Northern Scandinavia, 138 BC-2006 AD, maximum latewood density, living and subfossil pine, PAGES Euro-Med 2k Version Esper, J.; Frank, D.C.; Timonen, M.; Zorita, E.; Wilson, R.J.S.; Luterbacher, J.; Holzkämper, S.; Fischer, N.; Wagner, S.; Nievergelt, D.; Verstege, A.; Büntgen, U. Esper, J. Frank, D.C. Timonen, M. Zorita, E. Wilson, R.J.S. Luterbacher, J. Holzkämper, S. Fischer, N. Wagner, S. Nievergelt, D. Verstege, A. Büntgen, U. PAGES 2k Network PAGES Euro-Med 2k PISY Pinus sylvestris L. Scots pine Scotch pine earth science/paleoclimate/tree-ring (Northern Scandinavia, Sweden>LATITUDE 68>LONGITUDE 25) Solar insolation changes, resulting from long-term oscillations of orbital configurations, are an important driver of Holocene climate. The forcing is substantial over the past 2,000 years, up to four times as large as the 1.6Wm-2 net anthropogenic forcing since 1750, but the trend varies considerably over time, space and with season. Using numerous high-latitude proxy records, slow orbital changes have recently been shown6 to gradually force boreal summer temperature cooling over the common era. Here, we present new evidence based on maximum latewood density data from northern Scandinavia, indicating that this cooling trend was stronger (-0.31 deg C per 1,000 years, \pm 0.03 deg C) than previously reported, and demonstrate that this signature is missing in published tree-ring proxy records. The long-term trend now revealed in maximum latewood density data is in line with coupled general circulation models indicating albedo-driven feedback mechanisms and substantial summer cooling over the past two millennia in northern boreal and Arctic latitudes. These findings, together with the missing orbital signature in published dendrochronological records, suggest that large-scale nearsurface air-temperature reconstructions9–13 relying on treering data may underestimate pre-instrumental temperatures includingwarmth during Medieval and Roman times. STUDY NOTES: We here develop a 2,000-year summer temperature reconstruction based on 587 high-precision maximum latewood density (MXD) series from northern Scandinavia. The record was developed over three years using living and subfossil pine (Pinus sylvestris) trees from 14 lakes and 3 lakeshore sites >65 deg N, making it not only longer but also much better replicated than any existing MXD time series (for example, the widely cited Tornetraesk record contains 65 series. We carried out a number of tests to the MXD network and noted the robustness of the long-term trends, but also the importance of including living trees from the lakeshore to form a seamless transition to the subfossil material preserved in the lakes. Calibration/verification with instrumental data is temporally robust and no evidence for divergence was noted. The final reconstruction (N-scan) was calibrated against regional JJA temperature and spans the 138 BC-2006 AD period. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Esper, J. Investigator : Frank, D.C. Investigator : Timonen, M. Investigator : Zorita, E. Investigator : Wilson, R.J.S. Investigator : Luterbacher, J. Investigator : Holzkämper, S. Investigator : Fischer, N. Investigator : Wagner, S. Investigator : Nievergelt, D. Investigator : Verstege, A. Investigator : Büntgen, U. 2013-05-15 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/1003406 https://www1.ncdc.noaa.gov/pub/data/paleo/reconstructions/pages2k/euro-med2k/Esper_et_al_NatureCC_2012.txt https://www1.ncdc.noaa.gov/pub/data/paleo/reconstructions/pages2k/euro-med2k/Esper_et_al_NatureCC_2012.txt English https://www.ncdc.noaa.gov/paleo/study/1003406 https://www1.ncdc.noaa.gov/pub/data/paleo/reconstructions/pages2k/euro-med2k/Esper_et_al_NatureCC_2012.txt Esper, J., D.C. Frank, M. Timonen, E. Zorita, R.J.S. Wilson, J. Luterbacher, S. Holzkämper, N. Fischer, S. Wagner, D. Nievergelt, A. Verstege, U. Büntgen2012Orbital forcing of tree-ring dataNature Climate Change2862-86610.1038/nclimate1589 START YEAR: -138 AD * END YEAR: 2006 AD 25 68 25 68