IB Biology SL

Revision Notes

4.2.8 Skills: Carbon Cycling & Climate Change

Drawing the Carbon Cycle

  • The many processes by which carbon is transferred from one store to another are collectively known as the carbon cycle
    • During the carbon cycle, carbon is present in both organic and inorganic forms
      • Organic carbon is found in the biomass of living organisms e.g. in carbohydrates and proteins
      • Inorganic carbon is found in the atmosphere as carbon dioxide and in the oceans as e.g. hydrogen carbonate ions
  • The carbon cycle can be represented using a diagram
    • Carbon cycle diagrams show:
      • Carbon stores, known as pools, e.g the ocean, fossil fuels, or living organisms
      • Processes of carbon transfer, known as fluxes e.g. dissolving, combustion, or photosynthesis
  • Diagrams can be illustrated, or can be simple, containing just text boxes and arrows
  • Diagrams can show terrestrial carbon cycling, marine carbon cycling, or both combined in one diagram

Simple Carbon Cycle, downloadable IB Biology revision notes

A simple carbon cycle diagram showing terrestrial carbon cycling

Estimation of Carbon Fluxes

  • The processes by which carbon is transferred from one pool to another are known as fluxes
  • Fluxes can be measured quantitatively, showing how much carbon is transferred by a particular process
  • The unit for carbon fluxes is gigatonnes, or GT
    • One gigatonne is a billion tonnes
  • It is difficult to measure global carbon fluxes precisely, but scientists can make estimates by measuring smaller ecosystems and scaling these measurements up

Estimated global yearly carbon fluxes table

Estimated Global Yearly Carbon Fluxes Table, downloadable IB Biology revision notes

  • Estimating carbon fluxes is very important as humans seek to predict the impacts of climate change and reduce carbon emissions
    • By calculating the total carbon fluxes that remove carbon from the atmosphere and the total carbon fluxes that add carbon into the atmosphere scientists can calculate atmospheric carbon increases
    • This enables scientists to predict levels of atmospheric warming

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