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

Recurring Resources


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:

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


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.


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.


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.

  • 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.

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: