Is Portland, Oregon Experiencing Global Warming?

Longwave Downward Flux

Image courtesy MY NASA DATA

Students will use long wave radiation data to determine whether the climate has changed in Portland, Oregon over a 20 year time span.
Grade Level: 6 – 9
Estimated Time for Completing Activity: 50 minutes
Learning Outcomes:
  • Students will understand the difference between climate and weather.
  • Students will practice line graphing skills.
  • Students will find the longitude and latitude of a city on a world map.
  • Students will learn the definition of longwave radiation and Watts per meters squared.
  • Students will discover that temperature and radiation changes vary on our planet
  • Familiarity with accessing websites on the Internet
  • Familiarity with latitude and longitude positions on a map
  • Basic familiarity with Microsoft Excel
  • Graphing skills
  • World map, globe, or atlas
  • Computer with Internet access and Microsoft Excel
  • Graph paper
Lesson Links:

Weather involves the daily fluctuations in temperature, humidity, clouds, winds, etc. By contrast, climate is the long term weather patterns in a region. Therefore, to assess changes in climate, one has to look at average changes over long periods of time. This long period of time is generally considered 30 years or more. However, in this activity we will be looking at changes averaged over 5 years in a 20 year span since that is the longest time period that this data base spans. Also, because surface temperature data was not available for this long of a time period, clear-sky longwave downward radiation flux is being used in place of temperature as an indicator of heat energy. It is measured in Watts per square meter (Watts per meters squared). This substitution is based on the assumption that most of the longwave downward radiation represents the heat energy scattered back to earth due to the Greenhouse Effect.


1. Have students write down their own definitions for weather and climate. Then discuss with their tablemates what the difference is between these two terms which are commonly used interchangeably in everyday language. Have tables share their ideas with the whole class and develop a correct definition together which the students should write down.
2. Make an overhead of the Radiation Budget Diagram and explain what longwave downward radiation is (as opposed to shortwave radiation) and the units it is measured in. Also discuss the difference between all-sky and clear-sky radiation (the Radiation Explanation link above may be helpful). Review the Greenhouse Effect at this time as well.
3. Click on the link above to access the Excel spreadsheet of Clear-sky LW Downward radiation data for Portland, Oregon. This data has been obtained from the MY NASA DATA Live Access Server and reformatted into 2 sets of five year data that have been averaged.
4. Have students plot the averaged data from sheet titled ‘Portland Averages’ in the Excel spreadsheet on paper creating 2 line graphs on one scale. Remind students about labels, units, a title and key on their graphs.
5. Answer the questions below.


1. According to your graph, has the climate in Portland changed significantly in the last 20 years? Explain your reasoning. (How do you account for the fact that the measurements for the same months are not identical over each 5-year span?)
2. Hypothesize reasons why you might expect Portland to experience more or less impact on its climate due to global warming.
3. Do you think the effects of global warming might be more pronounced in some months or seasons than others? Explain why or why not.


1. Pick a different city anywhere in the world. You might want to pick a city in the country you are studying in your science classroom or Global Studies class. You might also want to look at the world maps at the top of this lesson plan. One map shows the clear-sky longwave downward radiation distribution for 1984 and the other map shows the same data for 2004.

2. After you have chosen your city, find the longitude and latitude for this location.

3. Click on the link above to the Live Access Server.
4. Click on the ‘Choose dataset button at the top left corner should it not automatically show up and select ‘Atmospheric Radiation’
5. Click on Surface
6. Click on Monthly Surface Clear Sky LW Downward Flux (SRB)
7. From the menu to the left under ‘Line Plots’ select ‘Time Series’ then click on the radio button next to ‘update plot’ in the menu at the top of the page.
8. In the drop down menu for View, select Time series. For Output select Table of Values.
9. Using the text boxes, write in the latitude and longitude coordinates for the city you have selected that are located under the map to the left.
10. Select the time range between Jan 1984 and Dec 2004. Then click Next
11. To open in Excel click on the ‘Save as…’ button at the top of the plot, make sure your time range is complete, choose ASCII from the drop down menu and click OK. You can then highlight, copy then paste the data in Excel.
12. Copy and paste one year worth of data into Excel SpreadSheet titled ‘Your City Averages’ (see link above) in the appropriately labeled location. Repeat for the data of each of the other 9 years. Excel will automatically calculate the averages for you. Graph both sets of averages onto the same line graph.
13. Look for similarities and differences between the lines. What can you conclude about increased global warming in the area near your city? Compare your data with your classmates who have studied different cities. What can you conclude overall about the climactic changes that have occurred on our planet during this 20 year period?

Lesson plan contributed by Carol Ponganis, Portland, Oregon

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