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Abstract

With ongoing anthropogenic CO2 emissions, the Greenland ice sheet approaches critical thresholds of inevitable, long-term mass loss. Future technologies might be able to efficiently remove CO2 from the atmosphere and thereby cool down our planet. We explore whether and to what extent a realization of this concept could lead to a regrowth of the Greenland ice sheet once it has partly melted. Using the fully coupled Earth system model of intermediate complexity CLIMBER-X, emission pulses between 0 and 4000 GtC are released into the atmosphere, and 1 kyr, 2 kyr, and 5 kyr, the atmospheric CO2 concentration is reduced back to its pre-industrial value. We find that independent of a specific trajectory, once the southern part of the Greenland ice sheet has partly melted with a total mass loss of more than 0.4 m sea level equivalent, regrowth is inhibited. Uncertainties preclude determination of precise thresholds, but model results indicate that cumulative industrial-era emissions approaching 1000 to 1500 GtC and beyond increasingly risk irreversible mass loss of the Greenland ice sheet. Once this threshold is passed, artificial atmospheric carbon removal would need to be utilised within the next centuries at massive scale. Beyond that, artificial atmospheric carbon removal has limited abilities to avoid long-term mass loss of the Greenland ice sheet. In conclusion, keeping cumulative anthropogenic emissions below 1000 to 1500 GtC is the only safe way to avoid irreversible mass loss of the Greenland ice sheet.