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 that naturally traps heat from infrared radiation that would otherwise escape to space. These scientists invented the term "greenhouse effect" when they compared their observations to how the sun warms a greenhouse. Scientists now know that the carbon compounds—carbon dioxide, methane, and halocarbons—are greenhouse gases that absorb a wide range of energy, including infrared energy (heat) emitted by the Earth, and then re-emit it. The re-emitted energy travels out in all directions, but some returns to Earth, where it heats the surface. 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 no natural greenhouse 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. What causes this amplified greenhouse effect, and could it have consequences for the Earth's System? How do they 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!

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 infra-red radiation depends on how the radiation interacts with the structure of the molecule. Watch the Greenhouse Gas Molecules animationto help you understand this important concept. Then, watch a video of geoscientist, Dr. Scott Denning using his own personal dancing style to explain why greenhouse gases absorb infra-red(IR) heat energy. As you view the animation and video, 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.

Checking In

  1. If you could add more CO2 and methane (CH4) 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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