Transcript METO112-carbon - Department of Meteorology and Climate

MET 112 Global Climate Change
The Carbon Cycle
Professor Menglin Jin
San Jose State University, Department
of Meteorology
An Earth System Perspective
• Earth composed of:
– Atmosphere
– Hydrosphere
– Cryosphere
– Land Surfaces
– Biosphere
• These ‘Machines’ run the Earth
• Holistic view of planet…
The Carbon Cycle
 The complex series of reactions by which carbon
passes through the Earth's
– Atmosphere
– Land (biosphere and Earth’s 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)
The carbon cycle has different speeds!
Short Term Carbon Cycle
Long Term Carbon Cycle
A cartoon of the global carbon cycle.
Pools (in black) are gigatons (1Gt = 1x109 Tons) of carbon,
and fluxes (in purple) are Gt carbon per year.
Definition of Carbon Cycle
The movement of carbon, in its many forms,
between the atmosphere, oceans, biosphere, and geosphere
is described by the carbon cycle
This cycle consists of several storage pools of carbon (black text)
and the processes by which the various pools exchange carbon
(purple arrows and numbers)
net carbon sink: more carbon enters a pool than leaves it
net carbon source: more carbon leaves a pool than enters it
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 Earth’s 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.
Carbon: where is it?
 Exists:
– Atmosphere:
– Living biota (plants/animals)
–Carbon
– Soils and Detritus
–Carbon
– Oceans
–Most carbon in the deep ocean
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
Carbon conservation
 Initial carbon present during Earth’s formation
 Carbon is exchanged between different
components of Earth System.
Carbon conservation
 Initial carbon present during Earth’s formation
 Carbon doesn’t increase or decrease
globally
 Carbon is exchanged between different
components of Earth System.
Biosphere vs. CO2
The geological carbon cycle operates on a time scale of millions of years,
whereas the biological carbon cycle operates on
a time scale of days to thousands of years.
Biology plays an important role in the movement of carbon between land, ocean,
and atmosphere through the processes of photosynthesis and respiration.
Respiration:
C6H12O6 (organic matter) + 6O2 6CO2 + 6 H2O + energy
Photosynthesis:
energy (sunlight) + 6CO2 + H2O C6H12O6 + 6O2
Plants take in carbon dioxide (CO2) from the atmosphere during photosynthesis,
and release CO2 back into the atmosphere during respiration through the above
chemical reactions:
CO2 increases the atmosphere’s ability to hold heat,
it has been called a “greenhouse gas.”
Many attribute the observed 0.6 degree C increase
in global average temperature over the past century
mainly to increases in atmospheric CO2.
Without substantive changes in global patterns of
fossil fuel consumption and deforestation,
warming trends are likely to continue.
Through photosynthesis, green plants use solar energy to turn atmospheric
carbon dioxide into carbohydrates (sugars).
Plants and animals use these carbohydrates (and other products derived from them)
through a process called respiration, the reverse of photosynthesis.
Respiration releases the energy contained in sugars for use in
metabolism and changes carbohydrate “fuel” back into carbon dioxide,
which is in turn released to back to the atmosphere.
The amount of carbon taken up by photosynthesis and released
back to the atmosphere by respiration each year is about
1,000 times greater than the amount of carbon that moves
through the geological cycle on an annual basis.
The “Keeling curve,” a long-term record of atmospheric CO2
concentration measured at the Mauna Loa Observatory (Keeling et al.).
Although the annual oscillations represent natural, seasonal variations,
the long-term increase means that concentrations are higher than
they have been in 400,000 years (see text and Figure 3).
Graphic courtesy of NASA’s Earth Observatory.
Seasonality and Diurnal Variation related to CO2
On land, the major exchange of carbon with the atmosphere
results from __________and ______________.
Daytime:
During daytime in the growing season, leaves absorb sunlight and take up
carbon dioxide from the atmosphere.
Nighttime:
At the same time plants, animals, and soil microbes consume
the carbon in organic matter and return carbon dioxide to the
atmosphere.
Photosynthesis stops at night when the sun cannot provide
the driving energy for the reaction, though respiration continues.
This kind of imbalance between these two processes is reflected
in diurnal changes in the atmospheric CO2 concentrations.
Seasonality and Diurnal Variation related to CO2
Photosynthesis stops at night when the sun cannot provide
the driving energy for the reaction, though respiration continues.
This kind of imbalance between these two processes is reflected
in seasonal changes in the atmospheric CO2 concentrations.
During winter in the northern hemisphere, photosynthesis ceases
when many plants lose their leaves, but respiration continues.
This condition leads to an increase in atmospheric CO2 concentrations
during the northern hemisphere winter.
With the onset of spring, however, photosynthesis resumes
and atmospheric CO2 concentrations are reduced.
Countries for CO2 emission
Who is most responsible for CO2 emission?
Unit: thousands of metric tons, based on January 2007
Carbon dioxide emissions from energy use in buildings in
the United States and Canada increased by 30% from
1990 to 2003, an annual growth rate of 2.1% per year.
Carbon dioxide emissions from buildings have grown with
energy consumption, which in turn is increasing with population
and income. Rising incomes have led to larger residential
buildings and increased household appliance ownership.
http://rs.resalliance.org/2007/11/14/building-transformation/
7.4 gigatons (GT) of CO2 are emitted to the atmosphere each year.
Mapping the U.S. carbon footprint
Credit: Vulcan Projec
C in Ocean
In the oceans, phytoplankton (microscopic marine plants that form
the base of the marine food chain)
use carbon to make shells of calcium carbonate (CaCO3 ).
The shells settle to the bottom of the ocean when phytoplankton die
and are buried in the sediments. The shells of phytoplankton and
other creatures can become compressed over time as they are buried and
are often eventually transformed into limestone.
Additionally, under certain geological conditions, organic matter can be buried
and over time form deposits of the carbon-containing fuels coal and oil.
It is the non-calcium containing organic matter that is transformed into fossil fuel.
Both limestone formation and fossil fuel formation are biologically
controlled processes and represent long-term sinks for atmospheric CO2.
New Science Paper Says Carbon
Emissions Threaten Coral Reefs
For you to read
http://www.noaanews.noaa.gov/stories2007/20071213_carboncoral.html
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
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
In Class Question
Explain why CO2 concentrations
goes up and down each year
Long Term Carbon Cycle
Long Term Carbon Cycle
•
Carbon is slowly and continuously being
transported around our earth system.
–
–
•
Between atmosphere/ocean/biosphere
And the Earth’s crust (rocks like limestone)
The main components to the long term carbon
cycle:
1. Chemical weathering (or called: “silicate to
carbonate conversion process”)
2. Volcanism/Subduction
3. Organic carbon burial
4. Oxidation of organic carbon
The Long-Term Carbon Cycle
(Diagram)
Subduction/
Volcanism
Atmosphere (CO2)
Ocean (Dissolved CO2)
Biosphere (Organic Carbon)
Silicate-toCarbonate
Conversion
Carbonates
Organic
Carbon
Burial
Buried Organic Carbon
Oxidation
of Buried
Organic
Carbon
Where is most of the carbon
today?
• Most Carbon is ‘locked’ away in the earth’s 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)
Granite (A Silicate Rock)
Limestone (A Carbonate Rock)
The Carbon Cycle
Long term (thousands of years)
Air
Land/Ocean
Short term (fast ~ 1-5 years)