The Science of Global Warming

Lesson Plans

Lesson Plan I: Lab on the Greenhouse Effect

This lab will demonstrate the greenhouse effect. The materials that are needed are a glass jar with a cotton swab to seal the opening, two thermometers and a movable light source. The procedure for the lab is to have the students put one of the thermometers inside the glass jar and seal it with the cotton swab. The students should then position the light source so that it shines on the glass jar and the second thermometer which is placed next to the glass jar. An equal amount of light should laminate both thermometers. The students should record the temperature of each thermometer before shining the light on them and then every 30 seconds for ten minutes. Once the students have taken all of their data they should plot a graph showing the readings of both thermometers. The students then compare what happened to the temperature of the two thermometers. Which one heated up the most and why? How does this demonstrate the greenhouse effect?

A variation on this lab is to include the factor of albedo which is the measurement of reflectivity of surfaces. This time have the students place two jars side by side with thermometers sealed inside of them. Have the bottom surface of one jar painted white and the other jar painted black. How does this effect the temperature readings? Plot your results.

Lesson Plan II: Math calculations of Energy formula of the Earth- Determining Earth's temperature

This lesson is designed for the students to use accessible mathematical formulas and known values to calculate the temperature of the Earth and Venus from the heating of the sun. These calculations are to determine what the average temperature of the Earth would be without the greenhouse effect. The results are dramatic because without the greenhouse effect the Earth would be frozen over and Venus would be comfortable. However, with the natural greenhouse effect the Earth is habitable and Venus is hot enough to melt lead.

To calculate the temperature of the Earth you use the following equation

L _s- luminousity of Sun= 3.86 x 10 ^{3 3} erg/sec

A - albedo = 0.39

d _s - distance of Earth from Sun = 1.496 x 10 ^{1 3} cm

r _E - radius of Earth = 6,378 km

Σ - Stefan-Boltzman constant = 5.67 x 10 ^{- 5}erg/cm ²deg ⁴sec

1 ^st term -"energy flux"

2 ^nd term - cross-sectional area of the Earth

3 ^rd term- amount of energy absorbed

Equals:

Surface area of the Earth x Boltzman constant( energy per meter) x temperature to the fourth power

Solving for temperature: (Πr _E ² cancels leaving: )

Substituting in the values gives:

T= 248K = -25°C

Now use the same equation to calculate the temperature of Venus.

Distance of distance of Venus from the sun: d= 0.72 AU

Although the albedo of Venusis currently 0.76, if no clouds were there (no atmosphere), the albedo should be similar to Earth, 0.39

A simplified formula is:

where d is the distance from the planet to the sun in units of AU (the mean distance between the sun and Earth)

Derive this formula and solve for T _{V e n u s}=

The students discuss the implications of their calculations of the temperature of the Earth from the sun's luminous heat and the temperature of Venus. Without the greenhouse effect we could not live on the Earth.

Lesson Plan III: Chaos Demonstration of Multiple Attractors

Provide the students with materials to build a rollercoaster like track that will allow a ball to roll from high spots to low spots. Have the students build the track with multiple low and high spots. Mark the high and low spots with relative temperatures ranging from (-25C) to (12C) to (100C). These temperatures represent the climate and indicate the average temperature of the Earth. Demonstrate how a ball will tend to stay at a low point which is a "strange attractor" unless it is given enough energy to clear the high point and then it will settle into another low point or "strange attractor." Indicate to the students that these low spots are stable states that tend to remain the same. The push that you give the ball to get it to move are the external forcings such as global warming that change the temperature of the Earth's system. So far we have remained in a stable climate, but what would happen if our ball, "the climate", were to end up at a higher or lower state? What would it mean for us if the climate were to change to -25C or 100C? What would happen to life on our planet?

Additional Lesson Plans

Using Verneer Probes demonstrate how luminousity varies with distance.

Possible clothes layering activity- get a body suit to demonstrate how it increases the temperature within- green house affect- explain that this is only an analogy because it is the result of convection instead of radiation.

Water Thermometer for thermal expansion- demonstrate that the sea level will rise significantly by the affect of thermal expansion. Heat a water thermometer to show that expansion due to heat is a significant affect.

Global Warming Debate: What is the likely effect of Global Warming and What can we do? As a summary of the unit the students will debate what they think the likely results from global warming will be and what we can do to control the impact. What do we have to do to limit the effects of global warming?

Write your Mayor. Encourage them to join the cities concerned about global warming and committed to making a difference.