The carbon cycle, stores, and fluxes

Lesson overview

This lesson reviews students’ knowledge about the carbon cycle within the context of the study of ecosystems for GSCE Science (Biology) and Geography, as well as the changing composition of the Earth’s atmosphere for GCSE Science (Chemistry). It covers the carbon cycle and major carbon stores and fluxes. The lesson combines a digital interactive carbon cycle diagram to reinforce knowledge of the processes in the carbon cycle, with a hands-on activity to introduce students to the size of the major carbon stores and fluxes. Exam style questions and a knowledge organiser provide a good revision focus.

Learning outcomes
  • Review basic processes in the carbon cycle
  • Develop fuller understanding of the carbon cycle
  • Compare the sizes of the major carbon stores
  • Demonstrate their understanding of carbon fluxes and how changes have contributed to climate change
Lesson steps
  1. Why is carbon important? (10 mins)
    Use the question prompt to see how much students know about the importance of carbon and the following slide to review some of the most important aspects of carbon. The next slide shows the different forms that carbon can take. The notes section of the slide lists the different forms of carbon shown in the imagery.
  2. What is the carbon cycle? (10 mins)
    The next slides prompt a review of some of the basic processes in the carbon cycle that students should know from key stage 3. These are photosynthesis, respiration and consumption. Word and chemical equations for photosynthesis and respiration are included for revision purposes. The concept of the carbon cycle is developed through looking at how the terrestrial processes also occur in the ocean, as well as the impact of human activity on the carbon cycle. Some classes may need to review some of the processes. This can be done using the interactive carbon cycle (intermediate) and questions on the Student Sheet Carbon cycle and climate change.
  3. Where is carbon and how does it move? (20 mins)
    This stage of the lesson examines carbon stories and fluxes in more detail. Review the terms carbon store and carbon flux, definitions are included on the slides, and then use the Carbon budget activity. Organise students into groups of four to six. Students should cut out the cash and carbon store area cards. The first task is for students to distribute the carbon cards between the carbon stores to show where carbon was around the planet before the Industrial Revolution.

    Students should take five minutes to distribute the carbon ‘cash’ between the stores to represent how many GtC (gigatonnes of carbon) were in each store at the start of industrialisation, roughly 250 years ago. Student groups should present back their decisions and rationale and note their decision on the Carbon budget record sheet.

    Review the decisions that students have made either using the correct figures on the slides or use the Carbon stores interactive (advanced) to check estimates, noting any surprises between these figures.

    Students should then use the Carbon fluxes interactive (advanced) to investigate both the natural fluxes between stores, and the overall impact of human activity on the sizes of carbon stores. The impact of human activity is also shown on the slide deck.
  4. Carbon fluxes and climate change (5 mins)
    Students are prompted to think about how the carbon cycle has changed and how this has affected the planet. In short, an increase in the combustion of fossil fuels has increased atmospheric concentrations of carbon dioxide. Approximately 30% of anthropogenic carbon emissions have been absorbed into the ocean. This has caused ocean acidification, with a decrease in ocean pH by 0.1pH since the Industrial Revolution, a 30% increase in acidity. Students should know about the associated increase in global temperatures and be reminded that 90% of the heat increase has been absorbed by the ocean. Students can consolidate their learning answering the questions in class or as home learning.
  5. Exam style questions (15 mins)
    Students consolidate learning using the exam style questions on the Student Sheet.