The rapid loss of sea ice in the Arctic is one of the most striking manifestations of climatechange. As sea ice melts, more open water is exposed to solar radiation, absorbing heat and generating asea ice–albedo feedback that reinforces Arctic warming. Recent studies stress the significance of this feed-back mechanism and suggest that ice-free summer conditions in the Arctic Ocean may occur faster thanpreviously expected, even under low-emissions pathways. Here, we use an integrated assessment modelto explore the implications of a potentially rapid sea ice-loss process. We consider a scenario leading toa full month free of sea ice in September 2050, followed by three potential scenarios afterward: partialrecovery, stabilization, and continued loss of sea ice. We analyze how these scenarios affect the mitigationefforts to keep global temperature increase below 2∘C. Our results show that sea-ice melting in the Arcticrequires more stringent mitigation efforts globally. We find that global CO2emissions would need to reachzero levels 5–15 years earlier and that the carbon budget would need to be reduced by 20–51% to offsetthis additional source of warming. The extra mitigation effort would imply an 18–59% higher mitigationcost to society. Our results also show that to achieve the 1.5∘C target in the presence of ice-free summers,negative emissions would be needed. This study highlights the need for a better understanding of howthe rapid changes observed in the Arctic may impact our society
