Tornetrask MXD temperature reconstruction AD500-2004

A new temperature reconstruction based on maximum density (MXD) from Tornetrask in northern Sweden, now covering the period AD 500?2004. By including data from relatively young trees for the most recent period, a previously noted decline in recent MXD is eliminated. Non-climatological growth trends in the data are removed using Regional Curve Standardization (RCS), thus producing an MXD chronology with preserved low-frequency variability. The chronology is calibrated using local and regional instrumental climate records. A bootstrapped response function analysis using regional climate data shows that tree growth is forced by April?August temperatures. The robustness of the reconstruction equation is verified by independent temperature data and shows that 63?64% of the instrumental inter-annual variation is captured by the tree-ring data. This is a significant improvement compared to previously published reconstructions based on tree-ring data from Tornetrask. The
new data show generally higher temperature estimates than previous reconstructions based on Tornetrask tree-ring data. The late-twentieth century, however, is not exceptionally warm in the new record: On decadal-to-centennial timescales, periods around AD 750, 1000, 1400, and 1750 were equally warm, or warmer. The 200-year long warm period centered on AD 1000 was significantly warmer than the late-twentieth century (p 0.05) and is supported by other local and regional paleoclimate data. The new tree-ring evidence from Tornetra¨sk suggests that this ??Medieval WarmPeriod?? in northern Fennoscandia was much warmer than previously recognized.