Greenhouse Effect
Dana Desonie, Ph.D.
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Printed: September 10, 2014
AUTHOR
Dana Desonie, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. Greenhouse Effect
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Greenhouse Effect
• Describe the greenhouse effect.
• Explain how human actions contribute to the greenhouse effect.
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 ( Figure 1.1). The added gases have
caused a greater greenhouse effect. How do you think this affects Earth’s temperature?
FIGURE 1.1
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
is because of insulation by greenhouse gases. Greenhouse gases are the component of the atmosphere that moderate
Earth’s temperatures.
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Greenhouse Gases
Greenhouse gases include CO2 , H2 O, methane, O3 , nitrous oxides (NO and NO2 ), and chlorofluorocarbons (CFCs).
All are a normal part of the atmosphere except CFCs. The table below shows how each greenhouse gas naturally
enters the atmosphere ( Table 1.1).
TABLE 1.1: How Greenhouse Gases Enter the Atmosphere
Greenhouse Gas
Carbon dioxide
Methane
Nitrous oxide
Ozone
Chlorofluorocarbons
Source
Respiration, volcanic eruptions, decomposition of plant
material; burning of fossil fuels
Decomposition of plant material under some conditions, biochemical reactions in stomachs
Produced by bacteria
Atmospheric processes
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 CO2 molecule. One CFC-12 molecule (a type of CFC) traps 10,600 times as much heat as one
CO2 . Still, CO2 is a very important greenhouse gas, because it is much more abundant in the atmosphere.
Vocabulary
• greenhouse effect: 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: Material that inhibits conduction of heat or electricity.
Summary
• Greenhouse gases include CO2 , H2 O, methane, O3 , nitrous oxides (NO and NO2 ), 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.
Explore More
Use the resource below to answer the questions that follow.
• What is Greenhouse Effect? at http://www.hippocampus.org/Earth Science → Environmental Science →
Search: Greenhouse Effects (first resource, starts with "About 50% of solar radiation...")
1.
2.
3.
4.
5.
How much solar radiation is absorbed by the surface of the Earth?
What reflects the radiation?
What type of energy waves are re-emitted into atmosphere?
What is the net effect of this heating?
What are the primary greenhouse gases?
Review
1. What is insulation? What effect does insulation have on global temperature?
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Chapter 1. Greenhouse Effect
2. What is the greenhouse effect?
3. How does Earth’s atmosphere resemble a greenhouse?
References
1. Courtesy of Will Elder, National Park Service. Diagram of the natural and human enhanced greenhouse effect.
Public Domain
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