Change search
Link to record
Permanent link

Direct link
Alternative names
Publications (10 of 51) Show all publications
Lashgari, K., Brattström, G., Moberg, A. & Sundberg, R. (2022). Evaluation of simulated responses to climate forcings: a flexible statistical framework using confirmatory factor analysis and structural equation modelling – Part 1: Theory. Advances in Statistical Climatology, Meteorology and Oceanography, 8(2), 225-248
Open this publication in new window or tab >>Evaluation of simulated responses to climate forcings: a flexible statistical framework using confirmatory factor analysis and structural equation modelling – Part 1: Theory
2022 (English)In: Advances in Statistical Climatology, Meteorology and Oceanography, E-ISSN 2364-3587, Vol. 8, no 2, p. 225-248Article in journal (Refereed) Published
Abstract [en]

Evaluation of climate model simulations is a crucial task in climate research. Here, a new statistical framework is proposed for evaluation of simulated temperature responses to climate forcings against temperature reconstructions derived from climate proxy data for the last millennium. The framework includes two types of statistical models, each of which is based on the concept of latent (unobservable) variables: confirmatory factor analysis (CFA) models and structural equation modelling (SEM) models. Each statistical model presented is developed for use with data from a single region, which can be of any size. The ideas behind the framework arose partly from a statistical model used in many detection and attribution (D&A) studies. Focusing on climatological characteristics of five specific forcings of natural and anthropogenic origin, the present work theoretically motivates an extension of the statistical model used in D&A studies to CFA and SEM models, which allow, for example, for non-climatic noise in observational data without assuming the additivity of the forcing effects. The application of the ideas of CFA is exemplified in a small numerical study, whose aim was to check the assumptions typically placed on ensembles of climate model simulations when constructing mean sequences. The result of this study indicated that some ensembles for some regions may not satisfy the assumptions in question.

National Category
Probability Theory and Statistics Earth and Related Environmental Sciences
Research subject
Mathematical Statistics
Identifiers
urn:nbn:se:su:diva-214598 (URN)10.5194/ascmo-8-225-2022 (DOI)2-s2.0-85145563123 (Scopus ID)
Funder
Swedish Research Council, C0592401
Available from: 2023-02-06 Created: 2023-02-06 Last updated: 2023-02-10Bibliographically approved
Lashgari, K., Moberg, A. & Brattström, G. (2022). Evaluation of simulated responses to climate forcings: a flexible statistical framework using confirmatory factor analysis and structural equation modelling – Part 2: Numerical experiment. Advances in Statistical Climatology, Meteorology and Oceanography, 8(2), 249-271
Open this publication in new window or tab >>Evaluation of simulated responses to climate forcings: a flexible statistical framework using confirmatory factor analysis and structural equation modelling – Part 2: Numerical experiment
2022 (English)In: Advances in Statistical Climatology, Meteorology and Oceanography, E-ISSN 2364-3587, Vol. 8, no 2, p. 249-271Article in journal (Refereed) Published
Abstract [en]

The performance of a new statistical framework, developed for the evaluation of simulated temperature responses to climate forcings against temperature reconstructions derived from climate proxy data for the last millennium, is evaluated in a so-called pseudo-proxy experiment, where the true unobservable temperature is replaced with output data from a selected simulation with a climate model. Being an extension of the statistical model used in many detection and attribution (D&A) studies, the framework under study involves two main types of statistical models, each of which is based on the concept of latent (unobservable) variables: confirmatory factor analysis (CFA) models and structural equation modelling (SEM) models. Within the present pseudo-proxy experiment, each statistical model was fitted to seven continental-scale regional data sets. In addition, their performance for each defined region was compared to the performance of the corresponding statistical model used in D&A studies. The results of this experiment indicated that the SEM specification is the most appropriate one for describing the underlying latent structure of the simulated temperature data in question. The conclusions of the experiment have been confirmed in a cross-validation study, presuming the availability of several simulation data sets within each studied region. Since the experiment is performed only for zero noise level in the pseudo-proxy data, all statistical models, chosen as final regional models, await further investigation to thoroughly test their performance for realistic levels of added noise, similar to what is found in real proxy data for past temperature variations.

National Category
Probability Theory and Statistics Earth and Related Environmental Sciences
Research subject
Mathematical Statistics
Identifiers
urn:nbn:se:su:diva-214600 (URN)10.5194/ascmo-8-249-2022 (DOI)2-s2.0-85145548029 (Scopus ID)
Funder
Swedish Research Council, C0592401
Available from: 2023-02-06 Created: 2023-02-06 Last updated: 2023-02-10Bibliographically approved
Jansson, U. & Moberg, A. (2022). Svenska forskares syn på hantering av rumsliga data - enkätundersökning 2021. Stockholm: Svensk nationell datatjänst (SND)
Open this publication in new window or tab >>Svenska forskares syn på hantering av rumsliga data - enkätundersökning 2021
2022 (Swedish)Report (Other academic)
Abstract [en]

A survey, aimed at Swedish researchers in the field of spatial data, was conducted in 2021. 113 individuals responded to the questionnaire, which gives us insight into how researchers in the field view; sharing of data, how they work with data, which metadata they think are central and what support they ask for in order to be able to handle spatial data.

According to the survey a majority of the researchers share and use data shared by others in their research. Central metadata that is emphasized are coordinate systems, projections, time of the information, data capture, data content and author. The question of how to make data available is very varied among the respondents. The questionnaire responses contain a wide range of individual solutions to make the information available. A majority of researchers believe that the work with data management and accessibility has increased over the past 5 years. As an obstacle to working more with this is time, but there are also other obstacles. The researchers are seeking additional support that can be summarized as: support, technical guidance, storage, information, time and money.

Abstract [sv]

En enkätundersökning genomfördes under 2021. Den var riktad till svenska forskare inom fältet rumsliga data. 113 individer svarade på enkäten som ger oss insikt hur forskare inom fältet ser på tillgängliggörande av data, hur man arbetar med data, vilka metadata man tycker är centrala och vilket stöd man efterfrågar för att kunna hantera specifikt rumsliga data.

Bland huvudresultaten från enkäten kan nämnas att en majoritet av forskarna delar och använder data som delats av andra i sin forskning. Centrala metadata som man framhåller är koordinatsystem, projektioner, tidpunkt för informationen, datafångst, datainnehåll och upphovsman. Frågan om hur man tillgängliggör data är mycket varierande bland respondenterna. I enkätsvaren återfinns en lång rad individuella lösningar för att kunna tillgängliggöra informationen. En majoritet av forskarna menar att arbetet med datahantering och tillgängliggörandet har ökat under de senaste 5 åren. Hinder för att arbeta mer med detta menar man är tid, men det finns också andra hinder. Forskarna efterlyser ytterligare stöd som kan sammanfattas som: stöd/support, teknisk vägledning, lagring, information, tid och pengar.

Place, publisher, year, edition, pages
Stockholm: Svensk nationell datatjänst (SND), 2022. p. 32
Keywords
Geografiska data, Datahantering, Enkät, GIS
National Category
Information Studies
Identifiers
urn:nbn:se:su:diva-203098 (URN)
Available from: 2022-03-23 Created: 2022-03-23 Last updated: 2022-04-06Bibliographically approved
Wilcke, R. A., Kjellström, E., Lin, C., Matei, D., Moberg, A. & Tyrlis, E. (2020). The extremely warm summer of 2018 in Sweden - set in a historical context. Earth System Dynamics, 11(4), 1107-1121
Open this publication in new window or tab >>The extremely warm summer of 2018 in Sweden - set in a historical context
Show others...
2020 (English)In: Earth System Dynamics, ISSN 2190-4979, E-ISSN 2190-4987, Vol. 11, no 4, p. 1107-1121Article in journal (Refereed) Published
Abstract [en]

Two long-lasting high-pressure systems in summer 2018 led to persisting heatwaves over Scandinavia and other parts of Europe and an extended summer period with devastating impacts on agriculture, infrastructure, and human life. We use five climate model ensembles and the unique 263-year-long Stockholm temperature time series along with a composite 150-year-long time series for the whole of Sweden to set the latest heatwave in the summer of 2018 into historical perspective. With 263 years of data, we are able to grasp the pre-industrial period well and see a clear upward trend in temperature as well as upward trends in five heatwave indicators. With five climate model ensembles providing 20 580 simulated summers representing the latest 70 years, we analyse the likelihood of such a heat event and how unusual the 2018 Swedish summer actually was. We find that conditions such as those observed in summer 2018 are present in all climate model ensembles. An exception is the monthly mean temperature for May for which 2018 was warmer than any member in one of the five climate model ensembles. However, even if the ensembles generally contain individual years like 2018, the comparison shows that such conditions are rare. For the indices assessed here, anomalies such as those observed in 2018 occur in a maximum of 5 % of the ensemble members, sometimes even in less than 1 %. For all of the indices evaluated, we find that the probability of a summer such as that in 2018 has increased from relatively low values in the pre-industrial era (1861-1890, one ensemble) and the recent past (1951-1980, all five ensembles) to higher values in the most recent decades (1989-2018). An implication of this is that anthropogenic climate change has strongly increased the probability of a warm summer, such as the one observed 2018, occurring in Sweden. Despite this, we still find such summers in the pre-industrial climate in our simulations, albeit with a lower probability.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-189008 (URN)10.5194/esd-11-1107-2020 (DOI)000598405500001 ()
Available from: 2021-01-15 Created: 2021-01-15 Last updated: 2022-02-25Bibliographically approved
Charpentier Ljungqvist, F., Zhang, Q., Brattström, G., Krusic, P. J., Seim, A., Li, Q., . . . Moberg, A. (2019). Centennial-Scale Temperature Change in Last Millennium Simulations and Proxy-Based Reconstructions. Journal of Climate, 32(9), 2441-2482
Open this publication in new window or tab >>Centennial-Scale Temperature Change in Last Millennium Simulations and Proxy-Based Reconstructions
Show others...
2019 (English)In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 32, no 9, p. 2441-2482Article in journal (Refereed) Published
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.

Keywords
Paleoclimate, Surface temperature, Ranking methods, Climate models, Model comparison
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-168313 (URN)10.1175/JCLI-D-18-0525.1 (DOI)000464467700001 ()
Available from: 2019-05-26 Created: 2019-05-26 Last updated: 2022-03-23Bibliographically approved
Brönnimann, S., Allan, R., Ashcroft, L., Baer, S., Barriendos, M., Brázdil, R., . . . Wyszyński, P. (2019). Unlocking Pre-1850 Instrumental Meteorological Records: A Global Inventory. Bulletin of The American Meteorological Society - (BAMS), 100(12), ES389-ES413
Open this publication in new window or tab >>Unlocking Pre-1850 Instrumental Meteorological Records: A Global Inventory
Show others...
2019 (English)In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 100, no 12, p. ES389-ES413Article in journal (Refereed) Published
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.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-178701 (URN)10.1175/BAMS-D-19-0040.1 (DOI)000506029100005 ()
Available from: 2020-02-27 Created: 2020-02-27 Last updated: 2022-03-23Bibliographically approved
Jungclaus, J. H., Bard, E., Baroni, M., Braconnot, P., Cao, J., Chini, L. P., . . . Zorita, E. (2017). The PMIP4 contribution to CMIP6-Part 3: The last millennium, scientific objective, and experimental design for the PMIP4 past1000 simulations. Geoscientific Model Development, 10(11), 4005-4033
Open this publication in new window or tab >>The PMIP4 contribution to CMIP6-Part 3: The last millennium, scientific objective, and experimental design for the PMIP4 past1000 simulations
Show others...
2017 (English)In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 10, no 11, p. 4005-4033Article in journal (Refereed) Published
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).

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-149828 (URN)10.5194/gmd-10-4005-2017 (DOI)000414599900001 ()
Available from: 2017-12-13 Created: 2017-12-13 Last updated: 2022-03-23Bibliographically approved
Drobyshev, I., Bergeron, Y., de Vernal, A., Moberg, A., Ali, A. A. & Niklasson, M. (2016). Atlantic SSTs control regime shifts in forest fire activity of Northern Scandinavia. Scientific Reports, 6, Article ID 22532.
Open this publication in new window or tab >>Atlantic SSTs control regime shifts in forest fire activity of Northern Scandinavia
Show others...
2016 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 6, article id 22532Article in journal (Refereed) Published
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.

National Category
Climate Research
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-127853 (URN)10.1038/srep22532 (DOI)000371292000001 ()
Funder
Swedish Research Council Formas, 239-2014-1866
Available from: 2016-03-14 Created: 2016-03-14 Last updated: 2022-09-15Bibliographically approved
Brugnara, Y., Auchmann, R., Brönnimann, S., Allan, R. J., Auer, I., Barriendos, M., . . . Yin, X. (2015). A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 1816. Climate of the Past, 11(8), 1027-1047
Open this publication in new window or tab >>A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 1816
Show others...
2015 (English)In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 11, no 8, p. 1027-1047Article in journal (Refereed) Published
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.

National Category
Climate Research
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-119501 (URN)10.5194/cp-11-1027-2015 (DOI)000360642800001 ()
Available from: 2015-08-17 Created: 2015-08-17 Last updated: 2022-03-23Bibliographically approved
Bothe, O., Hind, A., Moberg, A. & Zorita, E. (2015). Continental-scale temperature variability in PMIP3 simulations and PAGES 2k regional temperature reconstructions over the past millennium. Climate of the Past, 11(12), 1673-1699
Open this publication in new window or tab >>Continental-scale temperature variability in PMIP3 simulations and PAGES 2k regional temperature reconstructions over the past millennium
2015 (English)In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 11, no 12, p. 1673-1699Article in journal (Refereed) Published
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.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-124314 (URN)10.5194/cp-11-1673-2015 (DOI)000367351500006 ()
Projects
Palaeoclimatology, Last Millennium
Available from: 2015-12-17 Created: 2015-12-17 Last updated: 2022-02-23Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5177-9347

Search in DiVA

Show all publications