Atmospheric CO₂ Two Box Model Accurately Tracks 14C and 13C without Requiring the "Revelle Isotopic Exception"

Although nett CO₂ flows can be estimated with reasonable accuracy, the contributing gross fluxes between the atmosphere and the earth's surface are poorly understood. This paper presents a means by which the global outflow and inflow of CO₂ between atmosphere and "mixing reservoirs" can be calculated, using the radiocarbon isotopes ¹⁴CO₂ and ¹³CO₂ as a tracer. It has been asserted that isotopic CO₂ cannot be directly used as a tracer in flow studies because Δ¹⁴C is not subject to the Revelle factor; evidence is provided showing that this view is mistaken. The model contains 7 key parameters which are used to provide outputs of Δ¹⁴C and d¹³C as a function of time. By optimising the fit of these two outputs with historical records spanning 200 years or more, including during the bomb pulse, the key parameters are determined. The quality of fit of Δ¹⁴C and d¹³C is excellent and the internal parameters optimise at reasonable values. The global flux to and from the effective mixing reservoir, whose size is six times that of the atmosphere, is currently 58 GTC/yr in 2020, not including annually cycled carbon.