Fig. 3. Key parameter changes to the CARLIOS model and its results for Scenario 8.

a–g, Parameter changes for: an injection of CO₂ to the atmosphere (a), a change in the normalized uplift (b), a change to the global erosion-to-silicate-weathering ratio (E:W) (c), a pulsed continental eruption of unradiogenic osmium which is then subaerially weathered (d), scalings for the burial of marine organic carbon (F_bg-sea, blue), reverse weathering (F_rw, dashed gold) and the carbonate land area (f_L, red) (e), a change to the Mg/Ca ratio in the oceans ([Mg]_sw/[Ca]_sw) (f) and the factor that apportions carbonate burial (F_bc) to shelf environments, where a lower number indicates more burial on shelves (g). h–p, Key model results for atmospheric $p_{{\mathrm{CO}}_2}$ (black) plotted against proxy estimations from boron isotope (δ¹¹B) data¹⁸ (see Supplementary Information) (h), global average surface temperature (GAST) plotted against proxy estimations from δ¹⁸O data (see Supplementary Information) (i), ocean pH (for a low-latitude surface (gold), a high-latitude surface (blue) and a deep ocean (green), and where the red dots and line denote individual pH estimations from δ¹¹B data¹⁸ and a smoothed fit, respectively) (j), modelled lysocline depth (k), deep-ocean Ω_calcite saturation (l), the modelled mean δ⁷Li_sw offset by a fractionation factor (3–5‰, dark grey band; 2–6‰, light grey band) (m), the modelled weathering intensity through time (n), the contribution of rivers versus the combined sinks to the δ⁷Li_sw signature (o) and the modelled ¹⁸⁷Os/¹⁸⁸Os_initial of seawater (p). In all panels (apart from e, j and m) the black line is the model average and the grey band denotes ±1σ. In m and p, the blue line and band are from Fig. 2. ALK, ocean alkalinity.