Lab 6: Trees and Paleoclimate: How Do We Know What We Know?The lab activity described here was created by Betsy Youngman of TERC for the EarthLabs project.
Use the button at the right to navigate to the student activity pages for this lab. To open the student pages in a new tab or window, right-click (control-click on a Mac) the "Open the Student Activity" button and choose "Open Link in New Window" or "Open Link in New Tab."
Investigation Summary and Learning Objectives
After completing this investigation, students will be able to:
- explain what "proxy data" is and give examples of how proxy data provides information about climate of the past
For more information about the topic, check the section titled Background Information under Additional Resources below
Activity Overview and Teaching Materials
In Part A: Students learn about proxy data, the various sources of proxy data that scientists use, and how that data allows scientists to reconstruct climate records from the past. This lab requires a live Internet connection.
Time required: 50 minutes
In Part B: Using an animation based on North American pollen data extracted from lake sediments, students track 21,000 years of plant / biome migration as the Wisconsin ice sheet retreats. This lab requires a live Internet connection.
Time required: 50 minutes
In Part C: Students use their knowledge of biomes and proxy data to reconstruct climate over a period of several thousand years using data from simulated lake bottom sediment core. Teachers need to prepare lab materials and instructions in advance. This lab can be completed offline.
Time required: 50 minutes
Tools needed: Internet browser, Adobe Reader, Flash Player, JAVA, Lab Materials, PowerPoint.
Time required: 150 minutes, or 3 class periods, are needed to complete these labs. (Part A can be done as homework.)
Printable MaterialsTo download one of the PDF or Word files below, right-click (control-click on a Mac) the link and choose "Save File As" or "Save Link As."
- Stop and Think Questions (Word (Microsoft Word 72kB Dec7 12) and PDF (Acrobat (PDF) 77kB Dec7 12))
- Suggested Answers (Microsoft Word 2007 (.docx) 101kB Dec7 12) to Stop and Think Questions
- Student Worksheet: Pollen and Paleoclimate (Acrobat (PDF) 82kB Apr25 12)
- Key to Pollen Core Activity (Acrobat (PDF) 69kB Apr25 12)
Teaching Notes and Tips
About Proxy Data
What is Proxy Data? Before scientists can truly understand the possible human impact to Earth's climate system, they need to understand the natural, long-term patterns of Earth's climate, patterns that pre-date significant human impact on the system. Of course, there were no instruments collecting climate data 1,000 years ago or 100,000 years ago, so how do scientists come to understand those climate patterns from the past? Through what is referred to as proxy data: i.e., data such as fossilized pollen in ancient lake bed sediments, coral growth, or tree rings, which are natural recorders of Earth's climate patterns. Teachers may want to engage students in a discussion of how nature records weather and climate before beginning this lab. Often students are familiar with ice core records and can relate sediment cores to ice cores. Ice cores are discussed in detail in the Cyrosphere module of Earthlabs.
To begin this part, students view an interactive timeline Climate Timeline. This timeline may be difficult to interpret for some students, so teachers may choose to have students work in pairs or may want to review this section with the whole class.
Next, students review a PowerPoint file that shows the many proxy records, how they were constructed, and how they show similar patterns in the data. Teachers may want to share this as a large class discussion. Download and view the Climate Change: Past, Present, and Future (PowerPoint 2.3MB Dec10 12) PowerPoint file. Teachers should emphasize the significance of the alignment amongst such a large variety of independent data sets.
Note: This PowerPoint file was adapted from Climate Change: Past, Present, and Future, presentation NSTA Climate Change Symposium, March 2011. Courtesy of: LuAnn Dahlman, NOAA.
The Pollen Viewer is an easy-to-use tool based on the records of fossilized pollen found in North American lake bed sediments. Using the pollen data, the Pollen Viewer reconstructs the changing ranges of dozens of trees and plants across a 21,000-year time span as Wisconsin Ice Sheet retreated. Take time in this lab to make the connection between plant specie distribution and past climate. Ask students to contemplate: a) how do we know about ancient tree species locations and b) what plants might have lived in your neighborhood in the distant past?
The hands-on Pollen lab in Pollen and Paleoclimate requires lab materials and teacher pre-lab preparation which are described below. Additional detailed instructions for the teacher are included in this word document: teaching notes for lab 6C (Microsoft Word 95kB Apr26 12). The preparation for this lab is time-consuming (60-90 minutes). Teachers may want to have several students assist in the preparation of the lab materials. The good news is: if dry soil, gravel, or sand is used as the base materials, the lab materials can be saved and re-used for many years. Another recommendation that aids in the longevity of the materials is to use beads instead of paper punches for the "pollen" grains. There are two printable files for this activity: a student worksheet and an activity key, both are linked above, and on the student page.
Prepare for the investigationThese materials will need to assembled before class begins.
- Pollen pictures. One image is on the student site, other images are available at this website: USGS. Either print the images or prepare to show them to the whole class, via projector.
- One large graduated cylinder (1000 ml at least) for the "sediment" column. Only one is needed as a demonstration for the whole class. Note: If you do not have access to a cylinder, a transparent "Smart Water" brand bottle, or tennis ball can are good substitutes. See schematic of core pictured below.
- Five different types of "sediment" for the Washington data (any soil, sand, potting mixture, etc. that can be layered to show the five distinct layers). You will need enough for the sediment column and corresponding "samples." A sample bag pictured below. The pollen grains are made of plastic beads, buttons, or colored paper punches. You will need 11 different colored beads, buttons, (or paper punches). The quantities range from 3 to 24. You will also need the Teachers key for setting up the sample bags for the Washington Model. Each bag will have 25 beads total. You will need to decide on your color or shape key. The color (or shape) is listed here by letter, for example A could be red, or square... depending on how you set up the lab. This quantity of beads will make up 5 bags, one of each type. If you have more than 5 lab teams, you can adjust the number of bags. In other words, double the recipe.
- A small, re-sealable plastic bag containing the sediment layer sample.
- A pie pan for the sediment layer sample.
- Tables of the different "pollen" colors showing which colors represent which plants and information about the climatic requirements for each plant species. (A blank one is included the student worksheet, teachers will need to define the color key before class)
- Tweezers, toothpicks, or forceps to sort through the pollen sample.
- A worksheet to record the data. (Included in the student worksheet.)
After you have completed the lab, conduct a data analysis discussion, described below.
Facilitation Tips: Write the primary discussion question on the board. If possible, seat students facing one another in a semi-circle. Have students stand at the front to share their climate stories. Ask students in the audience to listen carefully for similarities and differences amongst the teams' interpretations. Draw a graph of climate vs. time on the board to show the explanation for the rapid changes in plant life. Compare and contrast the stories, and then share the information in the teacher's key. Discuss interpretations of data and sources of error.
Primary discussion question: Share your climate stories with the rest of the class. After you have shared your stories, return to Pollen viewer (Lab 6B) and examine the advance and retreat of the glacial ice sheet and variations in species distribution for the region around Battleground Lake. How does your story fit with the data given in the pollen viewer?
Wrap Up: If possible, project the Pollen Viewer applet and spend time as a class reviewing the data that is given there. Look for species that were mentioned in the lab. Wrap the discussion up by reviewing the concepts of proxy data and paleoclimate.
Student NotebooksThe following items are suggestions for inclusion in optional printed student notebooks. The materials are linked in the Printable Materials section, above.
- Key Questions listed in introduction to lab
- Stop and Think questions
- Discussion Starters and a place to write notes
- Relevant vocabulary and a place to write definitions
- Extra blank sheets for sketches or notes
- Pollen viewer images (in print)
- Lab handout for pollen core lab 6C
- Recording sheet for lab 6C
AssessmentThere are several options for assessment of student understanding of material introduced in this lab. Teachers can choose from the following list, or create their own assessments.
State and National Science Teaching Standards
TO BE PROVIDED LATER
Developer will correlate activity to standards listed at this site:National Science Education Standards (SRI)
Background InformationAdditional background information about paleoclimate:
- Paleoclimate and Pollen LabWindows to the Universe.
- Paleoclimate and Pollen Lab - original versionUCAR version; simpler to read.
- Teachers key for setting up the bags for the Washington Model.
Content ExtensionStudents interested in ancient climate records that can be found in ocean sediment cores, going back thousands to millions of years, may be interested in completing these Earth Exploration Toolbook chapters.
This Earth Exploration Toolbook chapter Pollen and Climate, uses the Pollen Viewer data and gives students the opportunity for a more in-depth examination of tree migration.
Other resources for teaching about ancient climate can be found at Ideas for Teaching about Paleoclimate