The Carbon Cycle
Background on the Carbon Cycle
Perturbing the Global Carbon Cycle
The Carbon Cycle and Global Climate Change
Modeling the Carbon Cycle
Background on the Carbon Cycle
The circulation of carbon and
its compounds is one of Earth's fundamental biogeochemical cycles. It involves
the cycling of carbon through reservoirs in the geosphere, atmosphere, hydrosphere,
and biota over a wide range of space and time scales. This cycling has gone on
throughout most of Earth's history, and has greatly
modified the composition of Earth's atmosphere while producing great beds
of carbonate rocks in the geosphere.
The biota -- living things -- play key roles in the carbon cycle. Carbon,
in the form of carbon dioxide (CO2), is used by plants in photosynthesis
to generate the carbohydrates and the energy needed for their survival. In
this process, carbon is withdrawn from the atmosphere and locked up in complex
molecules; the oxygen is returned to the atmosphere. Animals -- non-photosynthetic
organisms -- breathe oxygen, consume carbon by eating plants and/or other
animals, and give back CO2 to the atmosphere. When either type
of organism dies, the organic matter decays and the carbon in the complex
molecules are released, generally as CO2, methane, etc
For practical purposes, the global carbon cycle can be taken to consist of exchanges of carbon via three biogeochemical loops that operate on vastly different time scales:
An atmosphere - terrestrial biosphere loop.
A terrestrial biosphere-geosphere-hydrosphere loop.
An atmosphere-geosphere-hydrosphere
loop.
RETURN TO FUNDAMENTAL CONCEPT 3