Permafrost as a critical factor in paleoclimate modelling: the Younger Dryas case in Europe

Simulations with an atmospheric climate model of the Younger Dryas climate, a distinct cooling event around 12 kyr cal B.P., were compared with temperature reconstructions based on fossil plant data. In one experiment we forced the model to maintain a wet and frozen soil at high latitudes to reproduce the effect of permafrost in the model. This measure resulted in a climate similar to the reconstructions with a depression of the summer temperatures in Eurasia by 4–8°C and an increase in precipitation. This suggests that permafrost may have played a more important role in driving paleoclimates (such as the Younger Dryas climate) than believed until now. This calls for re-evaluation of (paleo)climate simulations in which permafrost was not explicitly included.