MET%20112%20Global%20Climate%20Change%20-%20Lecture%206

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MET 112 Global Climate Change - Lecture 6

• The Carbon Cycle
• Eugene Cordero
• San Jose State University

• Outline
• Earth system perspective
• Carbon whats the big deal?
• Carbon exchanges
• Long term carbon exchanges

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Why are automakers suing California?

1. For regulating emissions of CFCs
2. For limiting number of SUV sales emissions of
   nitrogen
3. For limiting number of minivan sales.
4. For regulating GHG emissions

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Why is California suing automakers

1. For suing California in the first place
2. For violating emission standards
3. For producing autos that contribute to global
   warming
4. For producing ozone depleting gases

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Goals

• We want to understand the difference between
  short term and long term carbon cycle
• We want to understand the main components of the
  long term carbon cycle

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An Earth System Perspective

• Earth composed of
• These Machines run the Earth
• Holistic view of planet

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An Earth System Perspective

• Earth composed of
• Atmosphere
• Hydrosphere
• Cryosphere
• Land Surfaces
• Biosphere
• These Machines run the Earth
• Holistic view of planet

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The Earths history can be characterized by
different geologic events or eras.
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Hydrosphere

• Component comprising all liquid water
• Surface and subterranean (ground water)
• Thuslakes, streams, rivers, oceans
• Oceans
• Oceans currently cover
• Average depth of oceans
• Oceans store large amount of energy
• Oceans dissolve carbon dioxide (more later)
• Sea Level has varied significantly over Earths
  history

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Hydrosphere

• Component comprising all liquid water
• Surface and subterranean (ground water)
• Fresh/Salt water
• Thuslakes, streams, rivers, oceans
• Oceans
• Oceans currently cover 70 of earth
• Average depth of oceans 3.5 km
• Oceans store large amount of energy
• Oceans dissolve carbon dioxide (more later)
• Circulation driven by wind systems
• Sea Level has varied significantly over Earths
  history
• Slow to heat up and cool down

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Cryosphere

• Component comprising all ice
• Antarctica, Greenland, Patagonia
• Climate
• Typically high albedo surface
• Positive feedback possibility (more later)

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Cryosphere

• Component comprising all ice
• Glaciers
• Ice sheets
• Antarctica, Greenland, Patagonia
• Sea Ice
• Snow Fields
• Climate
• Typically high albedo surface
• Positive feedback possibility Store large amounts
  of water sea level variations.

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Land Surfaces

• Soils surfaces and vegetation
• Climate
• Location of continents controls ocean/atmosphere
  circulations
• Volcanoes return CO2 to atmosphere

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Land Surfaces

• Continents
• Soils surfaces and vegetation
• Volcanoes
• Climate
• Location of continents controls ocean/atmosphere
  circulations
• Volcanoes return CO2 to atmosphere
• Volcanic aerosols affect climate

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Biosphere

• All living organisms (Biota)
• Biota- "The living plants and animals of a
  region. or "The sum total of all organisms alive
  today
• Climate
• Photosynthetic process stores significant amount
  of carbon (from CO2)

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Biosphere

• All living organisms (Biota)
• Biota- "The living plants and animals of a
  region. or "The sum total of all organisms alive
  today
• Marine
• Terrestrial
• Climate
• Photosynthetic process store significant amount
  of carbon (from CO2)

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Some Interactions Between Components of Climate
System

• Hydrologic Cycle (Hydrosphere, Surface,and
  Atmosphere)
• Evaporation from surface puts water vapor into
  atmosphere
• Precipitation transfers water from atmosphere to
  surface
• Cryosphere-Hydrosphere

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Interactions Between Components of Earth System

• Hydrologic Cycle (Hydrosphere, Surface,and
  Atmosphere)
• Evaporation from surface puts water vapor into
  atmosphere
• Precipitation transfers water from atmosphere to
  surface
• Cryosphere-Hydrosphere
• When glaciers and ice sheets shrink, sea level
  rises
• When glaciers and ice sheets grow, sea level
  falls

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When ice sheets melt and thus sea levels rise,
which components of the earth system are
interacting?

1. Atmosphere-Cryosphere
2. Atmosphere-Hydropshere
3. Hydrosphere-Cryosphere
4. Atmosphere-Biosphere
5. Hydrosphere-Biosphere

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When water from lakes and the ocean evaporates,
which components of the earth system are
interacting?

• Land Surface atmosphere
• Hydrosphere-atmosphere
• Hydrosphere-land surface
• Crysophere-Atmosphere
• Biosphere-Atmosphere

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The Earths history can be characterized by
different geologic events or eras.
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Interactions (cont)

• Components of the Earth System are linked by
  various exchanges including
• In this lecture, we are going to focus on the
  exchange of Carbon within the Earth System

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Interactions (cont)

• Components of the Earth System are linked by
  various exchanges including
• Energy
• Water (previous example)
• Carbon
• In this lecture, we are going to focus on the
  exchange of Carbon within the Earth System

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Carbon what is it?

• Carbon (C), the fourth most abundant element in
  the Universe,
• Building block of life.
• Carbon cycles through the land, ocean,
  atmosphere, and the Earths interior
• Carbon found

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Carbon what is it?

• Carbon (C), the fourth most abundant element in
  the Universe,
• Building block of life.
• from fossil fuels and DNA
• Carbon cycles through the land (bioshpere),
  ocean, atmosphere, and the Earths interior
• Carbon found
• in all living things,
• in the atmosphere,
• in the layers of limestone sediment on the ocean
  floor,
• in fossil fuels like coal.

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Carbon where is it?

• Exists
• Atmosphere
• Living biota (plants/animals)
• Soils and Detritus
• Carbon
• Oceans
• Most carbon in the deep ocean

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Carbon where is it?

• Exists
• Atmosphere
• CO2 and CH4 (to lesser extent)
• Living biota (plants/animals)
• Carbon
• Soils and Detritus
• Carbon
• Methane
• Oceans
• Dissolved CO2
• Most carbon in the deep ocean

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Carbon conservation

• Initial carbon present during Earths formation
• Carbon is exchanged between different components
  of Earth System.

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Carbon conservation

• Initial carbon present during Earths formation
• Carbon doesnt increase or decrease globally
• Carbon is exchanged between different components
  of Earth System.

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The Carbon Cycle

• The complex series of reactions by which carbon
  passes through the Earth's
• Atmosphere
• Carbon is exchanged in the earth system at all
  time scales
• Short term cycle (from seconds to a few years)

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The Carbon Cycle

• The complex series of reactions by which carbon
  passes through the Earth's
• Atmosphere
• Land (biosphere and Earths crust)
• Oceans
• Carbon is exchanged in the earth system at all
  time scales
• Long term cycle (hundreds to millions of years)
• Short term cycle (from seconds to a few years)

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The carbon cycle has different speeds Short Term
Carbon Cycle Long Term Carbon Cycle
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Short Term Carbon Cycle

• One example of the short term carbon cycle
  involves plants
• Photosynthesis
• Plants require
• Sunlight, water and carbon, (from CO2 in
  atmosphere or ocean) to produce carbohydrates
  (food) to grow.
• When plants decays, carbon is mostly returned to
  the atmosphere (respiration)
• During spring (more photosynthesis)
• During fall (more respiration)

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Short Term Carbon Cycle

• One example of the short term carbon cycle
  involves plants
• Photosynthesis is the conversion of carbon
  dioxide and water into a sugar called glucose
  (carbohydrate) using sunlight energy. Oxygen is
  produced as a waste product.
• Plants require
• Sunlight, water and carbon, (from CO2 in
  atmosphere or ocean) to produce carbohydrates
  (food) to grow.
• When plants decays, carbon is mostly returned to
  the atmosphere (respiration)
• Global CO2

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Short Term Carbon Cycle

• One example of the short term carbon cycle
  involves plants
• Photosynthesis is the conversion of carbon
  dioxide and water into a sugar called glucose
  (carbohydrate) using sunlight energy. Oxygen is
  produced as a waste product.
• Plants require
• Sunlight, water and carbon, (from CO2 in
  atmosphere or ocean) to produce carbohydrates
  (food) to grow.
• When plants decays, carbon is mostly returned to
  the atmosphere (respiration)
• During spring (more photosynthesis)
• atmospheric CO2 levels go down (slightly)
• During fall (more respiration)
• atmospheric CO2 levels go up (slightly)

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Carbon exchange (short term)

• Other examples of short term carbon exchanges
  include
• Soils and Detritus
• Surface Oceans
• also release CO2

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Carbon exchange (short term)

• Other examples of short term carbon exchanges
  include
• Soils and Detritus
• organic matter decays and releases carbon
• Surface Oceans
• absorb CO2 via photosynthesis
• also release CO2

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Short Term Carbon Exchanges
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In Class Question Explain why CO2
concentrations goes up and down each year
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Long Term Carbon Cycle
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Long Term Carbon Cycle

• Carbon is slowly and continuously being
  transported around our earth system.
• Between atmosphere/ocean/biosphere
• And the Earths crust (rocks like limestone)
• The main components to the long term carbon
  cycle

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Long Term Carbon Cycle

• Carbon is slowly and continuously being
  transported around our earth system.
• Between atmosphere/ocean/biosphere
• And the Earths crust (rocks like limestone)
• The main components to the long term carbon
  cycle
• Chemical weathering (or called silicate to
  carbonate conversion process)
• Volcanism/Subduction
• Organic carbon burial
• Oxidation of organic carbon

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The Long-Term Carbon Cycle (Diagram)
Atmosphere (CO2) Ocean (Dissolved CO2) Biosphere
(Organic Carbon)
Subduction/Volcanism
Oxidation of Buried Organic Carbon
Silicate-to-Carbonate Conversion
Organic Carbon Burial
Carbonates
Buried Organic Carbon
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Where is most of the carbon today?

• Most Carbon is locked away in the earths crust
  (i.e. rocks) as
• Limestone is mainly made of calcium carbonate
  (CaCO3)
• Carbonates are formed by a complex geochemical
  process called

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Where is most of the carbon today?

• Most Carbon is locked away in the earths crust
  (i.e. rocks) as
• Carbonates (containing carbon)
• Limestone is mainly made of calcium carbonate
  (CaCO3)
• Carbonates are formed by a complex geochemical
  process called
• Silicate-to-Carbonate Conversion (long term
  carbon cycle)

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Silicate to carbonate conversion chemical
weathering One component of the long term carbon
cycle
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Granite (A Silicate Rock)
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Limestone (A Carbonate Rock)
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Silicate-to-Carbonate Conversion

• Chemical Weathering Phase
• Carbonic acid dissolves silicate rock
• Transport Phase
• Formation Phase
• In oceans, calcium carbonate precipitates out of
  solution and settles to the bottom

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Silicate-to-Carbonate Conversion

• Chemical Weathering Phase
• CO2 rainwater ? carbonic acid
• Carbonic acid dissolves silicate rock
• Transport Phase
• Solution products transported to ocean by rivers
• Formation Phase
• In oceans, calcium carbonate precipitates out of
  solution and settles to the bottom

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Silicate-to-Carbonate Conversion
Rain
1. CO2 Dissolves in Rainwater
2. Acid Dissolves Silicates
3. Dissolved Material Transported to Oceans
4.
Land
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Silicate-to-Carbonate Conversion
Rain
1. CO2 Dissolves in Rainwater
2. Acid Dissolves Silicates (carbonic acid)
3. Dissolved Material Transported to Oceans
4. CaCO3 Forms in Ocean and Settles to the Bottom
Land
Calcium carbonate
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Changes in chemical weathering

• The process is temperature dependant
• rate of evaporation of water is temperature
  dependant
• Thus as CO2 in the atmosphere rises, the planet
  warms. Evaporation increases, thus the flow of
  carbon into the rock cycle increases removing CO2
  from the atmosphere and lowering the planets
  temperature

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Changes in chemical weathering

• The process is temperature dependant
• rate of evaporation of water is temperature
  dependant
• so, increasing temperature increases weathering
  (more water vapor, more clouds, more rain)
• Thus as CO2 in the atmosphere rises, the planet
  warms. Evaporation increases, thus the flow of
  carbon into the rock cycle increases removing CO2
  from the atmosphere and lowering the planets
  temperature
• Negative feedback

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Earth vs. Venus

• The amount of carbon in carbonate minerals (e.g.,
  limestone) is approximately
• On Earth, most of the CO2 produced is
• On Venus, the silicate-to-carbonate conversion
  process apparently never took place

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Earth vs. Venus

• The amount of carbon in carbonate minerals (e.g.,
  limestone) is approximately
• the same as the amount of carbon in Venus
  atmosphere
• On Earth, most of the CO2 produced is
• now locked up in the carbonates
• On Venus, the silicate-to-carbonate conversion
  process apparently never took place

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Subjuction/Volcanism

• Another Component of the Long-Term Carbon Cycle

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Subduction
During this processes, extreme heat and
pressure convert carbonate rocks eventually into
CO2
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Subduction
Definition The process of the ocean plate
descending beneath the continental plate.
During this processes, extreme heat and
pressure convert carbonate rocks eventually into
CO2
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Volcanic Eruption
Eruption injected (Mt megatons) 17 Mt SO2,
3 Mt Cl,
Mt. Pinatubo (June 15, 1991)
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Volcanic Eruption
Eruption injected (Mt megatons) 17 Mt SO2, 42
Mt CO2, 3 Mt Cl, 491 Mt H2O
Can inject large amounts of CO2 into the
atmosphere
Mt. Pinatubo (June 15, 1991)
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Organic Carbon Burial/Oxidation of Buried Carbon

• Another Component of the Long-Term Carbon Cycle

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Buried organic carbon (1)

• Living plants remove CO2 from the atmosphere by
  the process of
• When dead plants decay, the CO2 is put back into
  the atmosphere
• However, some carbon escapes oxidation when it is
  covered up by sediments

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Buried organic carbon (1)

• Living plants remove CO2 from the atmosphere by
  the process of
• photosynthesis
• When dead plants decay, the CO2 is put back into
  the atmosphere
• fairly quickly when the carbon in the plants is
  oxidized
• However, some carbon escapes oxidation when it is
  covered up by sediments

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Organic Carbon Burial Process
O2
C
C
Some Carbon escapes oxidation
C
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Organic Carbon Burial Process
O2
CO2 Removed by Photo-Synthesis
CO2 Put Into Atmosphere by Decay
C
C
Some Carbon escapes oxidation
C
Result Carbon into land
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Oxidation of Buried Organic Carbon

• Eventually, buried organic carbon may be exposed
  by erosion
• The carbon is then oxidized to CO2

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Oxidation of Buried Organic Carbon
Atmosphere
Buried Carbon (e.g., coal)
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Oxidation of Buried Organic Carbon
Atmosphere
Erosion
Buried Carbon (e.g., coal)
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Oxidation of Buried Organic Carbon
Atmosphere
CO2
O2
C
Buried Carbon
Result Carbon into atmosphere (CO2)
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The Long-Term Carbon Cycle

• Inorganic Component
• Subduction/Volcanism
• Organic Component
• Oxidation of Buried Organic Carbon

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The (Almost) Complete Long-Term Carbon Cycle

• Inorganic Component
• Silicate-to-Carbonate Conversion
• Subduction/Volcanism
• Organic Component
• Organic Carbon Burial
• Oxidation of Buried Organic Carbon

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The Long-Term Carbon Cycle (Diagram)
Atmosphere (CO2) Ocean (Dissolved CO2) Biosphere
(Organic Carbon)
Silicate-to-Carbonate Conversion
Organic Carbon Burial
Carbonates
Buried Organic Carbon
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The Long-Term Carbon Cycle (Diagram)
Atmosphere (CO2) Ocean (Dissolved CO2) Biosphere
(Organic Carbon)
Subduction/Volcanism
Oxidation of Buried Organic Carbon
Silicate-to-Carbonate Conversion
Organic Carbon Burial
Carbonates
Buried Organic Carbon
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• Review of Long Term Carbon Cycle

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If volcanism was to increase over a period of
thousands of years, how would this affect
atmospheric CO2 levels?
Atmospheric CO2 levels would

• Increase
• Decrease
• Stay the same
• Are not related to volcanism

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If the silicate to carbonate conversion process
was to increase over a period of millions of
years, how would this affect volcanism?
Volcanism would

• Increase
• Decrease
• Stay the same
• Not be affected by the silicate to carbonate
  conversion process

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If the oxidation of organic carbon was to
increase, how would global temperatures respond?
Global temperatures

• Would increase
• Would decrease
• Would stay the same
• Are not affected by the oxidation of organic
  carbon

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If there was a decline in the silicate to
carbonate conversion process, how would global
temperatures respond?
Global temperatures

• Would increase
• Would decrease
• Would stay the same
• Are not affected by the silicate to carbonate
  conversion process

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Activity (groups of two)

• Imagine that the global temperature were to
  increase significantly for some reason.
• How would the silicate-to-carbonate conversion
  process change during this warming period.
  Explain.
• How would this affect atmospheric CO2 levels and
  as a result, global temperature?
• What type of feedback process would this be and
  why (positive or negative)?

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The silicate to carbonate conversion processes
would

• Imagine that the global temperature were to
  increase significantly for some reason.

• Increase
• Decrease
• Remain unchanged
• Impossible to tell

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How would atmospheric CO2 levels change?

1. Increase
2. Decrease
3. Stay the same
4. Impossible to tell

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How would this affect global temps?

1. Increase
2. Decrease
3. Stay the same
4. Impossible to tell

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What type of feedback process would this be

1. Positive
2. Negative
3. Neither
4. Both

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• End

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Effect of Imbalances
Atmosphere-Ocean-Biosphere
What would happen?
Earths Crust
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Long term carbon cycle
If the carbon cycle was in balance, then the
amount of carbon going into the Earths crust
would equal the amount leaving
Atmosphere-Ocean-Biosphere
Earths Crust
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Effect of Imbalances

• Imbalances in the long-term carbon cycle can
  cause slow, but sizeable changes in atmospheric
  CO2

Atmosphere-Ocean-Biosphere
What would happen?
Earths Crust
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• Consider the long term carbon cycle as seen below
• Suppose the Atmosphere-Ocean-Biosphere has 40,000
  Gt of carbon and the earths crust has
  40,000,000 Gt of carbon

Atmosphere-Ocean-Biosphere
1 Gt 1015 grams
Earths Crust
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• Suppose that an imbalance developed in which the
  amount leaving the Atm/Ocean/Biosphere was to
  decrease by 1.
• If the arrows represent flux (carbon moving), and
  flux from the Earths crust to the atm/ocean/bio
  (labeled B) is 0.03Gt/year, what would the flux
  be for arrow A?

Atmosphere-Ocean-Biosphere 40,000 Gt
1 Gt 1015 grams
0.0300 Gt./yr
A
B
Earths Crust 40,000,000 Gt
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Arrow A would be

• 0.03 Gt/yr
• 0.3 Gt/yr
• 0.0297 Gt/yr
• 0.0303 Gt/yr

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• For such an imbalance as shown below, what is the
  net carbon flux and in what direction?

Atmosphere-Ocean-Biosphere 40,000 Gt
1 Gt 1015 grams
0.0297 Gt./yr
0.0300 Gt./yr
A
B
Earths Crust 40,000,000 Gt
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For such an imbalance as shown below, what is the
net carbon flux and in what direction?

• 0.033 - up
• 0.033 down
• 0.0003 up
• 0.0003 down

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• Based on the below Carbon Flux information, how
  many years will it take for the carbon in the
  atm/ocean/bio to double?

1 Gt 1015 grams
Atmosphere-Ocean-Biosphere 40,000 Gt
Net Carbon Flux
0.0297 Gt./yr
0.0300 Gt./yr
0.0003 Gt./yr
A
B
Earths Crust 40,000,000 Gt
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How many years will it take for the carbon in the
atm/ocean/bio to double?

1. 0.03 years
2. 12 years
3. 100,000 years
4. 133 million years

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• Based on the below Carbon Flux information, how
  many years will it take for the carbon in the
  atm/ocean/bio to double?

Answer 40, 000/.0003 years 133 million years
1 Gt 1015 grams
Atmosphere-Ocean-Biosphere
Net Carbon Flux
0.0297 Gt./yr
0.0300 Gt./yr
0.0003 Gt./yr
A
B
Earths Crust
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Long-Term CO2 Changes
Source Berner, R. A., The rise of plants and
their effect on weathering and atmospheric CO2.
Science, 276, 544-546.
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Time Scale (Continued)

• The preceding operation would remove 40, 000 Gt.
  of carbon from the crust
• This is only 0.1 of the carbon in the crust
• Thus, it is perfectly plausible that such an
  imbalance could be sustained

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Carbon cycle inorganic/organic

• Inorganic
• Carbon exists in the atmosphere (CO2, CH4) and
  many rocks (sedimentary)
• CO2 is exchanged between the atmosphere and
  oceans by diffusion.
• CO2 and water produces chemical weathering
• Organic
• Carbon enters biological cycle through
  photosynthesis
• Carbon stored in the woody parts of vegetation,
  especially trees.
• Carbon leaves the biological cycle through
  respiration.
• Some carbon stored in organisms bodies or soil,
  rather than being released through respiration.

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Carbon in the oceans

• CO2 dissolved in water is used in formation of
  the shells and skeletons of marine organisms
  (mostly CaCO3).
• When organisms die, shells either dissolve or are
  incorporated into marine sediments, entering the
  rock cycle as sedimentary rocks
• This process has created the planets largest
  carbon reservoir - rocks

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The Carbon Silicate Cycle

• About 80 of the CO2 exchanged between solid
  earth and atmosphere
• uses the Carbon-Silicate cycle
• Cycle very slow, 0.5 billion yrs per cycle
• CO2 dissolves in water to give carbonic acid
• Acid causes erosion of the rocks which are mostly
  rich in silicate
• Weathering releases calcium and bicarbonate ions
  that find their way to the sea
• Marine organisms use those elements to form their
  shells
• Dead marine organisms enter sedimentary rocks.

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The Carbon Cycle
Air
Land/Ocean
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Long-Term Carbon Cycle (Quantitative Assessment)
Carbon Content 40, 000 Gt.
Atmosphere-Ocean-Biosphere
Carbon Content 40, 000, 000 Gt.
Earths Crust
1 Gt 1015 grams
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Long-Term Carbon Cycle (Quantitative Assessment)
Carbon Content 40, 000 Gt.
Atmosphere-Ocean-Biosphere
Carbon Flux 0.03 Gt/yr
Carbon Flux 0.03 Gt/yr
Carbon Content 40, 000, 000 Gt.
Earths Crust
1 Gt 1015 grams
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Time Scale of Long-Term Carbon Cycle

• Suppose that a 1 imbalance developed
• How long would it take to double the amount of
  carbon in the atmosphere-ocean-biosphere?

Carbon Content 40, 000 Gt.
0.0300 Gt./yr
Net Carbon Flux
Carbon Content 40, 000, 000 Gt.
Answer
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Time Scale of Long-Term Carbon Cycle

• Suppose that a 1 imbalance developed
• How long would it take to double the amount of
  carbon in the atmosphere-ocean-biosphere?

Carbon Content 40, 000 Gt.
0.0297 Gt./yr
0.0003 Gt./yr
0.0300 Gt./yr
Net Carbon Flux
Carbon Content 40, 000, 000 Gt.
Answer 40, 000/.0003 years 133 million years
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The Carbon Cycle
Short term (fast 1-5 years)
Long term (thousands of years)
Air
Land/Ocean