Assessing the spatial signature of European climate reconstructions

Much progress has recently been made in reconstructing European temperature variability over centuries to millennia. In contrast, there are only a few attempts at long-term precipitation and/or drought reconstruction, which are spatially less significant. Here we discuss the possibility of using climate reconstructions from tree-ring density and width to make spatially explicit estimates of European temperature and drought variability, respectively. Four experiments were performed to assess spatial field correlations of (1) parameter-specific mean reconstructions, (2) individual site reconstructions, (3) instrumental stations, and (4) model analogues. The simple mean of 4 temperature reconstructions from northern Scandinavia and high-elevation sites in the Tatra, Alps, and Pyrenees revealed a significant positive correlation (r > 0.4) with the gridded Central European summer temperature south of 55 degrees N and west of 25 degrees E. In contrast, the mean of 11 hydro-climatic reconstructions located between Sweden and Turkey had a significant positive correlation with only a handful of small patches scattered along an east-west corridor from the British Isles over Germany to the Baltic. The significant positive correlation increased to 71% of the European landmass between 35-70 degrees N and 10 degrees W-40 degrees E when using the individual 4 temperature reconstructions instead. The 11 individual hydro-climatic reconstructions had a significant positve correlation with summer drought over only 16% of the area. The proxy-based correlation fields are greatly supported by the spatial significance of instrumental station measurements and model analogues corresponding to the initial tree-ring site locations.