Another new study finds Iceland was ~2°C warmer and the Arctic region had much less sea ice as recently as ~1400 to 1000 years ago (Miles et al., 2020).

What’s most interesting is that in the last 1400 years the Arctic experienced marked climate changes (~1.5°C in decades)that may have occurred "spontaneously, ” or without requiring "an external trigger”. In other words, these warming events may arise due to unforced natural variability.

If climate changes of these magnitudes can and do occur without an external forcing mechanism, there is little reason to assume that the much more modest changes in SSTs in the last century fall outside the range of internal variability either.