Mariano Barriendos

Trends of Extreme Temperatures in Europe and China Based on Daily Observations

Ten of the longest daily temperature series presently available in Europe and China are analysed, focusing on changes in extremes since pre-industrial times. We consider extremes in both a relative (with respect to the time of year) and an absolute sense. To distinguish changes in extremes from changes affecting the main part of the temperature distribution, a percentile smaller than 10 (and/or larger than 90) is recommended for defining an extreme. Three periods of changes in temperature extremes are identified: decreasing warm extremes before the late 19th century; decreasing cold extremes since then and increasing warm extremes since the 1960s. The early decreases and recent increases of warm extremes dominate in summer, while the decrease of cold extremes for winter persists throughout the whole period. There were more frequent combined (warm plus cold) extremes during the 18th century and the recent warming period since 1961 at most of the ten stations, especially for summer. Since 1961, the annual frequency of cold extremes has decreased by about 7% per century with warm extremes increasing by more than 10% per century but with large spatial variability. Compared with recent annual mean warming of about 2–3 ° C/century, the coldest winter temperatures have increased atthree times this rate, causing a reduced within-season range and therefore less variable winters. Changes in the warmest summer temperatures since 1961 exhibit large spatial variability, with rates of change ranging from slightly negative to 6 ° C/century. More extensive station observations since 1961 indicate that the single site results are representative of larger regions, implying also that the extremes studied are the result of large-scale changes. Recent circulation changes in daily gridded pressure data, used as an indicator of wind speed changes, support the results by explaining some of the trends.

Chapter 1 Mediterranean climate variability over the last centuries: A review

Publisher Summary This chapter discusses a necessary task for assessing to which degree the industrial period is unusual against the background of pre-industrial climate variability. It is the reconstruction and interpretation of temporal and spatial patterns of climate in earlier centuries. There are distinct differences in the temporal resolution among the various proxies. Some of the proxy records are annually or even higher resolved and hence record year-by-year patterns of climate in past centuries. Several of the temperature reconstructions reveal that the late twentieth century warmth is unprecedented at hemispheric scales and is explained by anthropogenic, greenhouse gas (GHG) forcing. The chapter discusses the availability and potential of long, homogenized instrumental data, documentary, and natural proxies to reconstruct aspects of past climate at local- to regional-scales within the larger Mediterranean area, which includes climate extremes and the incidence of natural disasters. The chapter describes the role of external forcing, including natural and anthropogenic influences, and natural, internal variability in the coupled ocean–atmosphere system at subcontinental scale.

Daily mean sea level pressure reconstructions for the European-North Atlantic region for the period 1850-2003

Abstract The development of a daily historical European–North Atlantic mean sea level pressure dataset (EMSLP) for 1850–2003 on a 5° latitude by longitude grid is described. This product was produced using 86 continental and island stations distributed over the region 25°–70°N, 70°W–50°E blended with marine data from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS). The EMSLP fields for 1850–80 are based purely on the land station data and ship observations. From 1881, the blended land and marine fields are combined with already available daily Northern Hemisphere fields. Complete coverage is obtained by employing reduced space optimal interpolation. Squared correlations (r 2) indicate that EMSLP generally captures 80%–90% of daily variability represented in an existing historical mean sea level pressure product and over 90% in modern 40-yr European Centre for Medium-Range Weather Forecasts Re-Analyses (ERA-40) over most of the region. A lack of sufficient observations over Greenland and...

Monthly mean pressure reconstructions for Europe for the 1780–1995 period

Monthly grid-point pressure data are reconstructed from station records of pressure for Europe since 1780. The region encompasses 35-70°N to 30°W-40°E. The reconstructions are based on a principal components regression technique, which relates surface pressure patterns to those of the station pressure data. The relationships are derived over a calibration period (1936-1995) and the results tested with independent data (the verification period, 1881-1935). The reconstructions are of excellent quality, although this is slightly lower for regions with poor station coverage in the early years, particularly during the summer months. The reconstructions are compared with other monthly mean pressure maps produced by Lamb and Johnson (1966) for the years 1780-1872 and by Kington (1980, 1988) for 1781-1785. Both of these map series show systematic biases relative to the present reconstructions.

European summer temperatures since Roman times

The spatial context is criticalwhen assessing present-day climate anomalies, attributing them to potential forcings and making statements regarding their frequency and severity in a long-term perspective. Recent international initiatives have expanded the number of high-quality proxy-records and developed new statistical reconstruction methods. These advances allow more rigorous regional past temperature reconstructions and, in turn, the possibility of evaluating climate models on policy-relevant, spatiotemporal scales. Here we provide a new proxy-based, annually-resolved, spatial reconstruction of the European summer (June-August) temperature fields back to 755 CE based on Bayesian hierarchical modelling (BHM), together with estimates of the European mean temperature variation since 138 BCE based on BHM and composite-plus-scaling (CPS). Our reconstructions compare well with independent instrumental and proxy-based temperature estimates, but suggest a larger amplitude in summer temperature variability than previously reported. Both CPS and BHM reconstructions indicate that the mean 20th century European summer temperature was not significantly different from some earlier centuries, including the 1st, 2nd, 8th and 10th centuries CE. The 1st century (in BHM also the 10th century) may even have been slightly warmer than the 20th century, but the difference is not statistically significant. Comparing each 50 yr period with the 1951-2000 period reveals a similar pattern. Recent summers, however, have been unusually warm in the context of the last two millennia and there are no 30 yr periods in either reconstruction that exceed the mean average European summer temperature of the last 3 decades (1986-2015 CE). A comparison with an ensemble of climate model simulations suggests that the reconstructed European summer temperature variability over the period 850-2000 CE reflects changes in both internal variability and external forcing on multi-decadal time-scales. For pan-European temperatures we find slightly better agreement between the reconstruction and the model simulations with high-end estimates for total solar irradiance. Temperature differences between the medieval period, the recent period and the Little Ice Age are larger in the reconstructions than the simulations. This may indicate inflated variability of the reconstructions, a lack of sensitivity and processes to changes in external forcing on the simulated European climate and/or an underestimation of internal variability on centennial and longer time scales.

Documentary Evidence on Climate in Sixteenth-Century Europe

The known documentary climatic evidence from six European countries - Switzerland, Germany, the Czech Republic, ancient Hungary, Italy and Spain - is presented and classified in this article and then further analyzed in subsequent papers included in this volume. The sixteenth century witnessed an increase in the number and variety of sources in Switzerland, Germany and the Czech Republic as well as in the western and northern parts of ancient Hungary (present Slovakia). In northern Italy, the relevant sources are more abundant and widespread than in central Europe, but they have hardly been explored. Town chronicles written by members of the literate elite comprise the basic type of evidence in central Europe (including northern Italy and Hungary). This kind of source reports exceptional climatic events (e.g. anomalies and natural disasters) along with their impact on the environment and on society. Documentary data are the only evidence known to exist for reconstructing time series of natural disasters prior to the twentieth century. In order to document the extreme character of an event, chroniclers frequently referred to features in the cryosphere, biosphere or hydrosphere that were known to be more accurate yardsticks of temperature and precipitation patterns than subjective impressions. When records of such events are compiled with the description of some of the known effects, the results can be transformed into a severity index. Whereas chroniclers usually focused upon extreme events, long, continuous and seemingly homogeneous series of different kinds of proxy data are drawn from administrative records. Most of them are connected to the timing of certain kinds of agricultural work (hay-making, beginning of grain harvest or vintage) or to the amount and quality of agricultural production (per hectare yield of vineyards, sugar content of wine, etc.). In most cases the timing of these works was found to be directly related to temperature patterns over the preceding months and weeks.All the Iberian peninsula towns, which had an institutionalized municipal authority, have preserved documents generated from the late Middle Ages. These records frequently contain references to floods and meteorological anomalies such as droughts and long wet spells. They also include mention of the system of rogations, those religious rites performed in a standardized way within the Spanish world with a view to putting an end to an alleged meteorological stress.The data for Switzerland, Hungary and Spain as well as much of the data for Germany are stored in the EURO-CLIMHIST database set up at the Institute of History at the University of Bern. At present, EURO-CLIMHIST comprises some 600,000 data for the period from AD 750 to the beginning of the period of instrumental networks. About 120,000 records for Germany are currently stored in a data bank called HISKLID located at the Department of Geography of the University of Würzburg. The database for the Czech Republic includes records for the time-span AD 975-1900 and is housed with the Department of Geography of Masaryk University in Brno. Data on Italy were collected with different purposes and are stored in two data banks, the CNR-ICTIMA (climatic data and natural disasters) and the SGA (extreme events).

Flood Events of Selected European Rivers in the Sixteenth Century

The severity and frequency of sixteenth-century floods of the Rhine, the Main, the middle and upper Elbe with its tributaries, rivers of northern and central Italy, the Garonne and rivers in Catalonia and Andalusia are analyzed using documentary evidence. The basic topographical and hydrological characteristics of the rivers investigated as well as the synoptic causes of their flooding during the instrumental period are presented. Different examples of modifications of the run-off process due to anthropogenic activity are discussed. Prevalence in flood occurrence during the second half of the sixteenth century in comparison to the first half is typical for central European and Andalusian rivers (mainly in the 1560s and 1590s) and agrees with the evolution of precipitation patterns. On the other hand, Italian and Catalonian rivers, in part, had a higher occurrence of floods during the first half of the century. Changes in the flooding seasons in both halves of the century are not unambiguous. Results of an analysis on a broader European scale show floods to be a random natural phenomena with limited areal extent defined by the spatial influence of forcing meteorological factors (continuous heavy rains, sudden melting of thick snow cover, etc.). Despite some limitations of documentary evidence, series of reconstructed historical floods are valuable sources of proxy data which can be utilized for the study of the flooding fluctuations in the pre-instrumental period.

Study of historical flood events on Spanish rivers using documentary data

Abstract Series of reconstructed historical floods are valuable sources of proxy data that can be utilized for the study of flooding fluctuations in the pre-instrumental period. In this work, the severity and frequency of historical flood events in different Spanish rivers are analysed using documentary evidence. The occurrence of floods in the past is analysed bearing in mind the basic topographical and hydrological characteristics of the rivers investigated, as well as the climatological causes of their flooding during the instrumental period. Flood frequency oscillations identified in the present work coincide in general terms with already detected oscillations in previous research for shorter number of chronologies. Analysis for events covering more than two basins shows a relatively small number of cases. Meanwhile, as the climatic context produces simultaneous increases in frequency, geographical characteristics provoke a limitation on the extension of flood impacts during every severe weather event.

The Case of the `Maldá' Anomaly in the Western Mediterranean Basin (AD 1760–1800): An Example of a Strong Climatic Variability

The study of climatic anomalies on the basis of various types of instrumental information and proxy-data allows unusual events to be identified. The objective of this paper is to introduce and explain a hydrometeorological anomaly that occurred between 1760 and 1800 (Maldá Anomaly), characterised by a sequence of both anomalous droughts and floods, and to compare it with the features of the second part of the 20th century. Firstly, some climatic indices obtained from proxy-data (mainly documentary sources) have been generated. Secondly, instrumental observations made in earlier times, in conjunction with data from the bibliography, have been used in order to relate this period to the different circulation patterns and to analyse the geographical extension of the anomaly. The results confirm the presence of considerable variations in the atmospheric action centres, especially between 1780 and 1795, which in the Western Mediterranean gave rise to a simultaneous increase in the frequency of droughts and heavy rainfalls, either having nothing comparable or sharing similarities with periods in the 19th and 20th centuries.

Monthly mean pressure reconstruction for the Late Maunder Minimum Period (AD 1675–1715)

The Late Maunder Minimum (LMM; 1675-1715) delineates a period with marked climate variability within the Little Ice Age in Europe. Gridded monthly mean surface pressure fields were reconstructed for this period for the eastern North Atlantic-European region (25°W-30°E and 35-70°N). These were based on continuous information drawn from proxy and instrumental data taken from several European data sites. The data include indexed temperature and rainfall values, sea ice conditions from northern Iceland and the Western Baltic. In addition, limited instrumental data, such as air temperature from central England (CET) and Paris, reduced mean sea level pressure (SLP) at Paris, and monthly mean wind direction in the Oresund (Denmark) are used. The reconstructions are based on a canonical correlation analysis (CCA), with the standardized station data as predictors and the SLP pressure fields as predictand. The CCA-based model was performed using data from the twentieth century. The period 1901-1960 was used to calibrate the statistical model, and the remaining 30 years (1961-1990) for the validation of the reconstructed monthly pressure fields. Assuming stationarity of the statistical relationships, the calibrated CCA model was then used to predict the monthly LMM SLP fields. The verification results illustrated that the regression equations developed for the majority of grid points contain good predictive skill. Nevertheless, there are seasonal and geographical limitations for which valid spatial SLP patterns can be reconstructed. Backward elimination techniques indicated that Paris station air pressure and temperature, CET, and the wind direction in the Oresund are the most important predictors, together sharing more than 65% of the total variance. The reconstructions are compared with additional data and subjectively reconstructed monthly pressure charts for the years 1675-1704. It is shown that there are differences between the two approaches. However, for extreme years the reconstructions are in good agreement.