ESTONIAN ACADEMY
PUBLISHERS
eesti teaduste
akadeemia kirjastus
PUBLISHED
SINCE 1952
 
Earth Science cover
Estonian Journal of Earth Sciences
ISSN 1736-7557 (Electronic)
ISSN 1736-4728 (Print)
Impact Factor (2022): 1.1
Research article
Boreal temperature variability inferred from latewood maximum density and historical plant phenology records; pp. 83–95
PDF | 10.3176/earth.2025.06

SUPPLEMENTARY MATERIAL

Authors
Samuli Helama, Jari Holopainen, Mauricio Fuentes, Eva Rocha, Björn E. Gunnarson
Abstract

Plant-based data from southern Finland were used to reconstruct late Holocene warm-season temperature variability on inter-annual to longer scales. Temperature-sensitive records representing maximum latewood density of Pinus sylvestris tree rings (since AD 760) and phenological stages of several plant species (since AD 1750) explained ~60% and ~70% of instrumentally observed temperature variance, respectively. The value of a multi-proxy approach was demonstrated by statistical models including both variables, which explained ~80% of the temperature variance. Temperatures from the CRUTEM5 and Berkeley datasets had slight variations in their correlativity with proxy data, possibly resulting from their differing spatial representativeness over the proxy sites. Temperature history inferred from maximum latewood densities extended over the past millennium and correlated with previously published data from similar proxy records in Fennoscandia and adjacent areas. These data indicate that the region cooled since the Medieval Climate Anomaly and warmed markedly since the Little Ice Age/Maunder Minimum. In the study region, the magnitude of this long-term warming was 2.1 °C and 2.8 °C, calculated between the coldest and warmest 100-year and 30-year intervals, respectively. Collectively, our results display the potential of plant-based data from low-lying and mild boreal sites to extend our understanding of preindustrial and recent climatic changes.

References

Aalto, J., Pirinen, P., Heikkinen, J. and Venäläinen, A. 2013. Spatial interpolation of monthly climate data for Finland: comparing the performance of kriging and generalized additive models. Theoretical and Applied Climatology112, 99–111. 
https://doi.org/10.1007/s00704-012-0716-9  

Aalto, J., Pirinen, P. and Jylhä, K. 2016. New gridded daily climatology of Finland: permutation-based uncertainty estimates and temporal trends in climate. Journal of Geophysical Research: Atmospheres121(8), 3807–3823. 
https://doi.org/10.1002/2015jd024651   

Ahti, T., Hämet-Ahti, L. and Jalas, J. 1968. Vegetation zones and their sections in northwestern Europe. Annales Botanici Fennici5(3), 169–211.

Anchukaitis, K. J., Wilson, R., Briffa, K. R., Büntgen, U., Cook, E. R., D’Arrigo, R. et al. 2017. Last millennium Northern Hemisphere summer temperatures from tree rings: part II, spatially resolved reconstructions. Quaternary Science Reviews163, 1–22. 
https://doi.org/10.1016/j.quascirev.2017.02.020  

Aono, Y. and Kazui, K. 2008. Phenological data series of cherry tree flowering in Kyoto, Japan, and its application to reconstruction of springtime temperatures since the 9th century. International Journal of Climatology28(7), 905–914. 
https://doi.org/10.1002/joc.1594  

Aono, Y. and Nishitani, A. 2022. Reconstruction of April temperatures in Kyoto, Japan, since the fifteenth century using the floral phenology of herbaceous peony and rabbit-ear iris. International Journal of Biometeorology66, 883–893. 
https://doi.org/10.1007/s00484-022-02245-x  

Babst, F., Poulter, B., Trouet, V., Tan, K., Neuwirth, B., Wilson, R. et al. 2013. Site- and species-specific responses of forest growth to climate across the European continent. Global Ecology and Biogeography22(6), 706–717. 
https://doi.org/10.1111/geb.12023  

Bianchi, G. G. and McCave, I. N. 1999. Holocene periodicity in North Atlantic climate and deep-ocean flow south of Iceland. Nature397, 515–517. 
https://doi.org/10.1038/17362  

Bradley, R. S. and Jones, P. D. 1993. ‘Little Ice Age’ summer temperature variations: their nature and relevance to recent global warming trends. The Holocene3(4), 367–376. 
https://doi.org/10.1177/095968369300300409  

Bräker, O. U. 1981. Der Alterstrend bei Jahrringdichten und Jahrringbreiten von Nadelhölzern und sein Ausgleich. Mittei­lungen der forstlichen Bundesversuchsanstalt Wien142, 75–102.

Briffa, K. R., Jones, P. D., Pilcher, J. R. and Hughes, M. K. 1988. Reconstructing summer temperatures in northern Fennoscandinavia back to A.D. 1700 using tree-ring data from Scots pine. Arctic and Alpine Research20(4), 385–394. 
https://doi.org/10.1080/00040851.1988.12002691  

Briffa, K. R., Jones, P. D., Bartholin, T. S., Eckstein, D., Schweingruber, F. H., Karlén, W. et al. 1992. Fennoscandian summers from AD 500: temperature changes on short and long timescales. Climate Dynamics7, 111–119. 
https://doi.org/10.1007/BF00211153  

Briffa, K. R., Jones, P. D., Schweingruber, F. H., Karlén, W. and Shiyatov, S. G. 1996. Tree-ring variables as proxy-climate indicators: problems with low-frequency signals. In Climate Variations and Forcings Mechanisms of the Last 2000 Years (Jones, P. D., Bradley, R. S. and Jouzel, J., eds). Springer, Berlin, 9–41.
https://doi.org/10.1007/978-3-642-61113-1_2

Briffa, K. R., Osborn, T. J., Schweingruber, F. H., Jones, P. D., Shiyatov, S. G. and Vaganov, E. A. 2002a. Tree-ring width and density data around the Northern Hemisphere: part 1, local and regional climate signals. The Holocene12(6), 737–751. 
https://doi.org/10.1191/0959683602hl587rp  

Briffa, K. R., Osborn, T. J., Schweingruber, F. H., Jones, P. D., Shiyatov, S. G. and Vaganov, E. A. 2002b. Tree-ring width and density data around the Northern Hemisphere: part 2, spatio-temporal variability and associated climate patterns. The Holocene12(6), 759–789. 
https://doi.org/10.1191/0959683602hl588rp

Chuine, I., Yiou, P., Viovy, N., Seguin, B., Daux, V. and Le Roy Ladurie, E. 2004. Historical phenology: grape ripening as a past climate indicator. Nature432, 289–290. 
https://doi.org/10.1038/432289a  

Cook, E. R. and Peters, K. 1981. The smoothing spline: a new approach to standardizing forest interior tree-ring width series for dendroclimatic studies. Tree-Ring Bulletin41, 45–53.

Ebisuzaki, W. 1997. A method to estimate the statistical significance of a correlation when the data are serially correlated. Journal of Climate10(9), 2147–2153. 
https://doi.org/10.1175/1520-0442(1997)010<2147:AMTETS>2.0.CO;2  

Eddy, J. A. 1976. The Maunder Minimum. Science192(4245), 1189–1202. 
https://doi.org/10.1126/science.192.4245.1189  

Edvardsson, J., Stoffel, M., Corona, C., Bragazza, L., Leuschner, H. H., Charman, D. J. and Helama, S. 2016. Subfossil peatland trees as proxies for Holocene palaeohydrology and palaeoclimate. Earth-Science Reviews163, 118–140. 
https://doi.org/10.1016/j.earscirev.2016.10.005  

Efron, B. and Tibshirani, R. 1986. Bootstrap methods for standard errors, confidence intervals, and other measures of statistical accuracy. Statistical Science1(1), 54–75. 
https://doi.org/10.1214/ss/1177013815  

Elfving, F. 1938. Fenologiset havainnot. Societas Scientiarum Fennica, Commentationes Humanarum Litterarum10, 204–213.

Elfving, G. and Mickwitz, G. 1988. Suomen Tiedeseuran kolmas puolivuosisata 1938–1987. Suomen Tiedeseura, Ekenäs.

Esper, J., Frank, D. C., Timonen, M., Zorita, E., Wilson, R. J. S., Luterbacher, J. et al. 2012. Orbital forcing of tree-ring data. Nature Climate Change2, 862–866. 
https://doi.org/10.1038/nclimate1589

Esper, J., Düthorn, E., Krusic, P. J., Timonen, M. and Büntgen, U. 2014. Northern European summer temperature variations over the Common Era from integrated tree-ring density records. Journal of Quaternary Science29(5), 487–494. 
https://doi.org/10.1002/jqs.2726  

Fritts, H. C. 1976. Tree rings and climate. Academic Press, New York.

Gordon, G. A., Gray, B. M. and Pilcher, J. R. 1982. Verification of dendroclimatic reconstructions. In Climate from Tree Rings (Hughes, M. K., Kelly, P. M., Pilcher, J. R. and LaMarche, V. V., Jr., eds). Cambridge University Press, Cambridge, 115–132.

Gray, L. J., Beer, J., Geller, M., Haigh, J. D., Lockwood, M., Matthes, K. et al. 2010. Solar influences on climate. Reviews of Geophysics48(4), RG4001. 
https://doi.org/10.1029/2009RG000282  

Grissino-Mayer, H. D. and Fritts, H. C. 1997. The International Tree-Ring Data Bank: an enhanced global database serving the global scientific community. The Holocene7(2), 235–238. 
https://doi.org/10.1177/095968369700700212  

Grove, J. M. 2004. Little Ice Ages: Ancient and Modern. Routledge, London.

Grudd, H. 2008. Torneträsk tree-ring width and density AD 500–2004: a test of climatic sensitivity and a new 1500-year reconstruction of north Fennoscandian summers. Climate Dynamics31, 843–857. 
https://doi.org/10.1007/s00382-007-0358-2  

Guay, R., Gagnon, R. and Morin, H. 1992. A new automatic and interactive tree ring measurement system based on a line scan camera. The Forestry Chronicle68(1), 138–141. 
https://doi.org/10.5558/tfc68138-1  

Gunnarson, B. E., Linderholm, H. W. and Moberg, A. 2011. Improving a tree-ring reconstruction from west-central Scandinavia: 900 years of warm-season temperatures. Climate Dynamics36, 97–108. 
https://doi.org/10.1007/s00382-010-0783-5  

Helama, S. 2017. An overview of climate variability in Finland during the Common Era. Geophysica52(1), 3–20.

Helama, S. 2023. Distinguishing Type I and II errors in statistical tree-ring dating. Quaternary Geochronology78, 101470. 
https://doi.org/10.1016/j.quageo.2023.101470  

Helama, S. and Bartholin, T. S. 2019. Åland churches as archives of tree-ring records sensitive to fluctuating climate. Acta Palaeobotanica59(1), 131–143. 
https://doi.org/10.2478/acpa-2019-0002  

Helama, S., Lindholm, M., Meriläinen, J., Timonen, M. and Eronen, M. 2005. Multicentennial ring-width chronologies of Scots pine along north-south gradient across Finland. Tree-Ring Research61(1), 21–32. 
https://doi.org/10.3959/1536-1098-61.1.21

Helama, S., Vartiainen, M., Kolström, T., Peltola, H. and Meriläinen, J. 2008. X-ray microdensitometry applied to subfossil tree-rings: growth characteristics of ancient pines from the southern boreal forest zone in Finland at intra-annual to centennial time-scales. Vegetation History and Archaeobotany17, 675–686.
https://doi.org/10.1007/s00334-008-0147-9  

Helama, S., Timonen, M., Holopainen, J., Ogurtsov, M. G., Mielikäinen, K., Eronen, M. et al. 2009. Summer temperature variations in Lapland during the Medieval Warm Period and the Little Ice Age relative to natural instability of thermohaline circulation on multi-decadal and multi-centennial scales. Journal of Quaternary Science24(5), 450–456. 
https://doi.org/10.1002/jqs.1291  

Helama, S., Vartiainen, M., Kolström, T. and Meriläinen, J. 2010. Dendrochronological investigation of wood extractives. Wood Science and Technology44, 335–351. 
https://doi.org/10.1007/s00226-009-0293-y  

Helama, S., Bégin, Y., Vartiainen, M., Peltola, H., Kolström, T. and Meriläinen, J. 2012. Quantifications of dendrochronological information from contrasting microdensitometric measuring circumstances of experimental wood samples. Applied Radiation and Isotopes70(6), 1014–1023. 
https://doi.org/10.1016/j.apradiso.2012.03.025  

Helama, S., Holopainen, J., Timonen, M. and Mielikäinen, K. 2014a. An 854-year tree-ring chronology of Scots pine for south-west Finland. Studia Quaternaria31(1), 61–68. 
https://doi.org/10.2478/squa-2014-0006

Helama, S., Vartiainen, M., Holopainen, J., Mäkelä, H., Kolström, T. and Meriläinen, J. 2014b. A palaeotemperature record for the Finnish Lakeland based on microdensitometric variations in tree rings. Geochronometria41(3), 265–277. 
https://doi.org/10.2478/s13386-013-0163-0  

Helama, S., Luoto, T. P., Nevalainen, L. and Edvardsson, J. 2017a. Rereading a tree-ring database to illustrate depositional histories of subfossil trees. Palaeontologia Electronica20(1), 2A. 
https://doi.org/10.26879/696  

Helama, S., Melvin, T. M. and Briffa, K. R. 2017b. Regional curve standardization: state of the art. The Holocene27(1), 172–177. 
https://doi.org/10.1177/0959683616652709

Helama, S., Kuoppamaa, M. and Sutinen, R. 2020. Subaerially preserved remains of pine stemwood as indicators of late Holocene timberline fluctuations in Fennoscandia, with comparisons of tree-ring and 14C dated depositional histories of subfossil trees from dry and wet sites. Review of Palaeobotany and Palynology278, 104223. 
https://doi.org/10.1016/j.revpalbo.2020.104223  

Helama, S., Ratilainen, R., Ruohonen, J. and Taavitsainen, J.-P. 2024. Developing millennial tree-ring chronology for Turku (Åbo) and comparing palaeoclimatic signals inferred from archaeological, subfossil and living Pinus sylvestris data in Southwest Finland. Studia Quaternaria41(1), 1–11. 
https://doi.org/10.24425/sq.2024.149969   

Holmes, R. L. 1983. Computer-assisted quality control in tree-ring dating and measurement. Tree-Ring Bulletin43, 69–78.

Holopainen, J. 2004. The Early Climatological Records of Turku. Edita, Helsinki.

Holopainen, J. 2006. Reconstructions of past climates from documentary and natural sources in Finland since the 18th century. PhD thesis. University of Helsinki, Finland.

Holopainen, J., Helama, S. and Timonen, M. 2006. Plant phenological data and tree-rings as palaeoclimate indicators since AD 1750 in SW Finland. International Journal of Biometeorology51, 61–72. 
https://doi.org/10.1007/s00484-006-0037-8  

Holopainen, J., Helama, S., Kajander, J. M., Korhonen, J., Launiainen, J., Nevanlinna, H. et al. 2009. A multiproxy recon­struction of spring temperatures in south-west Finland since 1750. Climatic Change92, 213–233. 
https://doi.org/10.1007/s10584-008-9477-y  

Holopainen, J., Gregow, H., Helama, S., Kubin, E., Lummaa, V. and Terhivuo, J. 2012. History of Finnish plant phenological observations since the 1750s. Sorbifolia43, 51–66.

Holopainen, J., Helama, S. and Väre, H. 2018. Digitizing the plant phenological dataset (1750–1875) from collections of Professor Adolf Moberg: towards the development of historical climate records. Agricultural and Forest Meteorology253−254, 141–150. 
https://doi.org/10.1016/j.agrformet.2018.02.006  

Holopainen, J., Helama, S. and Väre, H. 2023a. Plant phenological dataset collated by the Finnish Society of Sciences and Letters. Ecology104(2), e3962. 
http://doi.org/10.1002/ecy.3962  

Holopainen, J., Helama, S. and Väre, H. 2023b. The written history of plant phenology: shaping primary sources for secondary publications. The Science of Nature – Naturwissenschaften110, 34. 
http://doi.org/10.1007/s00114-023-01861-w  

Irannezhad, M., Chen, D. and Kløve, B. 2015. Interannual variations and trends in surface air temperature in Finland in relation to atmospheric circulation patterns, 1961–2011. International Journal of Climatology35(10), 3078–3092. 
https://doi.org/10.1002/joc.4193  

Jones, P. D. and Lister, D. H. 2002. The daily temperature record for St. Petersburg (1743–1996). Climatic Change53, 253–267. 
https://doi.org/10.1023/A:1014918808741  

Karanitsch-Ackerl, S., Mayer, K., Gauster, T., Laaha, G., Holawe, F., Wimmer, R. and Grabner, M. 2019. A 400-year reconstruction of spring–summer precipitation and summer low flow from regional tree-ring chronologies in north-eastern Austria. Journal of Hydrology577, 123986. 
https://doi.org/10.1016/j.jhydrol.2019.123986  

Kington, J. A. 1974. An application of phenological data to historical climatology. Weather29(9), 320–328. 
https://doi.org/10.1002/j.1477-8696.1974.tb03318.x  

Laaksonen, K. 1976. The dependence of mean air temperatures upon latitude and altitude in Fennoscandia (1921–1950). Annales Academiae Scientiarum Fennicae. Series A, III. Geologica-Geographica119, 5–19.

Lappalainen, M. 2001. Suomen kansallispuistot: ulapalta paljakalle (Finland’s National Parks: Seas of Blue, Seas of Green). Metsähallitus, Vantaa.

Li, J. S., Hamann, A. and Beaubien, E. 2020. Outlier detection methods to improve the quality of citizen science data. Inter­national Journal of Biometeorology64, 1825–1833. 
https://doi.org/10.1007/s00484-020-01968-z  

Linderholm, H. W., Björklund, J. A., Seftigen, K., Gunnarson, B. E., Grudd, H., Jeong, J.-H. et al. 2010. Dendroclimatology in Fennoscandia – from past accomplishments to future potential. Climate of the Past6(1), 93–114. 
https://doi.org/10.5194/cp-6-93-2010  

Linderholm, H. W., Björklund, J., Seftigen, K., Gunnarson, B. E. and Fuentes, M. 2014. Fennoscandia revisited: a spatially improved tree-ring reconstruction of summer temperatures for the last 900 years. Climate Dynamics45, 933–947. 
http://dx.doi.org/10.1007/s00382-014-2328-9  

Macias-Fauria, M., Grinsted, A., Helama, S. and Holopainen, J. 2012. Persistence matters: estimation of the statistical significance of paleoclimatic reconstruction statistics from autocorrelated time series. Dendrochronologia30(2), 179–187. 
https://doi.org/10.10 16/j.dendro.2011.08.003  

Mann, M. E. 2002. The value of multiple proxies. Science297(5586), 1481–1482. 
https://doi.org/10.1126/science.1074318  

Mann, M. E., Zhang, Z., Rutherford, S., Bradley, R. S., Hughes, M. K., Shindell, D. et al. 2009. Global signatures and dynamical origins of the Little Ice Age and Medieval Climate Anomaly. Science326(5957), 1256–1260. 
https://doi.org/10.1126/science.1177303  

Matskovsky, V. V. and Helama, S. 2014. Testing long-term summer temperature reconstruction based on maximum density chronologies obtained by reanalysis of tree-ring data sets from north­ernmost Sweden and Finland. Climate of the Past10(4), 1473–1487. 
https://doi.org/10.5194/cp-10-1473-2014  

Matthews, J. A. and Briffa, K. R. 2005. The ‘Little Ice Age’: re-evaluation of an evolving concept. Geografiska Annaler: Series A, Physical Geography87(1), 17–36. 
https://doi.org/10.1111/j.0435-3676.2005.00242.x  

McCarroll, D., Loader, N. J., Jalkanen, R., Gagen, M. H., Grudd, H., Gunnarson, B. E. et al. 2013. A 1200-year multiproxy record of tree growth and summer temperature at the northern pine forest limit of Europe. The Holocene23(4), 471–484. 
https://doi.org/10.1177/0959683612467483  

McDermott, F., Mattey, D. P. and Hawkesworth, C. 2001. Centennial-scale Holocene climate variability revealed by a high-resolution speleothem δ18O record from SW Ireland. Science294(5545), 1328–1331. 
https://doi.org/10.1126/science.1063678  

Melvin T. M. and Briffa K. R. 2008. A “signal-free” approach to dendroclimatic standardisation. Dendrochronologia26(2), 71–86. 
https://doi.org/10.1016/j.dendro.2007.12.001  

Melvin, T. M., Grudd, H. and Briffa, K. R. 2013. Potential bias in ‘updating’ tree-ring chronologies using regional curve standardisation: re-processing 1500 years of Torneträsk density and ring-width data. The Holocene23(3), 364–373. 
https://doi.org/10.1177/0959683612460791  

Mikkonen, S., Laine, M., Mäkelä, H. M., Gregow, H., Tuomenvirta, H., Lahtinen M. and Laaksonen, A. 2015. Trends in the average temperature in Finland, 1847–2013. Stochastic Environmental Re­search and Risk Assessment29, 1521–1529. 
https://doi.org/10.10 07/s00477-014-0992-2  

Monserud, R. A. and Marshall, J. D. 2001. Time-series analysis of δ13C from tree rings. I. Time trends and autocorrelation. Tree Physiology21(15), 1087–1102. 
https://doi.org/10.1093/treephys/21.15.1087   

Osborn, T. J., Briffa, K. R. and Jones, P. D. 1997. Adjusting variance for sample-size in tree-ring chronologies and other regional-mean timeseries. Dendrochronologia15, 89–99.

Osborn, T. J., Jones, P. D., Lister, D. H., Morice, C. P., Simpson, I. R., Winn, J. P. et al. 2021. Land surface air temperature variations across the globe updated to 2019: the CRUTEM5 data set. Journal of Geophysical Research: Atmospheres126(2), e2019JD032352. 
https://doi.org/10.1029/2019JD032352  

Peltola, H., Kilpeläinen, A., Sauvala, K., Räisänen, T. and Ikonen, V.-P. 2007. Effects of early thinning regime and tree status on the radial growth and wood density of Scots pine. Silva Fennica41(3), 285. 
http://dx.doi.org/10.14214/sf.285  

Rohde, R. A. and Hausfather, Z. 2020. The Berkeley Earth land/ocean temperature record. Earth System Science Data12(4), 3469–3479. 
https://doi.org/10.5194/essd-12-3469-2020  

Sagarin, R. 2001. False estimates of the advance of spring. Nature414, 600. 
https://doi.org/10.1038/414600a  

Sagarin, R. 2009. Using nature’s clock to measure phenology. Frontiers in Ecology and the Environment7(6), 296. 
https://doi.org/10.1890/09.WB.020  

Sagarin, R. and Micheli, F. 2001. Climate change in nontraditional data sets. Science294(5543), 811. 
https://doi.org/10.1126/science.1064218  

Schweingruber, F. H., Fritts, H. C., Braker, O. U., Drew, L. G. and Schär, E. 1978. The X-ray technique as applied to dendroclimatology. Tree-Ring Bulletin38, 61–91.

Schweingruber, F. H., Bräker, O. U. and Schär, E. 1987. Temperature information from a European dendroclimatological sampling network. Dendrochronologia5, 9–33.

Schweingruber, F. H., Briffa, K. R. and Jones, P. D. 1991. Yearly maps of summer temperatures in western Europe from A.D. 1750 to 1975 and western North America from 1600 to 1982: results of a radiodensitometrical study on tree rings. Vegetatio92, 5–71. 
https://doi.org/10.1007/BF00047132  

Speer, J. H. 2010. Fundamentals of Tree-ring Research. The University of Arizona Press, Tucson.

Tarand, A. and Kuiv, P. 1994. The beginning of the rye harvest – a proxy indicator of summer climate in the Baltic Area. In Climatic Trends and Anomalies in Europe 1675–1715: High Resolution Spatio-temporal Reconstructions from Direct Meteorological Observations and Proxy Data – Methods and Results (Frenzel, B., Pfister, C. and Gläser, B., eds). Gustav Fischer, Stuttgart, 61–72.

Tarand, A. and Nordli, P. Ø. 2001. The Tallinn temperature series reconstructed back half a millennium by use of proxy data. Climatic Change48, 189–199.
https://doi.org/10.1023/A:1005673628980  

Tietäväinen, H., Tuomenvirta, H. and Venäläinen, A. 2010. Annual and seasonal mean temperatures in Finland during the last 160 years based on gridded temperature data. International Journal of Climatology30(15), 2247–2256. 
https://doi.org/10.1002/joc.2046  

Tuomenvirta, H. 2004. Reliable estimation of climatic variations in Finland. Dissertation. University of Helsinki, Finland.

Virkkala, R., Korhonen, K. T., Haapanen, R. and Aapala, K. 2000. Protected forests and mires in forest and mire vegetation zones in Finland based on the 8th National Forest Inventory. The Finnish Environment395, 1–49.

Wilson, R., Anchukaitis, K., Briffa, K. R., Büntgen, U., Cook, E., D’Arrigo, R. et al. 2016. Last millennium northern hemisphere summer temperatures from tree rings: part I: the long term context. Quaternary Science Reviews134, 1–18. 
https://doi.org/10.1016/j.quascirev.2015.12.005  

Zhang, P., Linderholm, H. W., Gunnarson, B. E., Björklund, J. and Chen, D. 2016. 1200 years of warm-season temperature variability in central Scandinavia inferred from tree-ring density. Climate of the Past12(6), 1297–1312. 
https://doi.org/10.5194/cp-12-1297-2016  

Zheng, J., Hua, Z., Liu, Y. and Hao, Z. 2015. Temperature changes derived from phenological and natural evidence in South Central China from 1850 to 2008. Climate of the Past11(11), 1553–1561. 
https://doi.org/10.5194/cp-11-1553-2015

Back to Issue