1. Begin the class session by asking students if they think the average annual global temperature and CO2 levels have been consistent throughout the history of the Earth.

2. Introduce the Geologic Timeline to your students.  The Geologic Timeline shows the average global temperature, CO2 concentration (ppm), and the percent of global ice cover for nine distinct time periods throughout geologic history.  The pictures associated with each time period depict the location of the landmasses during that time period.  They also show the amount of ice cover for that time period.

3. The small thumbnail picture associated with each year is an “exploration image."  When the thumbnail picture is selected, a larger image will appear with a text box at the bottom of the screen. The text box contains additional information about the climate during that time period.

4. Review the following abbreviations that appear on the timeline with your students:

1. CO2 - carbon dioxide
2. ppm - parts per million
3. Ma - millions of years ago
4. ka - thousands of years ago

5. Show students how to navigate to different time periods with the timeline.  Students will need to scroll to the right in order to access the time periods.

Implementation Suggestion:
- Some low-ability students may require additional support for completing this learning task. You may wish to walk through each time period one at a time as an entire class using guided questions to analyze the climate data from each time period. This instructional strategy is effective using one computer in the classroom that displays the image to the front of the room.

6. Distribute the Student Exploration Sheet to each student.

7. Instruct students to record the Average Global Temperature, Average Global CO2 Concentration, and the % Global Ice Cover in the data table provided on the Student Exploration Sheet.

8. Have the students plot the data from their data table onto the provided graph and answer Analysis Questions on the Student Exploration Sheet.

Implementation Suggestion:
- Some low-ability students may require additional support with plotting the Average Global CO2 Concentration data on the graph. You may wish to explicitly model how to plot points that are less than 1000 ppm on the Average Global CO2 Concentration graph.

9. Review and discuss student responses to key questions.