Testing long-term summer temperature reconstruction based on maximum density chronologies obtained by reanalysis of tree-ring data sets from northernmost Sweden and Finland

Here we analyse the maximum latewood density (MXD) chronologies of two published tree-ring data sets: one from Torneträsk region in northernmost Sweden (TORN; Melvin et al., 2013) and one from northern Fennoscandia (FENN; Esper et al., 2012). We paid particular attention to the MXD low-frequency variations to reconstruct summer (June–August, JJA) long-term temperature history. We used published methods of tree-ring standardization: regional curve standardization (RCS) combined with signal-free implementation. Comparisons with RCS chronologies produced using single and multiple (non-climatic) ageing curves (to be removed from the initial MXD series) were also carried out. We develop a novel method of standardization, the correction implementation of signal-free standardization, tailored for detection of pure low-frequency signal in tree-ring chronologies. In this method, the error in RCS chronology with signal-free implementation is analytically assessed and extracted to produce an advanced chronology. The importance of correction becomes obvious at lower frequencies as smoothed chronologies become progressively more correlative with correction implementation. Subsampling the FENN data to mimic the lower chronology sample size of TORN data shows that the chronologies bifurcate during the 7th, 9th, 17th and 20th centuries. We used the two MXD data sets to reconstruct summer temperature variations over the period 8 BC through AD 2010. Our new reconstruction shows multi-decadal to multi-centennial variability with changes in the amplitude of the summer temperature of 2.2 °C on average during the Common Era. Although the MXD data provide palaeoclimate research with a highly reliable summer temperature proxy, the bifurcating dendroclimatic signals identified in the two data sets imply that future research should aim at a more advanced understanding of MXD data on distinct issues: (1) influence of past population density variations on MXD production, (2) potential biases when calibrating differently produced MXD data to produce one proxy record, (3) influence of the biological age of MXD data when introducing young trees into the chronology over the most recent past and (4) possible role of waterlogging in MXD production when analysing tree-ring data of riparian trees

Suicide mortality in European countries and Post-Soviet states since 1955: Illustrating the longtime trends and patterns of recent changes

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Digitizing the plant phenological dataset (1750–1875) from collections of Professor Adolf Moberg : Towards the development of historical climate records

Abstract Long records of phenological observations are commonly used as data in global change and palaeoclimate research and to analyse plants' responses to climatic changes. Here we delve into the historical archives of plant phenological observations (1750–1875) compiled and published previously by Professor Adolf Moberg (Imperial Alexander University of Finland). The digitized dataset represents 44,487 observations of 450 different plant species for their 15 different phenological phases made in 193 sites across Finland, and results in 662 different phenological variables. The five most frequently observed variables are the blooming of rye, the sowing of barley, the blooming of bird cherry, the leaf outbreak of birch, and the sowing of oat. The spring and summer observations demonstrate positive relationships between the onset date and the site latitude, this relationship becoming negative for observations made in the autumn. This latitudinal effect is evident in the raw data as demonstrated by the temporal correlations between the unadjusted mean phenological records and the mean latitude of the sites. After the latitudinal effect is removed from the original data such correlations are much reduced and the new set of phenological records based on the adjusted dates can be computed. The resulting mean phenological records correlate negatively and statistically significantly with the mean temperatures from April through July. Linear trends indicate (i) summer onsets having become delayed by more than one week over the full period and (ii) shortening of the growing seasons since 1846. The dataset is made available in an open repository.Peer reviewe

Plant phenological dataset collated by the Finnish Society of Sciences and Letters

Long records of phenological observations constitute data for ecological, climate and global change studies. Here we provide an extraordinary dataset of plant phenological observations made in Boreal Europe between 1750 and 1965 from locations situated across historical and modern Finland, mostly between 70° and 60°N and 30° and 20°E. This dataset has been initially generated by the efforts of several generations of volunteers representing naturalists whose field observations and notes have initially made the continuous collection of the data possible. Meanwhile, the data was collated by the Finnish Economic Society and the Finnish Society of Sciences and Letters and published irregularly in the form of several monographs and periodicals by contemporary academic enthusiasts. Each phenological observation contains 11 features including: site name, site latitude, site longitude, scientific species name, phenological stage and (if any) its substage, year, date (month and day) and the day since summer solstice, the original literature source, and outlier estimate. Species names given originally either in Latin, Finnish, German and/or Swedish were transformed into scientific species names. Moreover, outdated taxonomic names were updated as appropriate. Phenological stages given originally either in German, Finnish and/or Swedish were transformed into English and standardized by excluding synonyms. Site names were adopted at county level, with corresponding latitude and longitude generated herein. The digitized dataset represents 265478 observations of 985 taxa (assigned to variety/subspecies/species/hybrid/genus) for their 16 different phenological stages made in 371 locations across the region. We provide this dataset to support comparative studies and modeling projects seeking to improve understanding of terrestrial ecosystem dynamics and their responses to a changing environment from local to global scale. Use of this dataset for academic or educational purposes is encouraged as long as the data source is properly cited with attribution given to this presentation of the data. Users are free to use and analyze the data; additionally, we would like to hear from other researchers who use these data sets in teaching or for their own research. This article is protected by copyright. All rights reserved.Peer reviewe

ilmastonmuutoksen aika

Ilmastonmuutoksesta on viime vuosien kuluessa kirjoitettu tämän lehden sivuilla useaan otteeseen ja eri näkökulmista. Allekirjoittaneet ovat myös osallistuneet keskusteluun esittämällä ilmastonmuutoksen käsitteen merkityksen muutosta pohtivan artikkelin. Taannoisessa kirjoituksessa käsiteltiin mm. havaintovälineiden ja kellon tuloa osaksi meteorologista havaintojentekoa ja miten ne muuttivat tapaa hahmottaa säässä ja ilmastossa tapahtuvia vaihteluita aikaisempaan verrattuna. Tämä aihepiiri johti pohtimaan laajemmin ajan luonnetta ilmastonmuutoksen yhteydessä. Yllättäen teema osoittautui vähän käsitellyksi ilmastonmuutostutkimuksen piirissä