Lesson 9 Overview DRIVING QUESTION: What is the greenhouse effect and how does it affect Earth s surface temperature? LEARNING GOAL: Students develop and use models of the greenhouse effect to construct an explanation about the effects of greenhouse gases on the Earth s atmosphere. TOTAL TIME: 75 minutes LESSON SUMMARY: Students use different models (animation, computer simulation, diagram) of the greenhouse effect to learn how greenhouse gasses affect the temperature of Earth s atmosphere. Students use an animation to see what happens when heat energy reaches the Earth. Students then use a computer simulation to model what happens when the level of greenhouse gases in the atmosphere changes. Students develop their own model by drawing a representation of the process of the greenhouse effect. MATERIALS: Computers with access to the internet Greenhouse Effect simulation program LESSON 9: What is the greenhouse effect and how does it affect Earth s surface temperature? 1
BEFORE YOU BEGIN LESSON 9: Part 1 Please review the greenhouse animation used in Part 1, there are no special technology requirements for this animation, but you may wish to review it before introducing it to your students.note that there is a greenhouse effect feature that is missing from the animation, it does not show any heat energy (infrared radiation) leaving the Earth and its atmosphere. This is presented as a question for students to answer in the activity. Part 2 It is important to test the simulation program before beginning this lesson. To use the simulation, you must first download a java file onto students computers. The Simulation File can be downloaded from Resources in SPECIES. It is also available here: http://phet.colorado.edu/en/simulation/greenhouse. Further information on testing and using the simulation program can be found on page R4 in the Resources section of the teacher binder. Part 3 In Part 3 students create their own diagram of the greenhouse effect in their student notebooks. The following online educational video and website are recommended as supplemental resources for this lesson: NASA Earth s Energy Budget Poster: Available at: http://science-edu.larc.nasa.gov/energy_budget/ National Geographic Greenhouse Effect Interactive Video. Available at: http://environment. nationalgeographic.com/environment/global-warming/gw-overview-interactive/ Greenhouse Effect web page from LEARN: Atmospheric Science Explorers. Available at: http://www.ucar.edu/learn/1_3_1.htm LESSON 9: What is the greenhouse effect and how does it affect Earth s surface temperature? 2
Part 1: What is the Greenhouse Effect? Start the lesson by leading a class discussion about differences in atmosphere and temperature between the Earth and the moon. We know that light from the sun warms both the Earth and the Moon. The Moon is about the same distance from the Sun as the Earth, so it gets the same amount of light. Because they receive the same amount of light, we would expect them to have similar temperatures. But take a look at the extreme low and high temperatures for the Earth and the Moon: Earth: -89 C to 58 C Moon: -153 C to 107 C (a 50% larger range of temperatures!) Discussion Question: Why is Earth warmer than the Moon at night and cooler than the Moon during the day? What might explain this? Answer: The Moon is missing something important that the Earth has, an atmosphere, which is a blanket of gases that surround a planet, moon or other celestial body. Start this activity by showing students a short NOVA video about global warming and the greenhouse effect: http://www.teachersdomain.org/resource/phy03.sci.phys.matter.greenhouse2/ Follow this by having students work in pairs or groups to answer the questions below. LESSON 9: What is the greenhouse effect and how does it affect Earth s surface temperature? 3
Part 1: What is the Greenhouse Effect? Continue having students explore the Greenhouse Effect Animation and answering questions in pairs or groups. LESSON 9: What is the greenhouse effect and how does it affect Earth s surface temperature? 4
Part 1: What is the Greenhouse Effect? Lead a class discussion about the atmospheres of Venus, Mars, and Earth. Students should predict that Venus has more greenhouse gases in its atmosphere than Earth and that Mars has less. This is correct, but have students think about the distance of these planets from the sun. Maybe Venus is hot because it is closer to the Sun and Mars is cold because it is farther away? After discussing these points, have students open the Planets and Atmospheres Resource and continue the discussion. Venus is closer to the sun and Mars is further, but the distances don t explain temperature differences between the planets. It is a massive greenhouse effect on Venus and small greenhouse effect on Mars that explain the differences. The atmosphere of Venus is very dense and most of the atmosphere is made of greenhouse gas. The atmosphere on Mars is very thin and has very little greenhouse gas. Mars is so cold that two greenhouse gases, water vapor and carbon dioxide, are both frozen solid. LESSON 9: What is the greenhouse effect and how does it affect Earth s surface temperature? 5
Part 2: How does the greenhouse effect work? Walk students through the process of opening the simulation program on their computers. Students can watch the Simulation Instructions video in Resources for an example of how to use the simulator. Written instructions are included on SPECIES. LESSON 9: What is the greenhouse effect and how does it affect Earth s surface temperature? 6
Part 2: How does the greenhouse effect work? Students answer a set of questions about the photon absorption portion of the simulations. They then move on to the greenhouse effect portion of the simulation and observe changes in temperature with changes in greenhouse gases. LESSON 9: What is the greenhouse effect and how does it affect Earth s surface temperature? 7
Part 3: Greenhouse Effect Diagram Students use information from the previous activity to draw a diagram of aspects of the greenhouse effect. LESSON 9: What is the greenhouse effect and how does it affect Earth s surface temperature? 8
Part 3: Greenhouse effect explanation Students use their observations from the greenhouse effect simulation to answer the scientific question: What happens to the Earth s surface temperature if the level of carbon dioxide in the atmosphere increases? Simulation Extension Activity: The Greenhouse Simulation has a number of adjustable settings and there is much more that students can explore beyond what is required for this lesson. For instance, the Ice Age atmosphere setting has a different higher albedo (ice reflects more visible light). Additional questions include: What effect does adding clouds have? Is the effect of clouds different with high greenhouse gas levels than with low levels? Note that the simulation includes many more photons than are visible by default. You can see all of them with the View all photons checkbox at the bottom, but this makes it difficult to see how individual photons are absorbed or reflected. LESSON 9: What is the greenhouse effect and how does it affect Earth s surface temperature? 9