Climate and Earth's Energy Balance
Part C: Explore the Greenhouse Effect
Once incoming solar energy reaches Earth's atmosphere, what parts of the Earth system absorb and hold the energy, warming the planet? In this lab, you will explore some of the elements that absorb solar energy, the greenhouse gases. These gases include: carbon dioxide, methane, nitrous oxide, and water vapor. You will see how each gas responds differently to electromagnetic radiationa property that allows some forms of solar energy to pass through the "atmospheric window," of gases to the planet's surface and also back out to space, while retaining others to warm the atmosphere and Earth's surface. You will further your understanding of the Earth's energy balance that you investigated in the previous labs.
First, watch this short video from the National Science Foundation, describing the importance of the greenhouse effect in making the planet habitable, or able to support life. Click the link How does the sun's energy get into the climate system? to access the narrated video. After viewing the video, discuss the questions listed below with your classmates.
DiscussAfter viewing the video, discuss the following question with your neighbor or classmates:
- Why are greenhouse gases important to life on Earth?
What are the greenhouse gases?
Next, learn more about greenhouse gases and how they contribute to global warming by viewing a short animated presentation and reading a background article explaining the expanded greenhouse effect and the role of key atmospheric gases in this effect. Click the links to read the article and view the animation and then, answer the Checking In questions below.
- Greenhouse effect animation
Note: on the third to last slide in this presentation several words are omitted; see if you can add the needed words to complete the sentence. "These gases absorb the infrared radiation emitted by the Earth and re-radiate the energy as heat back towards the Earth, causing a warming known as ______ ."
- The article, A blanket around the Earth gives detailed information about the greenhouse gases and explains the expanded greenhouse effect.
- What words were omitted from the greenhouse effect animation? The phrase should read "These gases absorb the infrared radiation emitted by the Earth and re-radiate the energy as heat back towards the Earth, causing a warming known as the greenhouse effect."
- List the five greenhouse gases described in the 'A blanket around the Earth' article linked above.Five greenhouse gases include: Water vapor, Carbon Dioxide, Methane, Nitrous Oxide, and Chlorofluorocarbons (CFCs). Sources of these gases are shown in the Optional extension, below.
- Which of the greenhouse gases is most abundant in the atmosphere?Water Vapor is the most abundant GHG and plays an important role in feedback mechanisms that either amplify (speed up) or dampen (slow down) climate change. However it is very short-lived in the atmosphere. Once it reaches a certain concentration it quickly condenses into clouds and precipitates back out of the atmosphere.
- According to the article, which greenhouse gases are natural and which are man-made, or "anthropogenic?"Nitrous Oxide, and Chlorofluorocarbons (CFCs) are anthropogenic. The others are naturally occurring, but humans have altered their concentrations in the atmosphere.
- Which of the long-lived greenhouse gases is the most important ? Methane is a more potent greenhouse gas, but Carbon Dioxide is longer lived in the atmosphere, therefore it is more important.
Investigate the greenhouse effectNow that you have some background information about the factors that control the greenhouse effect, you are ready to try an experiment! Begin by reading the instructions and information in the flash interactive, shown below. Note: If you prefer, you can click the Greenhouse Gas Concentration vs Temperature link to access the interactive in a new page.
Explore the features of the animation
Once you are second screen of the interactive, there are three sliders to control the concentrations of greenhouse gases in the atmosphere. Move them and observe the changes that occur in the graphic. Note both the changes in the temperature and the color of the atmosphere.
After you have explored the sliders impact on temperature, use the three radio buttons to view Greenhouse Gas concentrations and average Earth surface temperatures; record your answers to the Stop and Think questions, below.
For more information about the data used in the interactive click the info button at the top of the screen, or view the information shown below.
A long-term record of the concentrations of these gases can be seen in the graphic below. Note the dramatic rise in the all three of the greenhouse gas concentrations in the most recent time period.
Graphic source: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/tssts-2-1-1.html
The Atmosphere Today
Begin with the Year button set to Today. Note the average global (land and ocean) temperature, shown in the thermometer above the graphic. Record the concentration of the three primary greenhouse gases, CO2, CH4, and NO2 in the table on your answer sheet. Note that the NO2 and CH4 concentrations are in parts per billion. In other words, there is very little of these two gases in the atmosphere as compared to CO2.
The Atmosphere in 1850
Next, click the 1850 radio button to select the period around 1850. Note the global temperature as well as the composition of the atmosphere. Record the composition of the atmosphere in the table on your answer sheet.
The Atmosphere in 2100
Next, click the 2100 radio button to select the period around 2100. Note the global temperature as well as the composition of the atmosphere. Record the composition of the atmosphere in the table on your answer sheet.
Stop and Think1. Complete the table below. Record the average global temperature and each of the greenhouse gas concentrations.
Year Temperature CO2 CH4 NO2 Today 1850 2100
Greenhouse gas slider
Once you have a sense of these three atmospheric states, explore the variable GHG concentration slider. As you reduced the greenhouse gases to zero, what happened to the temperature of Earth?
Stop and Think2. Why are greenhouse gases (GHG) important to life on the planet?
3. In the simulation, which was the most potent (caused the greatest change in temperature) of the three greenhouse gases, how did you discover this? (Hint: note the concentrations of the gases.)
Altering the energy balanceBoth instrumental and satellite data show that the years between 2000 to 2010 were the warmest decade of the past 150 years, and 2010 tied for the warmest year on record. (Source: NASA Research Finds 2010 Tied for Warmest Year on Record) What could be causing the heating of the planet? Which parts of the balance have changed? This NASA video, Piecing Together the Temperature Puzzle,(5:48 minutes) explains the scientific understanding of how various elements of the Earth-Sun system, including changes in the solar cycle, alterations in snow and cloud cover, and rising levels of heat-trapping gases, may be contributing to this new record.
As you watch the video, consider how the individual changes in Earth's climate are like a series of puzzle pieces that, when connected, begin to form a recognizable pattern. As you watch this video, you will also gain an appreciation for the contribution that NASA satellites have provided towards the solving of the global climate puzzle.
Preview the following discussion questions before watching the video. Use the controller to review sections of the video as needed.
DiscussAfter completing this lab, discuss your thoughts about the material covered in this lab with your classmates. Consider the following questions:
- Why do we study the planet as one interconnected system?
- How do we know that the Earth's climate is changing, and what is the role of GHG in that change?
Another, more complex, greenhouse gas interactive can be accessed here: Greenhouse gas interactive. This JAVA applet has several layers of complexity and includes a visualization of molecular interactions with photons.
Additional information about Greenhouse gases, their sources, and role in global warming can be found on this NOAA page.
The following graphic shows the sources of the greenhouse gases by sector. An interesting exercise would be to research each sector and consider ways to reduce the emissions of these gases.