From short-term uncertainties to long-term certainties in the future evolution of the Antarctic Ice Sheet

Robust projections of future sea-level rise are essential for coastal adaptation, yet they remain hampered by uncertainties in Antarctic ice-sheet projections-the largest potential contributor to sea-level change under global warming. Here, we combine two ice-sheet models, systematically sample parametric and climate uncertainties, and calibrate against historical observations to quantify Antarctic ice-sheet changes to 2300 and beyond. By 2300, the projected Antarctic sea-level contributions range from -0.09 m to +1.74 m under low emissions (SSP1-2.6, outer limits of 5-95% probability intervals), and from +0.73 m to +5.95 m under very high emissions (SSP5-8.5). Irrespective of the wide range of uncertainties explored, large-scale Antarctic ice-sheet retreat is triggered under SSP5-8.5, while reaching net-zero emissions well before 2100 strongly reduces multi-centennial ice loss. Yet, even under such strong mitigation, a significant sea-level contribution could still result from West Antarctica. Our results suggest that current mitigation efforts may not be sufficient to avoid self-sustained Antarctic ice loss, making emission decisions taken in the coming years decisive for future sea-level rise.