Climate changes have occurred throughout Earth's history, with dramatic consequences to the organisms that live there. Although some climate changes are a part of Earth's natural cycles, others are the byproduct of human activity. Many of these activities benefit society. However, there is a trade-off in that these activities can have an adverse effect on global climate. Global warming is of particular concern, as evidenced by the increasing levels of carbon dioxide (CO2 ) in the atmosphere. So at what point do the liabilities of these activities outweigh the benefits? And can individual actions make a difference? In this lesson, students conduct an experiment to learn about CO2 levels found in four different gases. Then they reflect on CO2 production on a global scale. They also look at evidence of global warming in our environment, and consider their own role in contributing to global warming.
(Note: This is the second of two global climate change lesson plans. You may want to precede this lesson with Global Climate Change: Understanding the Greenhouse Effect Lesson Plan.)
- Understand how atmospheric levels of CO2 relate to climate change and global warming.
- Explore the effects of global warming on the environment, as indicated by the changes in Earth's glacial ice.
- Consider the human contributions to global warming, particularly from the use of automobiles.
Grade Level: 9-12
- Three to four class periods
- CO2 Concentrations at Mauna Loa Observatory, Hawaiʻi Document
- Global Warming: Graphs Tell the Story Document
- Earth System: Ice and Global Warming Video
- Mountain of Ice: If the Ice Melts Interactive
- Snapshot of U.S. Energy Use Video
- Journals for recording observations and answering questions
- Family Mileage Record Worksheet Document
- Family CO2 Contribution Worksheet Document
- Bringing the Greenhouse Effect Down to Earth Worksheet (Teacher Version) Document
- Bringing the Greenhouse Effect Down to Earth Worksheet (Student Version) Document
For each team of two to four students:
- 5 vials or test tubes
- 1 graduated cylinder
- 1 funnel
- 1 straw
- 1 marble-size piece of modeling clay
- 4 different-colored balloons
- 4 twist ties
- 1 narrow-neck bottle (the neck should be narrow enough for a balloon to fit over it)
- 1 dropping bottle of bromthymol blue indicator solution
- 1 dropping bottle of dilute household ammonia (1 part ammonia to 50 parts distilled water)
- 100 mL vinegar
- 5 mL baking soda
- Safety goggles to wear at all times
Before the Lesson
If possible, arrange computer access for all students to work in pairs.
Make copies of all worksheets. Note: You may want to distribute the Family Mileage Record Worksheet Document at the beginning of the lesson, to give students sufficient time to estimate how many miles each family member drives for the activity in Part II.
Gather all materials for the activity in Part I. Be sure to read through the entire activity in advance, to determine what you need to prepare beforehand (e.g., filling balloons with car exhaust).
Part I: What Is Global Warming?
1. Tell students that this lesson will begin with an activity that compares the variable amounts of CO2 found in four different gases, namely, the air, our breath, car exhaust, and the product of a chemical reaction between baking soda and vinegar. Divide the class into groups of two to four, and distribute the Bringing the Greenhouse Effect Down to Earth Worksheet (Student Version) Document . Before they get started, remind students to use caution with all materials and to wear safety goggles at all times.
Note: This activity was adapted with permission from an early draft version of "Sampling Carbon Dioxide," in Chapter 5, pages 44-47, of the book Climate Change in the Global Systems Science (GSS) project series. Copyright 2004 by the Regents of the University of California. The latest version can be found at Global Systems Science . The GSS project materials are produced by the Lawrence Hall of Science, University of California, Berkeley.
2. Now that students have explored CO2 levels found in different gases, they can begin to examine CO2 levels on a more global scale. Show students the graph in the CO2 Concentrations at Mauna Loa Observatory, Hawaiʻi Document , also known as the Keeling Curve. Discuss the following questions as a class. The discussion should lead students to the idea that the increase in CO2 as seen in this data may indicate that increasing human dependence on burning fossil fuel for energy is affecting the atmosphere on a global scale. This will tie in to the next resource.
- Describe the trend in the levels of CO2 in the atmosphere over the past 50 years.
- By what percentage has the concentration of CO2 in the atmosphere increased since 1958?
- Note the periodic oscillation (zigzag pattern) in the concentration of CO2. How do scientists distinguish between "normal" oscillations and a departure? What is the time period of each oscillation? What could cause these oscillations? (Note: The answer is the loss of foliage in the Northern Hemisphere during the winter months. However, this may not be obvious to students because they know it is summer in the Southern Hemisphere at this time. They may need help understanding that, because there is so much more foliage in the Northern Hemisphere than in the Southern Hemisphere, the loss of that foliage is significant enough to cause the drop in CO2 from its level during the summer months.)
- Why is this periodicity important to interpreting the data?
- Why is Hawaii one of the more ideal locations to collect atmospheric CO2 as a model of the concentration for the world?
- How does this data collected at Mauna Loa tie in to scientists' recent predictions about climate change and global warming?
3. Continue the discussion of the relationship between climate change and global warming by showing students the Global Warming: Graphs Tell the Story Document . Discuss the following questions:
- Do you think that the graphs provide evidence of a correlation between human use of fossil fuels and the temperature and CO2 levels in the atmosphere? If so, which graphs show evidence of a correlation?
- Should we be concerned about the changes that are occurring in the environment due to technology? Why or why not?
4. The effect of global warming on our environment can be seen most dramatically by looking at glaciers and ice caps. Have students work in pairs and watch the Earth System: Ice and Global Warming Video . Ask students to answer the following questions in their journals:
- Why are glaciers indicators of climate change?
- Some of the factors that affect input and output of a glacier are temperature, precipitation, humidity, and reflectivity. Which appears to be the most important? Why?
- List some reasons why a decrease in glacial ice could increase the temperature of Earth.
5. Bring the class back together and have students share some of their responses to question (c) in Step 4. Then show students the Mountain of Ice: If the Ice Melts Interactive . Discuss the following questions:
- Why does this resource show how these areas looked 20,000 years ago? What was the climate like at that time (where was all the water)?
- In what ways does sea ice serve as a "canary in the mine shaft"? In other words, how does it serve as a warning system?
- What is the worst-case scenario for the world in these diagrams? How would you measure the volume of ice, and how would you calculate the rise in sea level?
- Imagine that by 2100, the sea level has risen 2 feet. What effects would this have on humans? List and explain as many as you can think of.
- How are the changes in sea ice a good example of a positive feedback cycle? (The cycle is as follows: The less ice there is, the greater the absorption of solar radiation, the higher the temperature, and the more ice that continues to melt — and vice versa.)
Part II: Human Contribution to Global Warming
6. Tell students that they will now look closer at human contributions to global warming by examining the use of fossil fuels. Break the class into pairs or small groups and have them watch the Snapshot of U.S. Energy Use Video . (Note: This video jumps into a discussion of power plants. You may wish to tell students that the first few lines are talking about how power plants are online and operating 24 hours a day to meet the demand for electricity.) Have students discuss the following questions in their groups and record responses in their journals.
- What are some of the energy sources used to meet humans' ever-increasing demand for power?
- What are some ways that we release CO2 into the atmosphere every day?
- On the average, each person in the United States produces over 20 tons of CO2 each year; collectively, this country produces 25 percent of all CO2 released into the atmosphere worldwide. Should the United States reduce its energy use? Why or why not? How much of the personal 20 tons per year is due to automobile usage?
7. Tell students that they will now calculate how much CO2 their family contributes to the atmosphere each year — just from vehicle use. Divide the class into small groups and ask them to take out the Family Mileage Record Worksheet Document they used to estimate how much their family drives or rides in a typical week. Students will use this data to calculate how much CO2 their family produces in a year. Distribute the Family CO2 Contribution Worksheet Document to students. Tell them to complete their calculations, and then have them answer the following questions:
- How much CO2 does your family contribute to the atmosphere in a year? How does this compare to the 20 tons produced on average by each person in the U.S.? (Keep in mind that you are comparing family usage to individual usage. You may want to first calculate how much each person in your family uses on average, then compare it to the national figure.)
- How might you and your family reduce the amount of CO2 that you generate? Note: Students may focus on the type of car(s) that their family owns — a factor that is often out of their control. Help them move toward other ideas, such as carpooling (dividing the family mileage by the number of people in the carpool), making fewer trips to the grocery store, walking, etc.
- If time allows, asks students to calculate how much their ideas from (b) could reduce the amount of CO2 their family generates.
Extension Activity (Optional)
8. As an optional activity, have students research and write a report about how the pattern of temperature change where they live is similar to or different from global temperature change patterns. Encourage them to include local data as well as national and worldwide data. Several good Web sites for research include the National Weather Service , Unisys Weather , and the National Climatic Data Center . You may want to begin by giving students the following information:
- Since the beginning of the twentieth century, Earth's mean surface temperature has increased by about 1.1°F (0.6°C).
- Over the last 40 years — which is the period with the most reliable data — the temperature increased by about 0.5°F (0.2-0.3°C).
- Warming in the twentieth century is greater than at any time during the past 400 to 600 years. Seven of the ten warmest years in the twentieth century occurred in the 1990s. In fact, the hottest year since reliable instrumental temperature measurements began was 1998, when global temperatures spiked due to one of the strongest El Niños on record.
Check for Understanding
Have students discuss the following:
- What has been the trend in recent atmospheric CO2 levels? What is likely causing this trend? How do the CO2 levels relate to climate change and global warming?
- How are glaciers indicators of climate change?
- List some of the ways in which human activities are contributing to global warming.
- If global warming continues into the coming centuries, what are some consequences predicted by models?
The Digital Library for Earth System Education (www.dlese.org) offers access to additional resources on this topic.
This lesson plan has been selected by CLEAN for climate literacy education!