38 The greenhousegases
345 350 355 360 365 370 375 380 385
− 60
− 55
− 50
− 45
− 40
− 35
− 30
− 25
− 20
1990
1992
1994
1996
1998
2000
1991
1993
1995
1997
1999
atmospheric
increase
land
uptake
ocean
uptake
outgassing
fossil
fuel
bur ning
O^2
concentration, difference from standard (ppm)
CO 2 concentration (ppm)
Figure 3.4Partitioning of fossil fuel carbon dioxide uptake using oxygen
measurements. Shown is the relationship between changes in carbon dioxide
and oxygen concentrations. Observations are shown by solid circles and
triangles. The arrow labelled ‘fossil fuel burning’ denotes the effect of the
combustion of fossil fuels based on the O 2 :CO 2 stoichiometric relation of the
different fuel types. Uptake by land and ocean is constrained by the
stoichiometric ratio associated with these processes, defining the slopes of the
respective arrows.