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Lesson 1
Climate factor: Greenhouse Gases
At a Glance
Focus: Students use an experiment with the greenhouse gas water vapor to observe the
greenhouse gas effect, gain an appreciation for the importance of greenhouse gases in
warming the Earth, and learn how levels of greenhouse gases have changed through time.
Major Concepts:
 Greenhouse gases help regulate the Earth’s climate – they are very important for life
on Earth!
 CO2 is an important greenhouse gas that has a long correlation with Earth’s
temperature through glacial and interglacial periods.
 Humans have increased the amount of CO2 in the atmosphere due to burning of fossil
fuels and land use change, which plays a major role in driving of current climate
change.
Prerequisite Knowledge: Students should be familiar with at least some factors that
regulate the global climate system and perhaps have an idea of the Earth’s energy
balance. Students should be able to make hypotheses and predictions and plot data on a
graph.
Wyoming Science Standards Addressed:
8.2.2 Students use inquiry to conduct scientific investigations.
Ask questions that lead to conducting an investigation
Collect, organize, and analyze and appropriately represent data
Draw conclusions based on evidence and make connections to applied scientific
concepts
Clearly and accurately communicate the result of the investigation
8.1.9 Students systematize the Earth’s history in terms of geologic evidence, comparing
past and present Earth processes and identifying catastrophic events and fossil evidence.
11.1.7 Geochemical Cycles: Students describe the Earth as a closed system and
demonstrate a conceptual understanding of the following systems: geosphere,
hydrosphere, atmosphere, and biosphere. Students explain the role of energy in each of
these systems, such as weather patterns, global climate, weathering and plate tectonics.
Introduction
This is taken directly from a background essay found at Teacher’s Domain: “Global
Warming: The Physics of the Greenhouse Effect”
http://www.teachersdomain.org/resources/phy03/sci/phys/matter/greenhouse2/index.html
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
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.
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, Hawaiʻ i and Earth
System: Ice and Global Warming.
Materials & Preparation
You will need the following materials to conduct these activities:
 Overheads of graphs, or capability to show computer simulations
 three thermometers
 two clear glass jars that will fit over the thermometers
 heat lamp
 paper towels and glass of water
 Large graph paper with the axes pre-drawn and posted in the front of the room
 One clock or stopwatch to time measurement intervals
Procedure
1. Begin by asking the class what they know about greenhouse gases. After students
explain what they know, show a demonstration of the greenhouse effect with either a
computer simulation or overhead diagram. Be sure students can understand the
concept of an Energy balance (energy is not created or destroyed, but can change
forms, be reflected, absorbed, or reemitted) and identify where short wave and long
wave radiation fit in.
2. Have students name some of the greenhouse gases: CO2, H2O vapor, CH4, N2O
Ask the question: What would the Earth be like if we did not have these gases in our
atmosphere? (Greenhouse effect warms the Earth approximately 33 degrees
Celsius, that’s 91.4 degrees Fahrenheit!
3. Tell the students: Now we will begin an experiment to test the greenhouse gas
effect.
Be sure that the thermometers all read the same room temperature. Cover two
thermometers with glass jars, leaving one thermometer uncovered. Students should place
a wet paper towel inside one of the two jars. Use water at room temperature to wet the
paper towel. (In this experiment, the water vapor will act like a greenhouse gas and
increase the temperature in the jar with the wet paper towel even more than the
temperature in the dry jar.) Continue with the lesson, but have students periodically check
all three thermometers and record the temperature and time on the graph at the front of
the room.
3. Ask the students if they can recall any time in Earth’s history where organisms
shaped the atmosphere. How do organisms shape the atmosphere today?
Remind students that the original Earth’s atmosphere did not have oxygen in it. It
is only the result of cyanobacteria (photosynthetic bacteria) that the Earth’s atmosphere
became oxygenated.
4. Discuss carbon dioxide: how does this cycle into and out of the atmosphere?
Plants take up CO2 during the growing season, and decomposition and respiration put
CO2 back into the atmosphere. Other sources of CO2 are forest fires, burning of fossil
fuels, and exchange with the oceans (both source and sink of CO2). Show the graph of
CO2 with oscillations corresponding with growing season CO2 sinks from Mona Loa and
have students identify where these growing seasons occur.
Suggest the thought question: Would this graph look different if the measurements
were taken somewhere along the equator? (As long as there are growing season
changes: wet and dry season, or summer and winter, there will be changes, but if a place
is fairly aseasonal, these changes will be less dramatic)
5. Put up the graph of the history of CO2 during glacial and interglacial history.
Discuss the patterns, and how glacial periods correspond with low CO2 in the
atmosphere… what was the Earth’s climate like during these times? Now point to
interglacial periods… what was the Earth’s climate like then?
6. Put up the graph of recent CO2 concentrations in the atmosphere… what
happened around 1850 that could make the CO2 concentration begin to rise? Does
this match the pattern with average temperatures as well?
Interesting fact: Many cities now monitor the composition of atmospheric gases
throughout the year, and peaks can be seen during rush hour traffic, and even on
weekends in the summer when many people are outside mowing their lawns! These
observations have led some states, like CA, to push for tougher emissions laws on
cars and small engines to improve air quality and try to decrease greenhouse gas
emissions because of global warming.
7. What does the graph look like from the greenhouse gas experiment? Was it
different for the two jars? How did the temperature change over time?
**This lesson was adapted from a lesson on climate change from Teacher’s Domain
(Global Climate Change: Understanding the Greenhouse Effect), here are some
great references that they provide with background and other great video clips and
visuals.
Lots of great graphs here:
http://en.wikipedia.org/wiki/User:Dragons_flight/Images
Climate Change:
http://www.teachersdomain.org/resources/ess05/sci/ess/watcyc/climatechange/index.html
Greenland Ice Sheet Project 2: A Record of Climate Change:
http://www.teachersdomain.org/resources/ess05/sci/ess/watcyc/greenland/index.html
Natural Climate Change in Djibouti, Africa:
http://www.teachersdomain.org/resources/ess05/sci/ess/watcyc/naturalchange/index.html
Global Warming: Carbon Dioxide and the Greenhouse Effect:
http://www.teachersdomain.org/resources/phy03/sci/ess/watcyc/co2/index.html
CO2 Concentrations at Mauna Loa Observatory, Hawaiʻ i:
http://www.teachersdomain.org/resources/ess05/sci/ess/watcyc/maunaloadata/index.html
Earth System: Ice and Global Warming:
http://www.teachersdomain.org/resources/ess05/sci/ess/earthsys/esglaciers/index.html
Or: