Short-Term Carbon Cycle

Content/concept goals:

• Compare the size of Earth's carbon reservoirs before and after industrialization
• Evaluate the magnitude of carbon movement (fluxes) between reservoirs
• Reflect on the difference between "natural" and anthropogenic fluxes to deduce the impact of human activity on Earth's carbon cycle

Higher-order goals:

• Contextualize human versus non-human ("natural") activities affect the Earth as a planetary system

This assignment is used as an in-class activity for a large (80 student) introductory-level/general education geology lecture course. Students typically work in groups of 2-4 to complete the activity. Approximately 25-40 minutes are required to complete the activity, depending on student engagement and aptitudes. After completion, the instructor reviews the activity at the end of class.
Students benefit from having a lecture in a class prior to the activity, where the carbon cycle is introduced, including concepts of carbon reservoirs, sources, sinks, and fluxes. However, this is not required to complete the activity.

This in-class activity includes a document that can be printed and provided to students. An instructor key is also provided.

Students use data provided in the IPCC AR6 report that includes Earth's carbon reservoir sizes and fluxes both before and subsequent to the Industrial Revolution. Students first summarize size of each of the main carbon reservoirs, rank the reservoirs by size, and then infer the kinds of carbon present in each reservoir. They then use a diagram of carbon fluxes before and after industrialization to calculate the net flux of carbon between individual reservoirs. Reflection questions are provided at the end of the activity, which help to spur a discussion with the instructor.

The activity is typically given as a credit/no-credit assignment. Instructors could adapt the materials to award point values for individual questions.

Student handout for Short-Term Carbon Cycle activity (Microsoft Word 2007 (.docx) 438kB Jun29 26)

Short-Term Carbon Cycle Activity_key.docx -- educator-only file

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Students with mathematical or quantitative aptitudes tend to finish the assignment rapidly but with relatively little reflection. Instructors are encouraged to coach those students to work with other students at their table and to spur discussions within each group.

A group discussion can be productive at the end of the assignment, once all of the answers are reviewed with the full class.

Some students get confused on how to add the fluxes in Figure 1. The flux values are situated so that positive values indicate carbon entering the atmosphere and negative values indicate carbon leaving the atmosphere. This results in positive values if the atmospheric carbon reservoir is gaining carbon or negative values if the atmospheric carbon reservoir is losing carbon.

The instructor usually will walk around the classroom and engage students in side discussions, coaching them if they have difficulty in the mechanics of the assignment. Anyone present is given credit for the assignment, given that it is usually offered to a large lecture class. Questions that test for comprehension of the material are included on the subsequent exam.

Data were retrieved from:
IPCC, 2023: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland, pp. 35-115, doi: 10.59327/IPCC/AR6-9789291691647.