I recently came across several apparently reputable sources (e.g., NASA, PBS) that describe a simple, elegant experiment intended to demonstrate carbon dioxide's role as a greenhouse gas. Each of them involves two sealed containers with thermometers - one containing air, the other containing high levels of CO2, both exposed to sources of light. The problem I'm having is that I haven't been able to obtain the anticipated results in any reliable way. In fact, I'm seeing no consistent variation in the temperatures of the two containers, and I'm starting to wonder if this experiment is based on wishful thinking rather than on hard science. My question is: Is anyone aware of any reliable, published experimental data demonstrating that CO2 in a sealed container will heat up more quickly and reach steady state at a higher temperature than a container filled with air? Here is my short list of sources: 1) NASA (I've copied the text of NASA's experimental procedure below. Note that this site claims "Some people measure a difference of five degrees Celsius or more". I'm not getting anywhere near that kind of temperature difference.) http://glory.gsfc.nasa.gov/globalwarmingexperiment.html" [Broken] 2) PBS/NOVA (This one comes complete with an interesting disclaimer: "NOTE: As with any demonstration, the results should, but do not necessarily, match those expected. If the temperatures in the bags do not support the role of greenhouse gases in heat capture, discuss the nature of scientific experimentation, including the importance of multiple trials, control of conditions, and measurement challenges." I also think the baggie concept is very flawed - I used a rigid plastic container.): http://www.pbs.org/wgbh/nova/teachers/viewing/0302_03_nsn.html" [Broken] 3) SCIENCE EXPERIMENTS ON FILE™ Revised Edition (similar to the two above): http://www.fofweb.com/Onfiles/SEOF/Science_Experiments/1-15.pdf" [Broken] I'm a chemical engineer by training and I think that my lab technique is still good enough to eliminate most sources that could bias the results of this experiment. I'm getting inconclusive results despite using a variety of light sources (sunlight, incandescent bulb, heat lamp) at a range of distances from the containers and a large number of runs. I am pretty apolitical on this topic ... my sole interest in this matter is to advise my son about his science project, which he's put a lot of effort into. Thank you for any advice on reliable sources of information regarding results of similar experiments. Ray = = = = = = = = = = = = Here's the experimental procedure presented on the NASA (GLORY satellite mission) webpage: = = = = = = = = = = = = In this activity, you will measure the effect of excess carbon dioxide on the temperature of gas inside of soda bottles and see what the effects of aerosols are on the heating of the gas. Materials: Two or more 2-liter clear soda bottles with the label removed. Identical thermometers for each soda bottle Opaque tape Source of carbon dioxide (CO2) Spray paint or spray glitter Modeling clay For your source of carbon dioxide, you may use one of the following methods: Dry CO2 source - Seltzer bottle charges - fill a dry seltzer bottle with one charge of carbon dioxide. You will use the carbon dioxide in the seltzer bottle to fill one of the bottles with carbon dioxide. For this method, both bottles can be left dry. Wet CO2 source - Alka-seltzer - you will put a cup of water into both bottles, then put a couple of alka-seltzers into the water in one of the bottles. A tablespoon of baking powder can be substituted for the Alka-seltzer. Wet CO2 source - Put a cup of club soda or seltzer water in one of the bottles and a cup of tap water into the other bottle Method: Drill the caps of the bottles to the same diameter as your thermometer. Place the thermometers through the holes in the caps several inches. Use the modeling clay to hold the thermometers in place and seal the hole. Use the seltzer bottle to fill one of the bottles with CO2, or, for the wet CO2 source, (method 2) fill the bottles with identical quantities of water and place the Alka-seltzer into one of the bottles, or (method 3) place identical quantities of seltzer/club soda into one of the bottles and plain tap water into the other. Make sure the liquids are at the same temperature when starting the experiment. Place the caps with thermometers onto the tops of the bottles. Put the bottles into sunshine. Make sure they receive the same amount of sun. NOTE: a heat lamp may be substituted for the sun, but you must be very careful to place the bottles exactly the same distance from the lamp. Shade the thermometers by putting a strip of opaque tape on the outside of the bottles. The tape must be the same length on both bottles. Measure the temperature of the bottles over time. Record the temperature of each bottle every five minutes for a half hour. The effects of carbon dioxide on the temperature The bottle with carbon dioxide in it will heat up faster and will stabilize at a higher temperature than the bottle with air. Some people measure a difference of five degrees Celsius or more, or the difference between a warm spring day and a hot summer day. What you will learn The Earth's temperature would be much colder without the CO2 in our atmosphere we have naturally. When we add more, the Earth warms up. The effects of atmospheric CO2 and aerosols on our planet's temperature are measurable with simple tools anyone can use. The effects are as real as touching the hoods of black and white cars that have been standing in the sun.