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Ch. 7.1 - Greenhouse Effect
and Global Warming
Dana Desonie, Ph.D.
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Printed: April 16, 2014
AUTHOR
Dana Desonie, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. Ch. 7.1 - Greenhouse Effect and Global Warming
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Ch. 7.1 - Greenhouse Effect
and Global Warming
Do polar bears belong in garbage dumps?
Changes due to warmer temperatures are becoming more visible. The Arctic is covered with ice less of the year, so
polar bears can’t hunt and are raiding garbage dumps for food. Extreme weather events are becoming more common
as weather becomes stranger. Sea levels are rising, which is a problem during storms.
The Greenhouse Effect
When sunlight heats Earth’s surface, some of the heat reflects back into the atmosphere, where it can be absorbed
by gases in the atmosphere. When the atmosphere traps heat, it is known as 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. Examples of greenhouse gases include
carbon dioxide (CO2 ), methane (CH4 ), ozone (O3 ) nitrous oxides (NO and NO2 ), chlorofluorocarbons (CFCs), and
water vapor. The table below shows how each greenhouse gas enters the atmosphere - notice that some greenhouse
gases come from natural sources, and some are from humans.
TABLE 1.1: Greenhouse Gas Entering the Atmosphere
Greenhouse Gas
Carbon dioxide
Methane
Where it Comes From
Respiration, volcanic eruptions, decomposition of plant
material, burning of fossil fuels
Decomposition of plant material under some conditions, biochemical reactions in stomachs
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TABLE 1.1: (continued)
Greenhouse Gas
Nitrous oxide
Ozone
Chlorofluorocarbons
Where it Comes From
Produced by bacteria
Atmospheric processes
Not naturally occurring - made by humans
Human actions in the past 100 years have increased the levels of greenhouse gases in the atmosphere (see figure
below). The added gases have caused the greenhouse effect to be greater than normal, which is affecting the Earth’s
temperature.
Global Warming
With more greenhouse gases trapping heat, average annual global temperatures are rising. This is known as global
warming.
Watch this NASA video about the basics of global warming science: Global Warming - How Humans are Affecting
our Planet: http://www.youtube.com/watch?feature=player_profilepage&v=VXvGPbHXxtc#! (7:58)
MEDIA
Click image to the left for more content.
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Chapter 1. Ch. 7.1 - Greenhouse Effect and Global Warming
Increasing Temperatures
In the past 10,000 years, global temperatures have risen slightly. However, the rate of increase has been more rapid
in the past century, and has risen even faster since 1990. The 12 warmest years on record have all occurred since
2001, and the 20 warmest years have occurred since 1987 (through 2011) ( Figure 1.1). The 2000s were the warmest
decade yet.
Between 1880 and 2010, the average global temperature has increased by about 0.8o C (1.5o F), according to the
Goddard Institute for Space Studies, NOAA. This number doesn’t seem very large. Why is it important?
FIGURE 1.1
Recent temperature increases show how
much temperature has risen since the
Industrial Revolution began.
Greenhouse Gas Emissions
The United States has long been the largest emitter of greenhouse gases, with about 20% of total worldwide
emissions in 2004. As a result of China’s rapid economic growth, its emissions surpassed those of the United States
in 2008. However, it’s also important to keep in mind that the United States has only about one-fifth the population
of China. What’s the significance of this? The average United States citizen produces far more greenhouse gas
emissions than a citizen from any other nation.
Watch this animation about CO2 released by different fossil fuels: http://www.nature.nps.gov/GEOLOGY/usgsnp
s/oilgas/CO2BTU_3.MPG
Watch this NASA animation of global temperature changes from 1884-2011:
http://www.nasa.gov/mp4/616923main_GISStemperature2011_withColorbar.mp4
Changes Due to Warming Temperatures
The Earth is experiencing many changes as global temperatures rise, including glaciers melting, vegetation zones
moving, and rising sea levels. This animation models climate-induced glacier change in Glacier National Park,
1850-2100: http://www.nrmsc.usgs.gov/research/glacier_model.htm . If fossil fuel use exploded in the 1950s, why
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do these changes begin early in the animation? Does this mean that the climate change we are seeing is caused by
natural processes and not by fossil fuel use?
With changing temperatures, the timing of events for species is changing. Mating and migrations take place earlier
in the spring months. Some species are moving to higher altitudes. Some agricultural regions are no longer able
to grow crops because they have become too warm or dry. Some other changes in organisms are see in the figures
below.
The following images show changes in the Earth and organisms as a result of global warming.
FIGURE 1.2
(a) Breakup of the Larsen Ice Shelf in Antarctica in 2002 was related to climate warming in the region. (b) The
Boulder Glacier has melted back tremendously since 1985. Other mountain glaciers around the world are also
melting.
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Chapter 1. Ch. 7.1 - Greenhouse Effect and Global Warming
FIGURE 1.3
Permafrost is melting and its extent decreasing. There are now fewer summer lakes in Siberia.
A number of videos on the National Geographic site have to do with global warming: http://video.nationalgeograp
hic.com/video/environment/global-warming-environment
• “A Way Forward: Facing Climate Change” - A no-nonsense look at global warming and what we can do about
it.
• “Antarctic Ice” - Describes the changes that are already happening to Antarctica and what the consequences
of future melting will be.
• “Glacier Melt” - Looks at melting in a large alpine glacier and the effects of glacier loss to Europe.
• “Greenhouse Gases” - Researchers look at the effects of additional greenhouse gases on future forests.
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• “Hamster-like Pika in Peril” - Researchers look for changes in the range of a mountain-top dwelling mammal,
the pika.
• “State of Polar Bears” - Shows how polar bears, in their specialized habitat in the Arctic, are among the species
already affected by warming temperatures.
Review Questions
Watch this video to help you answer Questions 1-7 below.
http://www.youtube.com/watch?v=oJAbATJCugs (3:03)
1. How much has the global temperature risen in the last few decades?
2. What contributes to global warming?
3. What is the greenhouse effect?
4. What is the evidence for global warming?
5. What was the warmest recorded year?
6. What gases have been recorded at their highest levels in history?
7. What do researchers predict will happen?
Critical Thinking
8. Why is it important to use average global temperature when talking about climate change and global warming?
9. What are some of the effects of global warming that are already being seen?
10. Do you believe that human activities are causing global temperatures to rise, or is there a different explanation
for this temperature increase? Give at least one piece of evidence to support your claim.
References
1. Robert A. Rohde/Global Warming Art. . GNU-FDL 1.2
2. (a) Courtesy of Ted Scambos, National Snow and Ice Data Center, NASA’s Earth Observatory (b) Peltoms. .
Both images under public domain
3. Courtesy of Jesse Allen, NASA’s Earth Observatory. . Public Domain
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