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tree-ring · temperature reconstructions · harvest dates · long-term 21 persistence · Hurst exponent
Abstract:
Tree-ring chronologies are the main source for annually resolved and absolutely dated temperature reconstructions of the last millennia and thus for 8 studying the intriguing problem of climate impacts. Here we focus on central Eu-9 rope and compare the tree-ring based temperature reconstruction with reconstruc-10 tions from harvest dates, long meteorological measurements, and historical model 11 data. We find that all data are long-term persistent, but in the tree-ring based 12 reconstruction the strength of the persistence quantified by the Hurst exponent is 13 remarkably larger (h =∼ 1.02) than in the other data (h = 0.52 − 0.69), indicating 14 an unrealistic exaggeration of the historical temperature variations. We show how 15 to correct the tree-ring based reconstruction by a mathematical transformation 16 that adjusts the persistence and leads to reduced amplitudes of the warm and 17 cold periods. The new transformed record agrees well with both the observational data and the harvest dates-based reconstructions and allows more realistic studies 19 of climate impacts. It confirms that the present warming is unprecedented.
