The Greenhouse Effect

The Earth's atmosphere is made up of a multitude of greenhouse gases such as Nitrogen, Oxygen, water vapor and trace amounts of Carbon Dioxide, Helium, Nitrous Oxide, Methane, Argo, Ozone and Hydrogen. These gases in our atmosphere absorb and trap heat and therefore keeps our atmosphere warm enough to support life. If the atmosphere did not trap any gases Earth would be extremely cold.

Students will understand how greenhouse gases keep our atmosphere warm enough to promote life. They will learn how human activities create a surplus of these greenhouse gases and therefore result in global warming.

1. Question the class: Have you ever noticed that how hot your parent's car gets on a sunny day even if its really cold outside?
2. Explain: Sun rays pass through the windows of the car and warms the car seat. The car seat then radiates heat back into the car, but it cannot pass back through the windows (heat is not sun rays). Therefore, the car warms up even though it is cold outside.
3. Ask the class if they can provide any other examples of this effect.
4. Explain: This same effect happens on Earth, but instead of having a glass wall to block the heat, we have an atmosphere full of greenhouse gases that absorbs and traps reflected radiation. This effect keeps our planet warm and allows life to exist here.
  • Short-wave rays from the sun pass through the atmosphere
  • The sun's rays are absorbed by plants, trees, soil, buildings etc.
  • Long-wave heat is radiated back
  • Some heat is absorbed by the greenhouse gases and radiated back to into our atmosphere
  • Some heat escapes into space.
5. There are a number of ways to illustrate this effect to the class.
  • Make 3 wooden boxes with an incandescent lamp in the roof and a small hole in the wall to insert a thermometer sealed with a wooden cork
    • Put plants in two of the boxes
    • Put 2-3 bottles of carbonated soft drink inside one of the boxes with plants and on of the boxes without plants
  • Have students take the temperature of each box
  • Let the sodas sit for a couple hours so that the carbon dioxide concentration inside the box raises (you may want to have this all set up before class, so that the sodas have already been sitting)
  • Have the students take the temperature of each box again (don't wait too long as the Carbon Dioxide will escape through the small openings in the box).
6. Analyze the results. Note that the temperature will increase due to the increase in carbon dioxide.
7. Explain how green plants absorb Carbon Dioxide and returns oxygen.
8. Ask the class where the Carbon Dioxide concentration comes from.
9. Have the class list the different ways humans increase the Carbon Dioxide concentration globally
10. Discuss Biomes and Anthromes. How have humans altered the classic view of biomes through the greenhouse effect and global warming?

Neal, P. (1991). The Greenhouse Effect and Ozone Layer. London: Dryad Press