Human Energy Systems | Activity 3.2

Target Student Performance

Students use a computer simulation to explain how carbon dioxide absorbs visible light and emits infrared radiation—the Greenhouse Effect.

Resources Provided

3.2 The Greenhouse Effect Reading
3.2 The Greenhouse Effect Simulation Worksheet
3.2 Grading The Greenhouse Effect Simulation Worksheet
Greenhouse Effect PhET simulation: https://phet.colorado.edu/en/simulation/greenhouse
Optional data (“Global Warming's Six Americas”) of attitudes toward climate change: https://www.americanprogress.org/issues/green/reports/2009/05/19/6042/global-warmings-six-americas/

Recurring Resources

Questions, Connections, Questions Student Reading Strategy

Setup

Prepare enough copies of the 3.2 The Greenhouse Effect Reading for each student to have one. Prepare enough copies of the 3.2 The Greenhouse Effect Simulation Worksheet for each pair or team of students. Download the PhET Simulation on the computers used by students by going to this link: https://phet.colorado.edu/en/simulation/greenhouse

Note that you may need to modify the security preferences on some computers in order to open the simulation.

Directions

1. Introduce the activity.

Tell students we spend a lot of time discussing the Keeling Curve in this unit, but why is this important? Ask students for their initial ideas: “Does anyone have an idea about why scientists might care so much about the Keeling curve?” It is important for understanding how increasing CO₂ in the air is connected to global climate change.

2. Introduce the reading.

Tell the students that the scientific community is concerned about the rising concentrations of CO₂ and what this means for the global atmospheric and oceanic temperatures, sea level, and how this might change the climate.

To understand why scientists are concerned, we have to talk about two things: the greenhouse effect and fossil fuels.

3. Have students complete the reading in small groups.

Give each student a copy of the 3.2 The Greenhouse Effect Reading. Before they complete the reading in small groups, inform students that they will be using this reading to better understand the greenhouse effect.

Instruct students to be prepared to explain the greenhouse effect as a group once they have completed the reading, and that they should work together as a team to come up with an explanation.

Have students read 3.2 The Greenhouse Effect Reading using the Questions, Connections, Questions Student Reading Strategy. See the
Questions, Connections, Questions Reading Strategy Educator Resource document for information about how to engage students with this strategy.

Once all student teams have had sufficient time to complete this activity, work as a class to explain mechanism of the greenhouse effect. Stress that the greenhouse effect is a naturally occurring phenomenon that keeps our planet warm and allows us to survive. This is different from global warming and climate change, which are caused by humans.¹Although the greenhouse effect is naturally occurring, the human-caused amplification of the greenhouse effect is not “natural.” Be sure to clarify the central idea that a greenhouse gas allows light energy (photons) to pass through the atmosphere but slows the loss of infrared radiation by absorbing and re-emitting some of that radiation back towards the surface of the earth.

Teacher Note:
“Light energy” from the sun refers to the sun’s electromagnetic radiation, which includes ultra violet radiation (among others). Ultraviolet radiation is shortwave and can pass through the atmospheric particles without getting trapped.

Explain that Light energy from the sun interacts with the earth’s surface, and is returned to the atmosphere in the form of infrared, or long-wave radiation. Some of this energy is trapped by greenhouse gases, which keeps the earth warm. Some goes back to space. When greenhouse gases trap infrared radiation, the planet stays warm.

Teacher Note: There are other greenhouse gases. In this unit, we focus mainly on carbon dioxide because this is the most important greenhouse gas and a product of fossil fuel combustion. Other greenhouse gases include methane, nitrous oxides, fluorinated gases, water, and others.

¹It is possible that some students will challenge the claim that climate change is caused by humans by pointing to natural cycles in the Earth’s history, claiming that the current highs are due to this natural cycle. Try to help them understand that part of what they are saying is true: Earth does have a history of CO₂ and temperature fluctuations. However, this does not contradict the scientific evidence for anthropogenic climate change: the current increase of CO₂ and other greenhouse gases in the atmosphere is a result of human use of fossil fuels and deforestation, which has caused the global temperature to rise 0.8° C (1.4° F) since 1900. That might not sound like a lot, but that is almost 10x faster than any other naturally occurring warming period in Earth’s history.

4. Have students complete 3.2 The Greenhouse Effect Simulation Worksheet.

For this activity, students will need access to a computer. It is advisable that you download the PhET simulation in advance. To do so, following this link and select download: https://phet.colorado.edu/en/simulation/greenhouse (Depending on the settings on students’ computers, they may need to go to System Preferences to give permission for the computer to run the simulation software.)

Give each student pair or team a copy of the 3.2 The Greenhouse Effect Simulation Worksheet. Have them use the printed instructions to complete the activity (you may prefer to provide a sample demonstration of how the program works using an overhead projector). Instruct students to complete the worksheet as they are using the simulation.

5. Discuss the Worksheet Questions.

After students have had sufficient time to complete the activity, have them prepare to address the three main questions as a team for the class.

Allow students to take a few minutes to review these questions as a group and then randomly select a couple of student teams to provide their response to each of the following:

How do different gases in the atmosphere interact with light?
How do gases in the atmosphere affect the Earth’s temperature?
Why is the Keeling Curve important?

6. Discuss how fossil fuels affect the earth’s temperature.

Explain that combustion of fossil fuels releases carbon dioxide, which is a primary greenhouse gas. Ask students if they can think of ways we use these fossil fuels in our daily lives.

7. (Optional). Have students review data about attitudes toward climate change and dig deeper into the greenhouse effect.

Review the Global Warming’s Six Americas data with students focusing on the graphs and figures. Discuss where students fall: Alarmed, Concerned, Cautious, Disengaged, Doubtful, or Dismissive. This discussion will allow you to assess the range of attitudes towards climate change in your classroom at the beginning of the unit.

You can also use the resources in Extending the Learning below (included in the Digging Deeper section of the reading) to help students develop a deeper understanding of the greenhouse effect.

7. Have students complete an exit ticket.

Conclusions: How does carbon dioxide interact with visible light and infrared radiation?

Predictions: How do you think that carbon dioxide affects the Earth’s temperature?

On a sheet of paper or a sticky note, have students individually answer the exit ticket questions. Depending on time, you may have students answer both questions, assign students to answer a particular question, or let students choose one question to answer. Collect and review the answers.

The conclusions question will provide you with information about what your students are taking away from the activity. Student answers to the conclusions question can be used on the Driving Questions Board (if you are using one). The predictions question allows students to begin thinking about the next activity and allows you to assess their current ideas as you prepare for the next activity. Student answers to the predictions question can be used as a lead into the next activity.

Assessment

Listen for students’ initial ideas about how atmospheric CO₂ and temperature are connected. Do they see a causal relationship? At this point, they may have many unanswered questions about how increasing greenhouse gases in the atmosphere lead to climate change. However, at the end of this activity, they should have a good understanding of how increasing greenhouse gases in the atmosphere lead to warmer temperatures as a result of the greenhouse effect. If the students are still having trouble making this connection, you may want to show the students different models of the greenhouse effect that help explain this phenomenon.

Tips

If you choose to have students take the optional survey in step 7, you may want to ask students to turn in their results anonymously. This will give you an assessment of the range of attitudes in your classroom but will not stigmatize individuals based on their profile results.

Differentiation

Allow students to work in pairs or groups to complete the PhET simulation.
Go through the PhET simulation as a whole class, completing the worksheet together.
Provide sentence stems for students to complete the questions on the worksheet.

Modifications

Ask students to share with the class their ideas about why increasing levels of carbon dioxide in the atmosphere is related to additional Earth systems other than temperature (e.g., sea level rise, arctic sea ice melt).

Extending the Learning

Encourage students to watch for references to climate change or global warming in the newspapers, magazines, and other media. Ask them to be “critical consumers,” and to consider the sources of the information. Does the author/speaker provide evidence to support the claim? What evidence does the author/speaker provide?

Advanced students may find it interesting to research differences on the Earth in the past when carbon dioxide levels and temperature were at their highest. What animals and plants lived on the Earth then? What was the climate like?

Some students may have questions about how infrared radiation interacts with greenhouse gas molecules to produce heat. Although we do not go into this amount of detail in this unit, students may find these resources helpful:

website has an animated GIF that models infrared radiation and molecule vibration. It uses “absorption-emission-absorption” and vibrations to explain this phenomenon. https://scied.ucar.edu/carbon-dioxide-absorbs-and-re-emits-infrared-radiation
This website from the American Chemical Society explains the phenomenon in more advanced terms, including the Global Warming Potential for each greenhouse gas molecule: http://www.acs.org/content/acs/en/climatescience/greenhousegases/properties.html
For more information about how this creates a feedback loop, see this website from the American Chemical Society: http://www.acs.org/content/acs/en/climatescience/atmosphericwarming/climatsensitivity.html
This 10 minute video of Richard Feynman explaining “jiggling atoms” might be helpful for students trying to understand how radiation interacts with atoms to produce heat: https://www.youtube.com/watch?v=NsdCzujHqAk