Fig. 5: Simulated and reconstructed annual mean surface temperatures and cooling across the Weissert Event.

a Model fields combine surface air temperatures over land with sea surface temperatures (SSTs) over the ocean and are linearly scaled to the calculated mean pCO₂ estimates of 1181 ppm during the Weissert warm interval (Supplementary Equation 5). Pink contours show associated maximum monthly mean sea ice concentrations. Symbols represent available proxy information. High-latitude sites (poleward of 45 °) also show approximated annual mean temperatures where the model-estimated difference between summer and annual mean values is subtracted from the original proxy temperatures to correct for a possible seasonal warm bias and to facilitate the model-data comparison. b Annual mean surface temperatures during the Weissert cold end scaled to the mean  pCO₂ estimate of 682 ppm. c Estimated surface cooling from the Weissert warm interval to the Weissert cold end, i.e. panel a minus b, with an associated pCO2 drop of ~40%.