THE CARBON CYCLE

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THE CARBON CYCLE
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THE CARBON CYCLE

• The movement of carbon, in its many forms,
  between the biosphere, atmosphere, oceans, and
  geosphere is described by the carbon cycle.
• In the cycle there are various sinks, or stores,
  of carbon and processes by which the various
  sinks exchange carbon.
• These processes of exchange include respiration,
  burning, combustion, decomposition, erosion, etc.

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THE CARBON CYCLE

• Over 300 million years ago (Carboniferous
  Period), large amounts of carbon accumulated in
  carbon sinks as coal, peat, oils and natural gas.
  

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THE CARBON CYCLE

• Coal, peat, and natural gas are fossil fuels. It
  took millions of years to make these fuels, but
  we are burning them all up in a few hundred
  years.

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THE CARBON CYCLE

• We are all familiar with how the atmosphere and
  vegetation exchange carbon (photosynthesis and
  respiration).
• Plants absorb CO2 from the atmosphere during
  photosynthesis, also called primary production,
  and release O2 back into the atmosphere.

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CO2
CO2
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• Another major exchange of CO2 occurs between the
  oceans and the atmosphere.
• The dissolved CO2 in the oceans is used by marine
  biota in photosynthesis.
• The ocean is the largest sink of Carbon Dioxide.

CO2
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THE CARBON CYCLE

• Photosynthesis producers take in CO2 from
  atmosphere.
• Respiration aerobic organisms release CO2 into
  atmosphere.
• Decay as a result of decay CO2 released into
  atmosphere.
• Combustion Burning of fossil fuels release CO2
  into atmosphere.

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• The uptake and return of CO2 are not in balance
• The carbon dioxide content of the atmosphere is
  gradually and steadily increasing.
• The increase in CO2 probably began with the start
  of the industrial revolution.
• Samples of air trapped over the centuries in the
  glacial ice of Greenland showed no change in CO2
  content until 300 years ago.

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THE CARBON CYCLE

• Since measurements of atmospheric CO2 began late
  in the nineteenth century, its concentration has
  risen over 20.
• This increase is surely caused by human
  activities
• burning fossil fuels (coal, oil, natural gas)
  returns carbon to the atmosphere, carbon that has
  been locked within the earth for millions of
  years.
• clearing and burning of forests, especially in
  the tropics. In recent decades, large areas of
  the Amazon rain forest have been cleared for
  agriculture and cattle grazing.

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Human Activities Increasing Carbon Dioxide in the
Atmosphere
CO2
CO2
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The Complete Carbon Cycle
CO2
CO2
CO2
CO2
CO2
CO2
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THE GREENHOUSE EFFECT GLOBAL WARMING

• Despite these "sinks" for our greatly increased
  CO2 production, the concentration of atmospheric
  CO2 continues to rise? Should we be worried?
• Carbon dioxide is transparent to light but rather
  opaque (not clear) to heat rays.
• Therefore, CO2 in the atmosphere slows the
  radiation of heat from the earth back into space
  the "greenhouse effect".

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GLOBAL WARMING

• Has the increase in carbon dioxide led to global
  warming?
• Average temperatures do seem to have increased
  slightly (0.6C) in the last century.
• Some evidence comes from
• Careful monitoring of both ocean and land
  temperatures.

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MORE EVIDENCE

• -Many glaciers and ice sheets are receding.
• -Woody shrubs are now growing in areas of
  northern Alaska that 50 years ago were barren
  tundra.
• -Many angiosperms in temperate climates are
  flowering earlier in the spring than they used
  to.
• -Many species of birds and butterflies are moving
  north and breeding earlier in the spring.

• Many glaciers and ice sheets are receding.
• -Woody shrubs are now growing in areas of
  northern Alaska that 50 years ago were barren
  tundra.
• -Many angiosperms in temperate climates are
  flowering earlier in the spring than they used
  to.
• -Many species of birds and butterflies are moving
  north and breeding earlier in the spring.

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GLOBAL WARMING

• Will continued increase in carbon dioxide lead to
  more global warming and, if so, how much?
• At this point, the answer depends on what
  assumptions you plug into your computer models.
• But as the different models have been improved,
  they seem to be converging on a consensus
• a doubling of the CO2 concentration (expected by
  the end of this century) will cause the earth to
  warm somewhere in the range of 2.53.5C.

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Assignment

• On page 35 of your booklet there are 5 questions.
• In groups answer these questions on chart paper
  and be prepared to present your groups answers
  to the class.