The Very Simple Climate Model Activity

Directions for the Teacher

Introduction

1. Ask students to share what comes to mind when they think about climate change in the future. Consider making a list of student ideas on the board.
2. Tell students that one thing scientists are studying is how fast the climate is changing. Share the following quote with students about the future of climate change:

   “Across the globe, in response to increases in heat-trapping gases such as carbon dioxide (CO₂) in the atmosphere, temperature and precipitation patterns are changing. The rate of climatic change in the next century is expected to be significantly higher than it has been in the past. At our current rate of emissions, the Intergovernmental Panel on Climate Change (IPCC) estimates that CO₂ levels in the atmosphere will double or triple during the next century, and the climate system will respond.”    -NOAA

   • Hold a brief discussion, asking students to share what they think the quote means.
3. Discuss the role of greenhouse gases, such as carbon dioxide, in recent climate change. Also discuss sources of greenhouse gas emissions, such as vehicle exhaust, generating electricity from burning coal and natural gas, and manufacturing.
4. Tell students that scientists use models to predict how Earth's climate will change in the future. Put simply, a computer model uses math to describe how the Earth works. Ensure that students have a good understanding of what a model is. Students could share examples of models that they are familiar with and compare them to computer models.

Interactive Activity: Part 1 - Learning how the model works

1. Tell students that they will use a model to answer the question: How will the amount of carbon emissions released into the atmosphere affect the climate during this century?
   • Consider posting this question on the board to reference throughout the lesson.
2. Project The Very Simple Climate Model for students to see. Ask students to share what they notice about the model (they should notice that all three lines on the graph are increasing over time). Introduce the variables to the left of the graph (see figure below) that students can manipulate as they run the model.
   • The carbon dioxide emissions rate is measured in gigatons of carbon dioxide per year.
   • The emissions rate is initially set at 10.5 gigatons of carbon per year, which was the actual rate during 2015.
   • The climate change sensitivity is initially set at 3 °C. The climate sensitivity represents the amount of temperature change estimated to occur when carbon dioxide doubles. There is some uncertainty about how the climate system will behave as carbon dioxide increases, so scientists test models with different climate sensitivities.
   • The recommended temperature limit line (15.81 °C) reflects 2 °C of warming above pre-industrial times, after which scientists predict life on Earth will be significantly impacted and it will be difficult to adapt.
   • Select the step forward button to advance the model by 5 year increments.
   • Select the play button to advance the model through the end of the century, 2100.
   • Select the reset button to restart the model from the year 2015.

3. Click the play button to see what will happen to Earth's temperature through the 21st century if each year we release the same amount of carbon dioxide into the atmosphere as we did in the year 2015 (10.5 GtC/yr).
   • Three points will appear on the graph for every five years of model time. The color of these points correlates with the colors of the three y-axis measures.
4. Discuss as a class what this graph is showing.
   • The blue circles (emissions rate) represent how much carbon we add to the atmosphere each year. Since the rate stayed the same for this model run, the blue circles form a horizontal line on the graph.
   • Black triangles represent how much carbon accumulates in the atmosphere over time. Units are "parts per million by volume" (ppmv). For reference, the actual concentration was 399.4 ppmv in the year 2015. In this run, the concentration rises from just under 400 ppmv to about 571 ppmv by the year 2100.
   • Red squares represent average global temperature in degrees Celsius. For reference, this value was around 14.65 °C in the year 2015. In this model run, the temperature steadily rose to about 16.2 °C by the year 2100. This surpassed the recommended temperature limit by 0.4 °C.
     • In this simple model, the temperature is determined entirely by the atmospheric CO₂ concentration via greenhouse warming of the atmosphere.
5. Give each pair of students a computer or tablet, and give them time to work through the three scenarios from the Future Climate: Explore the Possibilities page using The Simple Climate Modelsimulation.
   • You may wish to have students write down the answers to the questions that are asked throughout scenarios 1-3.
6. Remind students of the question that was posed at the beginning of Part 1: How will the amount of carbon emissions released into the atmosphere affect the climate during this century?
7. Hold a discussion to discover what students have learned about the relationship between CO₂ concentration and global average temperature.
   • Ask students to consider: “Why does temperature continue to rise even if emissions are decreasing?”
   • Have students share what they discovered from Scenario #3: How much do emissions need to decrease to stay below 2° C of warming?
     • Ask students to consider the importance of timing: Is a gradual reduction in emissions over time enough? Or do we need a rapid reduction to meet our goal?
8. Share that scientists expect temperatures to rise 3 °C every time the CO₂ concentration doubles (given a climate sensitivity of 3 °C, which scientists predict is likely). Discuss some of the effects that the warming climate has on people and ecosystems: drought, increased severity of hurricanes and tropical storms, extinctions, spreading or declining species ranges, sea level rise, etc.

Interactive Activity: Part 2 - Testing different scenarios of climate change

1. Tell students that the actions of humans are the largest unknown when it comes to future climate change. Survey student opinions about how people are likely to behave in the future:
   • Will we release the same amount of carbon dioxide into the atmosphere that we do now?
   • Will we release less?
   • Will we release more?
2. Brainstorm how and why carbon emissions may change in the future. For example, as the global population increases, so does the demand for energy. Carbon emissions will go up if more power plants are created that burn fossil fuels, yet carbon emissions will go down if more technologies are invented that reduce the use of fossil fuels.
3. Based on the survey and brainstorms, have students work in groups to come up with a scenario that they would like to test using the model. (Example: carbon dioxide emissions rise through the middle of the 21st Century, and then decline after that.) To be somewhat realistic, they should start with emissions around 10.5 GtC/yr since that is what it was in the year 2015.
   • To help students focus as they run the model, have each group come up with a question that their scenario will answer.
   • Have each group describe their scenario in a paragraph before they begin.
4. After investigating their question with the model, have each group prepare a five minute presentation about their scenario to share with the class during the next class period. They should create 1-2 slides or a poster as a visual aid. Their presentation should include:
   • The question they are trying to answer
   • A description of the scenario they tested with The Very Simple Climate Model
   • An explanation of what the model showed and what it means
   • What new questions they have as a result of their investigation, and/or what steps they could take next to go further

Interactive Activity: Part 3 - Sharing what we have learned with our peers

1. Each group should take turns presenting their scenario to the class. Allow time for questions & answers following each presentation, if possible.
2. Discuss as a class the results of various student scenarios:
   • What happened to temperature and carbon dioxide concentrations over time?
   • Is some global warming inevitable?
   • Which scenario had the least warming? Which had the most?
3. Discuss the limitations of The Very Simple Climate Model. Ask students to consider where The Very Simple Climate Model is accurate and also where it is oversimplified.
   • As a simplified model, many factors that influence climate such as changes in clouds and weather, changes in the amount of sea ice (which reflects sunlight), changes in air pollution and aerosols, changes in the amount of forests (which pull carbon out of the atmosphere), the effects of other greenhouse gases, or where CO₂ is in the atmosphere are not considered here.
4. If you have time, share an example of a more complex model of climate change used by scientists. Consider one or more of the model visualizations provided below, comparing/contrasting them with the Simple Climate Model used in this activity.

Climate model visualization options:

• Present and Future Climate in a Global Model
• Climate Change as Simulated by the NCAR Community Earth Systems Model
• Annual CCSM4 Global Surface Temperature Anomaly, 1850-2100
• Planetary Water Vapor

*Note: The above model visualizations show model data through time and across geography. The model data presented in The Simple Climate Model included global averages so there is change over time but no change across geography. To avoid confusion, ask students to focus on the different types of data that the models are showing. Ask students to imagine how the data in the Simple Climate Model might look as a visualization (increases in temperature could be shown as a change in color, for example).