The Natural Carbon Balance
Carbon continually exchanges within a closed system consisting
of the atmosphere, oceans, biosphere, and landmass. There are short-
and long-term cycles at work.
Short-Term Cycles:
Carbon is exchanged rapidly between plants and animals through respiration
and photosynthesis, and through gas exchange between the oceans and the atmosphere.
Long-Term Cycle:
Over millions of years, carbon in the air is combined with water to form weak
acids that very slowly dissolve rocks. This carbon is carried to the oceans
where some forms coral reefs and shells. These sediments may be moved deep
into the Earth by drifting continents and eventually released into the atmosphere
by volcanoes.
| THE EARTH'S
CARBON CYCLE |
 |
| The Earth
maintains a natural carbon balance. When concentrations
of carbon dioxide (CO2) are upset, the
system gradually returns to its natural state through
the processes shown here. These natural processes
work slowly, compared to the rapid rate at which
humans are moving carbon into the atmosphere by burning
fossil fuels. Natural carbon removal can't keep pace,
so the concentration of CO2 in the atmosphere
is increasing. |
OCEAN UPTAKE Dissolving
of CO2 gas into the oceans and inflow
of carbon carried from land by rivers.
OCEAN RELEASE Return of carbon
in the oceans directly back to the atmosphere as
CO2 gas.
SEDIMENTATION Slow burial
of plant and animal matter on land and on the ocean
floor, which eventually becomes limestone, coal,
gas, and oil.
RESPIRATION Slow combustion
of carbon compounds, producing energy within organisms
and releasing CO2.
PHOTOSYNTHESIS Conversion
of CO2 into energy-rich carbon compounds
by plants. |
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