Lab 3: Carbon-Life as a Greenhouse Gas

The lab activity described here was developed by Candace Dunlap of TERC for the EarthLabs project.

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Investigation Summary and Learning Objectives

Students use an animation, charts, and a short video to learn the basics of greenhouse chemistry, including what carbon compounds exist in the atmosphere and their relationship to the greenhouse effect. Students then compare historical ice core carbon dioxide and marine sediments temperature data to establish the relationship between global temperatures and atmospheric carbon dioxide levels. Finally, they analyze graphics of global and U.S carbon emissions to identify types and sources of carbon dioxide and watch a video about how satellite technology is used to track carbon fluxes over the United States.

After completing this investigation, students will be able to:

• Identify the important greenhouse gases and describe the role of greenhouse gases in warming the atmosphere.
• Describe how ice core data and other historical CO2 and temperature data reveal the relationship between atmospheric carbon dioxide and global temperature.
• Identify types and sources of carbon dioxide emissions in the United States and the World.

For more information about the TOPIC, read the section titled Background Information under Additional Resources below

Activity Overview

In Part A: Students use an animation, charts, and a short video to learn the basics of greenhouse gas chemistry, including what carbon compounds exist in the atmosphere and their relationship to the greenhouse effect.

In Part B: Students use a graph and videos on historical ice core CO2 data in order to investigate the relationship between ices ages, interglacial periods and changes in CO2 levels. Students then examine more current CO2 and temperature to establish the relationship between current trends in global temperatures and atmospheric carbon dioxide levels. They use CarbonTracker, developed by NOAA, to investigate and compare atmospheric carbon dioxide time series sampled from different parts of the world.

In Part C: Students use a carbon footprint calculator developed by The Nature Conservancy. They input family household data such as family's energy usage and are then able to compare their carbon footprint with each others and with the world.

Printable Materials

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• Stop and Think Questions Stop and Think Questions Lab 3 (Microsoft Word 2007 (.docx) 26kB Mar5 13)
  
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Teaching Notes and Tips

In Part A:

By the end of Part A, students should have constructed an understanding of the relationship between carbon dioxide and temperature of the atmosphere. They will then apply this understanding in Lab 2-B, when they analyze graphs of historical carbon dioxide data.

You may want to have a discussion about the size of the atmosphere in the first image comparing the atmospheres of Mars, Venus and the Earth. The ratio of the thickness of the atmosphere size to the diameter of the three planets is exaggerated for visual effect. It is important for students to understand that the Earth's atmosphere is not that thick in relation to the Earth's diameter. To get a sense of the thickness of the troposphere and stratosphere, two important layers of the atmosphere, try this simple exercise. Use a compass to draw a circle with a radius of 127 mm. This circle represents the Earth and the inner-most atmosphere. The 1 mm line, that your pencil draws, represents the average thickness of the the first two layers of the atmosphere: the troposphere, the region of weather, and the stratosphere, which protects us from most of the Sun's harmful ultraviolet (UV) radiation.

In Part B:

As with all the graphs, you may want to spend time projecting the graphs on the board and going over the graph elements with them.

Graph: CO2, Temperature and ice ages.

Students need to spend some time analyzing the first graph on CO2, ice ages and temperatures. By asking them to look for "elements of a story" in this graph, students will start to see that the changes in atmospheric CO2 are related to changes in temperature. You may want to talk about Milankovitch cycles and ice ages depending on your classes but it is not necessary. Students simply need to see that trends in carbon dioxide seem to correlate with trends in temperature and ice ages over the past 800,00 years.

As with any graph, it might be a good idea to project this graph on the board so you can have a class discussion on what the elements of the graph are.

Some resources are included below.

The Keeling Curve:

This is an iconic historical graph so you may to talk a little bit about the history. You will need to talk about variability versus the trend of the line. The "squiggy" lines represent seasonal variations in CO2 dioxide due primarily to seasonal changes in the photosynthetic rates of deciduous forests. The variability of the "squiggly lines" is discussed in greater detail in Lab 4.

Rather than give students a graph that illustrates where scientists think the CO2 levels will be in the year 2100, students should be able use a variety of strategies, such as line of best fit. You may want to consider putting the Keeling Curve up on the smartboard or overhead and then ask students to carryout the discussion. They use CarbonTracker, developed by NOAA, to investigate and compare atmospheric carbon dioxide time series sampled from different parts of the world - including the Keeling Curve data from Mauna Loa. They examine carbon dioxide time series data from at least three sampling sites around the world and then describe the overall trends of CO₂ at each site. When students compare their graphs from around the world, they will see both similarities (trends of rising CO₂) and differences (example - some show greater variability and some less). These similarities and differences will generated some rich discussions.

In Part C:

Students explores ways to reduce their family's carbon footprint. Students may not have some of the information they need to input so teachers may need to have information ready for some "typical families" and/or work with students to make a best "guesstimate." There are many carbon footprint calculators on the web which my be more appropriate based on student age.

Assessment

State and National Science Teaching Standards

Additional Resources

Background Information

Milankovitch

Wikipedia: Ice Ages

Wikipedia: Milankovitch Cycles

The Keeling Curve

Earth - The Operator's manual. Two of Richard Alley's video clips included in the LAB 3 investigation come from the Earth- The Operator's Manual website. This is truly an excellent site. You may want to consider having students watch the entire video.

Content Extension