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A 1250-Year History of Summer Temperature in the European Alps
Reference
Buntgen, U., Frank, D.C., Nievergelt, D. and Esper, J. 2006. Summer temperature variations in the European Alps, A.D. 755-2004. Journal of Climate 19: 5606-5623.

What was done
An annually-resolved mean summer (June-September) temperature record for the European Alps, covering the period AD 755-2004 and based on 180 recent and historic larch (Larix decidua Mill.) maximum latewood density series, was developed using the regional curve standardization method that preserves interannual to multi-centennial temperature-related variations.

What was learned
Among a number of other things, notable features identified by the authors were high temperatures in the late tenth, early thirteenth, and twentieth centuries and a prolonged cooling from ~1350 to 1700, or as they describe it: "warmth during medieval and recent times, and cold in between." Also of great interest, they report that the coldest decade of the record was the 1810s, and that even though the record extended all the way through 2004, the warmest decade of the record was the 1940s. In addition, they observed that "warm summers seem to coincide with periods of high solar activity, and cold summers vice versa." Finally, they report that comparing their newest temperature record with other regional- and large-scale reconstructions "reveals similar decadal to longer-term variability."

What it means
Buntgen et al. conclude - in the final sentence of their paper - that based upon their findings and the similar findings many others, "the twentieth-century contribution of anthropogenic greenhouse gases and aerosol remains insecure." Since these words appear to be particularly carefully chosen, we feel we should not attempt to rephrase or clarify them any further, assuming that most rational people will be able to correctly determine for themselves both what they mean and what they imply.

Reviewed 14 March 2007