World Climate Report
February 4, 2008
1,500 Years of Cooling in the Arctic
Filed under: Paleo/Proxy, Temperature History —
The Arctic is melting, right? There is simply no questioning this pillar of the greenhouse scare, and images of ice melting, polar bears struggling, and indigenous people crying the blues are all part of any self-respecting presentation of global warming. Imagine a study published in a major journal showing that a location in the Arctic has “a trend of -0.3°C over the last 1,500 years.” Of course, you would never have learned of such a result had you not discovered World Climate Report.
The article is forthcoming in Climate Dynamics, and the work was conducted by Håkan Grudd of Stockholm University’s Department of Physical Geography and Quaternary Geology, and despite the results, the research was not funded by industry. The focus here is the Torneträsk area in northern Sweden near 68.5°N (within the Arctic Circle) where Scots pines have been growing for millennia. Grudd not only sampled living trees, but he also collected subfossil samples found as dead wood on dry ground and from submerged logs retrieved from small mountain lakes. Many other studies have shown that the pines are sensitive to summer temperatures, so in theory, the tree samples should allow a very long term and relatively accurate reconstruction of past thermal conditions.
Grudd not only measured the width of each tree ring, he also measured the density of the wood in each ring using an Itrax WoodScanner from Cox Analytical Systems (the perfect gift for the man who thinks he has everything). The obvious trick here is to link the width and density time series to the climate in the growth area. Fortunately, Grudd was able to assemble records from “Abisko, a local record (AD 1913–2004) provided by Abisko Scientific Research Station, which is located within the Torneträsk area; (2) Tornedalen, a long composite record (AD 1802–2002) based on a combination of historical data and synoptic station data from Haparanda approx. 350 km south-east of Torneträsk; and (3) Bottenviken, a regional record (AD 1860–2004) provided by the Swedish Meteorological and Hydrological Institute and based on data from six synoptic stations in northern Sweden.” He used fairly standard multivariate statistical methods to link the climate records to the width and density measurements, and just like magic, response functions are developed to estimate summer temperatures from the tree ring data that extend back 1,500 years.
www.worldclimatereport.com/index.php/2008/02/04/1500-years-of-cooling-in-the-arctic/
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