Table 2. Initial values or initial value ranges assumed in our model.

Variable	Initial value or initial range	References
Modern pore-space carbonate precipitation, (Tmol C per year)	0.45*	18 (see Supplementary Methods)
Modern seafloor dissolution, (Tmol C per year)	0.225–0.675†	16
Modern outgassing, (Tmol C per year)	4–10	23,76
Modern carb. Weathering, (Tmol C per year)	7–14	77, their Table 2
Preindustrial mean surface temperature, TS (K)	285	2
Modern ocean pH	8.2	74
Ocean Ca abundance (mMol kg−1)	10.03	Polynomial fit to Tyrrell and Zeebe75, see Supplementary Fig. 8
Preindustrial atmospheric pCO2 (p.p.m.)	280	—
Modern fraction pelagic precip. fPEL	0.4–0.6	78

^*Because we are adopting wide ranges for and , it is unnecessary to include a range for because its size relative to outgassing and weathering fluxes already encompasses a wide range (only the relative sizes of carbon cycle fluxes matter for predicting observable variables).