Long-term summer temperature variations in the Pyrenees |
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Authors: | Ulf Büntgen David Frank Håkan Grudd Jan Esper |
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Institution: | (1) Swiss Federal Research Institute WSL, Dendro Sciences Unit, 8903 Birmensdorf, Switzerland;(2) Department of Physical Geography and Quaternary Geology, Stockholm University, 10691 Stockholm, Sweden |
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Abstract: | Two hundred and sixty one newly measured tree-ring width and density series from living and dry-dead conifers from two timberline
sites in the Spanish Pyrenees were compiled. Application of the regional curve standardization method for tree-ring detrending
allowed the preservation of inter-annual to multi-centennial scale variability. The new density record correlates at 0.53
(0.68 in the higher frequency domain) with May–September maximum temperatures over the 1944–2005 period. Reconstructed warmth
in the fourteenth to fifteenth and twentieth century is separated by a prolonged cooling from ∼1450 to 1850. Six of the ten
warmest decades fall into the twentieth century, whereas the remaining four are reconstructed for the 1360–1440 interval.
Comparison with novel density-based summer temperature reconstructions from the Swiss Alps and northern Sweden indicates decadal
to longer-term similarity between the Pyrenees and Alps, but disagreement with northern Sweden. Spatial field correlations
with instrumental data support the regional differentiation of the proxy records. While twentieth century warmth is evident
in the Alps and Pyrenees, recent temperatures in Scandinavia are relatively cold in comparison to earlier warmth centered
around medieval times, ∼1450, and the late eighteenth century. While coldest summers in the Alps and Pyrenees were in-phase
with the Maunder and Dalton solar minima, lowest temperatures in Scandinavia occurred later at the onset of the twentieth
century. However, fairly cold summers at the end of the fifteenth century, between ∼1600–1700, and ∼1820 were synchronized
over Europe, and larger areas of the Northern Hemisphere. |
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