Digital Media for the Classroom
and Professional Development
GLOBAL WARMING: THE PHYSICS OF THE GREENHOUSE EFFECT
Video Summary
Earth’s relatively stable and hospitable
average temperature is the result of a
phenomenon called the greenhouse
effect. The presence in the atmosphere
of naturally occurring compounds,
known as greenhouse gases, maintains
Earth’s temperature. This video segment
adapted from NOVA/FRONTLINE
www.teachersdomain.org/resource/phy03.sci.phys.matter.greenhouse2
describes how human activities are
increasing greenhouse gas concentrations and explains what effect this might have on
global temperatures.
Topics Covered:
– Earth and Space Science:
Recommended for Grades 6-12
Media Type: QuickTime Video
Water Cycle, Weather, and Climate
Video Length: 2m 15s
Earth System, Structure, and Processes
Permitted use: Download, Share
– Physical Science: Matter, Energy
Media Available for Purchase: Buy this full program on DVD
This media resource can be used only for non-commercial, educational purposes.
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Discussion Questions
 What is the greenhouse effect?
 Explain why the average temperature on Earth would be 0 degrees
Fahrenheit without the layer of greenhouse gases.
 What natural phenomena produce greenhouse gases?
 What are some everyday activities that result in carbon dioxide being
released into the air?
 Explain the relationship between increased amounts of carbon dioxide in
the atmosphere and global warming.
Background Essay
Scientific evidence has convinced most experts that there is a connection between global
warming and human activities. Since the start of the Industrial Revolution, the average
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temperature of the planet has increased by slightly less than one degree Celsius to its present
level of about 16°C (60°F). This seemingly insignificant change represents a fairly rapid
warming trend. According to the UN-sanctioned Intergovernmental Panel on Climate Change,
by the end of the twenty-first century, Earth’s inhabitants will be facing temperatures that are
at least two degrees Celsius—and possibly as much as six degrees —warmer.
To understand how human activities might cause global warming, we must first explore
why our planet is warm in the first place. As solar radiation from the Sun reaches Earth’s
surface, some of it is reflected back into space and some of it is absorbed. The absorbed
energy warms Earth’s surface, which in turn radiates the energy back toward space.
Molecules in the atmosphere, known as greenhouse gases, absorb some of this outgoing
energy and radiate a portion of it back to Earth’s surface. Through these two actions,
they slow the escape of heat and keep Earth warmer than it would be otherwise.
When the concentration of greenhouse gases in the atmosphere increases, the
atmosphere is capable of absorbing more energy. As a result, the planet warms up—until
it reaches the temperature at which it again radiates just enough energy to keep the
temperature stable. The higher the concentration of greenhouse gases in the atmosphere,
the warmer the planet becomes before it reaches the point at which it radiates all the
energy it receives and the temperature again stabilizes. Consequently, an increase in
greenhouse gas concentrations—whether as the result of natural causes or human
activities—causes the average global temperature to rise.
Scientists have documented changes in atmospheric carbon dioxide (CO2), one of the
four most important greenhouse gases, over the past 400 million years. Their findings
show a strong correlation between CO2 concentrations and global climate over
geological history. Of course, atmospheric and climate changes in Earth’s distant past
have been unrelated to human activities. Most peaks in atmospheric carbon dioxide
concentrations, for example, are attributed to the movement of carbon stored on Earth’s
surface — on land and in oceans — into the atmosphere through natural processes such as
volcanic eruptions. However, scientists have found no such natural causes for the
dramatic increase in CO2 observed since the Industrial Revolution.
Instead, human activities are the main source of CO2 and other greenhouse gases. Burning
wood and fossil fuels such as gas, coal, and oil contributes carbon dioxide; livestock and
coal production add methane; and agricultural and industrial processes add nitrous oxide.
While oceans and land plants absorb a portion of these gases, the rest accumulate in the
atmosphere, where they strengthen the greenhouse effect and cause the average global
temperature to increase.
To learn more about evidence of regular, extreme climate change throughout Earth’s
distant past, check out Climate Change, Greenland Ice Sheet Project 2: A Record of
Climate Change, and Natural Climate Change in Djibouti, Africa.
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To learn more about the role CO2 plays in Earth’s temperature, check out Global
Warming: Carbon Dioxide and the Greenhouse Effect.
To learn more about evidence suggesting a link between human activities and global
warming, check out CO2 Concentrations at Mauna Loa Observatory, Hawai’i and Earth
System: Ice and Global Warming.
Lesson Plans Using This Resource:
– Development of a Habitable Planet
– Global Climate Change: Understanding the Greenhouse Effect
Curricular Standards Correlations:
NSES, Project 2061, MCREL, and state standards correlations available at
www.teachersdomain.org. (Free registration required for your specific state standards correlated to this resource.)
Source: FRONTLINE/NOVA: “What’s up with the Weather?”
Attribution to be distributed with this media asset: Global Warming: The Physics of the Greenhouse Effect.
Downloaded from Teachers’ Domain, www.teachersdomain.org.
©2000 WGBH Educational Foundation. All Rights Reserved.
Collection developed and produced for Teachers’ Domain by:
Collection funded by:
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