What Factors Impact a Greenhouse?

The earth's atmospheric "greenhouse effect" is much more complex than the simple greenhouse experiment you completed in the previous activity. While the earth's temperature is dependent upon the greenhouse-like action of the atmosphere, the amount of heating and cooling are strongly influenced by several factors.

The type of surface that sunlight first encounters is the most important factor. Forests, grasslands, ocean surfaces, ice caps, deserts, and cities all absorb, reflect, and radiate radiation differently. Sunlight falling on a white glacier surface strongly reflects back into space, resulting in little heating of the surface and lower atmosphere. Sunlight falling on a dark desert soil is strongly absorbed, on the other hand, and contributes to significant heating of the surface and lower atmosphere. Cloud cover also affects greenhouse warming by both reducing the amount of solar radiation reaching the earth's surface and by reducing the amount of radiation energy emitted into space.

In this activity, you will use a model to investigate these other factors in greenhouse heating and cooling.

Materials (per team)

Procedure

  1. Form teams of four. If not already done, build 6 model greenhouses according to the directions in the previous activity.

  2. Paint the upper third of three of the bottles white.

  3. Label the bottles A, B, C, D, E, and F with bottles B, D, and F having the white paint.

  4. Fill the base of bottles A and B with dark soil, bottles C and D with white sand, and bottles E and F with room-temperature water.



  5. Tape a thermometer (using transparent tape or light-colored masking tape) to the inside of each bottle (facing out).

  6. Place the bottle tops in the bases. Make sure the bottles are capped.

  7. Make sure the bulbs of the thermometers are just above the top of the bases. If the bulbs are below the base, the thermometer may record the heat absorbed directly by the soil or water, complicating the results.

  8. Place the bottles approximately six inches away from the lamp with the thermometer facing away from the light. DO NOT TURN ON THE LAMP.

  9. Prepare a data table to record temperature in each bottle for twenty minutes, at 2-minute intervals. Make sure the table is neat and easy to read.

  10. Record the temperatures in each bottle before the light is turned on.

  11. As a team, decide which bottle will be the hottest. Why? Record your predictions.

  12. As a team, decide which bottle will be the coolest. Why? Record your predictions.

  13. Turn on the light and begin recording the temperatures every two minutes. Continue for at least 20 minutes.

 

Observations and Questions

  1. Prepare a labeled graph showing the temperature changes in the 6 bottles. Compare the graphed information from the different bottles. How do the results match your predictions? If different, can you explain what might have caused the differences?

  2. Relate the factors affecting the model greenhouses to the factors affecting the "global greenhouse." Which factors are the same? Which are different?

  3. In the global greenhouse, what functions as the white paint, the dark and light soil, and the water?

  4. If you had to design a greenhouse that would keep the temperatures inside as low as possible, what design would you use? Sketch and label your design. Where might you find conditions like that on earth?

  5. If you had to design a greenhouse that would keep the temperatures inside as high as possible, what design would you use? Sketch and label your design. Where might you find conditions like that on earth?

When you're finished with the activity, click on Back to Teacher Guide at the top of the page.