The Carbon Cycle

MET 112 Global Climate Change

Professor Menglin JinSan Jose State University, Department

of Meteorology

Video Show on Carbon Cycle

http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/carbon%20cycle/

Carbon Cycle-1.mp4

An Earth System Perspective

• Earth composed of:– Atmosphere– Hydrosphere – Cryosphere– Land Surfaces– Biosphere

• These ‘Machines’ run the Earth• Holistic view of planet…

The movement of carbon, in its many forms, between the atmosphere, oceans, biosphere, and geosphereis 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

Definition of Carbon Cycle

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. Illustration courtesy NASA Earth Science Enterprise.

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.

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:

Biosphere vs. CO2

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.

Why CO2 is important?

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.

On land, the major exchange of carbon with the atmosphere results from __________and ______________.

Seasonality and Diurnal Variation related to CO2

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.

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.

Seasonality and Diurnal Variation related to CO2

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.

New Science Paper Says Carbon Emissions Threaten Coral Reefs

http://www.noaanews.noaa.gov/stories2007/20071213_carboncoral.html

For you to read

Class Activity

Read the link below and write half page comments on how Carbon Emissions Threaten Coral Reefs,

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

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.

C in Ocean

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

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/Subduction3. Organic carbon burial4. Oxidation of organic carbon

The Long-Term Carbon Cycle (Diagram)

Atmosphere (CO2)

Ocean (Dissolved CO2)

Biosphere (Organic Carbon)

Carbonates Buried Organic Carbon

Subduction/Volcanism

Silicate-to-Carbonate Conversion

Organic Carbon Burial

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) Short term (fast ~ 1-5 years)

Land/Ocean

Air

Open notes quiz (class participation)

Explain why CO2 concentrations goes up and

down each year