Name _________________________________________________  Date_______________

    During the summer of 1987 the climate was drier and hotter than normal. During the last two decades (80s and 90s) the temperatures have been hotter than normal and the climate drier. Overall, around the earth there was the same amount of moisture, but some scientists were concerned that the tempeerature effects were global rather than local. For example, around here it has been warmer and drier than normal for the last several months. Other places got the moisture, but did the heat energy around the earth even out? It has been suggested that the climate of the earth is changing. NASA measurements have confirmed a general warming of the earth but there is some debate as to whether this could be caused by human activity or is it just a natural swing of the earth's climate. Indeed, the earth has seen ixce ages and warming. One thing is certain, the climate is changing and it is changing more rapidly today than it has in the history of the earth.

    The radiation absorbed from the sun that reaches the earth is partially reflected, partially absorbed and partially transmitted to the surface by the atmosphere. If all the energy were absorbed, we'd call it a black body.  But the atmosphere is somewhat transparent. It does not absorb visible light (although it absorbs UV, X-rays, IR and the like) or radio waves. Most of the energy from the sun is in the visible spectrum. A greenhouse works because light enters through the glass. (Glass is opaque to UV so we do not get suntans in our houses) When the light enters, it is absorbed by materials (plants, furniture, etc) in the greenhouse. Then it is reradiated at infrared wavelengths. (Bodies of aroun 300K radiate in the infrared.) The same glass that stoped UV also stops IR waves! So it traps the heat and the greenhouse gets hotter!.

    Much the same thing can happen in our atmosphere. venus, for example, has arunaway greenhouse effect. It is the hottest planet in the solar system, trapping IR energy beneaths its stupendous clouds. Our atmosphere can act like a glass enclosure around the earth. CH₄ and CO₂ (Methane and Carbon Dioxide) are two greenhouse gases that can lead to a greenhouse effect. These effects are discussed in class. In this lab we will try to (at least qualitatively) measure this effect.

    Your instructor will providenyou with some kind of apparatus (bottle, thermometer, light source,  etc.) to simulate the atmosphere environment. You will place a light source shining onto the container and measure the equilibrium temperature. If the temperature does not change for 3 - 5 minutes, you can probably assume it has reached equilibrium. Basically the system will radiate away as much heat as it is receiving, establishing an equilibrium.

    Then your instructor will introduce some carbon dioxide into the environment. Since CO₂ is opaque to infrared, it should trap some more heat and the temperature should increase. Look again for an equilibrium temperature. Scientists warn that the temperature of the earth will increase several degrees by 2100 so that enough ice will melt at the poles to raise the oceans about 8'.

PROCEDURE:

1. Describe the two different thermal equilibrium conditions, with and without CO₂.

2. Relate this to our planet earth.

3. List several sources of greenhouse gases.

4. Discuss whether human activity can affect the earth or is the earth so big it could never happen? remember, there are 6 billion people alive today!