Figure 3 – The central Greenland d18O history for the most recent 40,000 years. The smooth curve results when this history is filtered to mimic the thermal averaging in the ice sheet. All temperature histories that give this same curve when filtered are indistinguishable to borehole thermometry. The right axis shows the calibrated temperature scale. Reprinted figure with permission from Cuffey et al., Science, 270, 455-458. ©1995, American Association for the Advancement of Science.