Radiation Comparison Before and After 9-11

Contrails persist over Southeast US

Image courtesy NOAA

To determine if changes can be detected in cloud cover, temperature or radiation measurements due to the halt in air traffic post 9-11
Grade Level: 9 – 12
Estimated Time for Completing Activity: Two or three class periods
Learning Outcomes:
  • Students will be able to obtain data from a NASA Web site.
  • Students will be able to form charts and graphs using NASA obtained data.
  • Students will be able to form conclusions by comparing maps and charts.
  • Familiarity with accessing websites on the Internet
  • Familiarity with locating geographic locations using latitude and longitude coordinates
  • Live Access Server Introduction and Tutorial
  • Computer with Internet access
  • PowerPoint or other presentation software
AP Environmental Science Topics
Lesson Links:

Several research studies have suggested that contrails (condensation trails from aircraft) can alter the radiative budget of the Earth by increasing the cloud cover at high altitudes. Under the right conditions, contrails can persist, forming cirrus clouds, and cause more shortwave radiation to reflect back to space (cooling effect), as well as prevent longwave radiation from escaping to space (warming effect, like a blanket).

The tragic events of September 11, 2001, caused virtually all air traffic to be grounded over the US for nearly three days. The absence of contrails over the United States during this time gave scientists a unique opportunity to test this theory. Some scientists used data to show that the diurnal (daily) range of temperature increased during this three-day period, suggesting more warming during daylight hours and more cooling at night because contrails were not present. Other scientists contend that the dry air mass and the clear sky conditions that prevailed during this time could account for the temperature range (that is, it would have happened anyway).

In this lesson, you will read some scientific papers related to these studies and draw your own conclusions using appropriate data from the MY NASA DATA Live Access Server (LAS). Daily satellite data or three-day average data for cloud cover, temperature and radiation parameters are available in the LAS for inquiry.


Part I: Literature Review

1. Break into study groups of 4 students.
2. Choose one article to read from the Lesson Links. (Two students in the group should read Article 1 and the other two read Article 2 such that each group reads both viewpoints).
3. Write a brief summary of the conclusions (closing arguments) listed in your article. Your summary should include the point of view by the authors, what data parameters they used to prove their point, and any scientific reasoning stated in the article.
4. In your group, compare the viewpoints between the articles and discuss which stance your group will defend or counter.
5. Discuss what data parameters will be necessary to explore for your investigation.

Part II: Explore LAS to find data

1. Click on the Lesson Link to the Live Access Server.
2. Explore the lists of data parameters and find those relevant to your investigation. Be sure to select daily data, not monthly data.
3. Each group member should select or be assigned a data parameter for inquiry.
4. Follow the LAS links to your data parameter.
5. Select region North America (this can be done by selecting the double downward arrow located above the map in the upper left corner of the screen), and select relevant times before and after September 2001. Note: You may want to look at three-day averages before and after 9-11 by using the Apply Analysis option below the date input section by selecting Average and Area from the drop down menus . See LAS Help features if you have trouble with this feature.
6. Create plots of your data, save and print for further group discussion.

Part III: Present your investigation to the class

1. Show your data results to your group. Discuss whether the data support the conclusion you selected. If the data do not support the conclusion, discuss the viewpoint your group will present.
2. Design a PowerPoint presentation for your class. Be sure to include your data graphics and clarify the scientific viewpoint you have decided on as a group.
3. Take turns to present each section of the presentation (opening viewpoint, data output, data conclusions, closing arguments).


1. What different parameters were explored?
2. Were your data conclusive or inconclusive?
3. Did your data support your group stance?
4. What differences in conclusions did each group find?
5. What suggestions do you have to improve your group research?


1. Record the diurnal temperature range at your school for some period of time. Analyze the data.
2. Join the SCOOL Project to observe cloud cover at your school.
3. Read the GLOBE protocols on contrail observation. Begin to observe contrails at your school.

The next to last three Links can be used for further investigation about contrails on 09-11-2001.

Lesson plan contributed by Catherine Ryan, Alvin, Texas

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