Effect of Albedo on Greenhouse Effect (Wendy Banner)
Research Question and Hypothesis
Does the solar reflectance index, (albedo) of surface material affect the ambient temperature in a closed system under an incandescent light source?
If a range of materials are exposed to light, the darker materials will absorb more light and convert the energy to infra red radiation, raising the temperature more.
Standards
Old California Science Standards for middle school:
PS 7 6.a Visible light is a small band within the electromagnetic spectra.
PS 8 ; 9.a plan and conduct scientific experiment
6.b For an object to be seen, light must ...enter the eye.
6.f Light interacts with matter by transmission, absorption or scattering.
9c. Distinguish between variable and controlled parameters in a test.
9e. Construct appropriate graphs from data, develop quantitative statements, about the relationship between variables.
Next Generation Science Standards :
MS-PS4-2. Develop and use a model to describe that waves are reflected, absorbed, or transmitted through various materials
Earth and Human Activity
MS-ESS3-5.Ask questions to clarify evidence of the factors that have caused the rise in global temperatures over the past century.
Scientific and 'engineering practices
1. Asking questions (for science) and defining problems (for engineering)
2. Developing and using models
3. Planning and carrying out investigations
4. Analyzing and interpreting data
5. Using mathematics and computational thinking
6. Constructing explanations (for science) and designing solutions (for engineering)
7. Engaging in argument from evidence
8. Obtaining, evaluating, and communicating information
Experimental Design
Students will be modeling the greenhouse effect by measuring temperature change in four bottles containing materials that differ in darkness. While the four climate models are positioned beneath a lamp, students will record the temperatures at 5 minute intervals. the data will be graphed for analysis.
Independent variable
The indepanednt variable is time, as measurements of temperature will be taken at 5 minute intervals. For overall precision, a classroom timer will be used to avoid lapses in attention. If a digital temperature probe is used, measurements of temperature will be continuous.
Dependent variables
The dependent variable is the ambient temperature within each modeled environment. A small thermometer is suspended from the cap of each 2-liter bottle to measure temperature change with time.
Series
This is a study of temperature change (dependent variable) as a function of time, (independent variable) in various levels of albedo, (series) represented by light and dark materials.
The four variations of albedo are modeled in 2 liter bottles, each containing a different material;
Constants and Controls
The four 2 liter bottles must be the same size and manufacture. The level of material in each bottle must be the same so the air-space to be heated is equal. The four bottles are placed at the same distance and angle under the lamp. There is no control (non-intervention) model, or 'normal' condition. All four models must be left uncapped at room temperature away from direct light long enough to start at the same temperature.
Materials
Four similar clear 2 liter bottles with white lids, clean and dry.
Black charcoal granules, (soil amendment) found at garden center.
Perlite (white potting mix ingredient) from garden center.
Medium shade brown soil
White paint or liquid paper.
4 small thermometers hanging from a wire attached to each lid.
Ring stand with a clamp-on lamp
timer
Procedures
Put about 3" of each surface materials, (black, white, brown) in each of the first 3 bottles.
Paint the top 3 " of the fourth bottle white and put 3" of the brown soil in it.
Heat a nail and melt a hole in each bottle cap to suspend a small thermometer on a wire, (or unbent paper clip) Label the caps A,B,C & D.
Position the four bottles evenly under an overhead lamp so they are receiving light from the same distance and angle.
Prepare a timer for 5 minute intervals and turn on the lamp.
Record the temperature of each bottle every 5 minutes on a spread sheet.
Graph and analyze the results.
For repeated trials with successive class periods, cooling time will be required for the materials so that all substrates can return to room temperature. For this purpose alternate classes can run the procedure on different days; periods 1 and 3 on the first day and periods 2 and 4 on the second day. Inexpensive thermometers can read different temperatures in the same environment , so try to group them in sets of 4 that read similarly for each lab set up.
Sample data and graphs
Analysis & Conclusions
The analysis of data for this lab is fairly predictable. The bottles containing barker materials show the most rapid temperature increase. The results reliable spread along a spectrum with the white martial remaining the coolest. Very literally, if something looks white, it is because that material is reflecting more material out to your eye. Darker material is converting light energy to heat, Still on the electromagnetic wave spectrum, but unable to exit the transparent container.
One anomaly I experienced the first time I ran this test was that the white material in bottle B appeared to heat up just as fast as bottle A, (with black coal.) After a few minutes bottle B filled with water vapor and it was evident that another factor was heating the environment. I emptied the pearlite from bottle B, dried it out and returned it to the container to continue the experiment. The results are seen in the table and chart above.
Photos & Movies
References
My earliest personal reference to the Greenhouse Effect: SOYLENT GREEN 1973 (22 seconds)
Thomas Eugene Avery, Graydon Lennis Berlin. Fundamentals of Remote Sensing and Airphoto Interpretation
, Macmillan, 1992 -