4.2.8 Skills: Carbon Cycling & Climate Change

• 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

An illustrated carbon cycle diagram showing both terrestrial and marine cycling

A simple carbon cycle diagram showing terrestrial carbon cycling

• 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

• 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