Unit 4: Considering the Influence of Light and Thermal Phenomena on Global Clima
Unit 4: Considering the Influence of Light and Thermal Phenomena on Global Climate
IV. Using Central Ideas about Light and Thermal Phenomena to Explain the Greenhouse Effect
The greenhouse effect is often mentioned in discussions about global climate. The name of this effect refers to an analogy between what happens when the Sun shines on the entire Earth and what happens when the Sun shines on a greenhouse in a garden here on Earth.
A. Considering what happens during the greenhouse effect in a garden greenhouse
A student noted that sometimes people have no idea what is happening in a greenhouse here on Earth:
I asked my sister if she knew anything about the greenhouse effect and she said nothing. So I asked if she ever heard of it before and she said no. Then I reminded her that greenhouses are used for gardens. She went ‘Oh, right’ but didn’t know what they did for the gardens…
Physics 111 Student, Spring 2016
Therefore it can be helpful to start this discussion with a focus on greenhouses in gardens here on Earth
Question 4.7 What is the greenhouse effect that occurs within a greenhouse in a garden?
- Figure 4.10 shows a photograph of a greenhouse. What do you know about greenhouses: How are they made? What is their purpose? Why do they work?
To explore the greenhouse effect in a greenhouse in a garden, you will need:
- 2 identical clear glass or plastic containers,
- 2 thermometers that agree on the same number for room temperature or 2 digital temperature probes connected to a computer and calibrated so that they read the same temperature
- 2 rulers,
- 2 moist paper towels
- access to a place to put the containers in the Sun or 2 identical lamps with identical incandescent bulbs* or one lamp that can shine equally on both containers with an incandescent bulb
- clear plastic wrap or glass cover for one of the containers.
- How could you use this equipment to explore what happens when an energy source (the Sun or a lamp) shines on an open versus a closed container?
- To model the greenhouse effect that occurs in garden greenhouses, prepare two clear glass or plastic containers in the same way:
- put two paper towels moistened in the same way in the bottom of each container
- check that two thermometers or two temperature probes connected to a computer give the same reading for room temperature
- place a ruler diagonally in each container with one end on the bottom and the other end resting on an edge of the container
- lay a thermometer on the ruler in each container so that the bulb of the thermometer is not resting on the bottom of the container but is supported at about a third of the height of the container, with the scale facing up so that the thermometer reading is visible (or place a digital thermometer on the ruler in each container)
- record the initial temperatures of the air in the containers; these should be the same
- At the top of your physics notebook page, record the Topic of this exploration. Under Before, draw a picture of th