| 1. |
- 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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| 2. |
- Drobyshev, Igor, et al.
(författare)
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Atlantic SSTs control regime shifts in forest fire activity of Northern Scandinavia
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the drivers of the boreal forest fire activity is challenging due to the complexity of the interactions driving fire regimes. We analyzed drivers of forest fire activity in Northern Scandinavia (above 60 N) by combining modern and proxy data over the Holocene. The results suggest that the cold climate in northern Scandinavia was generally characterized by dry conditions favourable to periods of regionally increased fire activity. We propose that the cold conditions over the northern North Atlantic, associated with low SSTs, expansion of sea ice cover, and the southward shift in the position of the subpolar gyre, redirect southward the precipitation over Scandinavia, associated with the westerlies. This dynamics strengthens high pressure systems over Scandinavia and results in increased regional fire activity. Our study reveals a previously undocumented teleconnection between large scale climate and ocean dynamics over the North Atlantic and regional boreal forest fire activity in Northern Scandinavia. Consistency of the pattern observed annually through millennium scales suggests that a strong link between Atlantic SST and fire activity on multiple temporal scales over the entire Holocene is relevant for understanding future fire activity across the European boreal zone.
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| 3. |
- 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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| 4. |
- 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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| 5. |
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| 6. |
- 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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| 7. |
- Leijonhufvud, Lotta, et al.
(författare)
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Five centuries of Stockholm winter/spring temperatures reconstructed from documentary evidenceand instrumental observations
- 2010
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Ingår i: Climatic Change. - Netherlands : Springer. - 0165-0009 .- 1573-1480. ; 101:1-2, s. 109-141
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Tidskriftsartikel (refereegranskat)abstract
- Historical documentary sources, reflecting different port activities in Stockholm, are utilised to derive a 500-year winter/spring temperature reconstruction for the region. These documentary sources reflect sea ice conditions in the harbour inlet and those series that overlap with the instrumental data correlate well with winter/spring temperatures. By refining dendroclimatological methods,the time-series were composited to a mean series and calibrated (1756–1841;r2 = 66%) against Stockholm January–April temperatures. Strong verification was confirmed (1842–1892; r2 = 60%; RE/CE = 0.55). By including the instrumental data, the quantified (QUAN) reconstruction indicates that recent two decades have been the warmest period for the last 500 years. Coldest conditions occurred during the 16th/17th and early 19th centuries. An independent qualitative (QUAL)historical index was also derived for the Stockholm region. Comparison between QUAN and QUAL shows good coherence at inter-annual time-scales, but QUAL distinctly appears to lack low frequency information. Comparison is also made to other winter temperature based annually resolved records for the Baltic region.Between proxy coherence is generally good although it decreases going back in time with the 1500–1550 period being the weakest period—possibly reflecting data quality issues in the different reconstructions.
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| 8. |
- Loader, Neil J., et al.
(författare)
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Spring temperature variability in northern Fennoscandia AD 1693–2011
- 2011
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Ingår i: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 26:6, s. 566-570
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Tidskriftsartikel (refereegranskat)abstract
- A reconstruction of spring (April–May) temperature for northern Fennoscandia developed from the Tornionjoki (Tornio river) long cryophenological record of ice break-up dates, back to AD 1693, is presented. The record is strongly climatically sensitive and explains 67% of the variance in the instrumental data over the last 150 years. The record exhibits a stepped decrease in the duration of the river's ice cover by 14 days, equivalent to an increase in April–May mean temperature of approximately 2.5°C over the last three centuries. The relationship between the date of ice break-up, and accumulated daily mean temperatures (>0°C) is investigated. Uncertainty in the observation of ice break-up is also considered in addition to the potential of this time series for regional climate model validation.
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| 9. |
- Luterbacher, Jürg, et al.
(författare)
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Circulation dynamics and its influence on European and Mediterranean January–April climate over the past half millennium : results and insights from instrumental data,documentary evidence and coupled climate models
- 2010
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Ingår i: Climatic Change. - Netherlands : Springer. - 0165-0009 .- 1573-1480. ; 101:1-2, s. 201-234
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Tidskriftsartikel (refereegranskat)abstract
- We use long instrumental temperature series together with available field reconstructions of sea-level pressure (SLP) and three-dimensional climate modelsimulations to analyze relations between temperature anomalies and atmospheric circulation patterns over much of Europe and the Mediterranean for the late winter/early spring (January–April, JFMA) season. A Canonical Correlation Analysis(CCA) investigates interannual to interdecadal covariability between a new gridded SLP field reconstruction and seven long instrumental temperature series covering the past 250 years. We then present and discuss prominent atmospheric circulation patterns related to anomalous warm and cold JFMA conditions within different European areas spanning the period 1760–2007. Next, using a data assimilation technique, we link gridded SLP data with a climate model (EC-Bilt-Clio) for a better dynamical understanding of the relationship between large scale circulationand European climate. We thus present an alternative approach to reconstruct climate for the pre-instrumental period based on the assimilated model simulations.Furthermore, we present an independent method to extend the dynamic circulation analysis for anomalously cold European JFMA conditions back to the sixteenth century. To this end, we use documentary records that are spatially representative for the long instrumental records and derive, through modern analogs, large-scale SLP, surface temperature and precipitation fields. The skill of the analog method is tested in the virtual world of two three-dimensional climate simulations (ECHOGand HadCM3). This endeavor offers new possibilities to both constrain climate model into a reconstruction mode (through the assimilation approach) and to better assess documentary data in a quantitative way.
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| 10. |
- Moberg, Anders, 1961-
(författare)
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Comments on ''Reconstruction of the Extratropical NH Mean Temperature over the Last Millennium with a Method That Preserves Low-Frequency Variability''
- 2012
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Ingår i: Journal of Climate. - 0894-8755 .- 1520-0442. ; 25:22, s. 7991-7997
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Christiansen and Ljungqvist have presented an extratropical NH temperature reconstruction using a method (LOC) that they claim ''preserves'' low-frequency variability, at the expense of exaggerated high-frequency variability. Using theoretical arguments and a pseudoproxy experiment, it is demonstrated here that the LOC method is not guaranteed to preserve variability at any frequency. Rather, LOC reconstructions will have more variance than true large-scale temperature averages at all frequencies. This variance inflation, however, can be negligible at those frequencies where the noise variance in individual proxies is small enough to be effectively cancelled when computing an average over the available proxies. Because the proxy noise variance at low frequencies cannot be directly estimated, and thus has to be regarded as unknown, it is safer to regard a reconstruction with the LOC method as providing an estimate of the upper bound of the large-scale low-frequency temperature variability rather than one with a correct estimate of this variance.
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