Figure 3.5: Inverse model
estimates of fossil fuel CO2 uptake by latitude bands according to
eight models using different techniques and sets of atmospheric observations (results
summarised by Heimann, 2001). Positive numbers denote fluxes to the atmosphere;
negative numbers denote uptake from the atmosphere. The ocean-atmosphere fluxes
represent mainly the natural carbon cycle; the land-atmosphere fluxes may be considered
as estimates of the uptake of anthropogenic CO2 by the land (with some
caveats as discussed in the text). The sum of land-atmosphere and ocean-atmosphere
fluxes is shown because it is somewhat better constrained by observations than
the separate fluxes, especially for the 1980s when the measurement network was
less extensive than it is today. The 1990s are represented by the period 1990
to 1996 only, because when this exercise was carried out the modelling groups
did not have access to all of the necessary data for more recent years.
