Edexcel Geography A-level

The Carbon Cycle and Energy Security

Geological Carbon Cycle

• Movement and storage of carbon between land, ocean, and atmosphere.
• Three forms of carbon:
  • Inorganic: Rocks as bicarbonates and carbonates.
  • Organic: Plant material and living organisms.
  • Gaseous: CO₂ and CH₄ (methane).
• Balance between production and absorption (sources and sinks).

Stores of Carbon

• Terrestrial, Oceanic, Atmospheric stores.
• Carbon sink: Stores more carbon than it emits (e.g., intact tropical rainforest).
• Carbon source: Emits more carbon than it stores (e.g., damaged rainforest).

Main Carbon Stores:

• Marine Sediments & Sedimentary Rocks: Largest store, 66,000-100,000 million billion metric tons.
• Oceans: 38,000 billion metric tons.
• Fossil Fuel Deposits: 4000 billion metric tons.
• Soil Organic Matter: 1500 billion metric tons.
• Atmosphere: 750 billion metric tons.
• Terrestrial Plants: 560 billion metric tons.

Fluxes of Carbon Cycle

• Photosynthesis: Converts CO₂ and water into oxygen and glucose.
• Respiration: Converts oxygen and glucose into energy, water, and CO₂.
• Combustion: Fossil fuels and organic matter burn, releasing CO₂.
• Decomposition: Decomposers break down organisms, releasing CO₂.
• Diffusion: Oceans absorb CO₂, increasing acidity.
• Sedimentation: Formation of limestone from shell fragments.
• Weathering & Erosion: Releases inorganic carbon slowly.
• Metamorphosis & Volcanic Outgassing: Releases CO₂ from Earth's crust.

Variations in Carbon Fluxes

• Quick cycle: Photosynthesis and respiration.
• Long-term storage: Dead organic material turns into sedimentary rocks or hydrocarbons.

Complex Carbon Processes

• Ocean as Carbon Sink: Stores 50x more carbon than the atmosphere.
• Biological Carbon Pump: Phytoplankton photosynthesise, base of marine food web.
• Physical Pump: CO₂ saturation in ocean surface layer, thermohaline circulation.

Terrestrial Sequestration

• Primary producers (plants) sequester carbon via photosynthesis.
• Decomposition in tropical climates quickly recycles carbon.
• Diurnal and seasonal variations in carbon flux.

Soil's Capacity to Store Carbon

• Climate, soil type, and land use affect carbon storage.

The Natural Greenhouse Effect

• CO₂ levels maintain global temperatures.

Anthropogenic Interference

Enhanced Greenhouse Effect

• Increase in greenhouse gases since the 1750s.
• Major contributors: Fossil fuels, deforestation, urbanization.

Implications

• Temperature, climate, and precipitation changes.
• Severe weather, ecosystem shifts, hydrological cycle impacts.

Energy Security

Key Concepts

• Maximum energy security: Uninterrupted energy at affordable prices.
• Four aspects: Availability, Accessibility, Affordability, Reliability.
• Energy security evaluated at national level.

Energy Mix

• Non-renewable: Fossil fuels like coal, oil, natural gas.
• Renewable: Solar, wind, geothermal.
• Recyclable: Nuclear energy.

Primary Energy Sources

• Coal, oil, natural gas, uranium, biomass, hydroelectric power.

Energy Players

• TNCs play a major role in energy exploration, exploitation, distribution.
• OPEC: Controls majority of world oil reserves.
• National governments and consumers influence energy security.

Alternative Energy Sources

• Unconventional fossil fuels: Shale gas, deep-water oil, tar sands.
• Renewable energy: Solar, wind, wave, tidal, geothermal.

Reducing Carbon Emissions

Strategies

• Carbon Capture and Storage (CCS).
• Hydrogen fuel cells as alternative to oil.

Threats to Water and Carbon Cycle

Deforestation

• Reduces carbon storage, increases flooding risk.

Grassland Conversion

• Converts carbon sinks into carbon sources.

Ocean Health

• Overfishing and acidification impact economy and biodiversity.

Climate Change Impacts

• Severe weather, rising sea levels, ecosystem changes.

Tipping Points

• Forest die-back, thermohaline circulation disruption.