Implications of the Paris Climate Agreement for future sea-level rise from Antarctica

The agreement reached at the 21st Conference of the Parties (COP21) of the United Nations Framework Convention on Climate Change (UNFCC) is aimed at limiting the post-preindustrial rise in global mean temperature to less than 2 ºC at the end of this century, and to promote further efforts to limit the warming to 1.5 ºC. Here, we use a numerical ice sheet-shelf model, with physics tested and calibrated against modern and past ice-sheet behavior and coupled to highly resolved atmospheric and ocean components, to test the Antarctic Ice Sheet's response to a range of future climate scenarios representing COP21 aspirations versus a fossil-fuel intensive RCP8.5 emissions scenario. Assuming COP21 temperature targets are achievable and those temperatures will not be exceeded beyond 2100, we find that a global mean temperature rise less than 2 ºC substantially reduces both the short term (decadal-century) and long-term risk of catastrophic sea level rise from Antarctica. In contrast, we find that the current, Intended Nationally Determined Contributions (INDCs), allowing global mean temperature to approach 3 ºC by the end of this century, results in a substantial increase in Antarctica's contribution to sea-level rise, relative to 1.5 or 2 ºC. The results suggest that the current INCDs might not be sufficient to save the West Antarctic Ice Sheet and some East Antarctic outlets from substantial retreat.