Lecture 26: The Global Carbon Cycle

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Lecture 26 The Global Carbon Cycle  

• By the end of this lecture you should be able to
• Describe the main pools and fluxes in the global
  C cycle.
• Concepts and terms gigaton
•  Discuss the imbalance in the global C cycle.
• Concepts and terms missing sink
•  Discuss the relative contribution of fossil fuel
  combustion and changes in land use to the change
  in atmospheric CO2.
•  Describe the Mauna Loa Curve..
• Concepts and terms periodicity, latitude
  effect

• Describe the greenhouse effect.
• Concepts and terms greenhouse gas, radiative
  forcing
• Discuss observed temperature changes and the
  projections for rapid climate change resulting
  from human activities.
• Concepts and terms  global circulation model
• Assigned Readings Chapter 54, pages 1208-1221
  Intergovernmental Panel on Climate Change (IPCC
  http//www.ipcc.ch/) United Nations
  Environmental Program (UNEP http//www.grida.no/c
  limate/vital/06.htm)

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Pool, flux, source, sink, gigaton (1015 g),
missing carbon sink
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Carbon dioxide emissions comes from energy
production, industrial processes and
transport. http//www.grida.no/climate/vital/09.ht
m
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http//www.grida.no/climate/vital/11.htm
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Emissions of carbon dioxide due to changes in
land use mainly come from the cutting down of
forests and instead using the land for
agriculture or built-up areas, urbanisation,
roads etc. http//www.grida.no/climate/vital/10.h
tm
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An area of tropical forest the size of North
Carolina is deforested every year.
http//earthobservatory.nasa.gov/Library/Deforesta
tion/deforestation_2.html
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Annual net flux of carbon in the United States as
a result of changes in land use. Houghton et al.
Science 285, 574 (1999)
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http//cdiac.esd.ornl.gov/trends/landuse/houghton/
houghton.gif
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Mauna Loa, Hawaii, U.S.A.Barren lava field of an
active volcano1932' N, 15535' W, 3397 m above
MSL
http//cdiac.esd.ornl.gov/trends/co2/sio-mlo.htm
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Indicators of the Human Influenceon the
Atmosphere during the Industrial Era
Source IPCC TAR 2001
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Pool, flux, source, sink, gigaton (1015 g),
missing carbon sink
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Duke FACTS-1 experimenthttp//cdiac.esd.ornl.gov/
programs/FACE/face.html
18 year-old forest 6, 30-m plots 100 pine
trees/plot 50 woody species 5 years of CO2
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CO2 stimulation of photosynthesis

• Current CO2 level
• Elevated CO2 level future

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Basal area -- productivity -- CO2 uptake
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Carbon budget for a pine forest under CO2
enrichment in the Duke FACTS-1 experiment Open
bubbles represent ambient plots closed bubbles
represent fumigated plots.
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Infrared radiation
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http//www.climateark.org/vital/05.htm
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http//cdiac.esd.ornl.gov/trends/meth/methane.gif
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http//www.climateark.org/vital/04.htm
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Variations of the Earths Surface Temperature

• relative to 1961-1990 average

Source IPCC TAR 2001
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Projected Changes in Annual Temperatures for the
2050s
The projected change is compared to the present
day with a 1 increase per year in equivalent CO2
Source The Met Office. Hadley Center for Climate
Prediction and Research
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Projected Changes in Annual Precipitation for the
2050s
The projected change is compared to the present
day with a 1 increase per year in equivalent CO2
Source The Met Office. Hadley Center for Climate
Prediction and Research
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Extreme Events
Judgmental estimates of confidence by IPCC very
likely - 90-99 chance, likely - 66-90 chance.
Source IPCC TAR 2001