Elizabeth Clark and Mary Savina, Carleton College

Analysis and interpretation of data.

Construction of graphical data representations, analysis of graphs to understand broader scientific concepts, oral presentation, scientific writing.

undergraduate entry level, including science and nonscience majors

Students should have a basic understanding of climate and its relationship to temperature and precipitation; otherwise very little.

This can work as a stand-alone exercise. When the activity was originally used, students incorporated their findings, along with first-hand accounts of the Dust Bowl, into original theses about the causes of the Dust Bowl.

In order to run this activity, you need access to Microsoft Excel (or similar) and the NDP-041 data set. This data set can be downloaded from ftp://cdiac.esd.ornl.gov/ndp041 or ordered in CD-ROM format from the Historical Climatology Network at the Carbon Dioxide Information Analysis Center based in Oak Ridge National Laboratories, TN (see http://cdiac.esd.ornl.gov/), The CD-ROM format is possibly easier to use. Be aware that the precipitation is in yearly total, whereas the temperature is in yearly average; students have confused the data set units. Also precipitation is given in tenths of mm and temperature in tenths of degrees Celsius, which may be confusing if supplemental data sets are used to complete the record.

Because the data files are so large, users should open them in Word and then select and paste the data sets from particular stations into Excel. The "text to columns" command readies the data for analysis. We have found it most convenient to replace the -999 code for blank cells. This missing data will cause easily identifiable spurious peaks to appear on graphs. We do these steps for introductory geoscience students to allow them to focus on statistical analysis and graph interpretation. Advanced students work directly with the original files.
The stations we use for global warming are: Arhangel'sk, Colombo, De Bilt, Isfjord Radio, Madras/Minambakkam, Milano/Linate, New Haven/Tweed, Quito/Mariscal Sucre, Rio de Janeiro, San Antonio/Int., TX, Shanghai, Leningrad (TOWN), Upernavik AWS, Vardo, and Jakutsk. For the Dust Bowl, we use Leavenworth, KS, Peoria, IL, Des Moines, IA, Concord, NH, Pierre, SD, Minneapolis/St. Paul, MN, New Ulm, MN, Sacramento, CA, Laramie, WY, Lawrence, KS, Manhattan, KS, Logan, NE, Bismark, ND, and Independence, OK.

We are interested in whether students are able to actually construct and read graphs, understand the climate implications represented by these graphs, and eventually synthesize this information with periodicals and government documents (information literacy) in forming a thesis.

Students present their findings in PowerPoint presentations that they then save to a common folder, making these presentations available to other students during the paper-writing process and to the instructor for further consideration. We revisit these presentations and the final course papers in assessing the effectiveness of this project in achieving learning goals.

In this exercise, students are presented with two climatological problems. Questions to guide the exploration of global warming include: a) Has the earth been warming? b) If so, is the warming rate steady over time? and c) Is warming uniform over the globe? Investigation of the Dust Bowl is facilitated by these questions: a) What happened climatologically during the Dust Bowl years? and b) Were heat and dryness confined to the classic "Dust Bowl" area of the High Plains or were the climate changes broader in scope?

To answer these questions, students manipulate historical precipitation and temperature data from the NDP-041 Historical Climatological Network Data Set using basic statistical functions in Excel. Working in groups of 3-4, they generate plots of yearly average temperature, 5-year moving average of yearly average temperature, and comparable graphs for precipitation. They also plot temperature and precipitation anomalies (based on the averages from 1951-1980) and their 5-year moving averages. Other plots that may be completed, time allowing, including plots of summer precipitation (June+July+August).

Students create and interpret temperature graphs using data from globally distributed stations, including those located at high latitudes, to investigate the problem of global warming. They create and interpret plots of temperature and precipitation for stations across North America to examine the climatology of the Dust Bowl. By plotting both mean annual and 5-year moving average temperature and precipitation, students see the variability in climate trends over different time scales. They present their findings to their classmates, allowing an understanding of spatial effects on climate to develop.

The PowerPoint presentations allow for evaluation of the students' understanding of climate. Generally, students become more confident in their ability to work with data and to speak publicly.

A component of information literacy, as well as writing and critical thinking, has also been added in the context of a two-course "dyad" called "Agriculture and the American West" that combined American literature with geology. One theme that carried through the course was the question: "What caused the Dust Bowl?" Students were challenged to consider physical and societal factors: drought, soil types, land quality, capitalism, migrant farmers, and the Depression.

To evaluate these factors, students consulted first-hand/contemporary accounts of the Dust Bowl from government documents, newspapers and periodicals. They also considered the depictions of the Dust Bowl in fiction, music, art, film, and photography. Information from the Excel exercise presented here was incorporated as evidence related to the role of climate/drought in the Dust Bowl.