  The paper has been suggested by two observations: 1) the atmospheric CO$_2$
growth rate is smaller than that ascribed to the emission of fossil fuels
combustion, 2) the fossil fuel reserves are finite. The first observation has
lead the way to a simple kinetic mode, based on the balance of 1) land/ocean
CO$_2$ absorption and 2) CO$_2$ anthropogenic emission limited solely by
depletion of the present day fossil-fuel reserves, in a business-as-usual
scenario. The second observation has suggested to extrapolate past CO$_2$
emissions by fossil fuel combustion in the future years up to 2200 CE, by
constraining emissions to the physical limits of reserves availability. The
Meixner curve (hyperbolic secant distribution) has been used to model the
pathway of resource exploitation for the three main classes of fossil fuels,
crude oil, natural gas and coal. The kinetic model, driven by the extrapolated
emissions, has been employed to project the CO$_2$ atmospheric concentration
due to fossil fuel combustion close to the zero-reserve epoch. The result is
just the output of simple models tuned on well-known experimental data. Error
analysis of literature data provides the method robustness and the relevant
uncertainty band. Contribution of other greenhouse gases like methane and
nitrous oxide has been neglected, since their emissions cannot be projected
with the paper methodology (they do not derive from fossil reserves).
Notwithstanding this limitation, paper results clearly demonstrate that some of
the IPCC projections of the CO$_2$ concentration are largely overestimated if
compared to the physical limits of fossil fuel exploitation.
