Réf. Corona & al. 2010 - A

Référence bibliographique complète

CORONA, C., GUIOT, J., EDOUARD, J.L., CHALIÉ, F., BÜNTGEN, U., NOLA, P., URBINATI, C. 2010. Millennium-long summer temperature variations in the European Alps as reconstructed from tree rings. Climate of the Past, Vol. 6, 379–400. [Etude en ligne]

Abstract: This paper presents a reconstruction of the summer temperatures over the Greater Alpine Region (44.05°–47.41° N, 6.43°–13° E) during the last millennium based on a network of 38 multi-centennial larch and stone pine chronologies. Tree ring series are standardized using an Adaptative Regional Growth Curve, which attempts to remove the age effect from the low frequency variations in the series. The proxies are calibrated using the June to August mean temperatures from the HISTALP high-elevation temperature time series spanning the 1818–2003. The method combines an analogue technique, which is able to extend the too short tree-ring series, an artificial neural network technique for an optimal non-linear calibration including a bootstrap technique for calculating error assessment on the reconstruction. About 50% of the temperature variance is reconstructed. Low-elevation instrumental data back to 1760 compared to their instrumental target data reveal divergence between (warmer) early instrumental measurements and (colder) proxy estimates. The proxy record indicates cool conditions, from the mid-11th century to the mid-12th century, related to the Oort solar minimum followed by a short Medieval Warm Period (1200–1420). The Little Ice Age (1420–1830) appears particularly cold between 1420 and 1820 with summers that are 0.8 °C cooler than the 1901–2000 period. The new record suggests that the persistency of the late 20th century warming trend is unprecedented. It also reveals significant similarities with other alpine reconstructions.

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Organismes / Contact

CEREGE, UMR 6635 CNRS/Aix-Marseille Univ., BP 80, 13545 Aix-en-Provence cedex 4, France
IMEP, UMR 6116 CNRS/Aix-Marseille Univ., BP 80, 13545 Aix-en-Provence cedex 4, France
Swiss Federal Research Institute WSL, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
Università degli Studi di Pavia, Dip. Ecologia del Territorio a degli Ambienti Terrestri, Via S. Epifanio, 14, 27100 Pavia, Italy
Università Politecnica delle Marche, Dip. SAPROV, Forest Ecology and Management, Via Brecce Bianche, 60131 Ancona, Italy

This research has been supported by the program ESCARSEL (2007–2010), “Evolution Séculaire du Climat dans les régions circum-Atlantiques et Réponse de Systèmes Eco-Lacustres” funded by the French ANR “Vulnérabilité: milieux et climat”.

 

(1) - Paramètre(s) atmosphérique(s) modifié(s)

(2) - Elément(s) du milieu impacté(s)

(3) - Type(s) d'aléa impacté(s)

(3) - Sous-type(s) d'aléa

 

 

 

 

 

Pays / Zone

Massif / Secteur

Site(s) d'étude

Exposition

Altitude

Période(s) d'observation

 

 

 

 

 

 

 

(1) - Modifications des paramètres atmosphériques

Reconstitutions

A new larch/pine composite chronology is presented, integrating populations from western Alps and providing evidence of Alpine summer temperature variations back to 1000. The Adaptive Regional Growth Curve method is used to preserve both low to high frequency information from the data. Instrumental measurements from the HISTALP high temperatures time series back to 1818 are used for calibration and low-elevation series were used for verification. The new record correlates with high-elevation JJA temperatures back to 1818, but indicates discrepancies between “cooler” proxy-inferred and “warmer” instrumental values prior to 1850. The multidecadal to centennial variations properly match with solar forcings particularly during solar minima and some annual to decadal coolings are related to volcanic eruptions especially at the beginning of the 19th century. The record indicates a short Medieval Warm Period with warmer conditions beginning as late as the early 13th. The LIA is particularly cold between 1420 and 1720 with a mean summer temperature of −0.80°C compared to the 1901–2000 reference period. After 1720, temperatures increase with distinct depressions during the 1810–20s, the 1910s, and 1970s. According to this regional analysis, the last decade of the 20th is the warmest period over the past millennium: +0.9°C (compared to the 1901–2000 reference period). The amplitude of this warming compared to the previous period is even higher. It largely exceeds the warming reconstructed for the Medieval Warm Period in both its amplitude and abruptness. This particular feature (outstanding intense and rapid warming) is consistent with the fact that it might be attributed to the contribution of anthropogenic greenhouse gases and aerosols. These periods are seen in Alpine, European or hemispheric reconstructions but also in independent proxies (historical archives, speleothems) indicating the relevance of this new record and the Alps to large-scale studies of global climate change.

Observations

 

Modélisations

 

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Informations complémentaires (données utilisées, méthode, scénarios, etc.)

In this paper, the authors present a millennium-long summer temperature reconstruction covering most of the Alpine arc by various existing and newly updated composite dataset that combine living trees with dendroarchaeological material. Unlike previous reconstruction, this reconstruction is built from series widely distributed in the Alpine arc, and, in particular, series from Western Alps are incorporated in the dataset. In an effort to capture the natural range of high- to low- frequency temperature variations and to provide a refined reconstruction of their amplitude over past millennium, they combined version of the well-established RCS technique for tree-ring detrending, an analog method for data aggregation, and a neural network approach for reconstruction. This approach has been applied successfully in palaeoclimatology and in dendroclimatology. It differs from linear statistical methods in that it introduces non-linearity to the system and appears particularly adapted to tree-ring based reconstructions due to the complexity of tree growth, dependent on climate but also on time, tree geometry and other factors. Results are compared to existing alpine reconstructions, and comparison with NH reconstructions is conducted to place our regional reconstruction in a larger-scale context. [see methodology and references in the study]

 

(2) - Effets du changement climatique sur le milieu naturel

Reconstitutions

 

Observations

 

Modélisations

 

Hypothèses

 

 

Sensibilité du milieu à des paramètres climatiques

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

 

 

 

(3) - Effets du changement climatique sur l'aléa

Reconstitutions

 

Observations

 

Modélisations

 

Hypothèses

 

 

Paramètre de l'aléa

Sensibilité des paramètres de l'aléa à des paramètres climatiques

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

 

 

 

 

(4) - Remarques générales

 

 

(5) - Syntèses et préconisations

 

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