|This subset of
the carbon cycle defines annual changes from fossil fuel use and land use
changes and identifies them as the human perturbation.
|It shows 5.3
billion tonnes being added to the atmosphere from fossil fuel use and another
0.1 billion tonnes from cement production which drives carbon dioxide from
the limestone used to make it.
converting some land to different uses – presumably from forests to
agriculture – adding another 1.7 billion tonnes to the atmosphere.
|At the same time
it seems, land based ecosystems are absorbing a net amount of 1.9 billion
tonnes and the oceans absorb about 1.9 billion tonnes.
|The net addition
to the atmosphere from these activities is 3.3 billion tonnes annually.