Atmospheric circulation-constrained model sensitivity recalibrates Arctic climate projections

The Arctic has been suggested to see seasonally ice-free conditions within two-to-three decades under high-emissions scenarios. However, the time of emergence of the first ice-free month remains uncertain due to a wide range of estimates for Arctic climate sensitivity to anthropogenic forcing. Here, we propose a recalibration of the sea ice and Greenland ice sheet response to climate change, based on the finding that the sensitivity of the Arctic cryosphere to atmospheric circulation in climate models substantially differs from the observed one. Assuming that Arctic climate sensitivity of models recalibrated by observations remains unchanged in coming decades, this approach yields a delay in the projected timing of the first September sea-ice-free Arctic and widespread Greenland melting of roughly a decade compared to the uncalibrated ensemble. This indicates the importance of accounting for the role of large-scale atmospheric forcing and circulation changes in Arctic climate change.