Elevated CO2 and the global C cycle

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Elevated CO2 and the global C cycle

• I. Is atmospheric CO2 increasing?
• - Historic, millenial, and ice age patterns
• II. Is it caused by humans?
• - 3 lines of evidence
• III. Consequences
• Direct
• Indirect

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Rising atmospheric CO2
Schlesinger 1997
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Questions

• 1. How does this fit into Earths long-term
  history?
• 2. How do we know if recent changes are caused by
  human activities?
• 3. What might be the consequences?

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23.22
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23.21
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http//www.realclimate.org/index.php/archives/2005
/11/650000-years-of-greenhouse-gas-concentrations/
Heres the more recent 650,000 year record from
the EPICA ice core in Antarctica. The black line
is the temperature proxy.
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Questions

• 1. How does this fit into Earths long-term
  history?
• 2. How do we know if recent changes are caused by
  human activities?
• a. Timing
• b. C budgeting
• c. C signatures 14C
• 3. What might be the consequences?

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Rising atmospheric CO2
Schlesinger 1997
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Global carbon budgeting
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The Global Carbon Cycle - 1990sUnits Gt C and Gt
C y-1
Atmosphere
3.2
are leading to a build up of CO2 in the
atmosphere.
750
63
6.3
Fossil Deposits
About 16,000
1.6
60
Plants
Fossil emissions ...
500
Soil
91.7
90
2000
and land clearing in the tropics...
The KP seeks to reduce net carbon emissions by
about 0.3 Gt C below 1990 levels from
industrial countries
Oceans
39,000
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Questions

• 1. How does this fit into Earths long-term
  history?
• 2. How do we know if recent changes are caused by
  human activities?
• 3. What might be the consequences?

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Consequences of Elevated CO2

• Direct effects more on these later
• On plant growth
• On decomposition
• 2. Indirect effects
• Warming
• Effects of warming
• Sea level rise
• Changes in precipitation
• Storm frequency and intensity?
• Biological changes species range shifts,
  diseases?

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Enhanced greenhouse effect
StarrTaggart Fig. 37.12
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Elevated CO2 effects increased temperature
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Global Warming effects sea level rise
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Global Warming effects extreme weather
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Remaining questions

• How much warming will occur?
• How distributed?
• Consequences?
• What can be done? (Adaptation, mitigation)

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Greenhouse gas emission scenarios
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Global Warming effects long-term
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The Global Carbon Cycle - 1990sUnits Gt C and Gt
C y-1
Atmosphere
3.2
are leading to a build up of CO2 in the
atmosphere.
750
63
6.3
Fossil Deposits
About 16,000
1.6
60
Plants
Fossil emissions ...
500
Soil
91.7
90
2000
and land clearing in the tropics...
The KP seeks to reduce net carbon emissions by
about 0.3 Gt C below 1990 levels from
industrial countries
Oceans
39,000
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Questions

• What causes uptake by natural systems?
• How much capacity to continue absorbing CO2?
• What might limit their uptake capacity?
• What can we do to enhance ecosystem uptake and
  thereby slow the atmospheric increase?

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The End
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Global Warming effects change in precipitation