Earth system models and various climate proxy sources indicate global warming is unprecedented during at least the Common Era1. However, tree-ring proxies often estimate temperatures during the Medieval Climate Anomaly (950-1250 CE) that are similar to, or exceed, those recorded for the past century2,3, in contrast to simulation experiments at regional scales4. This not only calls into question the reliability of models and proxies but also contributes to uncertainty in future climate projections5. Here we show that the current climate of the Fennoscandian Peninsula is substantially warmer than that of the medieval period. This highlights the dominant role of anthropogenic forcing in climate warming even at the regional scale, thereby reconciling inconsistencies between reconstructions and model simulations. We used an annually resolved 1,170-year-long tree-ring record that relies exclusively on tracheid anatomical measurements from Pinus sylvestris trees, providing high-fidelity measurements of instrumental temperature variability during the warm season. We therefore call for the construction of more such millennia-long records to further improve our understanding and reduce uncertainties around historical and future climate change at inter-regional and eventually global scales.

Bolin Centre for Climate Research Stockholm University Stockholm Sweden

Climate Change Impacts and Risks in the Anthropocene University of Geneva Geneva Switzerland

Dendrolab ch Department of Earth Sciences University of Geneva Geneva Switzerland

Department F A Forel for Environmental and Aquatic Sciences University of Geneva Geneva Switzerland

Department of Geography Johannes Gutenberg University Mainz Germany

Department of Land Environment Agriculture and Forestry University of Padua Padua Italy

Department of Physical Geography Stockholm University Stockholm Sweden

Earth and Life Institute Université Catholique de Louvain Louvain la Neuve Belgium

Global Change Research Institute of the Czech Academy of Sciences Brno Czech Republic

Laboratory of Tree Ring Research University of Arizona Tucson AZ USA

Oeschger Centre for Climate Change Research University of Bern Bern Switzerland

Regional Climate Group Department of Earth Sciences University of Gothenburg Gothenburg Sweden

Swedish Polar Research Secretariat Abisko Scientific Research Station Abisko Sweden

Swiss Federal Institute for Forest Snow and Landscape Research WSL Birmensdorf Switzerland

Zobrazit více v PubMed

Neukom, R. et al. Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era. Nat. Geosci. 12, 643–649 (2019). PubMed DOI PMC

Esper, J., Düthorn, E., Krusic, P. J., Timonen, M. & Büntgen, U. Northern European summer temperature variations over the Common Era from integrated tree‐ring density records. J. Quat. Sci. 29, 487–494 (2014). DOI

Luterbacher, J. et al. European summer temperatures since Roman times. Environ. Res. Lett. 11, 024001 (2016). DOI

Fernández-Donado, L. et al. Large-scale temperature response to external forcing in simulations and reconstructions of the last millennium. Clim. Past 9, 393–421 (2013). DOI

Masson-Delmotte, V. et al. (eds) Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge Univ. Press, 2021).

Neukom, R., Steiger, N., Gómez-Navarro, J. J., Wang, J. & Werner, J. P. No evidence for globally coherent warm and cold periods over the preindustrial Common Era. Nature 571, 550–554 (2019). PubMed DOI

Frank, D., Esper, J., Zorita, E. & Wilson, R. A noodle, hockey stick, and spaghetti plate: a perspective on high‐resolution paleoclimatology. Wiley Interdiscip. Rev. Clim. Change 1, 507–516 (2010). DOI

Anchukaitis, K. J. & Smerdon, J. E. Progress and uncertainties in global and hemispheric temperature reconstructions of the Common Era. Quat. Sci. Rev. 286, 107537 (2022). DOI

Wilson, R. et al. Last millennium northern hemisphere summer temperatures from tree rings: Part I: the long term context. Quat. Sci. Rev. 134, 1–18 (2016). DOI

Schneider, L. et al. Revising midlatitude summer temperatures back to A.D. 600 based on a wood density network. Geophys. Res. Lett. 42, 4556–4562 (2015). DOI

Zhao, B. et al. Prolonged drying trend coincident with the demise of Norse settlement in southern Greenland. Sci. Adv. 8, eabm4346 (2022). PubMed DOI PMC

Bradley, R. S., Wanner, H. & Diaz, H. F. The Medieval Quiet Period. Holocene 26, 990–993 (2016). DOI

Knutti, R. & Hegerl, G. C. The equilibrium sensitivity of the Earth’s temperature to radiation changes. Nat. Geosci. 1, 735–743 (2008). DOI

PAGES2kConsortium. A global multiproxy database for temperature reconstructions of the Common Era. Sci. Data 4, 170088 (2017). DOI

Cook, E. R., Briffa, K. R., Meko, D. M., Graybill, D. A. & Funkhouser, G. The ‘segment length curse’ in long tree-ring chronology development for palaeoclimatic studies. Holocene 5, 229–237 (1995). DOI

Esper, J. et al. Orbital forcing of tree-ring data. Nat. Clim. Change 2, 862–866 (2012). DOI

Franke, J., Frank, D., Raible, C. C., Esper, J. & Brönnimann, S. Spectral biases in tree-ring climate proxies. Nat. Clim. Change 3, 360–364 (2013). DOI

Esper, J., Schneider, L., Smerdon, J. E., Schöne, B. R. & Büntgen, U. Signals and memory in tree-ring width and density data. Dendrochronologia 35, 62–70 (2015). DOI

Zhang, H. et al. Modified climate with long term memory in tree ring proxies. Environ. Res. Lett. 10, 084020 (2015). DOI

Esper, J. et al. Ranking of tree-ring based temperature reconstructions of the past millennium. Quat. Sci. Rev. 145, 134–151 (2016). DOI

McCarroll, D., Young, G. H. & Loader, N. J. Measuring the skill of variance-scaled climate reconstructions and a test for the capture of extremes. Holocene 25, 618–626 (2015). DOI

Büntgen, U. Scrutinizing tree-ring parameters for Holocene climate reconstructions. Wiley Interdiscip. Rev. Clim. Change 13, e778 (2022). DOI

Battipaglia, G. et al. Five centuries of Central European temperature extremes reconstructed from tree-ring density and documentary evidence. Glob. Planet. Change 72, 182–191 (2010). DOI

Von Storch, H. et al. Reconstructing past climate from noisy data. Science 306, 679–682 (2004). DOI

Belmecheri, S., Babst, F., Wahl, E. R., Stahle, D. W. & Trouet, V. Multi-century evaluation of Sierra Nevada snowpack. Nat. Clim. Change 6, 2–3 (2016). DOI

Lücke, L. J., Hegerl, G. C., Schurer, A. P. & Wilson, R. Effects of memory biases on variability of temperature reconstructions. J. Clim. 32, 8713–8731 (2019). DOI

von Arx, G., Crivellaro, A., Prendin, A. L., Čufar, K. & Carrer, M. Quantitative wood anatomy—practical guidelines. Front. Plant Sci. 7, 781 (2016).

Prendin, A. L. et al. New research perspectives from a novel approach to quantify tracheid wall thickness. Tree Physiol. 37, 976–983 (2017). PubMed DOI

Björklund, J. et al. Scientific merits and analytical challenges of tree‐ring densitometry. Rev. Geophys. 57, 1224–1264 (2019). DOI

Björklund, J., Seftigen, K., Fonti, P., Nievergelt, D. & von Arx, G. Dendroclimatic potential of dendroanatomy in temperature-sensitive Pinus sylvestris. Dendrochronologia 60, 125673 (2020). DOI

Lopez-Saez, J. et al. Tree-ring anatomy of Pinus cembra trees opens new avenues for climate reconstructions in the European Alps. Sci. Total Envir. 855, 158605 (2023).

Seftigen, K. et al. Prospects for dendroanatomy in paleoclimatology – a case study on Picea engelmannii from the Canadian Rockies. Clim. Past 18, 1151–1168 (2022). DOI

Allen, K. J., Nichols, S. C., Evans, R. & Baker, P. J. Characteristics of a multi-species conifer network of wood properties chronologies from Southern Australia. Dendrochronologia 76, 125997 (2022). DOI

Melvin, T. M., Grudd, H. & Briffa, K. R. Potential bias in ‘updating’ tree-ring chronologies using regional curve standardisation: re-processing 1500 years of Torneträsk density and ring-width data. Holocene 23, 364–373 (2013). DOI

Linderholm, H. W. & Gunnarson, B. E. Were medieval warm-season temperatures in Jämtland, central Scandinavian Mountains, lower than previously estimated? Dendrochronologia 57, 125607 (2019). DOI

Grudd, H. Torneträsk tree-ring width and density AD 500–2004: a test of climatic sensitivity and a new 1500-year reconstruction of north Fennoscandian summers. Clim. Dyn. 31, 843–857 (2008). DOI

Matskovsky, V. & Helama, S. Testing long-term summer temperature reconstruction based on maximum density chronologies obtained by reanalysis of tree-ring data sets from northernmost Sweden and Finland. Clim. Past 10, 1473–1487 (2014). DOI

Büntgen, U. et al. Prominent role of volcanism in Common Era climate variability and human history. Dendrochronologia 64, 125757 (2020). DOI

Guillet, S. et al. Climate response to the Samalas volcanic eruption in 1257 revealed by proxy records. Nat. Geosci. 10, 123–128 (2017). DOI

Wu, T. et al. An overview of BCC climate system model development and application for climate change studies. J. Meteorol. Res. 28, 34–56 (2014).

Landrum, L. et al. Last millennium climate and its variability in CCSM4. J. Clim. 26, 1085–1111 (2013). DOI

Dufresne, J.-L. et al. Climate change projections using the IPSL-CM5 Earth System Model: from CMIP3 to CMIP5. Clim. Dyn. 40, 2123–2165 (2013). DOI

Yukimoto, S. et al. A new global climate model of the Meteorological Research Institute: MRI-CGCM3 – model description and basic performance–. J. Meteorol. Soc. Japan. Ser. II 90A, 23–64 (2012). DOI

Bao, Q. et al. The flexible global ocean-atmosphere-land system model, spectral version 2: FGOALS-s2. Adv. Atmos. Sci. 30, 561–576 (2013). DOI

Phipps, S. et al. The CSIRO Mk3L climate system model version 1.0 – part 1: description and evaluation. Geosci. Model Dev. 4, 483–509 (2011). DOI

Miller, R. L. et al. CMIP5 historical simulations (1850–2012) with GISS ModelE2. J. Adv. Model. Earth Syst. 6, 441–478 (2014). DOI

Giorgetta, M. A. et al. Climate and carbon cycle changes from 1850 to 2100 in MPI‐ESM simulations for the Coupled Model Intercomparison Project phase 5. J. Adv. Model. Earth Syst. 5, 572–597 (2013). DOI

Marsh, D. R. et al. Climate change from 1850 to 2005 simulated in CESM1(WACCM). J. Clim. 26, 7372–7391 (2013). DOI

Watanabe, S. et al. MIROC-ESM 2010: model description and basic results of CMIP5-20c3m experiments. Geosci. Model Dev. 4, 845–872 (2011). DOI

Johns, T. C. et al. Anthropogenic climate change for 1860 to 2100 simulated with the HadCM3 model under updated emissions scenarios. Clim. Dyn. 20, 583–612 (2003). DOI

Taylor, K. E., Stouffer, R. J. & Meehl, G. A. An overview of CMIP5 and the experiment design. Bull. Am. Meteorol. Soc. 93, 485–498 (2012). DOI

Braconnot, P. et al. Evaluation of climate models using palaeoclimatic data. Nat. Clim. Change 2, 417–424 (2012). DOI

Wigley, T. M. L., Briffa, K. R. & Jones, P. D. On the average value of correlated time series, with applications in dendroclimatology and hydrometeorology. J. Appl. Meteorol. Climatol. 23, 201–213 (1984). DOI

Helama, S., Melvin, T. M. & Briffa, K. R. Regional curve standardization: state of the art. Holocene 27, 172–177 (2017). DOI

Andersson, G. Om talltorkan i öfra Sverige våren 1903 (Statens skogsförsöksanstalt, 1905).

Pallardy, S. G. Physiology of Woody Plants 3rd edn (Academic, 2008).

Vaganov, E. A., Hughes, M. K. & Shashkin, A. V. Growth Dynamics of Conifer Tree Rings: Images of Past and Future Eenvironments Vol. 183 (Springer Science & Business Media, 2006).

Abbott, P. M. et al. Cryptotephra from the Icelandic Veiðivötn 1477 CE eruption in a Greenland ice core: confirming the dating of volcanic events in the 1450s CE and assessing the eruption’s climatic impact. Clim. Past 17, 565–585 (2021). DOI

Stoffel, M. et al. Estimates of volcanic-induced cooling in the Northern Hemisphere over the past 1,500 years. Nat. Geosci. 8, 784–788 (2015). DOI

Anchukaitis, K. J. et al. Last millennium Northern Hemisphere summer temperatures from tree rings: part II, spatially resolved reconstructions. Quat. Sci. Rev. 163, 1–22 (2017). DOI

McCarroll, D. et al. A 1200-year multiproxy record of tree growth and summer temperature at the northern pine forest limit of Europe. Holocene 23, 471–484 (2013). DOI

Neukom, R. et al. Inter-hemispheric temperature variability over the past millennium. Nat. Clim. Change 4, 362–367 (2014). DOI

PAGES2k-PMIP3 group. Continental-scale temperature variability in PMIP3 simulations and PAGES 2k regional temperature reconstructions over the past millennium. Clim. Past 11, 1673–1699 (2015). DOI

Lorenz, E. N. Deterministic nonperiodic flow. J. Atmos. Sci. 20, 130–141 (1963). DOI

D’Arrigo, R., Wilson, R., Liepert, B. & Cherubini, P. On the ‘divergence problem’ in northern forests: a review of the tree-ring evidence and possible causes. Glob. Planet. Change 60, 289–305 (2008). DOI

Büntgen, U. et al. The influence of decision-making in tree ring-based climate reconstructions. Nat. Commun. 12, 3411 (2021). PubMed DOI PMC

Pawlowicz, R. M_Map: a mapping package for MATLAB, MATLAB package v.1.4m. https://www.eoas.ubc.ca/~rich/map.html (2020).

Morice, C. P. et al. An updated assessment of near‐surface temperature change from 1850: The HadCRUT5 data set. J. Geophys. Res. Atmos. 126, e2019JD032361 (2021). DOI

Schweingruber, F. H., Bartholin, T., Schār, E. & Briffa, K. R. Radiodensitometric‐dendroclimatological conifer chronologies from Lapland (Scandinavia) and the Alps (Switzerland). Boreas 17, 559–566 (1988). DOI

Briffa, K. R. et al. A 1,400-year tree-ring record of summer temperatures in Fennoscandia. Nature 346, 434–439 (1990). DOI

Briffa, K. R. et al. Fennoscandian summers from AD 500: temperature changes on short and long timescales. Clim. Dyn. 7, 111–119 (1992). DOI

Gärtner, H., Lucchinetti, S. & Schweingruber, F. A new sledge microtome to combine wood anatomy and tree-ring ecology. IAWA J. 36, 452–459 (2015). DOI

von Arx, G. & Carrer, M. ROXAS – a new tool to build centuries-long tracheid-lumen chronologies in conifers. Dendrochronologia 32, 290–293 (2014). DOI

Denne, M. P. Definition of latewood according to Mork (1928). IAWA J. 10, 59–62 (1989). DOI

Björklund, J. A., Gunnarson, B. E., Seftigen, K., Esper, J. & Linderholm, H. W. Blue intensity and density from northern Fennoscandian tree rings, exploring the potential to improve summer temperature reconstructions with earlywood information. Clim. Past 10, 877–885 (2014). DOI

Schmidt, G. et al. Climate forcing reconstructions for use in PMIP simulations of the Last Millennium (v1.1). Geosci. Model Dev. 5, 185–191 (2012). DOI

National Research Council. Surface Temperature Reconstructions for the Last 2,000 Years (National Academies Press, 2007).

Cook, E. R. & Peters, K. The smoothing spline: a new approach to standardizing forest interior tree-ring width series for dendroclimatic studies. Tree Ring Bull. 41, 45–53 (1981).

Matalas, N. C. Statistical properties of tree ring data. Int. Assoc. Sci. Hydrol. Bull. 7, 39–47 (1962). DOI

Piermattei, A., Crivellaro, A., Carrer, M. & Urbinati, C. The “blue ring”: anatomy and formation hypothesis of a new tree-ring anomaly in conifers. Trees 29, 613–620 (2015). DOI

Percival, D. B. & Walden, A. T. Spectral Analysis for Physical Applications (Cambridge Univ. Press, 1993).

Huybers, P. pmtmPH.m v.1.0.0.0. https://www.mathworks.com/matlabcentral/fileexchange/2927-pmtmph-m (MATLAB Central File Exchange, 2022).

Haurwitz, M. W. & Brier, G. W. A critique of the superposed epoch analysis method: its application to solar–weather relations. Mon. Weather Rev. 109, 2074–2079 (1981). DOI

Brad Adams, J., Mann, M. E. & Ammann, C. M. Proxy evidence for an El Nino-like response to volcanic forcing. Nature 426, 274–278 (2003). PubMed DOI

Blarquez, O. & Carcaillet, C. Fire, fuel composition and resilience threshold in subalpine ecosystem. PLoS ONE 5, e12480 (2010). PubMed DOI PMC

Gao, C., Robock, A. & Ammann, C. Volcanic forcing of climate over the past 1500 years: an improved ice core‐based index for climate models. J. Geophys. Res. Atmos. 113, D23111 (2008). DOI

Toohey, M. & Sigl, M. Volcanic stratospheric sulfur injections and aerosol optical depth from 500 BCE to 1900 CE. Earth Syst. Sci. Data 9, 809–831 (2017). DOI

Quantitative vessel mapping on increment cores: a critical comparison of image acquisition methods

Blue rings in trees and shrubs as indicators of early and late summer cooling events at the northern treeline