An atlas of megadroughts in Europe and in the Mediterranean Basin during the Common Era provides insights into climate variability.

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[1] Previous tree-ring-based Northern Hemisphere temperature reconstructions portray a varying amplitude range between the ''Medieval Warm Period'' (MWP), ''Little Ice Age'' (LIA) and present. We describe a new reconstruction, developed using largely different methodologies and additional new data compared to previous efforts. Unlike earlier studies, we quantify differences between more traditional (STD) and Regional Curve Standardization (RCS) methodologies, concluding that RCS is superior for retention of low-frequency trends. Continental North American versus Eurasian RCS series developed prior to merging to the hemispheric scale cohere surprisingly well, suggesting common forcing, although there are notable deviations (e.g., fifteenth to sixteenth century). Results indicate clear MWP (warm), LIA (cool), and recent (warm) episodes. Direct interpretation of the RCS reconstruction suggests that MWP temperatures were nearly 0.7°C cooler than in the late twentieth century, with an amplitude difference of 1.14°C from the coldest (1600-1609) to warmest (1937)(1938)(1939)(1940)(1941)(1942)(1943)(1944)(1945)(1946) decades. However, we advise caution with this analysis. Although we conclude, as found elsewhere, that recent warming has been substantial relative to natural fluctuations of the past millennium, we also note that owing to the spatially heterogeneous nature of the MWP, and its different timing within different regions, present palaeoclimatic methodologies will likely ''flatten out'' estimates for this period relative to twentieth century warming, which expresses a more homogenous global ''fingerprint.'' Therefore we stress that presently available paleoclimatic reconstructions are inadequate for making specific inferences, at hemispheric scales, about MWP warmth relative to the present anthropogenic period and that such comparisons can only still be made at the local/regional scale.

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Aim To evaluate the climate sensitivity of model-based forest productivity estimates using a continental-scale tree-ring network

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Monthly temperature series for Central Europe back to AD 1500 are developed from documentary index series from Germany, Switzerland and the Czech Republic (1500-1854) and 11 instrumental temperature records . Documentary evidence from the Low Countries, the Carpathian Basin and Poland are used for cross-checking for earlier centuries. The instrumental station records are corrected for inhomogeneities, including insufficient radiation protection of early thermometers and the urban heat island effect. For overlapping period (1760-1854), the documentary data series correlate with instrumental temperatures, most strongly in winter (86% explained variance in January) and least in autumn (56% in September). For annual average temperatures, 81% of the variance is explained. Verification statistics indicate high reconstruction skill for most months and seasons. The last 20 years (since 1988) stand out as very likely the warmest 20-year period, accounting for the calibration uncertainty and decreases in proxy data quality before the calibration period. The new reconstruction displays a previously unobserved P. Dobrovolný (B) · R. Brázdil · M. Halíčková · J. Macková Climatic Change (2010) 101:69-107 long-term decrease in DJF, MAM and JJA temperature variability over last five centuries. Compiled monthly, seasonal and annual series can be used to improve the robustness of gridded large-scale European temperature reconstructions and possible impact studies. Further improvement of the reconstruction would be achieved if documentary data from other European countries are further developed.

Climate field reconstructions from networks of tree-ring proxy data can be used to characterize regional-scale climate changes, reveal spatial anomaly patterns associated with atmospheric circulation changes, radiative forcing, and large-