Fig. 16.6 Annual increments to atmospheric CO 2 calculated from the annual average
data for Fig. 16.4.
(^) (Data provided by R.F. Keeling, Scripps Institution of Oceanography.)
(^) We need a comparison for scaling these numbers of gigatonnes. A good one is an
estimate from satellite data (Behrenfeld & Falkowski 1997) of global, oceanic,
primary production at ∼44 GtC yr−1. Annual fossil-fuel burning at approximately 8.5
GtC yr−1 is about 19% of that, and ocean-sequestered fossil-fuel CO 2 is about 4.5%.
Terrestrial photosynthesis is of the same general magnitude as oceanic. To a close
approximation, both in the ocean and on land, the carbon newly bound into organic
matter each year is equal in amount to that released by respiration, hence the obvious
cycling in Fig. 16.4. Thus, additions of CO 2 from burned fossil fuel are equal to a
major part of the global carbon cycle each year. They are the main source of net
change.
(^) Fossil carbon not retained in the atmosphere on year-to-year time scales is
accumulating primarily in two places: dissolved in the oceans and taken up and stored