| 1. |
- Björck, Svante, et al.
(författare)
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Historiska varningssignaler
- 2010
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Ingår i: Sverige i nytt klimat - våtvarm utmaning. - Stockholm : Forskningsrådet Formas. - 9789154060405 ; , s. 71-86
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Bokkapitel (populärvet., debatt m.m.)abstract
- De senaste tjugo årens klimat i Stockholmstrakten är troligen det varmaste under den senaste femhudraårsperioden. Människans utsläpp av växthusgaser har bidragit, men även naturliga faktorer. Av historien kan vi lära oss att klimatet plötsligt kan slå om till att fungera på ett helt nytt sätt - en förändring som kan bli en obehaglig överraskning för människans samhälle och dess känsliga infrastruktur. Därför bör vi vara lyhörda för varningssignaler från jordens klimatsystem. Varningssignaler är den geologiska historien full av, skriver Svante Björck och Anders Moberg.
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| 2. |
- Brázdil, Rudolf, et al.
(författare)
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European climate of the past 500 years: new challenges for historical climatology
- 2010
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Ingår i: Climatic Change. - Netherlands : Springer. - 0165-0009 .- 1573-1480. ; 101:1-2, s. 7-40
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Tidskriftsartikel (refereegranskat)abstract
- Temperature reconstructions from Europe for the past 500 years basedon documentary and instrumental data are analysed. First, the basic documentarydata sources, including information about climate and weather-related extremes, aredescribed. Then, the standard palaeoclimatological reconstruction method adoptedhere is discussed with a particular application to temperature reconstructions fromdocumentary-based proxy data. The focus is on two new reconstructions; January–April mean temperatures for Stockholm (1502–2008), based on a combination ofdata for the sailing season in the Stockholm harbour and instrumental temperaturemeasurements, and monthly Central European temperature (CEuT) series (1500–2007) based on documentary-derived temperature indices of the Czech Republic,Germany and Switzerland combined with instrumental records from the samecountries. The two series, both of which are individually discussed in greater detail in subsequent papers in this special edition, are here compared and analysed usingrunning correlations and wavelet analysis. While the Stockholm series shows apronounced low-frequency component, the CEuT series indicates much weaker lowfrequencyvariations. Both series are analysed with respect to three different longperiodreconstructions of the North Atlantic Oscillation (NAO) and are comparedwith other European temperature reconstructions based on tree-rings, wine-harvestdata and various climate multiproxies. Correlation coefficients between individualproxy-based series show weaker correlations compared to the instrumental data.There are also indications of temporally varying temperature cross-correlationsbetween different areas of Europe. The two temperature reconstructions have alsobeen compared to geographically corresponding temperature output from simulationswith global and regional climate models for the past few centuries. The findingsare twofold: on the one hand, the analysis reinforces the hypothesis that the indexdatabased CEuT reconstruction may not appropriately reflect the centennial scalevariations. On the other hand, it is possible that climate models may underestimateregional decadal variability. By way of a conclusion, the results are discussed froma broader point of view and attention is drawn to some new challenges for futureinvestigations in the historical climatology in Europe.
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| 3. |
- Brugnara, Y., et al.
(författare)
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A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 1816
- 2015
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 11:8, s. 1027-1047
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Tidskriftsartikel (refereegranskat)abstract
- The eruption of Mount Tambora (Indonesia) in April 1815 is the largest documented volcanic eruption in history. It is associated with a large global cooling during the following year, felt particularly in parts of Europe and North America, where the year 1816 became known as the "year without a summer". This paper describes an effort made to collect surface meteorological observations from the early instrumental period, with a focus on the years of and immediately following the eruption (1815–1817). Although the collection aimed in particular at pressure observations, correspondent temperature observations were also recovered. Some of the series had already been described in the literature, but a large part of the data, recently digitised from original weather diaries and contemporary magazines and newspapers, is presented here for the first time. The collection puts together more than 50 sub-daily series from land observatories in Europe and North America and from ships in the tropics. The pressure observations have been corrected for temperature and gravity and reduced to mean sea level. Moreover, an additional statistical correction was applied to take into account common error sources in mercury barometers. To assess the reliability of the corrected data set, the variance in the pressure observations is compared with modern climatologies, and single observations are used for synoptic analyses of three case studies in Europe. All raw observations will be made available to the scientific community in the International Surface Pressure Databank.
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| 4. |
- Chen, Deliang, 1961, et al.
(författare)
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European Trend Atlas of Extreme Temperature and Precipitation Records
- 2015
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- This Atlas presents records of climatic variability and change in Europe starting before 1901 and focuses especially on trends of extreme temperatures and precipitation. The authors have used software developed within EMULATE (European and North Atlantic daily to MULtidecadal climATE variability) to obtain the extremes indices and temporal trends. The trend atlas provides an easy way to identify spatial patterns for a given time period, region, season, and index. The Atlas clearly shows that climate in Europe has changed over the last 100 to 150 years, such that the occurrence and intensity of warm temperature extremes have increased. Precipitation extremes have also changed, but with a less clear pattern compared to the temperature extremes.
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| 5. |
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| 6. |
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| 7. |
- Dobrovolný, Petr, et al.
(författare)
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Monthly, seasonal and annual temperature reconstructions for Central Europe derived from documentary evidence and instrumental records since AD 1500
- 2010
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Ingår i: Climatic Change. - Netherlands : Springer. - 0165-0009 .- 1573-1480. ; 101:1-2, s. 69-107
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Tidskriftsartikel (refereegranskat)abstract
- Monthly temperature series for Central Europe back to AD 1500 aredeveloped from documentary index series from Germany, Switzerland and theCzech Republic (1500–1854) and 11 instrumental temperature records (1760–2007).Documentary evidence from the Low Countries, the Carpathian Basin and Polandare used for cross-checking for earlier centuries. The instrumental station recordsare corrected for inhomogeneities, including insufficient radiation protection ofearly thermometers and the urban heat island effect. For overlapping period (1760–1854), the documentary data series correlate with instrumental temperatures, moststrongly in winter (86% explained variance in January) and least in autumn (56%in September). For annual average temperatures, 81% of the variance is explained.Verification statistics indicate high reconstruction skill for most months and seasons.The last 20 years (since 1988) stand out as very likely the warmest 20-year period,accounting for the calibration uncertainty and decreases in proxy data quality beforethe calibration period. The new reconstruction displays a previously unobserved long-term decrease in DJF, MAM and JJA temperature variability over last fivecenturies. Compiled monthly, seasonal and annual series can be used to improve therobustness of gridded large-scale European temperature reconstructions and possibleimpact studies. Further improvement of the reconstruction would be achieved ifdocumentary data from other European countries are further developed.
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| 8. |
- Drobyshev, Igor, et al.
(författare)
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Atlantic SSTs control regime shifts in forest fire activity of Northern Scandinavia
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the drivers of the boreal forest fire activity is challenging due to the complexity of the interactions driving fire regimes. We analyzed drivers of forest fire activity in Northern Scandinavia (above 60 N) by combining modern and proxy data over the Holocene. The results suggest that the cold climate in northern Scandinavia was generally characterized by dry conditions favourable to periods of regionally increased fire activity. We propose that the cold conditions over the northern North Atlantic, associated with low SSTs, expansion of sea ice cover, and the southward shift in the position of the subpolar gyre, redirect southward the precipitation over Scandinavia, associated with the westerlies. This dynamics strengthens high pressure systems over Scandinavia and results in increased regional fire activity. Our study reveals a previously undocumented teleconnection between large scale climate and ocean dynamics over the North Atlantic and regional boreal forest fire activity in Northern Scandinavia. Consistency of the pattern observed annually through millennium scales suggests that a strong link between Atlantic SST and fire activity on multiple temporal scales over the entire Holocene is relevant for understanding future fire activity across the European boreal zone.
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| 9. |
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| 10. |
- Jansson, Ulf, 1966-, et al.
(författare)
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Svenska forskares syn på hantering av rumsliga data - enkätundersökning 2021
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A survey, aimed at Swedish researchers in the field of spatial data, was conducted in 2021. 113 individuals responded to the questionnaire, which gives us insight into how researchers in the field view; sharing of data, how they work with data, which metadata they think are central and what support they ask for in order to be able to handle spatial data.According to the survey a majority of the researchers share and use data shared by others in their research. Central metadata that is emphasized are coordinate systems, projections, time of the information, data capture, data content and author. The question of how to make data available is very varied among the respondents. The questionnaire responses contain a wide range of individual solutions to make the information available. A majority of researchers believe that the work with data management and accessibility has increased over the past 5 years. As an obstacle to working more with this is time, but there are also other obstacles. The researchers are seeking additional support that can be summarized as: support, technical guidance, storage, information, time and money.
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| 11. |
- Lashgari, Katarina, 1974-, et al.
(författare)
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Evaluation of simulated responses to climate forcings : a flexible statistical framework using confirmatory factor analysis and structural equation modelling – Part 1: Theory
- 2022
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Ingår i: Advances in Statistical Climatology, Meteorology and Oceanography. - : Copernicus GmbH. - 2364-3587. ; 8:2, s. 225-248
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Tidskriftsartikel (refereegranskat)abstract
- Evaluation of climate model simulations is a crucial task in climate research. Here, a new statistical framework is proposed for evaluation of simulated temperature responses to climate forcings against temperature reconstructions derived from climate proxy data for the last millennium. The framework includes two types of statistical models, each of which is based on the concept of latent (unobservable) variables: confirmatory factor analysis (CFA) models and structural equation modelling (SEM) models. Each statistical model presented is developed for use with data from a single region, which can be of any size. The ideas behind the framework arose partly from a statistical model used in many detection and attribution (D&A) studies. Focusing on climatological characteristics of five specific forcings of natural and anthropogenic origin, the present work theoretically motivates an extension of the statistical model used in D&A studies to CFA and SEM models, which allow, for example, for non-climatic noise in observational data without assuming the additivity of the forcing effects. The application of the ideas of CFA is exemplified in a small numerical study, whose aim was to check the assumptions typically placed on ensembles of climate model simulations when constructing mean sequences. The result of this study indicated that some ensembles for some regions may not satisfy the assumptions in question.
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| 12. |
- Lashgari, Katarina, 1974-, et al.
(författare)
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Evaluation of simulated responses to climate forcings : a flexible statistical framework using confirmatory factor analysis and structural equation modelling – Part 2: Numerical experiment
- 2022
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Ingår i: Advances in Statistical Climatology, Meteorology and Oceanography. - : Copernicus GmbH. - 2364-3587. ; 8:2, s. 249-271
-
Tidskriftsartikel (refereegranskat)abstract
- The performance of a new statistical framework, developed for the evaluation of simulated temperature responses to climate forcings against temperature reconstructions derived from climate proxy data for the last millennium, is evaluated in a so-called pseudo-proxy experiment, where the true unobservable temperature is replaced with output data from a selected simulation with a climate model. Being an extension of the statistical model used in many detection and attribution (D&A) studies, the framework under study involves two main types of statistical models, each of which is based on the concept of latent (unobservable) variables: confirmatory factor analysis (CFA) models and structural equation modelling (SEM) models. Within the present pseudo-proxy experiment, each statistical model was fitted to seven continental-scale regional data sets. In addition, their performance for each defined region was compared to the performance of the corresponding statistical model used in D&A studies. The results of this experiment indicated that the SEM specification is the most appropriate one for describing the underlying latent structure of the simulated temperature data in question. The conclusions of the experiment have been confirmed in a cross-validation study, presuming the availability of several simulation data sets within each studied region. Since the experiment is performed only for zero noise level in the pseudo-proxy data, all statistical models, chosen as final regional models, await further investigation to thoroughly test their performance for realistic levels of added noise, similar to what is found in real proxy data for past temperature variations.
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| 13. |
- Leijonhufvud, Lotta, et al.
(författare)
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Five centuries of Stockholm winter/spring temperatures reconstructed from documentary evidenceand instrumental observations
- 2010
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Ingår i: Climatic Change. - Netherlands : Springer. - 0165-0009 .- 1573-1480. ; 101:1-2, s. 109-141
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Tidskriftsartikel (refereegranskat)abstract
- Historical documentary sources, reflecting different port activities in Stockholm, are utilised to derive a 500-year winter/spring temperature reconstruction for the region. These documentary sources reflect sea ice conditions in the harbour inlet and those series that overlap with the instrumental data correlate well with winter/spring temperatures. By refining dendroclimatological methods,the time-series were composited to a mean series and calibrated (1756–1841;r2 = 66%) against Stockholm January–April temperatures. Strong verification was confirmed (1842–1892; r2 = 60%; RE/CE = 0.55). By including the instrumental data, the quantified (QUAN) reconstruction indicates that recent two decades have been the warmest period for the last 500 years. Coldest conditions occurred during the 16th/17th and early 19th centuries. An independent qualitative (QUAL)historical index was also derived for the Stockholm region. Comparison between QUAN and QUAL shows good coherence at inter-annual time-scales, but QUAL distinctly appears to lack low frequency information. Comparison is also made to other winter temperature based annually resolved records for the Baltic region.Between proxy coherence is generally good although it decreases going back in time with the 1500–1550 period being the weakest period—possibly reflecting data quality issues in the different reconstructions.
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| 14. |
- Loader, Neil J., et al.
(författare)
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Spring temperature variability in northern Fennoscandia AD 1693–2011
- 2011
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Ingår i: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 26:6, s. 566-570
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Tidskriftsartikel (refereegranskat)abstract
- A reconstruction of spring (April–May) temperature for northern Fennoscandia developed from the Tornionjoki (Tornio river) long cryophenological record of ice break-up dates, back to AD 1693, is presented. The record is strongly climatically sensitive and explains 67% of the variance in the instrumental data over the last 150 years. The record exhibits a stepped decrease in the duration of the river's ice cover by 14 days, equivalent to an increase in April–May mean temperature of approximately 2.5°C over the last three centuries. The relationship between the date of ice break-up, and accumulated daily mean temperatures (>0°C) is investigated. Uncertainty in the observation of ice break-up is also considered in addition to the potential of this time series for regional climate model validation.
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| 15. |
- Luterbacher, Jürg, et al.
(författare)
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Circulation dynamics and its influence on European and Mediterranean January–April climate over the past half millennium : results and insights from instrumental data,documentary evidence and coupled climate models
- 2010
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Ingår i: Climatic Change. - Netherlands : Springer. - 0165-0009 .- 1573-1480. ; 101:1-2, s. 201-234
-
Tidskriftsartikel (refereegranskat)abstract
- We use long instrumental temperature series together with available field reconstructions of sea-level pressure (SLP) and three-dimensional climate modelsimulations to analyze relations between temperature anomalies and atmospheric circulation patterns over much of Europe and the Mediterranean for the late winter/early spring (January–April, JFMA) season. A Canonical Correlation Analysis(CCA) investigates interannual to interdecadal covariability between a new gridded SLP field reconstruction and seven long instrumental temperature series covering the past 250 years. We then present and discuss prominent atmospheric circulation patterns related to anomalous warm and cold JFMA conditions within different European areas spanning the period 1760–2007. Next, using a data assimilation technique, we link gridded SLP data with a climate model (EC-Bilt-Clio) for a better dynamical understanding of the relationship between large scale circulationand European climate. We thus present an alternative approach to reconstruct climate for the pre-instrumental period based on the assimilated model simulations.Furthermore, we present an independent method to extend the dynamic circulation analysis for anomalously cold European JFMA conditions back to the sixteenth century. To this end, we use documentary records that are spatially representative for the long instrumental records and derive, through modern analogs, large-scale SLP, surface temperature and precipitation fields. The skill of the analog method is tested in the virtual world of two three-dimensional climate simulations (ECHOGand HadCM3). This endeavor offers new possibilities to both constrain climate model into a reconstruction mode (through the assimilation approach) and to better assess documentary data in a quantitative way.
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| 16. |
- Moberg, Anders, 1961-
(författare)
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Comments on ''Reconstruction of the Extratropical NH Mean Temperature over the Last Millennium with a Method That Preserves Low-Frequency Variability''
- 2012
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Ingår i: Journal of Climate. - 0894-8755 .- 1520-0442. ; 25:22, s. 7991-7997
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Christiansen and Ljungqvist have presented an extratropical NH temperature reconstruction using a method (LOC) that they claim ''preserves'' low-frequency variability, at the expense of exaggerated high-frequency variability. Using theoretical arguments and a pseudoproxy experiment, it is demonstrated here that the LOC method is not guaranteed to preserve variability at any frequency. Rather, LOC reconstructions will have more variance than true large-scale temperature averages at all frequencies. This variance inflation, however, can be negligible at those frequencies where the noise variance in individual proxies is small enough to be effectively cancelled when computing an average over the available proxies. Because the proxy noise variance at low frequencies cannot be directly estimated, and thus has to be regarded as unknown, it is safer to regard a reconstruction with the LOC method as providing an estimate of the upper bound of the large-scale low-frequency temperature variability rather than one with a correct estimate of this variance.
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| 17. |
- Moberg, Anders, 1961-
(författare)
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Comparisons of simulated and observed Northern Hemisphere temperature variations during the past millennium - selected lessons learned and problems encountered
- 2013
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Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 65, s. 19921-
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Tidskriftsartikel (refereegranskat)abstract
- Comparison of simulated and reconstructed past climate variability within the last millennium provides an opportunity to aid the understanding and interpretation of palaeoclimate proxy data and to test hypotheses regarding external forcings, feedback mechanisms and internal climate variability under conditions close to those of the present day. Most such comparisons have been made at the Northern Hemispheric scale, of which a selection of recent results is briefly discussed here. Uncertainties in climate and forcing reconstructions, along with the simplified representations of the true climate system represented by climate models, limit our possibility to draw certain conclusions regarding the nature of forced and unforced climate variability. Additionally, hemispheric-scale temperature variations have been comparatively small, wherefore the last millennium is apparently not a particularly useful period for estimating climate sensitivity. Nevertheless, several investigators have concluded that Northern Hemispheric-scale decadal-mean temperatures in the last millennium show a significant influence from natural external forcing, where volcanic forcing is significantly detectable while solar forcing is less robustly detected. The amplitude of centennial-scale variations in solar forcing has been a subject for much debate, but current understanding of solar physics implies that these variations have been small – similar in magnitude to those within recent sunspot cycles – and thus they have not been a main driver of climate in the last millennium. This interpretation is supported by various comparisons between forced climate model simulations and temperature proxy data. Anthropogenic greenhouse gas and aerosol forcing has been detected by the end of Northern Hemispheric temperature reconstructions.
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| 18. |
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| 19. |
- Moberg, Anders, 1961-, et al.
(författare)
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Prediction intervals for climate reconstructions with autocorrelated noise : An analysis of ordinary least squares and measurement error methods
- 2011
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 308:3-4, s. 313-329
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Tidskriftsartikel (refereegranskat)abstract
- The estimation of past climate variations is a statistical prediction problem, where climate proxy data are calibrated against instrumental observations. Although noise is always present in both instrumental and proxy data, motivating the use of so-called errors-in-variables or measurement error methods, such methods have not yet been widely accepted by palaeoclimatologists. We define a univariate measurement error model that allows for white noise in instrumental and red noise in proxy data, and derive new formulae to construct prediction intervals for past climate values. The new method can be applied to either unsmoothed data or to data smoothed after calibration. Using synthetic simulated data, we demonstrate that the new formulae perform well for noise levels and calibration period lengths typical of many palaeoclimate series, in particular tree-rings and other annually resolved data. With an example, using a recently published 500-year long temperature reconstruction, we demonstrate that conclusions about the statistical significance of the difference between the present and past climates may be incorrect if the noise is not adequately modeled.
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| 20. |
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| 21. |
- Trachsel, Mathias, et al.
(författare)
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Multi-archive summer temperature reconstruction for the European Alps, AD 1053-1996
- 2012
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Ingår i: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 46, s. 66-79
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Tidskriftsartikel (refereegranskat)abstract
- We present a multi-archive, multi-proxy summer temperature reconstruction for the European Alpscovering the period AD 1053-1996 using tree-ring and lake sediment data. The new reconstruction isbased on nine different calibration approaches and errors were estimated conservatively. Summertemperatures of the last millennium are characterised by two warm (AD 1053-1171 and 1823-1996) andtwo cold phases (AD 1172-1379 and 1573-1822). Highest pre-industrial summer temperatures of the12th century were 0.3 degC warmer than the 20th century mean but 0.35 degC colder than proxy derivedtemperatures at the end of the 20th century. The lowest temperatures at the end of the 16th centurywere ~1 degC lower than the 20th century mean.
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| 22. |
- Wagner-Cremer, Friederike, et al.
(författare)
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Tracing growing degree-day changes in the cuticle morphology of Betula nana leaves : a new micro-phenological palaeo-proxy
- 2010
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Ingår i: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 25:6, s. 1008-1017
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Tidskriftsartikel (refereegranskat)abstract
- Changing growing-season properties in the northern latitudes are among the most obvious consequences of ongoing global change. Available techniques including satellite monitoring and phenological observations enable the detection of changes over the last few decades to centuries, but the full range of natural variability is still difficult to capture. Here we introduce a new approach to reconstruct growing season properties, by studying imprints of prolonged growing season on epidermal cell growth in Betula nana. A high correlation between cell expansion determined in annually collected B. nana leaves and subfossil leaf fragments collected from recent peat sections in northern Scandinavia, and climatic indices such as budburst date, growing-season degree-days and May–September mean temperatures, enable the establishment of a new micro-phenological proxy for growing season characteristics. The applicability of the epidermal cell undulation index (UI) is tested by comparison with historical instrumental records of growing-season degree-days for the last 200 a. The results demonstrate the potential of the new leaf-morphology-based technique to reconstruct and quantify past changes in growing degree-days beyond instrumental data series. Applied to abundant B. nana leaf remains from peat and lake sediments, the UI may enable a reconstruction of growing degree-days throughout the Holocene and other parts of the late Quaternary.
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| 23. |
- Zamora, Juan Carlos, et al.
(författare)
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Considerations and consequences of allowing DNA sequence data as types of fungal taxa
- 2018
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Ingår i: IMA Fungus. - : INT MYCOLOGICAL ASSOC. - 2210-6340 .- 2210-6359. ; 9:1, s. 167-185
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Tidskriftsartikel (refereegranskat)abstract
- Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.
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| 24. |
- Zorita, Eduardo, et al.
(författare)
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European temperature records of the past five centuries based on documentary/instrumental information compared to climate simulations
- 2010
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Ingår i: Climatic Change. - Netherlands : Springer. - 0165-0009 .- 1573-1480. ; 101:1-2, s. 143-168
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Tidskriftsartikel (refereegranskat)abstract
- Two European temperature reconstructions for the past half-millennium,January-to-April air temperature for Stockholm (Sweden) and seasonal temperaturefor a Central European region, both derived from the analysis of documentarysources and long instrumental records, are compared with the output of climate simulations with the model ECHO-G. The analysis is complemented by comparisonswith the long (early)-instrumental record of Central England Temperature(CET). Both approaches to study past climates (simulations and reconstructions)are burdened with uncertainties. The main objective of this comparative analysisis to identify robust features and weaknesses in each method which may help toimprove models and reconstruction methods. The results indicate a general agreementbetween simulations obtained with temporally changing external forcings andthe reconstructed Stockholm and CET records for the multi-centennial temperaturetrend over the recent centuries, which is not reproduced in a control simulation.This trend is likely due to the long-term change in external forcing. Additionally,the Stockholm reconstruction and the CET record also show a clear multi-decadalwarm episode peaking around AD 1730, which is absent in the simulations. Neitherthe reconstruction uncertainties nor the model internal climate variability caneasily explain this difference. Regarding the interannual variability, the Stockholmseries displays, in some periods, higher amplitudes than the simulations but thesedifferences are within the statistical uncertainty and further decrease if output froma regional model driven by the global model is used. The long-term trend of theCentral European temperature series agrees less well with the simulations. Thereconstructed temperature displays, for all seasons, a smaller difference between thepresent climate and past centuries than is seen in the simulations. Possible reasons forthese differences may be related to a limitation of the traditional ‘indexing’ techniquefor converting documentary evidence to temperature values to capture long-termclimate changes, because the documents often reflect temperatures relative to thecontemporary authors’ own perception of what constituted ‘normal’ conditions. Bycontrast, the amplitude of the simulated and reconstructed inter-annual variabilityagrees rather well.
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