Exam code: 9GE0
Study Figure 1, which shows the major global stores of carbon.
Figure 1: Selected global carbon stores
Store | Approx. size (gigatonnes of carbon, GtC) |
|---|---|
Oceans (dissolved, biological, sediment) | ~38,000 |
Seabed sediments | ~1,750 |
Atmosphere | ~600–800 |
Note ~93% of CO₂ is held in the oceans
Suggest one reason why the oceans are the largest active store of carbon.
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Study Figure 1, which compares two sources of carbon dioxide emissions.
Suggest one reason why human activity has unbalanced the carbon cycle more than volcanic activity.
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Study Figure 1, a diagram of the greenhouse effect.
Suggest one reason why rising concentrations of carbon dioxide lead to higher global temperatures.
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Study Figure 1, which shows net primary productivity (NPP) for different biomes.
Suggest one reason why net primary productivity is highest in tropical regions.
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Study Figure 1, which shows information about carbon stored in soils.
Figure 1: Soil carbon
Fact | Detail |
|---|---|
Share of global carbon held as dead organic matter in soils | ~20–30% |
Global soil carbon lost since 1850 | 40–90 billion tonnes (Gt) |
Main cause of loss | cultivation and disturbance of soils |
Where carbon is concentrated | mainly in the surface soil layer |
Suggest one reason why cultivating land reduces the amount of carbon stored in soil.
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Explain the geological processes that influence the levels of carbon in the atmosphere.
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Explain the role of photosynthesis in the ocean on the carbon cycle.
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Explain how oceans regulate the composition of the atmosphere.
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Explain how carbon becomes locked into long-term geological stores.
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Explain how the natural greenhouse effect helps to regulate the Earth's temperature.
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Explain how the oceans sequester and store carbon.
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Explain how the burning of fossil fuels has altered the natural carbon cycle.
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Study Figure 4b
Figure 4b
The global carbon cycle
Assess the role of oceans in regulating the carbon cycle.
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Study Figure 1, a diagram of the global carbon cycle showing the main ocean fluxes.
Assess the role of the oceans in regulating the carbon cycle.
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Assess the extent to which the carbon cycle can still be considered a balanced system.
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The processes of the carbon cycle operate at longer, slower (geological) and shorter, faster (biological) timescales. Evaluate the view that human activities are having a greater impact on the shorter-term biological processes than on the longer-term geological processes.
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