Extended Data Fig. 6: Impact of forcing on the model-proxy comparison.
From: Millennial-scale climate variability over land overprinted by ocean temperature fluctuations
a, Same as Fig. 1a, but with the local spectra of summer temperature variability of 8 fully-forced (that is including volcanic and solar forcing) millennium simulations added. Only the BEST instrumental spectra are reproduced for simplicity. b, Spectrum of the reconstructed aerosol optical depth, that is the volcanic forcing, over the late Holocene (0–8 ka)88. The fully forced simulations show similar local variability as the long Holocene simulations. As the volcanic forcing spectrum is flat on multi-decadal to millennial time-scales, missing volcanic forcing in the Holocene is unlikely to fully reconcile the model-proxy variability mismatch unless the amplitude of the response and its response time are both severely underestimated in the climate models. There are indications however that volcanic forcing could partially reduce the variability mismatch89. Shading indicates 90% confidence intervals around the mean.
