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 theQuestions, 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.