Mauri Timonen

• Researcher (retired) at Metla 1977-2014; Luke 2015-2021

The sun’s activity role in climate change has become a topic of debate. According to data from the IPCC, the global average temperature has shown an increasing trend since 1850, with an average increase of 0.06 °C/decade. Our analysis of summer temperature records from five weather stations in northern Fennoscandia (65°–70.4° N) revealed an increas...

The mechanism and even the existence of the Atlantic Multidecadal Oscillation (AMO) have remained under debate among climate researchers, and the same applies to general temperature oscillations of a 60–90‐year period. The objective of this study is to show that these temperature oscillations are real and not artifacts and that these oscillations h...

Tree-ring records constitute excellent high-resolution data and provide valuable information for climate science and paleoclimatology. Tree-ring reconstructions of past temperature variations agree to show evidence for annual-to-centennial anomalies in past climate and place the industrial-era warming in the context of the late Holocene climate pat...

Annual and sub-annual tree-ring ¹⁴C measurements allow the study of past natural phenomena such as rapid ¹⁴C increases and solar behavior. In addition, they provide precise calibration data sets that help in improving the dating accuracy of past natural and cultural events. However, for the data to be comparable, it is important that laboratories d...

There is growing evidence that the Sun is one of the main drivers of the Earth’s climate in the past. To investigate the possible Sun-climate connection during the Holocene, the super-long tree-ring chronology covering the period from 5634 BC and 2004 AD is analyzed. The chronology used, consists of more than 1200 series including ones from sedimen...

Holocene climate variability is punctuated by episodic climatic events such as the Little Ice Age (LIA) predating the industrial-era warming. Their dating and forcing mechanisms have however remained controversial. Even more crucially, it is uncertain whether earlier events represent climatic regimes similar to the LIA. Here we produce and analyse...

The long tradition of dendroclimatological studies in Fennoscandia is fostered by the exceptional longevity and temperature sensitivity of tree growth, as well as the existence of well-preserved subfossil wood in shallow lakes and extent peat bogs. Although some of the world's longest ring width and density-based climate reconstructions have been d...

Dating of wood is a major task in historical research, archaeology and paleoclimatology. Currently, the most important dating techniques are dendrochronology and radiocarbon dating. Our approach is based on molecular decay over time under specific preservation conditions. In the models presented here, construction wood, cold soft waterlogged wood a...

X‐ray microdensitometry on annually resolved tree‐ring samples has gained an exceptional position in last‐millennium paleoclimatology through the maximum latewood density (MXD) parameter, but also increasingly through other density parameters. For 50 years, X‐ray based measurement techniques have been the de facto standard. However, studies report...

The Sun's role in climate variability is now a subject of debates, especially in the context of understanding contribution of solar forcing to modern global warming. Besides, there are some evidences of the approaching new Grand Solar Minimum with Little Ice Age climatic conditions. This expectation is based on the occurrence of the extended solar...

Frost rings can provide direct evidence of anomalously cold summertime conditions on hemispheric scales. Here we report frost rings in subfossil pinewood from Finnish Lapland dated dendrochronologically to AD 536 and 1627 BC. These exact calendar dates have been vividly discussed in the literature in the respective contexts of a cold climate anomal...

Tree-ring stable isotope chronologies provide very high-resolution palaeoclimatic data, and the number of records is increasing rapidly worldwide. To extend the chronologies back in time, before the period covered by the old living trees, the use of subfossil wood samples is required. Typically, the longest continuous subfossil chronologies consist...

En este trabajo, se evalúa la respuesta del crecimiento de los árboles en la región polar (Península de Kola y la Laponia de Finlandia) a las erupciones volcánicas más potentes (VEI > 4) durante un periodo de 1445-2005. El análisis se basó en dos cronologías de anillos de árboles de elevada resolución: Loparskaya (1445-2005) y Finnish (~ 7500 años)...

The large volcanic eruptions of AD 536 and 540 led to climate cooling and contributed to hardships of Late Antiquity societies throughout Eurasia, and triggered a major environmental event in the historical Roman Empire. Our set of stable carbon isotope records from subfossil tree rings demonstrates a strong negative excursion in AD 536 and 541-544...

Key message Conifer radial growth reductions may be related to unusual snow conditions or a mismatch between frost hardiness level and minimum temperature, but not typically to low winter temperature extremes. Abstract The aim of this study was to examine if temperature conditions potentially causing frost damage have an effect on radial growth in...

Various studies report substantial increases in intrinsic water-use efficiency (W i ), estimated using carbon isotopes in tree rings, suggesting trees are gaining increasingly more carbon per unit water lost due to increases in atmospheric CO2. Usually, reconstructions do not, however, correct for the effect of intrinsic developmental changes in W...

Coniferous trees at the alpine and polar tree lines of the Northern Hemisphere represent the outermost limit of their ecological range. Under such conditions, even small temperature variations may cause growth responses, which therefore can be used as indicators for changing environmental conditions. In this study we analysed the radial growth of S...

Age-related alternation in the sensitivity of tree-ring width (TRW) to climate variability has been reported for different forest species and environments. The resulting growth-climate response patterns are, however, often inconsistent and similar assessments using maximum latewood density (MXD) are still missing. Here, we analyze climate signal ag...

Tree-ring chronologies are widely used to reconstruct high-to low-frequency variations in growing season temperatures over centuries to millennia. The relevance of these timeseries in large-scale climate reconstructions is often determined by the strength of their correlation against instrumental temperature data. However, this single criterion ign...

Climate model projections suggest widespread drying in the Mediterranean Basin and wetting in Fennoscandia in the coming decades largely as a consequence of greenhouse gas forcing of climate. To place these and other “Old World” climate projections into historical perspective based on more complete estimates of natural hydroclimatic variability, we...

Long stable isotope chronologies are increasingly constructed from tree rings. Averaging the mean chronologies necessitates that the contributing series contain no age-related trends. Therefore any set of dendroisotope data needs to be tested for age-dependency in isotope values before the chronology is compared with climate or other environmental...

This presentation deals with tree-ring based climatic and environmental research carried out in Finnish Forest research, especially in Metla (The Finnish Forest Research Institute).The document is not a detailed description of the whole Finnish Tree Ring Science, but just a set of excerpts telling about important advances and milestones in the almo...

Bit image graphics in printing was a "hot" method before GIS technology entered the Finnish Research Institute. The article, published in a commercial magazine in 1987, describes the innovative work done with one brand of dot matrix printers, called C.Itoh. Text in Finnish.

Tree-ring chronologies are commonly extended back in time by combining samples from living trees with relict material preserved in man-made structures or natural archives (e.g. lakes). Although spatially close, these natural archives and living-tree-sites often comprise different micro-climates. Inhomogeneous growth conditions among these habitats,...

This chapter introduces three algorithms. First, the scanning i-test is used for detecting significant changes in subperiod levels through tree-ring chronologies on multiple time-scale. Second, the scanning F- test is used for detecting significant changes in subperiod variances on corresponding scales. Third, an algorithm was developed for compari...

Tree-ring data is commonly used in forest science and dendrochronology. As the collected datasets represent restricted populations of theoretical infinite sample size, an interesting question deals with the sample selection that is carried out during the fieldwork and through the data analyses. This paper considers the latter issue, by statisticall...

Tree-ring chronologies of maximum latewood density are most suitable to reconstruct annually resolved summer temperature variations of the late Holocene. The two longest such chronologies have been developed in northern Europe stretching back to the 2nd century BC, and the 5th century AD. We show where similarities between the two chronologies exis...

A near-millennial tree-ring chronology (AD 1147–2000) is presented for south-west Finland and analyzed using dendroclimatic methods. This is a composite chronology comprising samples both from standing pine trees (Pinus sylvestris L.) and subfossil trunks as recovered from the lake sediments, with a total sample size of 189 tree-ring sam- ple serie...

Although not yet fully understood, reduced sensitivity of tree growth to temperature at high northern latitudes during the last ˜ 40 years is often linked to concurrent anthropogenic changes of atmospheric composition and global warming. The idea that a temporal localization of the problem could improve its understanding initiated a search for erra...

The results of comparison the dendrochronologies of Kola Peninsula, local temperatures records, ice cover of the Barents sea and sea surface temperature records are presented. Tree-ring series over the last 100 years showed a highly significant correlation with the ice cover (r=-0.57, p<0.05) and water temperature (r=0.49, p<0.05) of the Barents se...

Firm historical and proxy evidence (Arjava 2005, Larsen et al 2008) suggest that the most severe short term cold episode across the Northern hemisphere in the last two millennia took place following the climate anomaly in 535-536AD. It has been suggested that a volcanic eruption around 535AD caused a dust veil in Europe in 536AD, yielding crop fail...

Using the results of the dendrochronological analysis (68 Siberian tree-ring chronologies) it has been shown earlier that the increase in the tree-growth after the 1908 Tunguska event is observed at a large distance (more than 1500 km) from the explosion site (61N, 102E). A similar, but smaller, result has been obtained when analyzing changes in th...

Tree-ring archives of stable carbon isotopes (δ13C) have proven to be an excellent source of palaeoecological and palaecoclimatic information about photosythesis, the data thus yielding indirect estimations of temperature, moisture and cloudiness. Here we use a collection of modern and subfossil pinewood from northern Finnish Lapland for extracting...

Subfossil samples of Scots pine (Pinus sylvestris L.) were collected and tree-ring dated from the ground surface near the forest line from eight sites in North-West Finnish Lapland. The oldest tree-ring record spanned AD 471-638. Majority of samples originated from the period AD 1000-1800, whereas only a minor portion of the subfossils pre- or post...

It has been analyzed the external factor (solar activity, volcanic eruptions) influence on tree growth at the Kola Peninsula, northwestern Russia. Pinus sylvestris L. (Scots pine) tree-ring chronologies collected nearby the northern timberline (68.63N, 33.25E) include the oldest (1445-2005 AD) living pine tree found up to date in the Kola Peninsula...

Tree-ring chronologies are important indicators of pre-instrumental, natural climate variability. Some of the longest chronologies are from northern Fennoscandia, where ring width measurement series from living trees are combined with series from sub-fossil trees, preserved in shallow lakes, to form millennial-length records. We here assess the rec...

A total of 172 subfossil cross-sections of Scots pine (Pin us sylvestris L.) were collected from the ground surface near the forest line from eight sites in North West Finnish Lapland. The samples (snags and stumps) were dendrochronologically dated and analyzed for the temporal fluctuations, the altitudinal and latitudinal change. The oldest snag s...

Shifts of the alpine treelines towards higher elevations have been recorded, yet the role of spatial variability of snowpack and zonal pattern soil nutrient and water regimes is poorly understood. Norway spruce (Picea abies (L.) Karst) is best suited to fertile soils developed on glacial tills derived from mafic lithologies, hence we applied soil p...

Vpervye vyyavleny osobennosti vozdeistviya naibolee moshchnykh (VEI > 5) vulkanicheskikh izverzhenii na regional'nyi klimat Murmanskoi oblasti po dendrokhronologicheskim dannym Kol'skogo p-ova za period, prevyshayushchii 560 let. Dlya analiza ispol'zovalas' drevesno-kol'tsevaya khronologiya, okhvatyvayushchaya period s 1445 po 2005 gg. Dannaya khro...

For the first time we identify the peculiarities of the effect of the most powerful (VEI > 5) volcanic eruptions on the regional climate of the Murmansk region on the basis of Kola Peninsula dendrochronological data for a period of more than 560 years. The analysis was based on the tree�ring chronology covering the period from 1445 to 2005. This ch...

The drop in temperature following large volcanic eruptions has been identified as an important component of natural climate variability. However, due to the limited number of large eruptions that occurred during the period of instrumental observations, the precise amplitude of post-volcanic cooling is not well constrained. Here we present new evide...

We performedclimatic assessments of Scots pine growth variations in Finlandover recent decades by their tree-ring series andcomparing growth variations to those observedin meteorological records. Tree-ring indices showed non-significant growth trends over roughly the past four decades (1972–2007). The observedgrowth variability was explainedby conn...

Cryophenological records (i.e. observational series of freeze and breakup dates of ice) are of great importance when assessing the environmental variations in cold regions. Here we employed the extraordinarily long observational records of river ice breakup dates and air temperatures in northern Fennoscandia to examine their interrelations since 18...

It has been analyzed the external factor (solar activity, volcanic eruptions) influence on tree growth at the Kola Peninsula, northwestern Russia. Pinus sylvestris L. (Scots pine) tree-ring chronologies collected nearby the northern timberline (68.63N, 33.25E) include the oldest (1445-2005 AD) living pine tree found up to date in the Kola Peninsula...

Geochronological data of the conifer tree rings in a region sensitive to climatic effects of explosive eruptions were analysed for sudden growth reductions in association with extraordinarily cool reconstructed summer temperatures since 5500 B.C. Tree-ring data came from the stems of living trees and subfossil tree remains collected as increment co...

This study applies the scanning t-test to the tree-ring chronology of Scots pine (Pinus sylvestris L.) from Finnish Lapland for 7638 years for detecting significant changes of subseries means. Analyses are done on multi-centennial scales and the results are demonstrated both as figures and tables. Firstly, the tree-ring data were processed to smoot...

Luontaista ilmastohistoriaa koskevan katsauksemme pääsanoma on, ettei muutaman vuosikymmenen tai viimeisen vuosisadan ilmastokehitys anna riittävää kuvaa paikallisilmastomme tulevasta suunnasta tai muutoksen suuruudesta. Merellisen Atlantin ja mantereisen Siperian vaihettumavyöhykkeellä sijaitsevassa Suomessa on uhkarohkeaa tehdä metsänhoitoa koske...

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 1.6 W m -2 net anthropogenic forcing since 1750 (ref.A), but the trend varies considerably over time, space and with season. Us...

As a result of global changes, shifts of alpine tree lines towards higher elevations have been recorded, but the role of the spatial variability of the snowpack and zonal-pattern soil-nutrient regimes is poorly understood. Norway spruce (Picea abies (L.) Karst) is best suited to fertile soils, and hence we applied soil physical-chemical and snow me...

Palaeoclimatic evidence revealed synchronous temperature variations among Northern Hemisphere regions over the past millennium. The range of these variations (in degrees Celsius) is, however, largely unknown. We here present a 2000-year summer temperature reconstruction from northern Scandinavia and compare this timeseries with existing proxy recor...

Radial growth was examined in two Scots pine stands that were seeded during the 1920s and 1930s due to reforestation and afforestation activity on the timberline of northern Finnish Lapland. Tree-rings of seeded pines were calibrated against the instrumental records of local weather and large-scale atmospheric patterns and further compared to pines...

The paper deals with the analysis of the external factor (solar activity, volcanic eruptions) influence on tree growth at the Kola Peninsula, northwestern Russia. Pinus sylvestris L. (Scots pine) tree-ring chronologies collected nearby the northern timberline (68.63N, 33.25E) include the oldest (1445-2005 AD) living pine tree found up to date in th...

Based mainly on Dendrochronological research, this slide series tells about Holosene climate variations in Finnish Lapland.

Temperature reconstructions from Scandinavia (green) and the Northern Hemisphere that were 60-year low-pass filtered and standardized over their common period 831–1992. The two Northern Hemisphere versions either include (brown) or exclude (ochre) Scandinavian proxies. (EPS)

Characteristics of the (A) 25 MXD chronologies and (B) eight instrumental stations used. Grey site codes refer to less-sensitive chronologies, blue (green) refers to updated (pre-2000) site. The mean inter-series correlation (Rbar) and the Expressed Population Signal (EPS) were computed over 30-year windows lagged by 15 years [14]. Setting refers t...

Temporal coverage of the 1,179 MXD series, of which 387 were developed before 2000 AD with 792 added in 2006, covers the entire Scandinavian peninsula north of 65°N and has a mean segment length (MSL) of 161 years with an maximum latewood density (MXD) of 0.72 g/cm3 (inset denotes the relationship between tree age and MXD value). Site chronologies...

Correlation of the 25 MXD site chronologies after RCS detrending (circles) with monthly temperature means (CRUTEM3v) computed over the common 100 yr interval (1860–1977). Results are classified into 20 sensitive (green) and 5 less sensitive (grey; GLO, LOF, NAR, SKI, SKS) sites, with the horizontal lines referring to their average response. (EPS)

Spatial composite analysis at 500-hPa geopotential height of (A) the 20 coldest and (B) the 20 warmest reconstructed summers (JJA; 1659–1999), and (C) temporal comparison (1650–1975) of the reconstructed JJA temperatures (orange) with JJA estimates of the AO (light blue). Smoothed lines are 30-year low-pass filters and stars refer to the annual ext...

Summary information of the 5 Scandinavian tree-ring chronologies used for comparison with this study. ‘Season’ refers to the originally indicated response window, whereas ‘Response’ refers to correlations computed against Scandinavian JJA mean temperatures over the 1860–1970 common period. (EPS)

Supporting information. (DOC)

(A) Correlation (r>0.3) of the reconstruction against gridded JJA SAT (1901–2006) and four MXD-based summer temperature records: 1 = Polar Ural (0.06), 4 = Tyrol (−0.07), 3 = Lötschental (0.13) and 2 = Pyrenees (0.00). (B) Correlation of the reconstruction against gridded JJA SST (1901–2003). (EPS)

Spatial field correlation (r>0.3) between the new MXD-based reconstruction of northern Scandinavian summer temperature and gridded (5°×5°) SLP [HadSLP2r; 20] calculated for the June–August season and 1860–2006 period. (EPS)

(A) Temperature extremes of the target and proxy data computed over the common period 1860–2006. Italic letters refer to common extremes. (B) Reconstructed summer temperature extremes and associated error estimates computed over the full period 1483–2007. (EPS)

Tree rings dominate millennium-long temperature reconstructions and many records originate from Scandinavia, an area for which the relative roles of external forcing and internal variation on climatic changes are, however, not yet fully understood. Here we compile 1,179 series of maximum latewood density measurements from 25 conifer sites in northe...

We measured soil physical-chemical properties, snow and age chronology of Norway spruce along the elevation gradient (380-557 m a.s.l.) to address soil zonality hypothesis on mafic Lommoltunturi fell in Finnish Lapland. With regard to increasing elevation, we found an increase in soil NTOT, CTOT and Al, but a decrease in soil Ca, Mg, Ca:Al ratio as...

The paper deals with the analysis of the external factor (solar activity, volcanic eruptions) influence on tree growth at the Kola Peninsula, northwestern Russia. Pinus sylvestris L. (Scots pine) tree-ring chronologies collected nearby the northern timberline (68.63N, 33.25E) include the oldest (1445-2005 AD) living pine tree found up to date in t...

1. A role of solar activity and powerful volcanic eruptions as a trigger of changes in climate and environment is still a subject of scientific discussion. Here we present an analysis of some tree ring chronologies collected from living trees at Northern timberlines of Kola Peninsula. They are: a 676-year juniper (Juniperus Sibirica Burgst.) from K...

Scots pine (Pinus silvestris L.) is found to be suited to well-drained tills on felsic terrains in Finnish Lapland, but an excess soil water content 0y > 0.27 cm3cm-3 (e > 15) constitutes an edaphic constraint for pine. Norway spruce (Picea abies L. Karst.) is a dominant conifer on the glacial drift of the Greenstone Belt, but a low soil solute con...

Climatic gradients have been investigated in Finland from historical, cyclic, latitudinal, altitudinal and regional perspectives. Current temperature of July and, to a lesser degree, precipitation of May limit tree growth in Northern Finland. According to our studies, based on the Finnish 7644-yr supra-long tree-ring chronology of timberline Scot...

A comparison was performed of solar activity and terrestrial temperature records, both derived from tree rings (i.e., without dating uncertainties), with identification of detailed and highly quantified time-and timescale-dependent characteristics of solar forcing on climate through the current inter glacial in the context of oceanic variability. T...

We investigated the external factor (solar activity, volcanic eruptions) influence on tree growth at high latitudes. We analysed a 561-year tree-ring record of pine (Pinus sylvestris L.) and a 676-year juniper (Juniperus Sibirica Burgst.) tree-ring chronology collected nearby the northern timberline (67.77-68.63N; 33.25-36.52 E) at the Kola Peninsu...

We investigated the external factor (solar activity, volcanic eruptions) influence on tree growth at high latitudes. We analysed a 561-year tree-ring record of pine (Pinus sylvestris L.) and a 676-year juniper (Juniperus Sibirica Burgst.) tree-ring chronology collected nearby the northern timberline (67.77-68.63N; 33.25-36.52 E) at the Kola Peninsu...

WorldDendro 2010 took place June 13 – 18, 2010 in Rovaniemi, northern Finland. It is the largest regularly held conference on dendrochronology. About 350 researchers from over 40 countries participated the conference. The WorldDendro 2010 focused on climate change and sustainable development of the forests. Specific themes covered were, for example...

A common task in dendroclimatology is to identify climatic events from tree-rings. The many environmental factors affecting simultaneously to tree growth may, however, may make the task difficult. To minimize the problem, a good plan for the whole process of investigation is necessary. Cook’s conceptual aggregate growth model provides a framework m...

The paper deals with an analysis of the external factor (solar activity, volcanic eruptions) influence on tree growth at high latitudes. We analysed a 461-year record of Pinus sylvestris L. (Scots pine) collected nearby the northern timberline (68.63 N; 33.25 E) at the Kola Peninsula, northwestern Russia. As well known the climatic impacts of solar...

Reconstruction of post-glacial migration of Norway spruce (Picea abies (L.) Karst.) into northern Fennoscandia is based on pollen records and radiocarbon (14C) ages from organic deposits, no macrofossil evidence has been shown to indicate distribution of spruce beyond its present timberline-treeline ecotone. We applied total sampling to study Holoc...

Joint global wide climatic signals and trend changes were investigated from two tree-ring chronologies for the period of 7630 years. The compared series were the 7642-yr supra-long timberline chronology of Scots pine from Northern Finland and the tree-ring reconstruction for precipitation from Nevada, USA. A normalization algorithm of the Quantile...

New technologies will change radically our way of doing research, presenting our results and also storing our data. Traditional data management methods are still at a premium, but increasing object-oriented thinking is bringing new methods and tools for easier data and information management. Metla and the University of Lapland in their ongoing MID...

Tree-ring growth modelling was used to estimate short-term (1964-84) growth responses to the talc emissions at the Lahnaslampi mining area.

The growth of Scots pine (Pinus sylvestris L.) is highly sensitive to June-July temperatures at the Finnish pine timberline. Exceptional preservation of pine wood and its accumulation in non-oxygen muddy bottoms of ice-cold lakes have made it possible to build a 7641 years long continuous tree-ring chronology. The characteristics of this chronology...

MID (Multidimensional Information-Based Discipline) is a new scientific concept based on the old IT, on the multidisciplinary view and on the strong theoretical framework. MID may be in two roles: 1) The research themes are features of information and processing of information and 2) The science of methodology (MID) has theoretical tools, framework...

The twentieth-century migration of alpine treelines to higher elevations is attributed to the ongoing global change in Fennoscandia. The aim of this paper is to study the pattern and dynamics of the treeline advance to higher elevations on Lommoltunturi fell in Finnish Lapland by analysing a time series of aerial photographs with modern image inter...

Due to the present global change, shifts of the alpine treelines onto the higher elevations have been recorded, yet the role of environmental derivers for the advance of Norway spruce (Picea abies (L.) Karst.) is unclear. Spruce is best suited on fertile soils, we therefore propose that the advance of spruce is pronounced on mafic rock types.

We investigated growth of larches being planted at several cities of Northern Europe: St. Petersburg (59°57'N, 30°19'E), Rovaniemi (66°30'N, 25°44'E), Apatity (67°34'N, 33°23'E). The data were collected at several sites inside of each city, and at one site in the rural area outside of each cities (about 50 km apart). Totally we studied 10 series. T...

New tree ring-based analysis for climate variability at a regional scale is presented for high latitudes of Europe. Our absolutely dated temperature reconstruction seeks to characterise the summer temperatures since AD 750. The warmest and coolest reconstructed 250-year periods occurred at AD 931–1180 and AD 1601–1850, respectively. These periods s...

We reconstructed decadal to centennial variability of maximum sea ice extent in the Western Nordic Seas for A.D. 1200–1997 using a combination of a regional tree-ring chronology from the timberline area in Fennoscandia and δ18O from the Lomonosovfonna ice core in Svalbard. The reconstruction successfully explained 59% of the variance in sea ice ext...

Tree-rings tell of past climates. To do so, tree-ring chronologies comprising numerous climate-sensitive living-tree and subfossil time-series need to be "transferred" into palaeoclimate estimates using transfer functions. The purpose of this study is to compare different types of transfer functions, especially linear and nonlinear algorithms. Acco...

Dendrochronological crossdating was used to expand a pre-existing multi-millennial tree-ring chronology for Finnish Lapland. Twelve tree-ring series from sedimentary archives of five small lakes contributed to the oldest part of the chronology, extending the record to 5634 BC (previously 5520 BC). Today, the chronology is the longest conifer tree-r...