Comparison of simulated and observed vegetation for the mid-Holocene in Europe

Abstract. Past climates provide a testing bed for the predictive ability of general circulation models. A number of studies have been performed for periods where the climate forcings are relatively different from the present and there is a good coverage of data. For one of these periods, the mid-Holocene (6 ka before present), models and data show a good match over northern Europe, but disagree over the south, where the data show cooler summers and winters and more humid conditions. Understanding the reasons for this disagreement is important given the expected vulnerability of the region under scenarios of future change. We present here a set of different past climate scenarios and sensitivity studies with a global vegetation model in order to try and understand this disagreement. The results show that the vegetation changes can be explained by a combination of both increased precipitation, and a reduction in the length of the growing season, controlled by a reduction in winter temperatures. The matching simulated circulation patterns support the hypothesis of increased westerly flow over this region.