1 of 10

Greenhouse Gases and �Energy Budget

LP 3

1

2 of 10

What are the greenhouse gases?

Where do they come from?

How do they work?

2

3 of 10

What is the greenhouse effect?

3

4 of 10

Composition of the Earth’s Atmosphere

Nitrogen N₂ = 78 %
Oxygen O₂ = 21 %
Argon Ar = 0.9 %
Other = <0.1%

Carbon Dioxide CO₂
Methane CH₄
Nitrous Oxide NO₂
Ozone O₃
Hydrogen

4

DAY 1- RESONANCE MODELS

Most of our atmosphere is nitrogen and oxygen, neither of which is a greenhouse gas. Compare this to the Goldilocks effect. The GHGs in our atmosphere are less than 0.1% of the total amount of gas in the atmosphere and yet they are what make our planet inhabitable. Without the small amount of greenhouse gases, the average temperature on the planet would be 0 degrees F

There is a major misconception that the hole in the ozone layer is the primary reason for climate change. It is correct to say that the ozone hole has a small effect on climate change, but is not the main cause. The other connection between these issues is that CFCs and their non-ozone-destroying replacements are very potent greenhouse gases, which also contribute to climate change. Students may or may not bring up these ideas in their discussion.

5 of 10

Greenhouse Gases

5

Carbon Dioxide

Water

Methane

Nitrous Oxide

Ozone

RESONANCE MODELS- Show the tennis ball models of the gases

While this slide is up, students will complete the task card to use the models and discuss the following questions. Depending on your students it would also be possible to do this entirely as a demonstration.

Is there a frequency at which it is much easier to keep the model vibrating? At this frequency your model molecule better absorbs and retains your energy output. If there is such a frequency, determine what it is in vibrations per second by counting the number of vibrations in a 5-second interval and dividing by 5. Do at least three trials, letting different member of your group experiment and obtain the range of frequencies at which the maximum energy is absorbed. Repeat this procedure for all three models.

1. How do the resonant frequencies of the 3 models compare?

2. What hypothesis can you formulate to explain your observations?

3. Physicists tell us that the behavior of the models built from the tennis balls is a good analogy of the behavior of real molecules of carbon dioxide, methane, and nitrogen. From the observations of your models, can you explain why some gases in the atmosphere absorb infrared radiation and others do not?

4. Why do you think greenhouse gases absorb infrared radiation and do not absorb visible light?

6 of 10

Resonance Models

6

7 of 10

The “Goldilocks” Principle

7

Mars is too cold, Venus is too hot, but the Earth is just right!

Why is the greenhouse effect so important? This slide compares the temperatures on the three planets with and without greenhouse gases. All of them do experience warmer temperatures with the gases. The next slide is specifically the Earth and temperatures are reported in Fahrenheit (which might be more familiar to the students).

Recent calculations by NASA actually put the temperature change due to GHGs at only 20 degrees, not the 33 degrees in the chart. This is mostly because of using a different albedo number to consider the effects of solar and longwave radiation on the planetary albedo. The changed number is (-18 to -5) and is called the “atmosphere effect” of greenhouse gases, as opposed to the “enhanced atmospheric test” associated by the increase in greenhouse gases due to human activities.

8 of 10

What if Earth did not have greenhouse gases?

Main greenhouse gases	CO₂ H₂O
Temperature without greenhouse gases	-5 °C (23 °F)
Actual Average Temperature	15 °C (59 °F)
Temperature change because of greenhouse gases	20 °C (36 °F)

8

9 of 10

9

10 of 10

Frequency

10

OPTIONAL:

This slide is not required. If you have time and inclination at this point, you could repeat the rope experiment from the other day. Students will see that different amounts of energy causes the rope to resonate at different frequencies.

BACKGROUND

Every object that is free to vibrate has its own natural frequency. If you vibrate an object near one of its natural frequencies, its motion may grow to quite large values, a process known as resonance. Molecules behave in the same manner: they absorb energy near their resonant frequencies and vibrate, creating heat. In this demonstration of model molecules of atmospheric gases, students can make observations about resonant frequencies.

Be care that the students do not confuse the wavelength of the radiation (long and short wave) with the resonance frequency, although they are closely related. A molecule moves at a certain frequency and it is a certain wavelength of light that is absorbed by a specific molecule.