Researcher Håkan Grudd used tree proxy data to reconstruct the temperature record of Torneträsk, deep inside the Arctic Circle. Sampling was done on Scots pines, which have grown in the region for millenia, allowing for reconstruction of a continuous record.
Grudd, of Stockholm University's Department of Physical Geography and Quaternary Geology, compared both tree ring width and maximum density, to construct the most accurate data yet seen for the region. He found a sharp warming trend since the year 1900. However, over the entire period, several such warming events were seen with temperatures in at least four periods (AD 750, 1000, 1400, and 1750) all equally warm or warmer than at present.
Most surprising of all, he noted, when taken as a whole temperatures in the Arctic have actually declined 0.3 degrees over the past 1,000 years. As Grudd himself says, temperatures at present are "not especially warm."
The full temperature record also reveals why the last 100 years has appeared unusual -- the year 1900 was actually the coldest of the entire period.
According to Grudd, the Torneträsk data aligns well with ice core isotope records from Greenland, demonstrating these climate changes were widespread throughout the Arctic region.
Grudd's results contradict his earlier reconstructions of Arctic temperatures, which demonstrated significantly cooler temperatures prior to 1900. The difference, he claims, is due to more accurate scanning of samples, along with a better understanding of how tree ring widths and density respond to temperature changes.
Text of the full paper can be found here. The work is forthcoming in the peer-reviewed journal Climate Dynamics.