Fig. 3.

LOSCAR and Os cycle model simulations of the most likely MECO scenario. a Forcing for two scenarios involving a gradual, transient 20% increase in the volcanic CO₂ flux over ~500 kyr. The solid lines represent a scenario in which the silicate and carbonate weathering fluxes are allowed to vary in response to CO₂ forcing (normal weathering feedback), while the dashed lines represent a scenario in which these weathering fluxes are kept constant (diminished weathering feedback). Only the latter scenario corresponds to all observations. b Model response in the ¹⁸⁷Os/¹⁸⁸Os composition of the global ocean, shown against smoothed fits to the MECO Os_i records from the study sites. c Model CCD response of different ocean basins, shown against carbonate content (wt%) records for different depths in the Atlantic, Indian and Pacific oceans as compiled by Sluijs et al⁸. d Model atmospheric pCO₂ response and pH response for the surface Atlantic and Pacific oceans. e Model δ¹³C response for the DIC of the deep Atlantic and Pacific oceans. For a full description of the LOSCAR model, see Zeebe²³