Roger Cameron Creel , Jacqueline Austermann, Robert Kopp , Nicole S Khan, Torsten Albrecht, Jonathan Kingslake

Global mean sea-level (GMSL) change can provide insight on how ice sheets, glaciers, and oceans respond to warming[1;2]. The Holocene (11.7 ka to present) marks a time when temperatures may have exceeded early industrial (1850 CE) values[3]. Evidence from Greenland[4] and Antarctica[5;6] indicates that both ice sheets retreated inland of their present-day extents during the Holocene, yet previous GMSL reconstructions suggest that Holocene GMSL never surpassed early industrial levels7–9. We combine relative sea-level observations with glacial isostatic adjustment predictions from an ice-sheet model ensemble and new estimates of postglacial thermosteric sea-level and mountain glacier evolution to estimate Holocene GMSL and ice volume. We show it is likely (probability P =0.79) that GMSL exceeded early industrial levels in the mid-Holocene (8-4 ka) by up to 1.5 m and that the Antarctic Ice Sheet was likely (P =0.66) smaller than present in the last 6000 years. We demonstrate that Antarctic retreat lags Antarctic temperature by 250 years, underscoring future Antarctic vulnerability to present warming. Comparing our reconstruction to future projections indicates that GMSL rise in the next 125 years will very likely (P >0.9) be the fastest in the last 5000 years, and that by 2080 GMSL will more likely than not be the highest in 115,000 years.