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Coal deposit
3 000
Oil and gas deposit
300
The present carbon cycle
Sources: Center for Climatic Research, Institute for
Environmental Studies, University of Wisconsin at
Madison; Okanagan University College in Canada,
Department of Geography; World Watch, November-
December 1998; Nature.
Speed of exchange processes
Very fast (less than 1 year)
Fast (1 to 10 years)
Slow (10 to 100 years)
Very slow (more than 100 years)
Terrestrial
vegetation
540 - 610
Plant growth
and decay
60
121
Fossil fuel
emissions
5,5
Atmosphere
750
Soils and
organic matter
1 580
0,5
1,5
Fires
60
Land use
changes
Storage and flux of carbon in billions of tonnes
Arrows are proportional to the volume of carbon. Flux figures express the
volume exchanged each year
Fossil fuel and
cement production
4 000
Exchange
soil - Atmosphere
Carbon is one of the most abundant elements in the Universe. It is the basis of all organic sub-
stances, from fossil fuels to human cells. On Earth, carbon is continually on the move – cycling
through living things, the land, ocean, atmosphere, and even the Earth’s interior. In some areas it
moves quickly, in others it takes eons. The fast part of the cycle includes us – from birth to death
and decomposition in perhaps 80 years – whereas carbon locked in marine sediments may remain
undisturbed for millions of years.
What happens when humans start driving the carbon cycle? We have seen that we can make a seri-
ous impact – rapidly raising the level of carbon in the atmosphere. But we really have no idea what
we are doing. At the moment we don’t even know what happens to all the carbon we release from
burning fossil fuel. Obviously a lot of it goes into the atmosphere, but every year we loose track of
between 15 and 30% (NASA). Scientists speculate that it is taken up by land vegetation, but no one
really knows. This sort of uncertainty makes it doubly difficult to predict the outcome of tampering
with something as complex as the carbon cycle.
Carbon, carbon everywhere
THE CARBON CYCLE
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