EarthLabs > Climate and the Carbon Cycle: Unit Overview > Lab 3. Carbon and the Atmosphere: My Life as a Greenhouse Gas > 3A: CO2 - It's a Gas!

Carbon In the Atmosphere - My Life as a Greenhouse Gas

Part A: CO2: It's a Gas!


View the image below; on which planet would you like to live?


Discuss

With your group, compare the atmospheres of Mars, Earth, and Venus in the image above and then use the following questions to guide your discussion.

1. On which planet would it be possible for you to live? Why?

2. What relationship, if any, do you see between the amounts of carbon dioxide and the temperature in these three atmospheres?

3. You have probably heard about the'greenhouse effect' in previous science classes or in the media. Based on your current understanding of the greenhouse effect, which planet do you think has the strongest greenhouse effect? Why?

4. What if Earth's greenhouse effect amplified (became stronger)? Would Earth's atmosphere become more like that of Venus or more like Mars? Explain.


The Greenhouse Effect

Since the 1800s, scientists have known that carbon dioxide is one of several greenhouse gases Greenhouse gases (GHG) affect the temperature of Earth's lower atmosphere by absorbing and emitting thermal infrared radiation that would otherwise escape to outer space. The most important greenhouse gases include carbon dioxide, water vapor, methane, ozone and nitrous oxide. Without GHGs, Earth's atmosphere would be much colder. that naturally absorbs heat from infrared radiation is a long wave type of electromagnetic radiation. It is invisible to the human eye but we feel it as heat. The earth's surface absorbs solar radiation and re-emits energy in the form of infrared radiation. that would otherwise escape to space. These scientists invented the term greenhouse effect is a process by which greenhouse gases absorb thermal infrared radiation emitted from Earth's surface and re-emit infrared in all directions, including back to Earth. This process keeps thermal infrared radiation from escaping to space and has the effect of warming the lower atmosphere. when they compared their observations to how the sun warms a greenhouse. Even though scientists now know that the physics involved in heating an actual greenhouse is very different than the physics involved in heating the atmosphere, the term "greenhouse effect" is still used today. Scientists now know that the warm atmosphere we enjoy today is due to greenhouse gases such as carbon dioxide, methane and water vapor absorbing thermal infrared energy emitted by the Earth's surface and then re-emitting it. The re-emitted infrared radiation travels out in all directions, but some returns to Earth, where it heats the surface and is re-emitted once again as infrared. Without greenhouse gases, Earth would be a frozen -15 degrees Celsius (5 degrees Fahrenheit). With too many greenhouse gases, Earth could be like Venus, where the greenhouse atmosphere keeps temperatures around 400 degrees Celsius (750 degrees Fahrenheit). Thus, by trapping infrared radiation, carbon dioxide and other greenhouse gases warm the atmosphere enough to support and sustain the "lifestyle" of living organisms here on Earth. As a matter of fact, if nogreenhouse effect existed, the planet would be too cold to support and sustain the biodiversity that now exists on Earth.

If you would like to learn more about infra-red radiation, click on this link to a NASA video that explains infra-red radiation in greater depth: infra-red radiation


Scientists are now seeing an amplified greenhouse effect. Human activity is increasing the amount of greenhouse gases in the atmosphere - especially carbon dioxide. This is amplifying the greenhouse effect. What causes this amplified greenhouse effect, and could it have consequences for the Earth's System? How do scientists know? Before you begin exploring these questions, begin by first reviewing the greenhouse effect using the Greenhouse Effect Interactive developed by the Norwegian Center for Science Education. If you get most of the answers correct in the quiz at the end of the interactive, you are ready to continue with the lab investigation. Good luck! Note: It may take some time for this interactive to load.

Carbon Dioxide as a Greenhouse Gas

Does carbon dioxide have a role in the amplified greenhouse effect? If so, what is the evidence? Let's begin the exploration of this question by looking at a simple pie graph of the different gases that comprise the atmosphere.

As you can see by the graph, above right, nitrogen and oxygen make up 99% of the atmosphere. While both nitrogen and oxygen are important in supporting life on Earth, they are not greenhouse gases and play almost no direct role in warming the atmosphere. The 1% slice of the pie chart is comprised of those gases found only in trace amounts.

Consider the table below and then answer the Checking In questions that follow:


Checking In

  1. Which of the gases below are greenhouse gases? Select all the answers that are correct, and then check the Check Answers button at the bottom of the list.
    [CORRECT]
    [CORRECT]
    [CORRECT]
    [INCORRECT]
    [CORRECT]
    [INCORRECT]
  2. Which of the greenhouse gases in the table are carbon compounds? Select all the answers that are correct, and then check the Check Answers button at the bottom of the list.
    [CORRECT]
    [INCORRECT]
    [CORRECT]
    [INCORRECT]
  3.   

The Case of the Dancing Molecules

Why do some gases in the atmosphere contribute to the greenhouse effect whereas others do not? For example, why isn't nitrogen or oxygen a greenhouse gas? If carbon dioxide is just a trace gas, how can it contribute to the greenhouse effect? It turns out that the ability of an atmospheric gas to trap infrared radiation depends on how the radiation interacts with the structure of the molecule. First, watch a video of geoscientist Dr. Scott Denning using his own personal dancing style to explain why greenhouse gases absorb infrared radiation (IR). Then, use the animation of Greenhouse Gas Molecules below to deepen your understanding of greenhouse gas molecules and the greenhouse effect. As you view the video and the animation, make note of the following:

When you finish, share your notes from the animation and Scott Denning's molecular dance with your partner or group and answer the questions below.

This content is available in flash format only

Checking In

  1. If you could add more greenhouse gas molecules to the atmosphere in the animation, what would you expect to observe? Select all the answers that apply and then check the Check Answers button at the bottom of the list.
    [CORRECT]
    [INCORRECT]
    [INCORRECT]
    [CORRECT]
  2. Which of the following statements are true about greenhouse gases(GHG) and the greenhouse effect? Select all the answers that are correct and then check the Check Answers button at the bottom of the list.
    [INCORRECT]
    [CORRECT]
    [INCORRECT]
    [CORRECT]
  3.   

Stop and Think

Explain why carbon dioxide, methane and water molecules are greenhouse gases whereas nitrogen and oxygen are not. Try it in words or even your own dance!

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