DOI: 10.25921/wjk6-av22
title: NOAA/WDS Paleoclimatology - European Alps, 755-2004 AD, maximum latewood density temperature reconstruction, European Larch, PAGES Euro-Med 2k Version

description: Annually resolved summer temperatures for the European Alps are described. The reconstruction covers the a.d. 755-2004 period and is based on 180 recent and historic larch [Larix decidua Mill.] density series. The regional curve standardization method was applied to preserve interannual to multicentennial variations in this high-elevation proxy dataset. Instrumental measurements from high- (low-) elevation grid boxes back to 1818 (1760) reveal strongest growth response to current-year June-September mean temperatures. The reconstruction correlates at 0.7 with high-elevation temperatures back to 1818, with a greater signal in the higher-frequency domain (r = 0.8). Low-elevation instrumental data back to 1760 agree with the reconstruction's interannual variation, although a decoupling between (warmer) instrumental and (cooler) proxy data before 1840 is noted. This offset is larger than during any period of overlap with more recent high-elevation instrumental data, even though the proxy time series always contains some unexplained variance. The reconstruction indicates positive temperatures in the tenth and thirteenth century that resemble twentieth-century conditions, and are separated by a prolonged cooling from 1350 to 1700. Six of the 10 warmest decades over the 755-2004 period are recorded in the twentieth century. Maximum temperature amplitude over the past 1250 yr is estimated to be 3.1C between the warmest (1940s) and coldest (1810s) decades. This estimate is, however, affected by the calibration with instrumental temperature data. Warm summers seem to coincide with periods of high solar activity, and cold summers vice versa. The record captures the full range of past European temperature variability, that is, the extreme years 1816 and 2003, warmth during medieval and recent times, and cold in between. Comparison with regional- and large-scale reconstructions reveals similar decadal to longer-term variability.
description:   The dataset consists of 180 MXD larch [Larix decidua Mill.] series from near timberline sites (86 recent samples) and subalpine construction timbers (94 historic
       samples) dating from 735-2004. Recent samples were collected in the Swiss Alps at elevations between 1900 and 2200 m asl. Historic buildings are located in an altitudinal belt of 1500-1900 m asl, with their construction
       wood often originating from higher elevations: 110 samples derive from the Lötschental (1258-2004), 39 from the Simplon region (735-1510), and 31 from the Aletsch region and Simmental (1681-1986). 
       Samples were processed using a WALESCH 2003 X-ray densitometer with a resolution of 0.01 mm, and brightness variations transferred into g cm-3 using a calibration wedge (Eschbach et al. 1995; Lenz et al.1976). 
       The mean segment length (i.e., the average number of rings per core or disc sample) is 264 yr, with means of 239 and 289 yr for the recent and historic subsamples, respectively. 
       Average MXD is 0.87 g cm-3, with little difference between the recent (0.90 g cm-3) and historic (0.84 g cm-3) material. The mean interseries correlation of the 180 MXD series is
       r~0.59, calculated using COFECHA (Holmes 1983). For regional tree-ring comparison, the GAR June–August temperature reconstruction for the A.D. 951-2002 period by Büntgen et al. (2005a) is used. 
       This record combines 1527 subalpine larch and pine RW series from the Swiss and Austrian Alps. A fraction of this rather large wood collection is used for the density measurements as utilized in this current
       study, that is, 120 of the 180 larch MXD series derive from the RW dataset.