to extend the growing season. A greenhouse traps heat. Days that are too cool for a growing plant can be made to be just right. Similar to a greenhouse, greenhouse gases in the atmosphere keep Earth warm.

The Greenhouse Effect

When sunlight heats Earth’s surface, some of the heat radiates back into the atmosphere. Some of this heat is absorbed by gases in the atmosphere. This is the greenhouse effect , and it helps to keep Earth warm. The greenhouse effect allows Earth to have temperatures that can support life.

Gases that absorb heat in the atmosphere are called greenhouse gases . They include carbon dioxide and water vapor. Human actions have increased the levels of greenhouse gases in the atmosphere. This is shown in Figure below . The added gases have caused a greater greenhouse effect. How do you think this affects Earth’s temperature?

Human actions have increased the natural greenhouse effect.

Like a blanket on a sleeping person, greenhouse gases act as insulation for the planet. The warming of the atmosphere because of insulation by greenhouse gases. Greenhouse gases are the component of the atmosphere that moderate Earth’s temperatures.

Greenhouse Gases

Greenhouse gases include CO 2 , H 2 O, methane, O 3 , nitrous oxides (NO and NO 2 ), and chlorofluorocarbons (CFCs). All are a normal part of the atmosphere except CFCs. Table below shows how each greenhouse gas naturally enters the atmosphere.

Greenhouse Gas Where it Comes From
Carbon dioxide Respiration, volcanic eruptions, decomposition of plant material; burning of fossil fuels
Methane Decomposition of plant material under some conditions, biochemical reactions in stomachs
Nitrous oxide Produced by bacteria
Ozone Atmospheric processes
Chlorofluorocarbons Not naturally occurring; made by humans

Different greenhouse gases have different abilities to trap heat. For example, one methane molecule traps 23 times as much heat as one CO 2 molecule. One CFC-12 molecule (a type of CFC) traps 10,600 times as much heat as one CO 2 . Still, CO 2 is a very important greenhouse gas because it is much more abundant in the atmosphere.

Vocabulary

  • greenhouse effect : The trapping of heat by greenhouse gases in the atmosphere; moderates temperatures.
  • greenhouse gas : Gases that trap heat in the atmosphere. They include carbon dioxide, methane and CFCs.
  • insulation : A material that inhibits conduction of heat or electricity.

Summary

  • Greenhouse gases include CO 2 , H 2 O, methane, O 3 , nitrous oxides (NO and NO 2 ), and chlorofluorocarbons (CFCs).
  • greenhouse gases trap heat in the troposphere. Some greenhouse gases can trap more heat than others.
  • Levels of greenhouse gases in the atmosphere are increasing due to human activities.

Practice

Use this resource to answer the questions that follow.

http://www.hippocampus.org/Earth Science \rightarrow Environmental Science \rightarrow Search: Greenhouse Effects (first resource, starts with "About 50% of solar radiation...")

  1. How much solar radiation is absorbed by the surface of the Earth?
  2. What reflects the radiation?
  3. How is most radiation re-emitted?
  4. What is the net effect of this heating?
  5. What are the primary greenhouse gases?

Review

  1. What is insulation? What effect does insulation have on global temperature?
  2. What is the greenhouse effect?
  3. How does Earth's atmosphere resemble a greenhouse?

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Difficulty Level:

Basic

Grades:

6 , 7

Date Created:

Jan 04, 2013

Last Modified:

Sep 01, 2014
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