Figure 3. Carbon cycle model with moderate fit to data assuming weak temperature dependence of continental weathering and no weatherability change.

Selected model outputs and geochemical proxy data for a weak temperature dependence for continental weathering (T_e=30–40 K) and no change in silicate weatherability over the last 100 Myr ago (W=0). Grey- and red-shaded regions represent the model output 90% confidence obtained from 10,000 forward model runs using the parameter ranges described in Table 1. The grey- and red-solid lines are the median model outputs. Black and red dots represent binned geochemical proxy data, and error bars denote the range of binned proxy estimates (see main text for references and explanation). Panels denote (a) ocean pH, (b) atmospheric pCO₂, (c) ocean saturation state, (d) mean surface and deep ocean temperatures, (e) continental silicate weathering and ocean carbonate precipitation fluxes, and (f) seafloor dissolution and pore space carbonate precipitation fluxes. Here the model envelopes marginally encompass the proxy data. The upper end of the temperature and seafloor envelopes fit proxies, pCO₂ is an excellent fit, and the saturation state and ocean pH proxies are on the edge of the model envelope.