Carbon Cycle Content

• The Carbon Cycle


  Not just about the water cycle, carbon is found in all Earth's systems
• Carbon is an element, and a very important one
• Where carbon is found

  • Organic substances
  • Inorganic substances
  • Each of the Earth's systems
• Over 99.9% of the Earth's carbon is stored in sedimentary rocks such as limestone
• About 0.004% of the Earth's carbon is stored in fossil fuels, such as coal and oil
• The atmosphere contains about 0.001% of the Earth's carbon
• The oceans are the second-largest carbon store on Earth, containing approximately 0.04% of the Earth's carbon
• The biosphere contains approximately 0.004% of the Earth's total carbon
• The cryosphere contains less than 0.01% of the Earth's carbon
• Most of the carbon in the cryosphere is in the soil in permafrost
• The carbon cycle


  Carbon is stored and transferred
• The carbon cycle is a closed system with inputs and outputs of energy but the amount of carbon remains the same
• Some carbon is locked away (sequestered) in long-term stores like rock and fossil fuels
• Major stores and flows in the carbon cycle

  • Burning food
  • Combustion
  • Respiration
  • Vegetation
  • Atmosphere
  • Degrading
  • Respiration
  • Photosynthesis
  • Sequestration
  • Ocean uptake and release
  • Weathering
  • Decomposition
• Fast carbon flows


  Transfer carbon quickly, in minutes, hours or days (e.g. photosynthesis, respiration, combustion, decomposition)
• Slow carbon flows


  Take millions of years for carbon to be sequestered in sedimentary rocks
• Carbon flows depend on spatial scale - plant, ecosystem, continental
• Carbon sequestration


  Capturing and holding carbon in sedimentary rocks or fossil fuels
• Natural events like wildfires and volcanic eruptions can disrupt the carbon cycle
• Wildfires can rapidly release large quantities of carbon from biomass or soil to the atmosphere
• Volcanic eruptions release carbon stored in the lithosphere as CO2 into the atmosphere
• Since the industrial revolution, human impact on the carbon cycle has increased hugely
• Main human causes of carbon cycle changes


  • Hydrocarbon fuel extraction and use
  • Farming practices
  • Deforestation
  • Land use changes
• Extracting and burning fossil fuels releases CO2 into the atmosphere that would otherwise remain sequestered
• Agricultural activities release carbon into the atmosphere through animal respiration, methane from rice paddies, and soil disturbance
• Deforestation reduces the size of the carbon store in the biosphere and can rapidly release carbon if the cleared forest is burned
• Land use change from natural/agricultural to urban reduces carbon storage in vegetation and increases emissions from concrete production
• Carbon budget


  The balance between carbon inputs and outputs in a subsystem
• The carbon cycle affects the atmosphere, land and oceans
• Increased greenhouse gases in the atmosphere due to the carbon cycle can cause global warming
• Changes in the carbon cycle can reduce the amount of carbon stored in land, e.g. through permafrost thaw
• Increased CO2 in the oceans can increase ocean acidity and affect marine life