Fennoscandian summers from ad 500: temperature changes on short and long timescales |
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| Authors: | K R Briffa P D Jones T S Bartholin D Eckstein F H Schweingruber W Karlén P Zetterberg M Eronen |
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| Institution: | (1) Climatic Research Unit, School of Environmental Sciences, University of East Anglia, NR4 7TJ Norwich, UK;(2) Laboratory of Quaternary Biology, University of Lund, Tornavagen 13, S-22363 Lund, Sweden;(3) Institute of Wood Biology, University of Hamburg, Leuschnerstrasse 91, D-2050 Hamburg 80, Germany;(4) Swiss Federal Institute of Forest, Snow and Landscape Research, Zürcherstrasse 11, CH-8903 Birmensdorf, Switzerland;(5) Department of Physical Geography, University of Stockholm, S-10691 Stockholm, Sweden;(6) Karelian Institute, Section of Ecology, University of Joensuu, PO Box 111, SF-80101 Joensuu, Finland |
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| Abstract: | Quantitative estimates of 1480 years of summer temperatures in northern Fennoscandia have previously been derived from continuous treering records from northern Sweden. Here we show the results of spectral analyses of these data. Only a few peaks in the spectra are consistently significant when the data are analyzed over a number of sub-periods. Relatively timestable peaks are apparent at periods of 2.1, 2.5, 3.1, 3.6, 4.8,  32–33 and for a range between 55–100 years. These results offer no strong evidence for solar-related forcing of summer temperatures in these regions. Our previously published reconstruction was limited in its ability to represent long-timescale temperature change because of the method used to standardize the original tree-ring data. Here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales. Considerable variance is now reconstructed on timescales of several centuries. In comparison with modern normals (1951–70) generally extended periods when cool conditions prevailed, prior to the start of the instrumental record, include 500–700, 790–870, 1110–1150, 1190–1360, 1570–1750 (A.D.) with the most significant cold troughs centred on about 660, 800, 1140, 1580–1620 and 1640. Predominantly warm conditions occurred in 720–790, 870–1110 and 1360–1570 with peaks of warmth around 750, 930, 990, 1060, 1090, 1160, 1410, 1430, 1760 and 1820.This paper was presented at Clima Locarno 90, the International Conference on Past and Present Climate Dynamics: Reconstruction of Rates of Change, held in Locarno, Switzerland, September 24 to 28, 1991, organized by the Swiss National Climate Program — ProClim, with support from the Swiss Academy of Sciences. Guest editor for these papers is Dr. K. Kelts
Offprint requests to: KR Briffa |
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