Instructions:
• Set up a high intensity lamp (100 to 250 W) equidistant from each flask. Place a one-hole stopper in each flask with a thermometer or temperature probe in the hole. Start the experiment by turning the lamp on (t = 0 sec) and then noting the temperatures every minute.
• The "air only" flask is just a thermometer for comparison. It should not change much.
• The "air in flask" should heat up some, because the glass itself functions like a Greenhouse gas.
• Before hand, place ¼ tsp. water in the "water vapor" flask and let it evaporate.
• "Methane" is less dense than air. You can capture it in an inverted flask held above your stove with a stopper in hand.
• C02” is denser than air. Make it in a larger beaker by adding vinegar to baking soda, and pouring it into the flask.
• Verify that the flask is indeed filled with invisible CO2 by inserting a lit match. It will go out. You can prepare this ahead of time, but it is more impressive to do it in front of students, one you have your technique down.
Concepts:
Describe what would happen if you were to sit in your car with the windows rolled up in the parking lot on a sunny summer day? _________________________
Greenhouse affect - When carbon dioxide, methane, and water vapor ________ infrared
wavelengths coming from the ground, trapping solar energy and ______ the temperature.
Heating greenhouse gases; measuring temperature over time
• Set up a high intensity lamp (100 to 250 W) equidistant from each flask. Place a one-hole stopper in each flask with a thermometer or temperature probe in the hole. Start the experiment by turning the lamp on (t = 0 sec) and then noting the temperatures every minute.
• The "air only" flask is just a thermometer for comparison. It should not change much.
• The "air in flask" should heat up some, because the glass itself functions like a Greenhouse gas.
• Before hand, place ¼ tsp. water in the "water vapor" flask and let it evaporate.
• "Methane" is less dense than air. You can capture it in an inverted flask held above your stove with a stopper in hand.
• C02” is denser than air. Make it in a larger beaker by adding vinegar to baking soda, and pouring it into the flask.
• Verify that the flask is indeed filled with invisible CO2 by inserting a lit match. It will go out. You can prepare this ahead of time, but it is more impressive to do it in front of students, one you have your technique down.
Concepts:
Describe what would happen if you were to sit in your car with the windows rolled up in the parking lot on a sunny summer day? _________________________
Greenhouse affect - When carbon dioxide, methane, and water vapor ________ infrared
wavelengths coming from the ground, trapping solar energy and ______ the temperature.
Heating greenhouse gases; measuring temperature over time
The Role of Water and Water Vapor in the Earth System
The influence of greenhouse gases is only part of the process.
If the earth were in radiative equilibrium, with an atmosphere, the surface temperature would be 67 degrees C. This does not happen because water evaporates from the surface, mostly from tropical seas, cooling the surface (Philander, 1998: 78).
The simple picture of the greenhouse mechanism is seriously oversimplified. Many of us were taught in elementary school that heat is transported by radiation, convection, and conduction. The above representation [of the simple greenhouse effect] only refers to radiative transfer. As it turns out, if there were only radiative heat transfer, the greenhouse effect would warm the Earth to about seventy-seven degrees centigrade rather than to fifteen degrees centigrade. In fact, the greenhouse effect is only about 25 percent of what it would be in a pure radiative situation. The reason for this is the presence of convection (heat transport by air motions), which bypasses much of the radiative absorption ... The surface of the Earth is cooled in large measure by air currents (in various forms including deep clouds) that carry heat upward and poleward. One consequence of this picture is that it is the greenhouse gases well above the Earth's surface that are of primary importance in determining the temperature of the Earth. That is especially important for water vapor, whose density decreases by about a factor of 1,000 between the surface and ten kilometers above the surface. Another consequence is that one cannot even calculate the temperature of the Earth without models that accurately reproduce the motions of the atmosphere. Indeed, present models have large errors here--on the order of 50 percent. Not surprisingly, those models are unable to calculate correctly either the present average temperature of the Earth or the temperature ranges from the equator to the poles. Rather, the models are adjusted or "tuned'' to get those quantities approximately right.
Richard S. Lindzen, Former Alfred P. Sloan Professor of Meteorology at the Massachusetts Institute of Technology.
To understand earth's temperature, we must also understand the role of water, water vapor, and ice in the earth system.
1. The most important greenhouse gas is water vapor.
2. It evaporates, mostly by the tropical ocean, in response to heating by the sun. Sunlight warms the ocean's surface, which cools by evaporation. In simple terms, the ocean sweats to keep cool. The water vapor then continues through the Earth's hydrological cycle.
3. Some is carried into the Intertropical Convergence Zone (ITCZ) where it rises, condenses into rain, and releases the stored solar energy. Rain releases latent heat. This heats the air, drives the convection in the ITCZ, and it is the major heat source for driving the atmospheric circulation.
4. The atmospheric circulation carries heat poleward, reducing the temperature contrast between poles and tropics.
5. The circulation also carries water vapor high into the atmosphere, allowing it to radiate heat efficiently to space.
6. Some condenses into puffy clouds. These clouds, and the convective clouds in the ITCZ reflect sunlight leading to a cooler earth.
7. Some remains in the air and absorbs infrared energy emitted by earth. This increases the greenhouse effect leading to a warmer earth.
A major cause of concern is the relative importance of water in clouds and as vapor. Is the cooling by clouds more or less important than the warming by vapor? Water vapor and cloud drops can warm or cool earth's surface through feedback loops.
If the earth were in radiative equilibrium, with an atmosphere, the surface temperature would be 67 degrees C. This does not happen because water evaporates from the surface, mostly from tropical seas, cooling the surface (Philander, 1998: 78).
The simple picture of the greenhouse mechanism is seriously oversimplified. Many of us were taught in elementary school that heat is transported by radiation, convection, and conduction. The above representation [of the simple greenhouse effect] only refers to radiative transfer. As it turns out, if there were only radiative heat transfer, the greenhouse effect would warm the Earth to about seventy-seven degrees centigrade rather than to fifteen degrees centigrade. In fact, the greenhouse effect is only about 25 percent of what it would be in a pure radiative situation. The reason for this is the presence of convection (heat transport by air motions), which bypasses much of the radiative absorption ... The surface of the Earth is cooled in large measure by air currents (in various forms including deep clouds) that carry heat upward and poleward. One consequence of this picture is that it is the greenhouse gases well above the Earth's surface that are of primary importance in determining the temperature of the Earth. That is especially important for water vapor, whose density decreases by about a factor of 1,000 between the surface and ten kilometers above the surface. Another consequence is that one cannot even calculate the temperature of the Earth without models that accurately reproduce the motions of the atmosphere. Indeed, present models have large errors here--on the order of 50 percent. Not surprisingly, those models are unable to calculate correctly either the present average temperature of the Earth or the temperature ranges from the equator to the poles. Rather, the models are adjusted or "tuned'' to get those quantities approximately right.
Richard S. Lindzen, Former Alfred P. Sloan Professor of Meteorology at the Massachusetts Institute of Technology.
To understand earth's temperature, we must also understand the role of water, water vapor, and ice in the earth system.
1. The most important greenhouse gas is water vapor.
2. It evaporates, mostly by the tropical ocean, in response to heating by the sun. Sunlight warms the ocean's surface, which cools by evaporation. In simple terms, the ocean sweats to keep cool. The water vapor then continues through the Earth's hydrological cycle.
3. Some is carried into the Intertropical Convergence Zone (ITCZ) where it rises, condenses into rain, and releases the stored solar energy. Rain releases latent heat. This heats the air, drives the convection in the ITCZ, and it is the major heat source for driving the atmospheric circulation.
4. The atmospheric circulation carries heat poleward, reducing the temperature contrast between poles and tropics.
5. The circulation also carries water vapor high into the atmosphere, allowing it to radiate heat efficiently to space.
6. Some condenses into puffy clouds. These clouds, and the convective clouds in the ITCZ reflect sunlight leading to a cooler earth.
7. Some remains in the air and absorbs infrared energy emitted by earth. This increases the greenhouse effect leading to a warmer earth.
A major cause of concern is the relative importance of water in clouds and as vapor. Is the cooling by clouds more or less important than the warming by vapor? Water vapor and cloud drops can warm or cool earth's surface through feedback loops.
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