(Note: CO2 was at least 100 ppm lower than today yet the Arctic hit much higher temps and had to lose much of its ice as a result)
"Peak warmth occurred ~10 ka BP, with temperatures 7 °C warmer than today due to high radiative forcing and intensified inflow of warm Atlantic waters."
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...