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 temper ature reconstructions based on fossil plant data. In one experiment we forc ed the model to maintain a wet and frozen soil at high latitudes to reprodu ce the effect of permafrost in the model. This measure resulted in a climat e similar to the reconstructions with a depression of the summer temperatur es in Eurasia by 4-8 degrees C and an increase in precipitation. This sugge sts that permafrost may have played a more important role in driving paleoc limates (such as the Younger Dryas climate) than believed until now. This c alls for re-evaluation of (paleo)climate simulations in which permafrost wa s not explicitly included. (C) 2000 Elsevier Science B.V. All rights reserv ed.