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Carbon Cycle
Also see Chapter 6 of IPCC 2013
http://www.climatechange2013.org/report/full-report/
Carbon Cycle
Carbon Cycle
Approximately 0.2 Gtonne/year goes into solid earth
And 0.2 Gt/yr goes into atmosphere from outgassing
Today 2012 approximately 10 Gt/yr are put into the atomosphere from
Fossil fuel emission and cement manufactoring
Thus natural fluxes from volcanoes and outgassing account for about 2%
of the anthropogenic sources.
Carbon Cycle
1.6 Gt/yr from deforestation
6.4 Gt/yr from fossil fuel emission (1994)
1.6/8.0=0.20=20% (deforestation accounts for 20 % of total
Carbon flux into atmosphere)
Biosphere takes up (2.6 Gt /yr more ) carbon than it did in
preindustrial times.
Biosphere takes up (2.6 Gt /yr more ) carbon than it did in
preindustrial times.
Preindustrial RR=120 GT/yr Now it is 122.6 Gt/yr
RR=Content/lifetime
Preindustrial content =597 Gt
Now(1994)= 763 Gt
2000-2009 mean
land use changes
account for about
1.1/8.9=12 % of
anthropogenic
carbon emissiosn
Figure 6.1 IPCC 2013 WG1AR5
The atmosphere contains the least amount of carbon and
sediments and rocks contain the most.
The ultimate removal of carbon from the climate system is an extremely slow
process. In nature this is balanced by the slow injection of carbon into the
atmosphere by volcanoes and outgassing near mid ocean ridges. When humans
bring carbon in the form of fossil fuels (coal, natural gas, oil) to the surface they
rapidly disrupt this balance.
The annual cycle of vegetation is dominated by flucuations in the
Northern hemisphere.
Short Term Carbon Cycle
Short Term Carbon Cycle
As atmospheric CO2 increases
from photosynthesis or
combustion, O2 decreases.
O2 is presently decreasing faster
than atmospheric CO2 is
increasing. This indicates the
importance of the oceans in
removing CO2 from the
atmosphere.
13C/12C
ratios in atmospheric
CO2 are lower for human activity
than for natural processes.
Seasonal Cycle is driven by Northern Hemisphere Vegetation
When the atmospheric carbon dioxide increases plants are growing or decaying? Circle one.
When the atmospheric carbon dioxide decreases plants are growing or decaying? Circle one.
Seasonal Cycle is driven by Northern Hemisphere Vegetation
When the atmospheric carbon dioxide increases plants are growing or decaying? Circle one.
When the atmospheric carbon dioxide decreases plants are growing or decaying? Circle one.
From www.learner.org/courses/envsci/ Unit 12
Photosynthesis buffers climate change (i.e. is a negative feedback)
Between -10 deg C and 30 deg C
The rate of photosynthesis increases
With increasing temperature.
Atmospheric carbon dioxide concentrations are strongly
correlated with surface temperatures on most time scales.
+sunlight
The solubility of gases like CO2 in water increases
with decreasing temperature.
Positive climate feedback
Phytoplankton shell: Diatom (SiO2)
Phytoplankton Shell: coccolithophorid (CaCO3
Zooplankton shell: Foraminifer (CaCO3)
Zooplankton shell: Radiolarian SiO2
More Ice on continents leaves more 18O in oceans
Ocean Biological Pump. Slowly taking Carbon to the seafloor for
ultimate burial. Most of this carbon (~99%) is recycled back to the
surface a very small fraction is removed from the ocean into the
deep earth.
Coastal Zone Color scanner
http://earthobservatory.nasa.gov/IOTD/view.php?id=1297
pH 7.0 is neutral (not acidic not alkaline) less than 7.0 is
acidic greater than 7.0 is alkaline. pH of 2.0 is highly
acidic.
Long term Carbon Cycle
Draw a causal loop diagram
Describing the feedback
structure at left. Is this a positive
or negative feedback structure?
All loops are negative feedbacks
It appears that weathering of carbonate rock does not remove CO2
from the climate system.
However some of the newly formed CaCO3 IS incorporated into
shells and fall to the bottom of the ocean
Weather of silicate rock removes CO2 from the climate system.
Outgassing is the release of CO2 via volcanic activity and seafloor
spreading. Over the long term (millions of years) the CO2 flux
from outgassing is in near balance with the removal of carbon from
the subduction of carbonate sediments. CO2 from outgassing and
volcanoes contributes about 2% to the total global emissions in
2010.
Global temperatures
would increase with fast
sea floor spreading and
decrease with slow sea
floor spreading.
Small fragmented rocks have much more surface area
compared to large rocks and hence weather more easily.
80 % of chemically
weathered ions in
Amazon come from
the Andes.
The Andes have been
uplifted in the past 20
Million years.
Most uplift in the western US region occurred 70 to 45 Myr ago
Biomass growth (Lichen) on rocks can enhance the weathering
process.
The end
Residence Time
Residence Time
Source=inflow
Removal Rate= outflow
Content
Content
Content
Content
RR 



Resident Time lifetime ResponseTime Time Constant
Residence Time
Source=inflow
Removal Rate= outflow
At equilibrium (steady state)
inflow = outflow
 Equilibriu m Content 
Source  

 Resident Time 
Equilibriu m Content  Source * Residence time
A lake has an annual average outflow of 5 Mgallons per year
(5,000,000 gal/yr) and an annual average content of 10
Mgallons. From this information estimate the residence
time for the lake.
If the annual mean inflow into the lake increased to 20
Mgallons/yr what would be the new steady state content of
the lake?
A lake has an annual average outflow of 5 Mgallons per year (5,000,000
gal/yr) and an annual average content of 10 Mgallons. From this
information estimate the residence time for the lake.
Content
RR 
Resident Time
or
10
5
Resident Time
10 Mgal
Resident Time 
 2 yr
5 Mgal/yr
If the annual mean inflow into the lake increased to 20 Mgallons/yr what
would be the new steady state content of the lake?
Steady State Content  Source * Residence time
=20 Mgal/yr*2 yr=40 Mgal
CFC-12 has an atmospheric lifetime of 100 yrs. In the
1980s the emission rate of CFC-12 was 22 ppt/yr.
What is the corresponding equilibrium concentration of
CFC-12?
CFC-12 has an atmospheric lifetime of 100 yrs. In the
1980s the emission rate of CFC-12 was 22 ppt/yr.
What is the corresponding equilibrium concentration of
CFC-12?
Steady State Content  Source * Residence time
=22 ppt/yr*100yr=2200 ppt
Note: the highest CFC -12 concentration level reached was 540
ppt. International agreements to phase out production and use of
CFC-12 ( reduce emissions) were able to keep levels down.
CFC-12 has an atmospheric lifetime of 100 yrs. In the
1980s the emission rate of CFC-12 was 22 ppt/yr.
What emission rate (source) would limit the steady state
atmospheric concentration of CFC-12 to 500 ppt?
=22 ppt/yr*100yr=2200 ppt
CFC-12 has an atmospheric lifetime of 100 yrs. In the
1980s the emission rate of CFC-12 was 22 ppt/yr.
What emission rate (source) would limit the steady state
atmospheric concentration of CFC-12 to 500 ppt?
Steady State Content  Source * Residence time
or
Steady State Concentration 500 ppt
Emission source 

 5 ppt/yr
Residence time
100 yr
This is less than 25% of the 1980s emission rate.
water
Porosity: the fraction of rock that is pore space
Permeability: the ability of a fluid to be able to flow through
a rock formation.
Gas, oil, and water are often trapped in porous rock with an
impermeable cap. Gas on top, then oil, then water
From www.learner.org/courses/envsci/ Unit 1
http://en.wikipedia.org/wiki/File:Hubbert_peak_oil_plot.svg