Ice-free Arctic projections under the Paris Agreement

Under the Paris Agreement, emissions scenarios are pursued that would stabilize the global mean temperature at 1.5-2.0 degrees C above pre-industrial levels, but current emission reduction policies are expected to limit warming by 2100 to approximately 3.0 degrees C. Whether such emissions scenarios would prevent a summer sea-ice-free Arctic is unknown. Here we employ stabilized warming simulations with an Earth System Model to obtain sea-ice projections under stabilized global warming, and correct biases in mean sea-ice coverage by constraining with observations. Although there is some sensitivity to details in the constraining method, the observationally constrained projections suggest that the benefits of going from 2.0 degrees C to 1.5 degrees C stabilized warming are substantial; an eightfold decrease in the frequency of ice-free conditions is expected, from once in every five to once in every forty years. Under 3.0 degrees C global mean warming, however, permanent summer ice-free conditions are likely, which emphasizes the need for nations to increase their commitments to the Paris Agreement.