| 1. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 2. |
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| 3. |
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| 4. |
- Björck, Svante, et al.
(författare)
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Historiska varningssignaler
- 2010
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Ingår i: Sverige i nytt klimat - våtvarm utmaning. - Stockholm : Forskningsrådet Formas. - 9789154060405 ; , s. 71-86
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Bokkapitel (populärvet., debatt m.m.)abstract
- De senaste tjugo årens klimat i Stockholmstrakten är troligen det varmaste under den senaste femhudraårsperioden. Människans utsläpp av växthusgaser har bidragit, men även naturliga faktorer. Av historien kan vi lära oss att klimatet plötsligt kan slå om till att fungera på ett helt nytt sätt - en förändring som kan bli en obehaglig överraskning för människans samhälle och dess känsliga infrastruktur. Därför bör vi vara lyhörda för varningssignaler från jordens klimatsystem. Varningssignaler är den geologiska historien full av, skriver Svante Björck och Anders Moberg.
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| 5. |
- Bothe, Oliver, et al.
(författare)
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Continental-scale temperature variability in PMIP3 simulations and PAGES 2k regional temperature reconstructions over the past millennium
- 2015
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 11:12, s. 1673-1699
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Brázdil, Rudolf, et al.
(författare)
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European climate of the past 500 years: new challenges for historical climatology
- 2010
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Ingår i: Climatic Change. - Netherlands : Springer. - 0165-0009 .- 1573-1480. ; 101:1-2, s. 7-40
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Tidskriftsartikel (refereegranskat)abstract
- Temperature reconstructions from Europe for the past 500 years basedon documentary and instrumental data are analysed. First, the basic documentarydata sources, including information about climate and weather-related extremes, aredescribed. Then, the standard palaeoclimatological reconstruction method adoptedhere is discussed with a particular application to temperature reconstructions fromdocumentary-based proxy data. The focus is on two new reconstructions; January–April mean temperatures for Stockholm (1502–2008), based on a combination ofdata for the sailing season in the Stockholm harbour and instrumental temperaturemeasurements, and monthly Central European temperature (CEuT) series (1500–2007) based on documentary-derived temperature indices of the Czech Republic,Germany and Switzerland combined with instrumental records from the samecountries. The two series, both of which are individually discussed in greater detail in subsequent papers in this special edition, are here compared and analysed usingrunning correlations and wavelet analysis. While the Stockholm series shows apronounced low-frequency component, the CEuT series indicates much weaker lowfrequencyvariations. Both series are analysed with respect to three different longperiodreconstructions of the North Atlantic Oscillation (NAO) and are comparedwith other European temperature reconstructions based on tree-rings, wine-harvestdata and various climate multiproxies. Correlation coefficients between individualproxy-based series show weaker correlations compared to the instrumental data.There are also indications of temporally varying temperature cross-correlationsbetween different areas of Europe. The two temperature reconstructions have alsobeen compared to geographically corresponding temperature output from simulationswith global and regional climate models for the past few centuries. The findingsare twofold: on the one hand, the analysis reinforces the hypothesis that the indexdatabased CEuT reconstruction may not appropriately reflect the centennial scalevariations. On the other hand, it is possible that climate models may underestimateregional decadal variability. By way of a conclusion, the results are discussed froma broader point of view and attention is drawn to some new challenges for futureinvestigations in the historical climatology in Europe.
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| 7. |
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| 8. |
- Brugnara, Y., et al.
(författare)
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A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 1816
- 2015
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 11:8, s. 1027-1047
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Tidskriftsartikel (refereegranskat)abstract
- The eruption of Mount Tambora (Indonesia) in April 1815 is the largest documented volcanic eruption in history. It is associated with a large global cooling during the following year, felt particularly in parts of Europe and North America, where the year 1816 became known as the "year without a summer". This paper describes an effort made to collect surface meteorological observations from the early instrumental period, with a focus on the years of and immediately following the eruption (1815–1817). Although the collection aimed in particular at pressure observations, correspondent temperature observations were also recovered. Some of the series had already been described in the literature, but a large part of the data, recently digitised from original weather diaries and contemporary magazines and newspapers, is presented here for the first time. The collection puts together more than 50 sub-daily series from land observatories in Europe and North America and from ships in the tropics. The pressure observations have been corrected for temperature and gravity and reduced to mean sea level. Moreover, an additional statistical correction was applied to take into account common error sources in mercury barometers. To assess the reliability of the corrected data set, the variance in the pressure observations is compared with modern climatologies, and single observations are used for synoptic analyses of three case studies in Europe. All raw observations will be made available to the scientific community in the International Surface Pressure Databank.
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| 9. |
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| 10. |
- Brunet, Manola, et al.
(författare)
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Long-term changes in extreme temperatures and precipitation in Spain
- 2007
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Ingår i: Contributions to Science: The International Journal of the Institute for Catalan Studies (IEC). - 1575-6343. ; 3:3, s. 331-342
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The development of the Spanish daily adjusted temperatureseries (SDATS) and the Spanish daily adjusted precipitation series(SDAPS) datasets in the framework of the European Community(EC)-funded project EMULATE (European and North Atlanticdaily to MULtidecadal climATE variability) enabled theassessment of long-term annual changes of extreme temperatureand precipitation indices over peninsular Spain for the period1901–2005. Within this framework, a set of procedureswas developed to generate long-term (1850–2005) daily adjustedtemperature and precipitation series and to use them toassess changes in climatic extremes. The present report describesdetails of the data employed to analyze the behavior ofSpanish climate extremes and discusses the results of investigationsinto the annual changes in selected indices that occurredduring the 20th century: exceedances of upper and lowerpercentiles of daily maximum (Tmax) and minimum (Tmin)temperatures, cold-spell duration index (CSDI), warm-spell durationindex (WSDI), daily rainfall (R) exceeding the 95th and 99thpercentiles, simple daily intensity index (SDII), and greatest 1–and 5-day total precipitation. Upper and lower temperaturepercentiles increased during the 20th century over mainlandSpain, but changes in daytime extreme temperatures werelarger than the changes in night-time extreme temperatures.This pattern, however, shifted slightly in the recent period ofstrong warming, with more similar rates of change among daytimeand night-time extreme temperatures. Changes in extremeprecipitation indices were not as evident as those in extreme-temperature indices, but there was a tendency towardsheavier precipitation.
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| 11. |
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| 12. |
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| 13. |
- Brönnimann, Stefan, et al.
(författare)
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Unlocking Pre-1850 Instrumental Meteorological Records : A Global Inventory
- 2019
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - 0003-0007 .- 1520-0477. ; 100:12, s. ES389-ES413
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 14. |
- Bunne, Joakim, et al.
(författare)
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Increase in allergic sensitization in schoolchildren : two cohorts compared 10 years apart
- 2017
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Ingår i: Journal of Allergy and Clinical Immunology. - : Elsevier. - 2213-2198 .- 2213-2201. ; 5:2, s. 457-463
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Time trends of incidence of allergic sensitization are unknown and recent trends of prevalence and risk factors are lacking.OBJECTIVE: To estimate the incidence, prevalence, remission, risk factors, and time trends for allergic sensitization among schoolchildren followed from age 7 to 8 years to age 11 to 12 years.METHODS: In 2006, all children in grades 1 and 2 aged 7 to 8 years in 2 municipalities in northern Sweden were invited to a questionnaire survey and to skin prick testing to 10 common airborne allergens. The cohort was reexamined in 2010, with additional blood sampling for specific IgE. Participation rates were 90% (n = 1700) at age 7 to 8 years and 85% (n = 1657) at age 11 to 12 years. The results were compared with a cohort examined by identical methods 10 years earlier.RESULTS: The prevalence of positive skin prick test result to any allergen increased from 30% at age 7 to 8 years to 41% at age 11 to 12 years (P < .001). The cumulative 4-year incidence was 18%, while remission was low. Sensitization to pollen and furred animals was most common. A family history of allergy was significantly associated with incident sensitization, whereas the presence of furred animals at home was negatively associated. The prevalence at age 7 to 8 years and at age 11 to 12 years and the 4-year incidence were all significantly higher compared with the cohort examined 10 years earlier.CONCLUSIONS: The prevalence of allergic sensitization increased by age as a consequence of a high incidence and a low remission. The trends of increasing incidence and prevalence among schoolchildren imply future increases in the prevalence of allergic diseases.
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| 15. |
- Charpentier Ljungqvist, Fredrik, et al.
(författare)
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Centennial-Scale Temperature Change in Last Millennium Simulations and Proxy-Based Reconstructions
- 2019
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Ingår i: Journal of Climate. - 0894-8755 .- 1520-0442. ; 32:9, s. 2441-2482
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 16. |
- Chen, Deliang, 1961, et al.
(författare)
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European Trend Atlas of Extreme Temperature and Precipitation Records
- 2015
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- This Atlas presents records of climatic variability and change in Europe starting before 1901 and focuses especially on trends of extreme temperatures and precipitation. The authors have used software developed within EMULATE (European and North Atlantic daily to MULtidecadal climATE variability) to obtain the extremes indices and temporal trends. The trend atlas provides an easy way to identify spatial patterns for a given time period, region, season, and index. The Atlas clearly shows that climate in Europe has changed over the last 100 to 150 years, such that the occurrence and intensity of warm temperature extremes have increased. Precipitation extremes have also changed, but with a less clear pattern compared to the temperature extremes.
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| 17. |
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| 18. |
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| 19. |
- Dadfar, Hossein, 1946-, et al.
(författare)
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In search of Cultural Synergy in Multicultural Organizations
- 1999
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Ingår i: Meeting the Intercultural Challenge: Effective Approaches in Research, Education, Training and Business. - Germany : Verlag Wissenschaft & Praxis. - 3896730118
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 20. |
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| 21. |
- Dobrovolný, Petr, et al.
(författare)
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Monthly, seasonal and annual temperature reconstructions for Central Europe derived from documentary evidence and instrumental records since AD 1500
- 2010
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Ingår i: Climatic Change. - Netherlands : Springer. - 0165-0009 .- 1573-1480. ; 101:1-2, s. 69-107
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Tidskriftsartikel (refereegranskat)abstract
- Monthly temperature series for Central Europe back to AD 1500 aredeveloped from documentary index series from Germany, Switzerland and theCzech Republic (1500–1854) and 11 instrumental temperature records (1760–2007).Documentary evidence from the Low Countries, the Carpathian Basin and Polandare used for cross-checking for earlier centuries. The instrumental station recordsare corrected for inhomogeneities, including insufficient radiation protection ofearly thermometers and the urban heat island effect. For overlapping period (1760–1854), the documentary data series correlate with instrumental temperatures, moststrongly in winter (86% explained variance in January) and least in autumn (56%in September). For annual average temperatures, 81% of the variance is explained.Verification statistics indicate high reconstruction skill for most months and seasons.The last 20 years (since 1988) stand out as very likely the warmest 20-year period,accounting for the calibration uncertainty and decreases in proxy data quality beforethe calibration period. The new reconstruction displays a previously unobserved long-term decrease in DJF, MAM and JJA temperature variability over last fivecenturies. Compiled monthly, seasonal and annual series can be used to improve therobustness of gridded large-scale European temperature reconstructions and possibleimpact studies. Further improvement of the reconstruction would be achieved ifdocumentary data from other European countries are further developed.
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| 22. |
- Drobyshev, Igor, et al.
(författare)
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Atlantic SSTs control regime shifts in forest fire activity of Northern Scandinavia
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the drivers of the boreal forest fire activity is challenging due to the complexity of the interactions driving fire regimes. We analyzed drivers of forest fire activity in Northern Scandinavia (above 60 N) by combining modern and proxy data over the Holocene. The results suggest that the cold climate in northern Scandinavia was generally characterized by dry conditions favourable to periods of regionally increased fire activity. We propose that the cold conditions over the northern North Atlantic, associated with low SSTs, expansion of sea ice cover, and the southward shift in the position of the subpolar gyre, redirect southward the precipitation over Scandinavia, associated with the westerlies. This dynamics strengthens high pressure systems over Scandinavia and results in increased regional fire activity. Our study reveals a previously undocumented teleconnection between large scale climate and ocean dynamics over the North Atlantic and regional boreal forest fire activity in Northern Scandinavia. Consistency of the pattern observed annually through millennium scales suggests that a strong link between Atlantic SST and fire activity on multiple temporal scales over the entire Holocene is relevant for understanding future fire activity across the European boreal zone.
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| 23. |
- Ferritsius, Rita, et al.
(författare)
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Water Absorption and Wet Strength in Hot-pressed Paper
- 2022
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Ingår i: Proceedings of the International Mechanical Pulping Conference. ; , s. 168-170
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Effects of hot-pressing on anisotropic sheets with less good formation was here investigated. The main objective was to study water absorption capacity in relation to the wet strength of hot-pressed paper. A pilot paper machine was used to produce papers from TMP and CTMP furnishes. The results indicate that it is not only the high dry content after wetting that contributes to the high wet strength of the paper hot-pressed at 200C. If it is required to have a paper with both low absorption of water and high wet strength, hot-pressing at 200C seems to be more desirable than using con-ventional drying and adding wet chemical agents to the furnish.
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| 24. |
- Fetisova, Ekaterina
(författare)
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Evaluation of climate model simulations by means of statistical methods
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Evaluation of climate model simulations is a key issue within climate research. The statistical framework proposed by Sundberg et al., 2012, provides a theoretical underpinning of methods for evaluation of climate models by use of climateproxy data from the last millennium. In the present work, the statistical framework above is used to suggest several latent factor models of different complexity that can be used for estimating the amplitude of a forcing effect in aclimate model by comparison with the observed/reconstructed climate. The performance of the models is evaluated and compared in a pseudo-proxy experiment, in which the true unobservable temperature series is replaced by selected realizations of a climate simulation model. For different levels of added noise, different conclusions can be drawn. However, for realistic noise levels, we find that the simplest model, the just-identified two-indicator one-factor model, denoted j.i.FA(2,1), is a competitive alternative to models with more complicated structure. Moreover, we discover that the Fieller method of constructing confidence regions, associated with the j.i.FA(2,1)-model, outperforms the Wald confidence interval, which in most cases fails to provide sensible and interpretable conclusions about the climate model under consideration. Last but not least, the results indicate a good performance of the j.i.FA(2,1)-model even in the presence of heteroscedasticity.
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| 25. |
- Fetisova, Ekaterina, 1974-
(författare)
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Towards a flexible statistical modelling by latent factors for evaluation of simulated responses to climate forcings
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, using the principles of confirmatory factor analysis (CFA) and the cause-effect concept associated with structural equation modelling (SEM), a new flexible statistical framework for evaluation of climate model simulations against observational data is suggested. The design of the framework also makes it possible to investigate the magnitude of the influence of different forcings on the temperature as well as to investigate a general causal latent structure of temperature data. In terms of the questions of interest, the framework suggested here can be viewed as a natural extension of the statistical approach of 'optimal fingerprinting', employed in many Detection and Attribution (D&A) studies. Its flexibility means that it can be applied under different circumstances concerning such aspects as the availability of simulated data, the number of forcings in question, the climate-relevant properties of these forcings, and the properties of the climate model under study, in particular, those concerning the reconstructions of forcings and their implementation. It should also be added that although the framework involves the near-surface temperature as a climate variable of interest and focuses on the time period covering approximately the last millennium prior to the industrialisation period, the statistical models, included in the framework, can in principle be generalised to any period in the geological past as soon as simulations and proxy data on any continuous climate variable are available. Within the confines of this thesis, performance of some CFA- and SEM-models is evaluated in pseudo-proxy experiments, in which the true unobservable temperature series is replaced by temperature data from a selected climate model simulation. The results indicated that depending on the climate model and the region under consideration, the underlying latent structure of temperature data can be of varying complexity, thereby rendering our statistical framework, serving as a basis for a wide range of CFA- and SEM-models, a powerful and flexible tool. Thanks to these properties, its application ultimately may contribute to an increased confidence in the conclusions about the ability of the climate model in question to simulate observed climate changes.
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| 26. |
- Fetisova, Ekaterina, 1974-, et al.
(författare)
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Towards a flexible statistical modelling by latent factors for evaluation of simulated responses to climate forcings: Part I
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 27. |
- Fetisova, Ekaterina, 1974-, et al.
(författare)
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Towards a flexible statistical modelling by latent factors for evaluation of simulated responses to climate forcings: Part II
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 28. |
- Fetisova, Ekaterina, 1974-, et al.
(författare)
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Towards a flexible statistical modelling by latent factors for evaluation of simulated responses to climate forcings: Part III
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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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| 29. |
- Frölander, Anders, et al.
(författare)
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Ag+-Assisted Hydrosilylation : Complementary Behavior of Rh and Ir Catalysts (Reversal of Enantioselectivity)
- 2007
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 9:7, s. 1371-1374
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Tidskriftsartikel (refereegranskat)abstract
- The presence of a suitably situated hydroxy function in a PHOX ligand leads to an enhancement of the enantioselectivity in Rh-catalyzed hydrosilylations of prochiral ketones in the presence of AgBF4 (95% ee for acetophenone as compared to 75% using i-Pr-phosphinooxazoline (PHOX)). Exchanging Rh for Ir affords the product with the opposite absolute configuration (78% ee).
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| 30. |
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| 31. |
- Frölander, Anders, et al.
(författare)
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Conformational preferences and enantiodiscrimination of phosphino-4-(1-hydroxyalkyl)oxazoline-metal-olefin complexes resulting from an OH-metal hydrogen bond
- 2005
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 70:24, s. 9882-9891
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Tidskriftsartikel (refereegranskat)abstract
- Phosphinooxazolines carrying (1-hydroxy-1-phenyl)methyl and (1-methoxy-1-phenyl)methyl substituents in the 4 position of the oxazoline ring exhibit contrasting behavior in Pd-and Ir-catalyzed allylic alkylations. Whereas catalysts with the methoxy-containing ligand generally provide products with high ee's, use of catalysts prepared from the hydroxy-containing ligand results in products with low ee's or even racemates. DFT calculations suggest the presence of a hydrogen bond with Pd(0) as the proton acceptor in the hydroxy-containing olefin-Pd(0) complexes, which induces a conformational change in the ligand, leading to different stereoselectivity.
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| 32. |
- Frölander, Anders, 1977-
(författare)
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Impact of Secondary Interactions in Asymmetric Catalysis
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with secondary interactions in asymmetric catalysis and their impact on the outcome of catalytic reactions. The first part revolves around the metal-catalyzed asymmetric allylic alkylation reaction and how interactions within the catalyst affect the stereochemistry. An OH–Pd hydrogen bond in Pd(0)–π-olefin complexes of hydroxy-containing oxazoline ligands was identified by density functional theory computations and helped to rationalize the contrasting results obtained employing hydroxy- and methoxy-containing ligands in the catalytic reaction. This type of hydrogen bond was further studied in phenanthroline metal complexes. As expected for a hydrogen bond, the strength of the bond was found to increase with increased electron density at the metal and with increased acidity of the hydroxy protons. The second part deals with the use of hydroxy- and methoxy-containing phosphinooxazoline ligands in the rhodium- and iridium-catalyzed asymmetric hydrosilylation reaction. The enantioselectivities obtained were profoundly enhanced upon the addition of silver salts. This phenomenon was explained by an oxygen–metal coordination in the catalytic complexes, which was confirmed by NMR studies of an iridium complex. Interestingly, the rhodium and iridium catalysts nearly serve as pseudo-enantiomers giving products with different absolute configurations. The final part deals with ditopic pyridinobisoxazoline ligands and the application of their metal complexes in asymmetric cyanation reactions. Upon complexation, these ligands provide catalysts with both Lewis acidic and Lewis basic sites, capable of activating both the substrate and the cyanation reagent. Lanthanide and aluminum complexes of these ligands were found to catalyze the addition of the fairly unreactive cyanation reagents ethyl cyanoformate and acetyl cyanide to benzaldehyde, whereas complexes of ligands lacking the Lewis basic coordination sites failed to do so.
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| 33. |
- Frölander, Anders, et al.
(författare)
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OH-Metal hydrogen bond in Pd- and Ir-catalyzed allylic alkylations
- 2006
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Ingår i: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY. ; , s. ORGN-259-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Phosphinooxazolines carrying 4-hydroxybenzyl and 4-methoxybenzyl substituents exhibit contrasting behavior in Pd- and Ir-catalyzed allylic alkylations. Whereas catalysts with the methoxy-contg. ligand generally provide products with high ee's, use of catalysts prepd. from the hydroxy contg. ligand results in products with low ee's or even racemates. DFT calcns. suggest the presence of a hydrogen bond with Pd(0) as proton acceptor in the hydroxy contg. olefin Pd(0) complexes, which induces a conformational change in the ligand leading to different stereoselectivity. We have previously obsd. the same kind of dramatic changes of enantioselectivities in palladium-catalyzed allylations upon methylation of hydroxy-contg. pyridinooxazolines and bisoxazolines.
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| 34. |
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| 35. |
- Gouirand, Isabelle, et al.
(författare)
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Climate variability in Scandinavia for the past millennium simulated by an atmosphere-ocean general circulation model
- 2007
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Ingår i: Tellus: Tellus. - : Stockholm University Press. ; 59A, s. 30-49
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 36. |
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| 37. |
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| 38. |
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| 39. |
- Gunnarson, Björn, et al.
(författare)
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Improving a tree-ring reconstruction from west-central Scandinavia : 900 years of warm-season temperatures
- 2011
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 36:1-2, s. 97-108:36, s. 97-108
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 40. |
- Hallman, Kristina, et al.
(författare)
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OH–Pd(0) Interaction as a Stabilizing Factor in Palladium-Catalyzed Allylic Alkylations
- 2004
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 101:15, s. 5400-5404
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Tidskriftsartikel (refereegranskat)abstract
- In palladium-catalyzed alkylations of allylic acetates with malonate as nucleophile, catalysts with oxazoline ligands bearing hydroxymethyl substituents in 4-position have been shown by density functional theory computations to undergo a conformational change on nucleophilic attack, which is accompanied by reduction of Pd(II) to Pd(0). The conformations of the Pd(0) complexes were shown to be governed by the presence of a hydrogen bond with the metal center acting as a hydrogen bond acceptor. The conformational change, which is absent in catalysts with O-alkylated analogs, largely affects the enantioselectivity of the catalytic process. This process is a previously uninvestigated example of where this type of weak hydrogen bond has been shown to influence the stereochemistry of a chemical reaction.
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| 41. |
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| 42. |
- Hamberg, Anders, et al.
(författare)
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High Throughput Synthesis and Analysis of Acylated Cyanohydrins
- 2007
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 13:15, s. 4334-4341
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Tidskriftsartikel (refereegranskat)abstract
- The yields and optical purities of products obtained from chiral Lewis acid/Lewis base-catalysed additions of alpha-ketonitriles to prochiral aldehydes could be accurately determined by an enzymatic method. The amount of remaining aldehyde was determined after its reduction to an alcohol, whilst the two product enantiomers were analysed after subsequent hydrolysis first by the (S)-selective Candida antarctica lipase B and then by the unselective pig liver esterase. The method could be used for analysis of products obtained from a number of aromatic aldehydes and aliphatic ketonitriles. Microreactor technology was successfully combined with high-throughput analysis for efficient catalyst optimization.
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| 43. |
- Heidmarsson, Starri, et al.
(författare)
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Classification of lichen photomorphs
- 1997
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Ingår i: Taxon. - : Wiley. - 0040-0262 .- 1996-8175. ; :46, s. 519-520
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Tidskriftsartikel (refereegranskat)
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| 44. |
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| 45. |
- Hind, Alistair, et al.
(författare)
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Past millennial solar forcing magnitude : A statistical hemispheric-scale climate model versus proxy data comparison
- 2013
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Ingår i: Climate Dynamics. - : Springer Publishing Company. - 0930-7575 .- 1432-0894. ; 41:9-10, s. 2527-2537
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 46. |
- Hind, Alistair, et al.
(författare)
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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 forcing
- 2012
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Ingår i: Climate of the Past. - : European Geosciences Union (EGU). - 1814-9324 .- 1814-9332. ; 8:4, s. 1355-1365
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 47. |
- Ivner, Jenny, et al.
(författare)
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Swedish energy manager networks for energy-intensive industry as a driver for improved energy efficiency
- 2014
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Ingår i: Eceee Industrial Summer Study Proceedings. - : European Council for an Energy Efficient Economy. - 9789198048247 ; , s. 629-635
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Konferensbidrag (refereegranskat)abstract
- While the potential for improved energy efficiency in industry is large, deployment of measures is often inhibited by a number of barriers. In order to overcome these barriers, a number of energy end-use policies is functioning in Sweden, the two largest being a Voluntary Agreements (VA) for energy-intensive industry, an energy audit program, and in addition, various energy manager networks for improved energy efficiency. While the two former have been evaluated and are well-known, the Swedish energy efficiency networks have so far neither been presented nor evaluated previously. The aim of this paper is to present the current Swedish energy efficient network, and their role in the energy policy mix from a theoretical viewpoint. The Swedish energy network, Energiintensiven consisting of about 100 companies from the major electricity-intensive sectors is administrated by the Swedish Energy Agency. Participating companies are all part of the Swedish VA, the PFE. In addition the aluminum companies have an energy network (GeniAl), one network is functioning among Swedish saw mills (EESI), as well as there is a network in the iron- and steel industry ENET-Steel. Results of the paper show that despite the low emphasis on networks as a part of the policy mix, the networks have an important role in overcoming barriers to energy efficiency among the participating companies.
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| 48. |
- Jansson, Ulf, 1966-, et al.
(författare)
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Svenska forskares syn på hantering av rumsliga data - enkätundersökning 2021
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A survey, aimed at Swedish researchers in the field of spatial data, was conducted in 2021. 113 individuals responded to the questionnaire, which gives us insight into how researchers in the field view; sharing of data, how they work with data, which metadata they think are central and what support they ask for in order to be able to handle spatial data.According to the survey a majority of the researchers share and use data shared by others in their research. Central metadata that is emphasized are coordinate systems, projections, time of the information, data capture, data content and author. The question of how to make data available is very varied among the respondents. The questionnaire responses contain a wide range of individual solutions to make the information available. A majority of researchers believe that the work with data management and accessibility has increased over the past 5 years. As an obstacle to working more with this is time, but there are also other obstacles. The researchers are seeking additional support that can be summarized as: support, technical guidance, storage, information, time and money.
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| 49. |
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| 50. |
- Josephson, Filip, et al.
(författare)
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Treatment of HIV infection: Swedish recommendations 2009.
- 2009
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Ingår i: Scandinavian journal of infectious diseases. - : Informa UK Limited. - 1651-1980 .- 0036-5548. ; 41:11-12, s. 788-807
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Forskningsöversikt (refereegranskat)abstract
- On 4 previous occasions, in 2002, 2003, 2005 and 2007, the Swedish Medical Products Agency (Läkemedelsverket) and the Swedish Reference Group for Antiviral Therapy (RAV) have jointly published recommendations for the treatment of HIV infection. In November 2008, an expert group under the guidance of RAV once more revised the guidelines, of which this is a translation into English. The most important updates in the present guidelines include the following: (a) treatment initiation is now recommended at a CD4 cell count of approximately 350/microl; (b) new recommendations for first-line therapy: abacavir/lamivudine or tenofovir/emtricitabine in combination with efavirenz or a boosted protease inhibitor (PI/r); (c) an increased focus on reducing the use of antiretroviral drugs that may cause lipoatrophy; (d) an emphasis on quality assurance of HIV care through the use of InfCare HIV; (e) considerably altered recommendations for the initiation of antiretroviral therapy in children. All infants (<1 y) should start antiretroviral therapy, regardless of immune status. Also, absolute CD4+ cell counts, rather than percentage, may be used to guide treatment initiation in children above the age of 5 y.
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