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  • 1.
    Björck, Svante
    et al.
    Inst. för geo- och ekosystemvetenskaper Enheten för geologi, Lunds universitet.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Historiska varningssignaler2010Inngår i: Sverige i nytt klimat - våtvarm utmaning / [ed] Birgitta Johansson, Stockholm: Forskningsrådet Formas , 2010, s. 71-86Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    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.

  • 2. Bothe, Oliver
    et al.
    Hind, Alistair
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Zorita, Eduardo
    Continental-scale temperature variability in PMIP3 simulations and PAGES 2k regional temperature reconstructions over the past millennium2015Inngår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 11, nr 12, s. 1673-1699Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Estimated external radiative forcings, model results, and proxy-based climate reconstructions have been used over the past several decades to improve our understanding of the mechanisms underlying observed climate variability and change over the past millennium. Here, the recent set of temperature reconstructions at the continental-scale generated by the PAGES 2k project and a collection of state-of-the-art model simulations driven by realistic external forcings are jointly analysed. The first aim is to estimate the consistency between model results and reconstructions for each continental-scale region over the time and frequency domains. Secondly, the links between regions are investigated to determine whether reconstructed global-scale covariability patterns are similar to those identified in model simulations. The third aim is to assess the role of external forcings in the observed temperature variations. From a large set of analyses, we conclude that models are in relatively good agreement with temperature reconstructions for Northern Hemisphere regions, particularly in the Arctic. This is likely due to the relatively large amplitude of the externally forced response across northern and high-latitude regions, which results in a clearly detectable signature in both reconstructions and simulations. Conversely, models disagree strongly with the reconstructions in the Southern Hemisphere. Furthermore, the simulations are more regionally coherent than the reconstructions, perhaps due to an underestimation of the magnitude of internal variability in models or to an overestimation of the response to the external forcing in the Southern Hemisphere. Part of the disagreement might also reflect large uncertainties in the reconstructions, specifically in some Southern Hemisphere regions, which are based on fewer palaeoclimate records than in the Northern Hemisphere.

    Fulltekst (pdf)
    fulltext
  • 3. Brugnara, Y.
    et al.
    Auchmann, R.
    Brönnimann, S.
    Allan, R. J.
    Auer, I.
    Barriendos, M.
    Bergström, H.
    Bhend, J.
    Brázdil, R.
    Compo, G. P.
    Cornes, R. C.
    Dominguez-Castro, F.
    van Engelen, A. F. V.
    Filipiak, J.
    Holopainen, J.
    Jourdain, S.
    Kunz, M.
    Luterbacher, J.
    Maugeri, M.
    Mercalli, L.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Mock, C. J.
    Pichard, G.
    Řezníčková, L.
    van der Schrier, G.
    Slonosky, V.
    Ustrnul, Z.
    Valente, M. A.
    Wypych, A.
    Yin, X.
    A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 18162015Inngår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 11, nr 8, s. 1027-1047Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 4. Brunet, Manola
    et al.
    Jones, Philip D.
    Sigró, Javier
    Saladié, Oscar
    Aguilar, Enric
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Della-Marta, Paul M.
    Lister, David
    Walther, Alexander
    López, Diego
    Temporal and spatial temperature variability and change over Spain during 1850-20052007Inngår i: Journal of Gephysical Research: Atmospheres, Vol. 112, nr D12117Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyze temporal and spatial patterns of temperature change over Spain during the period 1850–2005, using daily maximum (T max), minimum (T min), and mean (T mean) temperatures from the 22 longest and most reliable Spanish records. Over mainland Spain, a significant (at 0.01 level) warming of 0.10°C/decade is found for the annual average of T mean. Autumn and winter contributed slightly more than spring and summer to the annual warming over the 1850–2005 period. The overall warming is also associated with higher rates of change for T max than T min (0.11° versus 0.08°C/decade for 1850–2005). This asymmetric diurnal warming increased in the twentieth century (0.17° versus 0.09°C/decade during 1901–2005). Nevertheless, at many (few) individual stations, the difference between T max and T min is not statistically significant over 1850–2005 (1901–2005). Principal Component Analysis has been carried out to identify spatial modes of Spanish long-term temperature variability (1901–2005). Three principal spatial patterns are found, Northern Spain, Southeastern and Eastern Spain, and Southwestern Spain. All three patterns show similar significant warming trends. The overall warming has been more associated with reductions in cold extremes, as opposed to increases in warm extremes. Estimated trends in the number of moderately extreme cold days (T max < 10th percentile) and moderately extreme cold nights (T min < 10th percentile) show significant reductions of 0.74 and 0.54 days/decade, respectively, over 1850–2005. Moderately extreme warm days and nights (T max and T min > 90th percentile) increased significantly but at lower rates of 0.53 and 0.49 days/decade.

  • 5. Brunet, Manola
    et al.
    Saladié, Oscar
    Jones, Phil
    Sigró, Javier
    Aguilar, Enric
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Lister, David
    Walther, Alexander
    Almarza, Carlos
    A case-study/guidance on the development of long-term daily adjusted temperature datasets: Climate Data and Monitoring WCDMP-No. 662008Rapport (Annet vitenskapelig)
  • 6. Brunet, Manola
    et al.
    Sigró, Javier
    Jones, Philip D.
    Saladié, Oscar
    Aguilar, Enric
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Lister, David
    Walther, Alexander
    Long-term changes in extreme temperatures and precipitation in Spain2007Inngår i: Contributions to Science: The International Journal of the Institute for Catalan Studies (IEC), ISSN 1575-6343, Vol. 3, nr 3, s. 331-342Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The development of the Spanish daily adjusted temperature

    series (SDATS) and the Spanish daily adjusted precipitation series

    (SDAPS) datasets in the framework of the European Community

    (EC)-funded project EMULATE (European and North Atlantic

    daily to MULtidecadal climATE variability) enabled the

    assessment of long-term annual changes of extreme temperature

    and precipitation indices over peninsular Spain for the period

    1901–2005. Within this framework, a set of procedures

    was developed to generate long-term (1850–2005) daily adjusted

    temperature and precipitation series and to use them to

    assess changes in climatic extremes. The present report describes

    details of the data employed to analyze the behavior of

    Spanish climate extremes and discusses the results of investigations

    into the annual changes in selected indices that occurred

    during the 20th century: exceedances of upper and lower

    percentiles of daily maximum (Tmax) and minimum (Tmin)

    temperatures, cold-spell duration index (CSDI), warm-spell duration

    index (WSDI), daily rainfall (R) exceeding the 95th and 99th

    percentiles, simple daily intensity index (SDII), and greatest 1–

    and 5-day total precipitation. Upper and lower temperature

    percentiles increased during the 20th century over mainland

    Spain, but changes in daytime extreme temperatures were

    larger than the changes in night-time extreme temperatures.

    This pattern, however, shifted slightly in the recent period of

    strong warming, with more similar rates of change among daytime

    and night-time extreme temperatures. Changes in extreme

    precipitation indices were not as evident as those in extreme-

    temperature indices, but there was a tendency towards

    heavier precipitation.

  • 7. Brázdil, Rudolf
    et al.
    Dobrovolný, Petr
    Luterbacher, Jürg
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Pfister, Christian
    Wheeler, Dennis
    Zorita, Eduardo
    European climate of the past 500 years: new challenges for historical climatology2010Inngår i: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 101, nr 1-2, s. 7-40Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 8. Brönnimann, Stefan
    et al.
    Allan, Rob
    Ashcroft, Linden
    Baer, Saba
    Barriendos, Mariano
    Brázdil, Rudolf
    Brugnara, Yuri
    Brunet, Manola
    Brunetti, Michele
    Chimani, Barbara
    Cornes, Richard
    Domínguez-Castro, Fernando
    Filipiak, Janusz
    Founda, Dimitra
    García Herrera, Ricardo
    Gergis, Joelle
    Grab, Stefan
    Hannak, Lisa
    Huhtamaa, Heli
    Jacobsen, Kim S.
    Jones, Phil
    Jourdain, Sylvie
    Kiss, Andrea
    Lin, Kuanhui Elaine
    Lorrey, Andrew
    Lundstad, Elin
    Luterbacher, Jürg
    Mauelshagen, Franz
    Maugeri, Maurizio
    Maughan, Nicolas
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Neukom, Raphael
    Nicholson, Sharon
    Noone, Simon
    Nordli, Øyvind
    Björg Ólafsdóttir, Kristín
    Pearce, Petra R.
    Pfister, Lucas
    Pribyl, Kathleen
    Przybylak, Rajmund
    Pudmenzky, Christa
    Rasol, Dubravka
    Reichenbach, Delia
    Řezníčková, Ladislava
    Rodrigo, Fernando S.
    Rohr, Christian
    Skrynyk, Oleg
    Slonosky, Victoria
    Thorne, Peter
    Valente, Maria Antónia
    Vaquero, José M.
    Westcottt, Nancy E.
    Williamson, Fiona
    Wyszyński, Przemyslaw
    Unlocking Pre-1850 Instrumental Meteorological Records: A Global Inventory2019Inngår i: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 100, nr 12, s. ES389-ES413Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Instrumental meteorological measurements from periods prior to the start of national weather services are designated early instrumental data. They have played an important role in climate research as they allow daily to decadal variability and changes of temperature, pressure, and precipitation, including extremes, to be addressed. Early instrumental data can also help place twenty-first century climatic changes into a historical context such as defining preindustrial climate and its variability. Until recently, the focus was on long, high-quality series, while the large number of shorter series (which together also cover long periods) received little to no attention. The shift in climate and climate impact research from mean climate characteristics toward weather variability and extremes, as well as the success of historical reanalyses that make use of short series, generates a need for locating and exploring further early instrumental measurements. However, information on early instrumental series has never been electronically compiled on a global scale. Here we attempt a worldwide compilation of metadata on early instrumental meteorological records prior to 1850 (1890 for Africa and the Arctic). Our global inventory comprises information on several thousand records, about half of which have not yet been digitized (not even as monthly means), and only approximately 20% of which have made it to global repositories. The inventory will help to prioritize data rescue efforts and can be used to analyze the potential feasibility of historical weather data products. The inventory will be maintained as a living document and is a first, critical, step toward the systematic rescue and reevaluation of these highly valuable early records. Additions to the inventory are welcome.

  • 9.
    Charpentier Ljungqvist, Fredrik
    et al.
    Stockholms universitet, Humanistiska fakulteten, Historiska institutionen. University of Cambridge, United Kingdom.
    Zhang, Qiong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Brattström, Gudrun
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Krusic, Paul J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. University of Cambridge, United Kingdom.
    Seim, Andrea
    Li, Qiang
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Zhang, Qiang
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Centennial-Scale Temperature Change in Last Millennium Simulations and Proxy-Based Reconstructions2019Inngår i: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 32, nr 9, s. 2441-2482Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Systematic comparisons of proxy-based reconstructions and climate model simulations of past millennium temperature variability offer insights into climate sensitivity and feedback mechanisms, besides allowing model evaluation independently from the period covered by instrumental data. Such simulation-reconstruction comparisons can help to distinguish more skillful models from less skillful ones, which may subsequently help to develop more reliable future projections. This study evaluates the low-frequency simulation-reconstruction agreement within the past millennium through assessing the amplitude of temperature change between the Medieval Climate Anomaly (here, 950-1250 CE) and the Little Ice Age (here, 1450-1850 CE) in PMIP3 model simulations compared to proxy-based local and continental-scale reconstructions. The simulations consistently show a smaller temperature change than the reconstructions for most regions in the Northern Hemisphere, but not in the Southern Hemisphere, as well as a partly different spatial pattern. A cost function analysis assesses how well the various simulations agree with reconstructions. Disregarding spatial correlation, significant differences are seen in the agreement with the local temperature reconstructions between groups of models, but insignificant differences are noted when compared to continental-scale reconstructions. This result points toward a limited possibility to rank models by means of their low-frequency temperature variability alone. The systematically lower amplitude of simulated versus reconstructed temperature change indicates either too-small simulated internal variability or that the analyzed models lack some critical forcing or have missing or too-weak feedback mechanisms. We hypothesize that too-cold initial ocean conditions in the models-in combination with too-weak internal variability and slow feedbacks over longer time scales-could account for much of the simulation-reconstruction disagreement.

  • 10. Chen, Deliang
    et al.
    Walther, Alexander
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Jones, Phil
    Jacobeit, Jucundus
    Lister, David
    European Trend Atlas of Extreme Temperature and Precipitation Records2015Bok (Fagfellevurdert)
  • 11. Dobrovolný, Petr
    et al.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Brázdil, Rudolf
    Pfister, Christian
    Glaser, Rüdiger
    Wilson, Rob
    van Engelen, Aryan
    Limanówka, Danuta
    Kiss, Andrea
    Halíčková, M
    Macková, J
    Riemann, Dirk
    Luterbacher, Jürg
    Böhm, Reinhard
    Monthly, seasonal and annual temperature reconstructions for Central Europe derived from documentary evidence and instrumental records since AD 15002010Inngår i: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 101, nr 1-2, s. 69-107Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 12. Drobyshev, Igor
    et al.
    Bergeron, Yves
    de Vernal, Anne
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Ali, Adam A.
    Niklasson, Mats
    Atlantic SSTs control regime shifts in forest fire activity of Northern Scandinavia2016Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikkel-id 22532Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 13.
    Fetisova, Ekaterina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Brattström, Gudrun
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Sundberg, Rolf
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Towards a flexible statistical modelling by latent factors for evaluation of simulated responses to climate forcings: Part IManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Evaluation of climate model simulations is a crucial task in climate research. In a work consisting of three parts, we propose a new statistical framework for evaluation of simulated responses to climate forcings, based on the concept of latent (unobservable) factors. Here, in Part I, we suggest several latent factor models of different complexity that can be used for evaluation of temperature data from climate model simulations against climate proxy data from the last millennium. Each factor model is developed for use with data from a single region, which can be of any size. To be able to test the hypotheses of interest, we have applied the technique of confirmatory factor analysis. We also elucidate the link between our factor models and the statistical methods used in Detection and Attribution (D\&A) studies. In particular, we demonstrate that our factor models can be used as an alternative approach to the methods used in D\&A studies. An additional advantage of their use is that they, in contrast to the commonly used D\&A methods, make it, in principle, possible to investigate whether the forcings of interest act additively or if any interaction effects exist.In Part II we investigate and illustrate the expansion of factor models to structural equation models, which permits the statistical modelling of more complicated climatological relationships. The performance of some of our statistical models suggested in Part I and Part is evaluated and compared in a numerical experiment, whose results are presented in Part III.

    Fulltekst (pdf)
    fulltext
  • 14.
    Fetisova, Ekaterina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Brattström, Gudrun
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Towards a flexible statistical modelling by latent factors for evaluation of simulated responses to climate forcings: Part IIManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Evaluation of climate model simulations is a crucial task in climate research. In a work consisting of three parts, we propose a new statistical framework for evaluation of simulated responses to climate forcings, based on the concept of latent (unobservable) variables. In Part I, several latent factor models were suggested for evaluation of temperature data from climate model simulations, forced by a varying number of forcings, against climate proxy data from the last millennium. Here, in Part II, focusing on climatological characteristics of forcings, we deepen the discussion by suggesting two alternative latent variable models that can be used for evaluation of temperature simulations forced by five specific forcings of natural and anthropogenic origin. The first statistical model is formulated in line with confirmatory factor analysis (CFA), accompanied by a more detailed discussion about the interpretation of latent temperature responses and their mutual relationships. Introducing further\emph{causal links} between some latent variables, the CFA model is extended to a structural equation model (SEM), which allows us to reflect more complicated climatological relationships with respect to all SEM's variables. Each statistical model is developed for use with data from a single region, which can be of any size. Associated with different hypotheses, the CFA and SEM models can, as a beginning, be fitted to observable simulated data only, which allows us to investigate the underlying latent structure associated with the simulated climate system. Then, the best-fitting model can be fitted to the data with real climate proxy data included, to test the consistency between the latent simulated temperature responses and their real-world counterparts embedded in observations. The performance of both these statistical models and some models suggested in Part I is evaluated and compared in a numerical experiment, whose results are presented in Part III.

    Fulltekst (pdf)
    fulltext
  • 15.
    Fetisova, Ekaterina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Brattström, Gudrun
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Towards a flexible statistical modelling by latent factors for evaluation of simulated responses to climate forcings: Part IIIManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Evaluation of climate model simulations is a crucial task in climate research. In a work consisting of three parts, we propose a new statistical framework for evaluation of simulated responses to climate forcings, based on the concept of latent (unobservable) variables. In Part I, several latent factor models were suggested for evaluation of temperature data from climate model simulations, forced by a varying number of forcings, against climate proxy data from the last millennium. In Part II, focusing on climatological characteristics of forcings, we deepen the discussion by suggesting two alternative latent variable models that can be used for evaluation of temperature simulations forced by five specific forcings of natural and anthropogenic origin. The first statistical model is formulated in line with confirmatory factor analysis (CFA), accompanied by a more detailed discussion about the interpretation of latent temperature responses and their mutual relationships. Introducing further causal links between some latent variables, the CFA model is extended to a structural equation model (SEM), which allows us to reflect more complicated climatological relationships with respect to all SEM's variables. Each statistical model is developed for use with data from a single region, which can be of any size. Here, in Part III, the performance of both these statistical models and some models suggested in Part I is evaluated and compared in a pseudo-proxy experiment, in which the true unobservable temperature is replaced by temperature data from a selected climate model simulation. The present analysis involves seven regional data sets. Focusing first on the ability of the models to provide an adequate and climatologically defensible description of the unknown underlying structure, we may conclude that given the climate model under consideration, the SEM model in general performed best. As for the factor model, its assumptions turned out to be too restrictive to describe the observed relationships in all but one region. The performance of another factor model, reflecting the assumptions typically made in many D\&A studies, can be characterised as unacceptable due to its high sensitivity to insignificant coefficient estimates. Regarding the fourth statistical model analysed - a factor model with two indicators and one latent factor - it can be recommended to apply it with caution due to its sensitivity to departures from the independence assumptions among the model variables, which can make the interpretation of the latent factor unclear. The conclusions above have been confirmed in some form of a cross-validation study, presuming the availability of several data sets within each region of interest. Importantly, the present pseudo-proxy experiment is performed only for zero noise level, implying that the five SEM models and one factor model await further investigation to fully test their performance for realistic levels of added noise.

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  • 16.
    Gouirand, Isabelle
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Linderholm, Hans W.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi. Meteorologiska institutionen (MISU).
    Wohlfarth, Barbara
    Institutionen för geologi och geokemi.
    On the spatio-temporal characteristics of Fennoscandian tree-ring based summer temperatures reconstructions2008Inngår i: Theoretical and Applied Climatology, Vol. 91, s. 1-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyse the spatial representation of five previously published multi-century to millennial length dendroclimatological reconstructions of Fennoscandian summer temperatures. The reconstructions, ranging from local to regional scale, were based on either tree-ring width (TRW) or maximum latewood density (MXD) data or on a combination of the two. TRW chronologies are shown to provide reasonably good spatial information mainly for July temperatures, but a combination of TRW and MXD yields a better spatial representation for the whole summer season (June–August). A multiple-site reconstruction does not necessarily provide better spatial representation than a single site reconstruction, depending on the criterion for selecting data and also on the strength of the climate signal in the tree-ring data. In a new approach to analyse the potential for further developing Fennoscandian temperature reconstructions, we selected from a network of TRW and MXD chronologies those having the strongest temperature information a priori, to obtain a strong common climate signal suitable for a regional-scale reconstruction. Seven separate, but not independent, reconstructions based on progressively decreasing numbers of chronologies were created. We show that it is possible to improve the spatial representation of available reconstructions back to around AD 1700, giving high correlations (>0.7) with observed summer temperatures for nearly the whole of Fennoscandia, and even higher correlations (>0.85) over much of central-northern Fennoscandia. Further sampling of older trees (e.g. dry-dead and subfossil wood) would be needed to achieve the same high correlations prior to AD 1700. Our analysis suggests that it should be possible to select a few key sites for improving the reconstructions before AD 1700. Since tree-ring data from northern Fennoscandia are used in all available hemispheric-scale temperature reconstructions for the last millennium, there is also a potential for slightly improving the quality of the hemispheric-scale reconstructions, by including an improved reconstruction for Fennoscandia. However, adding new chronologies from previously unsampled regions would potentially improve hemispheric-scale temperature reconstructions more substantially.

  • 17.
    Gouirand, Isabelle
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi. Meteorologiska institutionen (MISU).
    Zorita, Eduardo
    Climate variability in Scandinavia for the past millennium simulated by an atmosphere-ocean general circulation model2007Inngår i: Tellus: Tellus, Vol. 59A, s. 30-49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The atmosphere-ocean model ECHO-G, run with solar, volcanic and greenhouse gas forcing for the past millennium, is used to analyse winter and summer temperature variability in Scandinavia. Relationships with atmospheric circulation, North Atlantic SSTs and Northern Hemisphere (NH) temperatures are investigated at timescales longer and shorter than 10 yr. The simulated response to volcanic forcing is also analysed. Realistic relationships with the atmospheric circulation, with some deficiencies in summer, are found. High-frequency co-variations with SSTs and NH temperatures are too weak, but low-frequency co-variations with NH temperatures in winter are apparently too strong. The summer cooling response to volcanic forcing is realistic, but the expected winter warming is absent. The simulated long-term temperature evolution agrees broadly with proxy data. Combinations of several forcing factors can lead to decadal and multidecadal anomalies from the centennial trends. Decreased solar forcing can account for cold intervals in both summer and winter. A systematic negative North Atlantic Oscillation (NAO) phase can explain the coldest winter temperatures during 1590–1650. Several strong volcanic forcing events can have contributed to a simultaneous summer cooling. Proxy data also indicate cold summers and winters, and a negative NAO in winter, in the same period.

  • 18.
    Gunnarson, Björn
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Linderholm, Hans W.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Improving a tree-ring reconstruction from west-central Scandinavia: 900 years of warm-season temperatures2011Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 36, nr 1-2, s. 97-108Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dendroclimatological sampling of Scots pine (Pinus sylvestris L.) has been made in the province of Jamtland, in the west-central Scandinavian mountains, since the 1970s. The tree-ring width (TRW) chronology spans several thousand years and has been used to reconstruct June August temperatures back to 1632 BC. A maximum latewood density (MXD) dataset, covering the period AD 1107-1827 (with gap 1292-1315) was presented in the 1980s by Fritz Schweingruber. Here we combine these historical MXD data with recently collected MXD data covering AD 1292-2006 into a single reconstruction of April September temperatures for the period AD 1107 2006. Regional curve standardization (RCS) provides more low-frequency variability than non-RCS and stronger correlation with local seasonal temperatures (51% variance explained). The MXD chronology shows a stronger relationship with temperatures than the TRW data, but the two chronologies show similar multi-decadal variations back to AD 1500. According to the MXD chronology, the period since AD 1930 and around AD 1150-1200 were the warmest during the last 900 years. Due to large uncertainties in the early part of the combined MXD chronology, it is not possible to conclude which period was the warmest. More sampling of trees growing near the tree-line is needed to further improve the MXD chronology.

  • 19.
    Hind, Alistair
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Past millennial solar forcing magnitude: A statistical hemispheric-scale climate model versus proxy data comparison2013Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 41, nr 9-10, s. 2527-2537Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A set of global climatemodel simulations for the lastthousand years developed by the Max Planck Institute is comparedwith paleoclimate proxy data and instrumental data,focusing on surface temperatures for land areas between 30 and75N. The proxy data are obtained from six previously publishedNorthern Hemispheric-scale temperature reconstructions, here recalibratedfor consistency, which are compared with the simulationsutilizing a newly developed statistical framework forranking several competing simulations by means of their statisticaldistance against past climate variations. The climate modelsimulations are driven by either ‘‘low’’ or ‘‘high’’ solar forcingamplitudes (0.1 and 0.25 % smaller total solar irradiance in the Maunder Minimum period compared to the present) in addition toseveral other known climate forcings of importance. Our resultsindicate that the high solar forcing amplitude results in a poorermatch with the hemispheric-scale temperature reconstructionsand lends stronger statistical support for the low-amplitude solarforcing. However, results are likely conditional upon the sensitivityof the climate model used and strongly dependent on thechoice of temperature reconstruction, hence a greater consensus isneeded regarding the reconstruction of past temperatures as thiscurrently provides a great source of uncertainty.

  • 20.
    Hind, Alistair
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Sundberg, Rolf
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Statistical framework for evaluation of climate model simulations by use of climate proxy data from the last millennium – Part 2: A pseudo-proxy study addressing the amplitude of solar forcing2012Inngår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 8, nr 4, s. 1355-1365Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The statistical framework of Part 1 (Sundberg et al., 2012), for comparing ensemble simulation surface temperature output with temperature proxy and instrumental records, is implemented in a pseudo-proxy experiment. A set of previously published millennial forced simulations (Max Planck Institute – COSMOS), including both "low" and "high" solar radiative forcing histories together with other important forcings, was used to define "true" target temperatures as well as pseudo-proxy and pseudo-instrumental series. In a global land-only experiment, using annual mean temperatures at a 30-yr time resolution with realistic proxy noise levels, it was found that the low and high solar full-forcing simulations could be distinguished. In an additional experiment, where pseudo-proxies were created to reflect a current set of proxy locations and noise levels, the low and high solar forcing simulations could only be distinguished when the latter served as targets. To improve detectability of the low solar simulations, increasing the signal-to-noise ratio in local temperature proxies was more efficient than increasing the spatial coverage of the proxy network. The experiences gained here will be of guidance when these methods are applied to real proxy and instrumental data, for example when the aim is to distinguish which of the alternative solar forcing histories is most compatible with the observed/reconstructed climate.

  • 21. Jungclaus, Johann H.
    et al.
    Bard, Edouard
    Baroni, Mélanie
    Braconnot, Pascale
    Cao, Jian
    Chini, Louise P.
    Egorova, Tania
    Evans, Michael
    González-Rouco, J. Fidel
    Goosse, Hugues
    Hurtt, George C.
    Joos, Fortunat
    Kaplan, Jed O.
    Khodri, Myriam
    Goldewijk, Kees Klein
    Krivova, Natalie
    LeGrande, Allegra N.
    Lorenz, Stephan J.
    Luterbacher, Jürg
    Man, Wenmin
    Maycock, Amanda C.
    Meinshausen, Malte
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Muscheler, Raimund
    Nehrbass-Ahles, Christoph
    Otto-Bliesner, Bette I.
    Phipps, Steven J.
    Pongratz, Julia
    Rozanov, Eugene
    Schmidt, Gavin A.
    Schmidt, Hauke
    Schmutz, Werner
    Schurer, Andrew
    Shapiro, Alexander I.
    Sigl, Michael
    Smerdon, Jason E.
    Solanki, Sami K.
    Timmreck, Claudia
    Toohey, Matthew
    Usoskin, Ilya G.
    Wagner, Sebastian
    Wu, Chi-Ju
    Yeo, Kok Leng
    Zanchettin, Davide
    Zhang, Qiong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Zorita, Eduardo
    The PMIP4 contribution to CMIP6-Part 3: The last millennium, scientific objective, and experimental design for the PMIP4 past1000 simulations2017Inngår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 10, nr 11, s. 4005-4033Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The pre-industrial millennium is among the periods selected by the Paleoclimate Model Intercomparison Project (PMIP) for experiments contributing to the sixth phase of the Coupled Model Intercomparison Project (CMIP6) and the fourth phase of the PMIP (PMIP4). The past1000 transient simulations serve to investigate the response to (mainly) natural forcing under background conditions not too different from today, and to discriminate between forced and internally generated variability on interannual to centennial timescales. This paper describes the motivation and the experimental set-ups for the PMIP4-CMIP6 past1000 simulations, and discusses the forcing agents orbital, solar, volcanic, and land use/land cover changes, and variations in greenhouse gas concentrations. The past1000 simulations covering the pre-industrial millennium from 850 Common Era (CE) to 1849 CE have to be complemented by historical simulations (1850 to 2014 CE) following the CMIP6 protocol. The external forcings for the past1000 experiments have been adapted to provide a seamless transition across these time periods. Protocols for the past1000 simulations have been divided into three tiers. A default forcing data set has been defined for the Tier 1 (the CMIP6 past1000) experiment. However, the PMIP community has maintained the flexibility to conduct coordinated sensitivity experiments to explore uncertainty in forcing reconstructions as well as parameter uncertainty in dedicated Tier 2 simulations. Additional experiments (Tier 3) are defined to foster collaborative model experiments focusing on the early instrumental period and to extend the temporal range and the scope of the simulations. This paper outlines current and future research foci and common analyses for collaborative work between the PMIP and the observational communities (reconstructions, instrumental data).

  • 22.
    Leijonhufvud, Lotta
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Ekonomisk-historiska institutionen.
    Wilson, Rob
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Documentary data provide evidence of Stockholm average winter to spring temperatures in the eighteenth and nineteenth centuries2008Inngår i: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 18, nr 2, s. 333-343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Swedish archives provide several types of documentary sources relating to port activities in Stockholm for the eighteenth and nineteenth centuries. These documentary sources reflect sea ice conditions in the harbour inlet and correlate well with late-winter to early-spring temperatures. Instrumental measurements of temperature in Stockholm began in 1756, which allow for careful empirical assessment of the proxies from that date. After combining proxy series from several sources to derive a mean time series, calibration and verification trials are made and a preliminary January–April temperature reconstruction is developed from 1692 to 1892. This series, which explains 67% of the temperature variance, is further verified against independent temperature data from Uppsala, which go back to 1722. This additional verification of the reconstruction also assesses the quality of the early instrumental data from Uppsala, which has potential homogeneity problems before 1739 as a result of the thermometer being located indoors. Our analysis suggests that before this date, the instrumental data may be ‘too warm’ and need correction. Together, the documentary and instrumental data identify the post-1990 period as the warmest in three centuries. Continuing assessment of the historical archives should result in some of the documentary records being extended back into the early sixteenth century, allowing the future development of a southern Swedish winter temperature reconstruction for the last ~500 years.

  • 23.
    Leijonhufvud, Lotta
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Wilson, Rob
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Söderberg, Johan
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Ekonomisk-historiska institutionen.
    Retsö, Dag
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Ekonomisk-historiska institutionen.
    Söderlind, Ulrica
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Ekonomisk-historiska institutionen.
    Five centuries of Stockholm winter/spring temperatures reconstructed from documentary evidenceand instrumental observations2010Inngår i: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 101, nr 1-2, s. 109-141Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 24. Linderholm, HW
    et al.
    Moberg, A
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Grudd, H
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Peatland pines as climate indicators? A regional comparison of the climatic influence on Scots pine growth in Sweden2002Inngår i: Canadian Journal of Forest Research, Vol. 32, nr 8, s. 1400-1410Artikkel i tidsskrift (Fagfellevurdert)
  • 25. Loader, Neil J.
    et al.
    Jalkanen, Risto
    McCarroll, Danny
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Spring temperature variability in northern Fennoscandia AD 1693–20112011Inngår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 26, nr 6, s. 566-570Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 26. Luterbacher, Jürg
    et al.
    Koenig, S.J.
    Franke, Jörg
    van der Schrier, Gerard
    Zorita, Eduardo
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Jacobeit, Jucundus
    Della-Marta, Paul M.
    Küttel, Marcel
    Xoplaki, Elena
    Wheeler, Dennis
    Rutishauser, This
    Stössel, M.
    Wanner, Heinz
    Brázdil, Rudolf
    Dobrovolný, Petr
    Camuffo, Dario
    Bertolin, Chiara
    van Engelen, Aryan
    Gonzalez-Rouco, F.J.
    Wilson, Rob
    Pfister, Christian
    Limanówka, Danuta
    Nordli, Oyvind
    Leijonhufvud, Lotta
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Söderberg, Johan
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Ekonomisk-historiska institutionen.
    Allan, Rob
    Barriendos, Mariano
    Glaser, Rüdiger
    Riemann, Dirk
    Zao, Z.
    Zerefos, C.S.
    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 models2010Inngår i: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 101, nr 1-2, s. 201-234Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 27.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Comments on ''Reconstruction of the Extratropical NH Mean Temperature over the Last Millennium with a Method That Preserves Low-Frequency Variability''2012Inngår i: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 25, nr 22, s. 7991-7997Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    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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  • 28.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Comparisons of simulated and observed Northern Hemisphere temperature variations during the past millennium - selected lessons learned and problems encountered2013Inngår i: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 65, s. 19921-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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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  • 29.
    Moberg, Anders
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Brattström, Gudrun
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Prediction intervals for climate reconstructions with autocorrelated noise: An analysis of ordinary least squares and measurement error methods2011Inngår i: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 308, nr 3-4, s. 313-329Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 30.
    Moberg, Anders
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Holmgren, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Renssen, Hans
    Sundqvist, Hanna S.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Zhang, Qiong
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Preface "Holocene climate variability over Scandinavia – A special issue originating from a workshop organized by the Bert Bolin Centre for Climate Research"2010Inngår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 6, s. 719-721Artikkel i tidsskrift (Annet vitenskapelig)
  • 31.
    Moberg, Anders
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Mohammad, Rezwan
    Institutionen för geologi och geokemi.
    Mauritsen, Thorsten
    Meteorologiska institutionen (MISU).
    Analysis of the Moberg et al. (2005) hemispheric temperature reconstruction2008Inngår i: Climate Dynamics, Vol. 31, nr 7-8, s. 957-971Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Moberg et al. (Nature 433(7026):613–617, 2005. doi:10.1038/nature03265; M05) reconstruction of northern hemisphere temperature variations from proxy data has been criticised; the M05 method may artificially inflate low-frequency variance relative to reality. We test this assertion by undertaking several pseudoproxy experiments in three climate model simulations—one control run and two forced simulations that include several time-varying radiative forcings. The pseudoproxy series are designed to have the same variance spectra as the real M05 proxies, primarily to mimic the low-resolution character of several series. A simple composite-plus-scale (CPS) method is also analysed. In the CPS case all input data behave like annually resolved proxies. The spectral domain performance of both M05 and CPS is found to be dependent on the noise type and noise level in pseudoproxies, on the variance spectrum of the climate model simulation, and on the degree of data smoothing. CPS performs better than M05 in most investigated cases with the control run, but leads to deflated lowfrequency variance in some cases. With M05, low-frequency variance tend to be inflated for the control run but not for one of the forced runs and only very slightly with the other forced simulation. Hence, the M05 approach does not routinely

    inflate low-frequency variance. In our experiment, the M05 approach performs better in the spectral domain than CPS when applied to forced climate model simulations. The results underscore the importance of evaluating the variance spectrum of climate reconstructions.

  • 32.
    Moberg, Anders
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Sundberg, Rolf
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Grudd, Håkan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Hind, Alistair
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Statistical framework for evaluation of climate model simulations by use of climate proxy data from the last millennium - Part 3: Practical considerations, relaxed assumptions, and using tree-ring data to address the amplitude of solar forcing2015Inngår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 11, nr 3, s. 425-448Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A statistical framework for evaluation of climate model simulations by comparison with climate observations from instrumental and proxy data (part 1 in this series) is improved by the relaxation of two assumptions. This allows autocorrelation in the statistical model for simulated internal climate variability and enables direct comparison of two alternative forced simulations to test whether one fits the observations significantly better than the other. The extended framework is applied to a set of simulations driven with forcings for the pre-industrial period 1000-1849 CE and 15 tree-ring-based temperature proxy series. Simulations run with only one external forcing (land use, volcanic, small-amplitude solar, or large-amplitude solar) do not significantly capture the variability in the tree-ring data - although the simulation with volcanic forcing does so for some experiment settings. When all forcings are combined (using either the small- or large-amplitude solar forcing), including also orbital, greenhouse-gas and non-volcanic aerosol forcing, and additionally used to produce small simulation ensembles starting from slightly different initial ocean conditions, the resulting simulations are highly capable of capturing some observed variability. Nevertheless, for some choices in the experiment design, they are not significantly closer to the observations than when unforced simulations are used, due to highly variable results between regions. It is also not possible to tell whether the small-amplitude or large-amplitude solar forcing causes the multiple-forcing simulations to be closer to the reconstructed temperature variability. Proxy data from more regions and of more types, or representing larger regions and complementary seasons, are apparently needed for more conclusive results from model-data comparisons in the last millennium.

  • 33.
    Moberg, Anders
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Söderberg, Johan
    Samhällsvetenskapliga fakulteten, Ekonomisk-historiska institutionen.
    Leijonhufvud, Lotta
    Samhällsvetenskapliga fakulteten, Ekonomisk-historiska institutionen.
    Retsö, Dag
    Samhällsvetenskapliga fakulteten, Ekonomisk-historiska institutionen.
    Söderlind, Ulrica
    Samhällsvetenskapliga fakulteten, Ekonomisk-historiska institutionen.
    500 års väder i Stockholm2008Inngår i: Forskning och framsteg, ISSN ISSN 0015-7937, Vol. 43, nr 5, s. 12-17Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    En helt ny klimatkurva har forskare tagit fram ur gamla sjöfartsdokument. Kurvan sträcker sig flera hundra år längre tillbaka än temperaturmätningarna från och med mitten av 1700-talet. Den visar att de senaste två årtiondenas varmare klimat avviker från de senaste fwem seklernas.

  • 34. Philipp, Andreas
    et al.
    Della-Marta, Paul-M.
    Jacobeit, Jucundus
    Fereday, David R.
    Jones, Philip D.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Wanner, Heiz
    Long-Term Variability of Daily North Atlantic–European Pressure Patterns since 1850 Classified by Simulated Annealing Clustering2007Inngår i: Journal of Climate, ISSN 1520-0442, Vol. 20, nr 16, s. 4065-4095Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reconstructed daily mean sea level pressure patterns of the North Atlantic–European region are classified for the period 1850 to 2003 to explore long-term changes of the atmospheric circulation and its impact on long-term temperature variability in the central European region. Commonly used k-means clustering algorithms resulted in classifications of low quality because of methodological deficiencies leading to local optima by chance for complex datasets. In contrast, a newly implemented clustering scheme combining the concepts of simulated annealing and diversified randomization (SANDRA) is able to reduce substantially the influence of chance in the cluster assignment, leading to partitions that are noticeably nearer to the global optimum and more stable. The differences between conventional cluster analysis and the SANDRA scheme are significant for subsequent analyses of single clusters—in particular, for trend analysis. Conventional indices used to determine the appropriate number of clusters failed to provide clear guidance, indicating that no distinct separation between clusters of circulation types exists in the dataset. Therefore, the number of clusters is determined by an external indicator, the so-called dominance criteria for t-mode principal component analysis. Nevertheless, the resulting partitions are stable for certain numbers of clusters and provide meaningful and reproducible clusters. The resulting types of pressure patterns reveal pronounced long-term variability and various significant trends of the time series of seasonal cluster frequency. Tentative estimations of central European temperature changes based solely on seasonal cluster frequencies can explain between 33.9% (summer) and 59.0% (winter) of temperature variance on the seasonal time scale. However, the signs of long-term changes in temperature are correctly reproduced even on multidecadal–centennial time scales. Moreover, linear warming trends are reproduced, implying from one-third up to one-half of the observed temperature increase between 1851/52 and 2003 (except for summer, but with significant trends for spring and autumn), indicating that changes in daily circulation patterns contribute to the observed overall long-term warming in the central European region.

  • 35. Rutgersson, Anna
    et al.
    Jaagus, Jaak
    Schenk, Frederik
    Stendel, Martin
    Bärring, Lars
    Briede, Agrita
    Claremar, Björn
    Hanssen-Bauer, Inger
    Holopainen, Jari
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Nordli, Øyvind
    Rimkus, Egidijus
    Wibig, Joanna
    Recent Change - Atmosphere2015Inngår i: Second Assessment of Climate Change for the Baltic Sea Basin / [ed] The BACC II Author Team, Springer, 2015, s. 69-97Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    This chapter describes observed changes in atmospheric conditions in the Baltic Sea drainage basin over the past 200-300 years. The Baltic Sea area is relatively unique with a dense observational network covering an extended time period. Data analysis covers an early period with sparse and relatively uncertain measurements, a period with well-developed synoptic stations, and a final period with 30+ years of satellite data and sounding systems. The atmospheric circulation in the European/Atlantic sector has an important role in the regional climate of the Baltic Sea basin, especially the North Atlantic Oscillation. Warming has been observed, particularly in spring, and has been stronger in the northern regions. There has been a northward shift in storm tracks, as well as increased cyclonic activity in recent decades and an increased persistence of weather types. There are no long-term trends in annual wind statistics since the nineteenth century, but much variation at the (multi-)decadal timescale. There are also no long-term trends in precipitation, but an indication of longer precipitation periods and possibly an increased risk of extreme precipitation events.

  • 36. Scaife, Adam
    et al.
    Folland, Chris
    Alexander, Lisa
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Knight, Jeff
    European climate extremes and the North Atlantic Oscillation2008Inngår i: Journal of Climate, ISSN 1520-0442, Vol. 21, nr 1, s. 72-83Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The authors estimate the change in extreme winter weather events over Europe that is due to a long-term change in the North Atlantic Oscillation (NAO) such as that observed between the 1960s and 1990s. Using ensembles of simulations from a general circulation model, large changes in the frequency of 10th percentile temperature and 90th percentile precipitation events over Europe are found from changes in the NAO. In some cases, these changes are comparable to the expected change in the frequency of events due to anthropogenic forcing over the twenty-first century. Although the results presented here do not affect anthropogenic interpretation of global and annual mean changes in observed extremes, they do show that great care is needed to assess changes due to modes of climate variability when interpreting extreme events on regional and seasonal scales. How changes in natural modes of variability, such as the NAO, could radically alter current climate model predictions of changes in extreme weather events on multidecadal time scales is also discussed.

  • 37.
    Sundberg, Rolf
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Hind, Alistair
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Statistical framework for evaluation of climate model simulations by use of climate proxy data from the last millennium – Part 1: Theory2012Inngår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 8, nr 4, s. 1339-1353Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A statistical framework for comparing the output of ensemble simulations from global climate models with networks of climate proxy and instrumental records has been developed, focusing on near-surface temperatures for the last millennium. This framework includes the formulation of a joint statistical model for proxy data, instrumental data and simulation data, which is used to optimize a quadratic distance measure for ranking climate model simulations. An essential underlying assumption is that the simulations and the proxy/instrumental series have a shared component of variability that is due to temporal changes in external forcing, such as volcanic aerosol load, solar irradiance or greenhouse gas concentrations. Two statistical tests have been formulated. Firstly, a preliminary test establishes whether a significant temporal correlation exists between instrumental/proxy and simulation data. Secondly, the distance measure is expressed in the form of a test statistic of whether a forced simulation is closer to the instrumental/proxy series than unforced simulations. The proposed framework allows any number of proxy locations to be used jointly, with different seasons, record lengths and statistical precision. The goal is to objectively rank several competing climate model simulations (e.g. with alternative model parameterizations or alternative forcing histories) by means of their goodness of fit to the unobservable true past climate variations, as estimated from noisy proxy data and instrumental observations.

    Fulltekst (pdf)
    fulltext
  • 38.
    Sundqvist, Hanna S.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Holmgren, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Spötl, Christoph
    Mangini, Augusto
    Stable oxygen isotopes in a stalagmite from Jämtland, NW Sweden, record large temperature variations over the last 4000 years2010Inngår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 39, nr 1, s. 77-86Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

     

     

     

    This study of a 4000-year-old stalagmite from Korallgrottan in northwestern Sweden highlights the potentials and challenges when using stable isotopes in stalagmites as climate proxies, as well as the fact that the relationship between climate and proxy may change through time. Both the oxygen and the carbon isotopes display an overall trend of enrichment together with decreasing growth rates over the time period covered by the stalagmite, which is considered a generally cooling period according to current palaeoclimate understanding. The stable isotope records show enriched isotopic values during the, for Scandinavia, comparatively cold period AD 1300–1700 and depleted values during the warmer period AD 800–1000. The indication of a negative relationship between measured

    d18O and surface temperature concurs with earlier reported stalagmite records from regions with a seasonal snow cover and is further supported by the fact that the stalagmite d18

    O record shows general similarities with both regional and hemispheric temperature reconstructions available for the past 500 and 2000 years, respectively.

    Compared with a stable isotope record of lacustrine carbonates from northern Sweden, however, shifting correlations over time between the two records indicate that a local hydrological change may have taken place at Korallgrottan, or at the lake, compared with around 1000 years ago. The earlier part of the stalagmite

    d18O might thus be influenced, to some extent, by another process than the later part, which means that a negative relationship between d18O and surface temperature might not hold for the entire 4000-year-old record.

  • 39.
    Sundqvist, Hanna S.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Zhang, Qiong
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Holmgren, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Körnich, Heiner
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Nilsson, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Northern high-latitude climate change between the mid and late Holocene: Part 1: Proxy data evidence2009Inngår i: Climate of the Past Discussions, ISSN 1814-9340, Vol. 5, nr 4, s. 1819-1852Artikkel i tidsskrift (Annet vitenskapelig)
  • 40.
    Sundqvist, Hanna S.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Zhang, Qiong
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Holmgren, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Körnich, Heiner
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Nilsson, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Brattström, Gudrun
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Climate change between the mid and late Holocene in the northern high latitudes: Part I: Survey of temperature and precipitation proxy data2010Inngår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 6, s. 591-608Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We undertake a study in two parts, where theoverall aim is to quantitatively compare results from climateproxy data with results from several climate model simulationsfrom the Paleoclimate Modelling IntercomparisonProject for the mid-Holocene period and the pre-industrial,conditions for the pan-arctic region, north of 60 N. In thisfirst paper, we survey the available published local temperatureand precipitation proxy records. We also discuss andquantifiy some uncertainties in the estimated difference inclimate between the two periods as recorded in the availabledata. The spatial distribution of available published localproxies has a marked geographical bias towards land areassurrounding the North Atlantic sector, especially Fennoscandia.The majority of the reconstructions are terrestrial, andthere is a large over-representation towards summer temperaturerecords. The available reconstructions indicate that thenorthern high latitudes were warmer in both summer, winterand the in annual mean temperature at the mid-Holocene(6000 BP±500 yrs) compared to the pre-industrial period(1500AD±500 yrs). For usage in the model-data comparisons(in Part 1), we estimate the calibration uncertainty andalso the internal variability in the proxy records, to derive acombined minimum uncertainty in the reconstructed temperaturechange between the two periods. Often, the calibrationuncertainty alone, at a certain site, exceeds the actual reconstructedclimate change at the site level. In high-density regions,however, neighbouring records can be merged into aCorrespondence to: H. S. Sundqvist(hanna.sundqvist@natgeo.su.se)composite record to increase the signal-to-noise ratio. Thechallenge of producing reliable inferred climate reconstructionsfor the Holocene cannot be underestimated, consideringthe fact that the estimated temperature and precipitationfluctuations during this period are in magnitude similar to, orlower than, the uncertainties the reconstructions. We advocatea more widespread practice of archiving proxy recordsas most of the potentially available reconstructions are notpublished in digital form.

    Fulltekst (pdf)
    FULLTEXT01
  • 41. The BACC Author Team,
    et al.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Assessment of Climate Change for the Baltic Sea Basin2008Bok (Annet vitenskapelig)
  • 42. Trachsel, Mathias
    et al.
    Kamenik, Christian
    Grosjean, Martin
    McCarroll, Danny
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Brázdil, Rudolf
    Büntgen, Ulf
    Dobrovolný, Petr
    Esper, Jan
    Frank, David C.
    Friedrich, Michael
    Glaser, Rüdiger
    Larocque-Tobler, Isabelle
    Nicolussi, Kurt
    Riemann, Dirk
    Multi-archive summer temperature reconstruction for the European Alps, AD 1053-19962012Inngår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 46, s. 66-79Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 43. Turney, C
    et al.
    Duncan, R
    Nicholls, N
    Moberg, Anders
    Stockholms universitet.
    Pollack, H
    Towards an Australasian climate reconstruction for the past two millennia2008Inngår i: PAGES News, Vol. 16, nr 2, s. 34-Artikkel i tidsskrift (Annet vitenskapelig)
  • 44.
    Wagner-Cremer, Friederike
    et al.
    Institute of Environmental Biology, Utrecht University.
    Finsinger, Walter
    University of Montpellier.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Tracing growing degree-day changes in the cuticle morphology of Betula nana leaves: a new micro-phenological palaeo-proxy2010Inngår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 25, nr 6, s. 1008-1017Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 45.
    Zhang, Qiong
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Sundqvist, Hanna
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Holmgren, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Körnich, Heiner
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Nilsson, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Northern high-latitude climate change between the mid and late Holocene: Part 2: Model-data comparisons2009Inngår i: Climate of the Past Discussions, ISSN 1814-9340, Vol. 5, nr 3, s. 1659-1696Artikkel i tidsskrift (Annet vitenskapelig)
  • 46.
    Zhang, Qiong
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Sundqvist, Hanna
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Körnich, Heiner
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Nilsson, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Holmgren, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Climate change between the mid and late Holocene in northern high latitudes: Part 2: Model-data comparisons2010Inngår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 6, s. 609-626Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The climate response over northern high latitudesto the mid-Holocene orbital forcing has been investigated inthree types of PMIP (Paleoclimate Modelling IntercomparisonProject) simulations with different complexity of themodelled climate system. By first undertaking model-datacomparison, an objective selection method has been appliedto evaluate the capability of the climate models to reproducethe spatial response pattern seen in proxy data. The possiblefeedback mechanisms behind the climate response havebeen explored based on the selected model simulations. Subsequentmodel-model comparisons indicate the importanceof including the different physical feedbacks in the climatemodels. The comparisons between the proxy-based reconstructionsand the best fit selected simulations show that overthe northern high latitudes, summer temperature change followsclosely the insolation change and shows a commonfeature with strong warming over land and relatively weakwarming over ocean at 6 ka compared to 0 ka. Furthermore,the sea-ice-albedo positive feedback enhances this response.The reconstructions of temperature show a strongerresponse to enhanced insolation in the annual mean temperaturethan winter and summer temperature. This is verified inthe model simulations and the behaviour is attributed to thelarger contribution from the large response in autumn. Despitea smaller insolation during winter at 6 ka, a pronouncedwarming centre is found over Barents Sea in winter in thesimulations, which is also supported by the nearby northernEurasian continental and Fennoscandian reconstructions.This indicates that in the Arctic region, the response of theocean and the sea ice to the enhanced summer insolationis more important for the winter temperature than the synchronousdecrease of the insolation.

    Fulltekst (pdf)
    FULLTEXT01
  • 47. Zorita, Eduardo
    et al.
    Moberg, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Leijonhufvud, Lotta
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Wilson, Rob
    Brázdil, Rudolf
    Dobrovolný, Petr
    Luterbacher, Jürg
    Böhm, Reinhard
    Pfister, Christian
    Riemann, Dirk
    Glaser, Rüdiger
    Söderberg, Johan
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Ekonomisk-historiska institutionen.
    González-Rouco, Fidel
    European temperature records of the past five centuries based on documentary/instrumental information compared to climate simulations2010Inngår i: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 101, nr 1-2, s. 143-168Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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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