Table 1 Climate conditions and ice sheet contributions to global mean sea level during three past warm periods that are often used as analogues for current or near-future climate conditions: Marine Isotope Stage (MIS) 5e, MIS 11 and the Mid Pliocene Warm Period (MPWP), Published data sources used to compile the Table are available in Supplementary Table 1

Forcing (peak values)

CO₂

287 ppm

286 ppm

350–450 ppm

Global mean temp. anomaly^b

1 °C

1–2? °C

2–5 °C

'Arctic’ temp. anomaly^c

4–8 °C

4–10 °C

4–11 °C

'Antarctic’ temp. anomaly^c

4–5 °C

2–3 °C

? °C

Greenland

Ice sheet response

Central portion of ice sheet largely intact; southern GrIS deglaciated

NW and southern GrIS deglaciated; complete deglaciation possible

Partial to complete deglaciation

GMSL contribution

Estimates range from 1 to >5 m

Estimates include: >1.4 m, 4.5–6 m; 6.1 (3.9–7) m

Up to 7.4 m

Antarctica

Ice sheet response

WAIS retreat, some EAIS retreat possible

EAIS retreat & increased runoff indicated

Retreat in WAIS and EAIS

GMSL contribution

Debated, up to 5 m (or higher if EAIS contributed)

Uncertain; up to 3–4 m

Possibly 13–17 m

2–9 m above present

6–13 m above present

10–20 m above present

GMSL exceeded present (H);

A portion of the GrIS retreated (H);

AIS contributed to GMSL rise (M)

GMSL exceeded present (M-H);

GrIS smaller than present (H); majority of the GrIS melted (M-H);

AIS smaller than present (M)

GrIS smaller than present (H);

AIS smaller than present (H)