In the last post we had set out to model geological isotope excursions and found that our conception of the current Carbon cycle is so messed up that any venture into deep time hopeless. Specifically, when d13C values are integrated into the fluxes the atmosphere goes negative d13C way faster than the observed rate.

To correct this irregularity either light Carbon atmospheric inputs must be reduced or heavy Carbon increased. We chose to try to balance the books by increasing heavy Carbon input from the ocean mixed layer.

Not only was the original model based on consensus values out of tune isotopically, it was out of mass balance as well, growing at over 60 GtC per year. We have chosen to modify the scarlet values to harmonize the atmospheric isotopic trend with the observed rate and to limit atmospheric growth to a bit over the human contribution.

Hunky dory, but we now have a 450 Gt Carbon cycle compared with the 210 Gt consensus cycle we began with. We have doubled the Carbon cycle.