Observationally-constrained projections of an ice-free Arctic even under a low emission scenario

A dominant influence of anthropogenic greenhouse gas increases on Arctic sea ice area is detectable in all months. By scaling climate models' sea ice response to best match observed trends, an ice-free Arctic in September is projected under all scenarios. The sixth assessment report of the IPCC assessed that the Arctic is projected to be on average practically ice-free in September near mid-century under intermediate and high greenhouse gas emissions scenarios, though not under low emissions scenarios, based on simulations from the latest generation Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Here we show, using an attribution analysis approach, that a dominant influence of greenhouse gas increases on Arctic sea ice area is detectable in three observational datasets in all months of the year, but is on average underestimated by CMIP6 models. By scaling models' sea ice response to greenhouse gases to best match the observed trend in an approach validated in an imperfect model test, we project an ice-free Arctic in September under all scenarios considered. These results emphasize the profound impacts of greenhouse gas emissions on the Arctic, and demonstrate the importance of planning for and adapting to a seasonally ice-free Arctic in the near future.

Automated summary

By comparing observational and simulation data, we found that anthropogenic greenhouse gas emissions have a significant impact on Arctic sea ice area, and it is projected that the Arctic will be without ice in September under all scenarios. These results emphasize the profound effects of greenhouse gas emissions on the Arctic region and highlight the need to plan and adapt to a seasonally ice-free Arctic in the near future.