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A portion of this study is supported by the Office of Health and Environmental Research, U.S. De- partment of Energy, as part of its Carbon Dioxide Research Program. The National Center for Atmo- spheric Research is sponsored by the National Science Foundation. 6 November 1992; accepted 4 March 1993 A 3620-Year Temperature Record from Fitzroya cupressoides Tree Rings in Southern South America Antonio Lara* and Ricardo Villalba A tree-ring width chronology of alerce trees (Fitzroya cupressoides) from southern Chile was used to produce an annually resolved 3622-year reconstruction of departures from mean summer temperatures (December to March) for southern South America. The longest interval with above-average temperatures was from 80 B.C. to A.D. 160. Long intervals with below-average temperatures were recorded from A.D. 300 to 470 and from A.D. 1490to 1700. Neitherthis proxy temperature record nor instrumentaldatafor southern South America for latitudes between 35" and 44"s provide evidence of a warming trend during the last decades of this century that could be related to anthropogenic causes. The data also indicate that alerce is the second longest living tree after the bristlecone pine (Pinus longaeva) . Climatic records from weather stations as well as nroxv sources are scant for the L ! Southern Hemisphere compared with those for the Northern Hemisphere ( 1 4 ) . How- ever, Southern Hemisphere climate records are crucial for understanding the global climatic system because climatic differences between the Northern and Southern hemi- spheres could provide relevant clues to the mechanisms that underlie global climatic change (5). Long, high-resolution paleo- temperature records from the Southern Hemis~here are needed to assess the snatial patterns and extent of global warming (2). Here, we present an annually resolved, 3622-year summer temperature reconstruc- tion from a tree-ring width chronology of alerce trees (Fitzroya cupressoides) from southern Chile. Southern South America presents a unique opportunity for obtaining terrestrial climate proxy records in a region that is under the influence of both Antarctic and mid-latitude atmospheric circulation pat- terns (6). Tree-ring records from Argentina and Chile have proved useful for tempera- ture and precipitation reconstruction (7, 8) as well as for estimating the latitudinal shifts of the Pacific high-pressure cell (9) and the occurrence of El Nifio-Southern Oscillation events (1 0). Earlier studies of alerce produced a 1534-year ring-width chronology (1 1) and a 1120-year recon- struction of mean summer temperature vari- ations for northern Patagonia (7). A. Lara, Laboratory of Tree-Ring Research, University We collected radial wedges from alerce of Arizona, Tucson, AZ 80721 R. Villalba, Department of Geography, University of StumpS from a mixed conifer-broad-leaved Colorado. Boulder. CO 80309. stand that was logged from 1975 to 1976 , , - -~ -- *Present address: lnstituto de Silvicultura, Universidad and Cores from living trees taken with Austral de Chile, Casilla 567, Valdivia, Chile. increment borers in other nearby unlogged 890-m elevation on the western slope of the Andes near Lenca in south-central Chile (41°33'S, 72'36'W; Fig. 1). The climate at the site is oceanic temperate with decreases in the summer rainfall (12). Lago Chapo, 18 km northeast of the study site at 240-m elevation, has a mean annual temperature of 10.3"C and receives 4140 mm of mean annual precipitation (1 3). Radial wedges and cores were surfaced and cross-dated, and ring widths were measured according to standard methods (1 4). Of the 96 samples examined, only 43 radii (2 1 wedges and 22 cores) from 38 trees were successfully cross-dated. The mean length radii was 867 years (the range was 325 to 2248 years). The oldest alerce tree was dated from a wedge collected from a stump of a tree cut in 1975. Cross dating of the inner 1440 years of this tree indicated that it was 3613 years old. There were 57 locally absent rings out of a total of 37,260 rings in the cross-dated data set (0.15%). We detrended ring widths into dimension- - less in dice.^ to remove the effects of changes in tree growth that resulted from aging, to homogenize the mean and variance, and to produce a standard chronology for the site (1 5). Different curve-fitting procedures for the computation of the tree-ring indices were tested (1 6). Pre-whitened residual se- ~, ries were combined to produce a mean chronology suitable for climate reconstruc- tion. Paleoclimatic intermetation of the Lenca chronology was based on the relation between alerce growth (expressed as annual tree-ring indices) and available regional temperature and precipitation records from Chile and Argentina between 39" and 44"s. We investigated these relations using response and correlation functions (1 7, 18) for various monthly and seasonal combina- tions of the meteoroloeical records. There - was a significant negative linear relation (slope = -2.24; SE = 0.45) between alerce tree-ring indices and previous sum- mer (December to March) mean tempera- ture for the period from 1910 to 1987 for a regional average of the following meteoro- logic stations: Collunc6, Bariloche, Esquel, Mascardi, and Sarmiento. These stations are located in Argentina east of the Andes, 140 to 485 km from the study site (Fig. 1). A similar but weaker negative relation be- tween tree-ring indices and mean prior summer temperature (slope = - 1.57; SE = 0.54) was seen for the interval from 1910 to 1987 with the use of a regional record from four stations (Valdivia, Isla Teja, Punta Galera, and Lago Chapo) located in Chile west of the Andes, 18 to 170 km from the sampling site (Fig. 1). The larger standard error associated with this regional record - mav be because the Chilean stations are 1104 SCIENCE VOL. 260 21 MAY 1993