Extended Data Fig. 6: Objective construction of the model ensemble solution.

Left panel. The forcings that enter the model with variable scaling (AABW formation scaled to WD-δ¹⁸O Antarctic sea-ice extent scaled to the log of WD Na, Subantarctic PO₄ scaled to WD-Ca, and NADW formation scaled to Bermuda Rise Pa/Th, not shown Antarctic PO₄ scaled to a combination of WD-Ca and sea ice extent). The maximum possible forcing is shown with the dotted red line along with the associated model response of atmospheric CO₂ (black line). The red shading shows the range of forcings (mean and 1-sigma) that produce model predictions consistent with the ice core data (that is the ‘combined scenario’). The middle panel shows the same 1-sigma range for temperature forcings in the ‘combined scenario’. The right panel shows various model predictions including those that are used to select the ‘combined scenario’ constraint: atmospheric CO₂, atmospheric δ¹³C-CO₂ (including spline-smoothed data from refs. ^44,59,60) and mean ocean temperature (MOT). All model results are slightly offset to match interglacial values in the data. Blue bars show the temporal range used in for each data constraint.