My experience is that if we deal with complex systems, it is wise to start with measurements and find out what they try to tell us. Also system images provide invaluable information about the level at which theoretical models and real measurements can be best compared and, last but not least, whether the available measurements allow us to estimate the model parameters with any statistical significance.
All external sources and internal flows in the CO2-system are leading to a CO2- increase in the atmospheric reservoir by +20 Gt/yr and CO2-increase in the natural reservoir by ≈ +19 Gt/yr. The yearly anthropogenic CO2-flow is onlly ~5% of the yearly natural incoming CO2- flow.
