Fig. 1: Observed climatology of surface air temperature, along with bias in ERA5 and the CMIP6 ensemble mean over the Arctic sea ice.

a The 20-year mean satellite-derived \({T}_{2{{{{{{{\rm{m}}}}}}}}}^{({{{{{{{\rm{SAT}}}}}}}})}\) over sea ice (SIC > 15%) for the period 1995–2014 (see Methods). The climatological mean difference of surface air temperature from (b) ERA5 \({T}_{2{{{{{{{\rm{m}}}}}}}}}^{({{{{{{{\rm{ERA}}}}}}}}5)}\) and (c) the CMIP6 ensemble mean \({T}_{2{{{{{{{\rm{m}}}}}}}}}^{({{{{{{{\rm{CMIP}}}}}}}}6)}\) versus \({T}_{2{{{{{{{\rm{m}}}}}}}}}^{({{{{{{{\rm{SAT}}}}}}}})}\) for the same period. The maps are bounded at 58 °N with the dashed line marking 66.5 °N. The red line in a indicates the observed SIC ≥70% (SIC70) averaged over 1995–2014. Units: °C.