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Drought represents a prevalent climate risk in the Mediterranean region. In the context of climate change, an increase in both frequency and intensity is anticipated over the next century. In order to effectively manage future scenarios where global warming overlays natural climate variability, a thorough analysis of the nature of droughts prior to the industrial age is crucial. This approach incorporates an extended temporal scale into the study of severe droughts, enabling the identification of low-frequency drought events that occurred before the instrumental period. The objective of this study is to examine the occurrence and magnitude of extreme droughts lasting over a year in the Spanish Mediterranean basin during the early 19th century (1790–1830). To achieve this objective, the research integrates the use of instrumental observations and information derived from historical documentary sources with daily to monthly resolutions (e.g., rogation ceremonies). The findings reveal that drought episodes were more frequent and severe during the early 19th century compared to the late 19th century. Moreover, drought episodes of similar severity were rare throughout the 20th century. Only in the current context of climate change, over the last 2 decades, has a pattern of high drought severity been identified that resembles the severity found during the early 19th century (especially between 1812 and 1825). This study underscores the presence of high variability in drought patterns over the last few centuries, justifying the need for intensified research on drought episodes with high temporal resolution for extended periods.

The spatial context is critical when 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, spatio-temporal 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.

The winter 1788/89 was one of the coldest winters Europe had witnessed in the past 300 years. Fortunately, for historical climatologists, this extreme event occurred at a time when many stations across Europe, both private and as part of coordinated networks, were making quantitative observations of the weather. This means that several dozen early instrumental series are available to carry out an in-depth study of this severe cold spell. While there have been attempts to present daily spatial information for this winter, there is more to be done to understand the weather variability and day-to-day processes that characterised this weather extreme. In this study, we seek to reconstruct daily spatial high-resolution temperature and sea level pressure fields of the winter 1788/89 in Europe from November through February. The reconstruction is performed with an analogue resampling method (ARM) that uses both historical instrumental data and a weather type classification. Analogue reconstructions are then post-processed through an ensemble Kalman fitting (EnKF) technique. Validation experiments show good skill for both reconstructed variables, which manage to capture the dynamics of the extreme in relation to the large-scale circulation. These results are promising for more such studies to be undertaken, focusing on different extreme events and other regions in Europe and perhaps even further back in time. The dataset presented in this study may be of sufficient quality to allow historians to better assess the environmental and social impacts of the harsh weather.

Current climate modelling frameworks present significant uncertainties when it comes to quantifying flood quantiles in the context of climate change, calling for new information and strategies in hazard assessments. Here, state-of-the-art methods on hydraulic and statistical modelling are applied to historical and contemporaneous flood records to evaluate flood hazards beyond natural climate cycles. A comprehensive flood record of the Duero River in Zamora (Spain) was compiled from documentary sources, early water-level readings and continuous gauge records spanning the last 500 years. Documentary evidence of flood events includes minute books (municipal and ecclesiastic), narrative descriptions, epigraphic marks, newspapers and technical reports. We identified 69 flood events over the period 1250 to 1871, of which 15 were classified as catastrophic floods, 16 as extraordinary floods and 38 as ordinary floods. Subsequently, a two-dimensional hydraulic model was implemented to relate flood stages (flood marks and inundated areas) to discharges. The historical flood records show the largest floods over the last 500 years occurred in 1860 (3450 m3 s−1), 1597 (3200 m3 s−1) and 1739 (2700 m3 s−1). Moreover, at least 24 floods exceeded the perception threshold of 1900 m3 s−1 during the period (1500–1871). Annual maximum flood records were completed with gauged water-level readings (pre-instrumental dataset, PRE: 1872–1919) and systematic gauge records (systematic dataset, SYS: 1920–2018). The flood frequency analyses were based on (1) the expected moments algorithm (EMA) and (2) the maximum likelihood estimator (MLE) method, using five datasets with different temporal frameworks (historic dataset, HISTO: 1511–2018; PRE–SYS: 1872–2018; full systematic record, ALLSYS: 1920–2018; SYS1: 1920–1969; and SYS2: 1970–2018). The most consistent results were obtained using the HISTO dataset, even for high quantiles (0.001 % annual exceedance probability, AEP). PRE–SYS was robust for the 1 % AEP flood with increasing uncertainty in the 0.2 % AEP or 500-year flood, and ALLSYS results were uncertain in the 1 % and 0.2 % AEP floods. Since the 1970s, the frequency of extraordinary floods (>1900 m3 s−1) declined, although floods on the range of the historical perception threshold occurred in 2001 (2075 m3 s−1) and 2013 (1654 m3 s−1). Even if the future remains uncertain, this bottom-up approach addresses flood hazards under climate variability, providing real and certain flood discharges. Our results can provide a guide on low-regret adaptation decisions and improve public perception of extreme flooding.

Combining historical climatology and environmental history, this article examines the diverse range of strategies deployed by the city government of Barcelona (Catalonia, NE Spain) to confront the recurrent drought episodes experienced between 1626 and 1650. Our reconstruction of drought in Barcelona for the period 1525–1821, based on pro pluvia rogations as documentary proxy data, identifies the years 1626–1635 and the 1640s as the most significant drought events of the series (highest drought frequency weighted index and drought duration index). We then focus on the period 1601–1650, providing a timeline that visualises rain rogation levels in Barcelona at a monthly resolution. Against this backdrop, we examine institutional responses to drought and discuss how water scarcity was perceived and confronted by Barcelona city authorities. Among the several measures implemented, we present the ambitious water supply projects launched by the city government, together with the construction of windmills as an alternative to watermills, as a diversification strategy aimed at coping better with diminishing water flows. We pay special attention to the institutional efforts to codify the knowledge about Barcelona's water supply, which in 1650 resulted in the Book of Fountains of the City of Barcelona (Llibre de les Fonts de la Ciutat de Barcelona). This manual of urban water supply, written by the city water officer after 3 decades of experience in his post, constitutes a rare and valuable source to study water management history but also includes significant information to interpret historical climate. We analyse the production of this manual in the context of 3 decades marked by recurrent episodes of severe drought. We interpret the city government aspiration to codify knowledge about urban water supply as an attempt to systematise and store historical information on infrastructure to improve institutional capacities to cope with future water scarcities.

In the northeast of the Iberian Peninsula, few studies have reconstructed drought occurrence and variability for the pre-instrumental period using documentary evidence and natural proxies. In this study, we compiled a unique dataset of rogation ceremonies – religious acts asking God for rain – from 13 cities in the northeast of Spain and investigated the annual drought variability from 1650 to 1899 CE. Three regionally different coherent areas (Mediterranean, Ebro Valley, and Mountain) were detected. Both the Barcelona and the regional Mediterranean drought indices were compared with the instrumental series of Barcelona for the overlapping period (1787–1899), where we discovered a highly significant and stable correlation with the Standardized Precipitation Index of May with a 4-month lag (r=-0.46 and r=-0.53; p, respectively). We found common periods with prolonged droughts (during the mid and late 18th century) and extreme drought years (1775, 1798, 1753, 1691, and 1817) associated with more atmospheric blocking situations. A superposed epoch analysis (SEA) was performed showing a significant decrease in drought events 1 year after the volcanic events, which might be explained by the decrease in evapotranspiration due to reduction in surface temperatures and, consequently, the higher availability of water that increases soil moisture. In addition, we discovered a common and significant drought response in the three regional drought indices 2 years after the Tambora volcanic eruption. Our study suggests that documented information on rogation ceremonies contains important independent evidence to reconstruct extreme drought events in areas and periods for which instrumental information and other proxies are scarce. However, drought index for the mountainous areas (denoted Mountain later in the text) presents various limitations and its interpretation must be treated with caution.

The higher frequency of severe flood events in Switzerland in recent decades has given fresh impetus to the study of flood patterns and their possible forcing mechanisms, particularly in mountain environments. This paper presents a new index of summer flood damage that considers severe and catastrophic summer floods in Switzerland between 1800 and 2009, and explores the influence of external forcings on flood frequencies. In addition, links between floods and low-frequency atmospheric variability patterns are examined. The flood damage index provides evidence that the 1817–1851, 1881–1927, 1977–1990 and 2005–present flood clusters occur mostly in phase with palaeoclimate proxies. The cross-spectral analysis documents that the periodicities detected in the coherency and phase spectra of 11 (Schwabe cycle) and 104 years (Gleissberg cycle) are related to a high frequency of flooding and solar activity minima, whereas the 22-year cyclicity detected (Hale cycle) is associated with solar activity maxima and a decrease in flood frequency. The analysis of low-frequency atmospheric variability modes shows that Switzerland lies close to the border of the principal summer mode. The Swiss river catchments situated on the centre and southern flank of the Alps are affected by atmospherically unstable areas defined by the positive phase of the pattern, while those basins located in the northern slope of the Alps are predominantly associated with the negative phase of the pattern. Furthermore, a change in the low-frequency atmospheric variability pattern related to the major floods occurred over the period from 1800 to 2009; the summer principal mode persists in the negative phase during the last cool pulses of the Little Ice Age (1817–1851 and 1881–1927 flood clusters), whereas the positive phases of the mode prevail during the warmer climate of the last 4 decades (flood clusters from 1977 to present).

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.

"Prediflood" is a database of historical floods that occurred in Catalonia (NE Iberian Peninsula), between the 11th century and the 21st century. More than 2700 flood cases are catalogued, and more than 1100 flood events. This database contains information acquired under modern historiographical criteria and it is, therefore, suitable for use in multidisciplinary flood analysis techniques, such as meteorological or hydraulic reconstructions.

Rapid advection of extremely warm and dry air is studied during two events in the Mediterranean Basin. On 27 August 2010 a rapid advection of extremely warm and dry air affected the northeast Iberian Peninsula during a few hours. At the Barcelona city center, the temperature reached 39.3 ° C, which is the maximum temperature value recorded during 230 yr of daily data series. On 23 March 2008 a rapid increase of temperature and drop of relative humidity were recorded for a few hours in Heraklion (Crete). During the morning on that day, the recorded temperature reached 34 °C for several hours on the northern coastline of this island. According to the World Meteorological Organization none of these events can be classified as a heat wave, which requires at least two days of abnormally high temperatures; neither are they a heat burst as defined by the American Meteorological Society, where abnormal temperatures take place during a few minutes. For this reason, we suggest naming this type of event flash heat. By using data from automatic weather stations in the Barcelona and Heraklion area and WRF mesoscale numerical simulations, these events are analyzed. Additionally, the primary risks and possible impacts on several fields are presented.

Among the different meteorological hazards, droughts are those with the highest socio-economical impact on the Iberian Peninsula. Drought events have been largely studied in the instrumental period, but very little is known about the characteristics of droughts in the preinstrumental period. In this work, several series of rogation ceremonies are used to identify severe droughts within the period 1750–1850. The overlapping of the rogation series with some instrumental series served to identify some climatic characteristics of rogation ceremonies: (a) during spring, rainfall deficits needed to celebrate rogation ceremonies are smaller than in any other season; (b) the hydrological deficit in a particular region increases with the number of locations celebrating rogations simultaneously. On the other hand, it was found that between 1750–1754 and 1779–1783 are probably the driest periods of the 101 analyzed years. Both show an important number of rogations all over Iberia and during all the seasons. The most extended drought of this period occurred during the spring of 1817, affecting 15 of the 16 locations studied. This drought was influenced by the Tambora eruption (1815). The study of the climate footprint of this eruption and its comparison with similar situations in the series suggest that the spring drought of 1824 may be associated with the eruptions of the Galunggung and Usu volcanoes (1822). Further studies are required to confirm this fact and understand the atmospheric mechanisms involved.

In this paper, series of drought occurrence and drought extension in the Iberian Peninsula are constructed for the 1600–1750 period from seven rogation series. These rogation ceremony records come from Bilbao, Catalonia, Zamora, Zaragoza, Toledo, Murcia and Seville. They are distributed across the Peninsula and include the areas with the most characteristic Iberian climate types, influenced by the Atlantic and the Mediterranean conditions, described from modern data. A seasonal division of the series shows that spring is a critical season for rogation series in most of Iberia, being Bilbao the only site were the highest number of rogations is detected for a different season. The annual analysis of the series shows a dramatic difference between the first half of the 17th century when droughts are characterized by its local character; and the rest of the period, when they affect to broader regions or even to the whole Peninsula. The analysis of spring series confirms the existence of the two periods detected in the annual analysis. Finally, secondary documentary sources are used to further characterise the two most extended droughts in the period, 1664 and 1680, and to verify the extension of the areas affected by droughts recorded through rogation series.

Every year, flash floods cause economic losses and major problems for undertaking daily activity in the Catalonia region (NE Spain). Sometimes catastrophic damage and casualties occur. When a long term analysis of floods is undertaken, a question arises regarding the changing role of the vulnerability and the hazard in risk evolution. This paper sets out to give some information to deal with this question, on the basis of analysis of all the floods that have occurred in Barcelona county (Catalonia) since the 14th century, as well as the flooded area, urban evolution, impacts and the weather conditions for any of most severe events. With this objective, the identification and classification of historical floods, and characterisation of flash-floods among these, have been undertaken. Besides this, the main meteorological factors associated with recent flash floods in this city and neighbouring regions are well-known. On the other hand, the identification of rainfall trends that could explain the historical evolution of flood hazard occurrence in this city has been analysed. Finally, identification of the influence of urban development on the vulnerability to floods has been carried out. Barcelona city has been selected thanks to its long continuous data series (daily rainfall data series, since 1854; one of the longest rainfall rate series of Europe, since 1921) and for the accurate historical archive information that is available (since the Roman Empire for the urban evolution). The evolution of flood occurrence shows the existence of oscillations in the earlier and later modern-age periods that can be attributed to climatic variability, evolution of the perception threshold and changes in vulnerability. A great increase of vulnerability can be assumed for the period 1850–1900. The analysis of the time evolution for the Barcelona rainfall series (1854–2000) shows that no trend exists, although, due to changes in urban planning, flash-floods impact has altered over this time. The number of catastrophic flash floods has diminished, although the extraordinary ones have increased.

In this paper the catastrophic and extraordinary floods occurring in Barcelona County (Catalonia, NE Spain) are studied, in order to characterise the temporal evolution of extreme flash floods in that area and their main features. These events usually cause economical losses and major problems for undertaking daily activity in Barcelona city. This kind of floods is a very common feature in the North-east of Spain and they are recorded every year in some point of Catalonia. This contribution also shows the frequency of those events, within the framework of all the floods that have occurred in Barcelona since the 14th century, but also describes the flooded area, urban evolution, impacts and the weather conditions for any of most severe events. The evolution of flood occurrence shows the existence of oscillations in the earlier and later modern age periods that can be attributed to climatic variability, evolution of the perception threshold and changes in vulnerability. A great increase of vulnerability can be assumed for the period 1850-1900. The analysis of the time evolution for the Barcelona rainfall series (1854-2000) shows that no trend exists, although, due to the changes in urban planning, flash-floods impact has changed over this time. The number of catastrophic flash floods has diminished, although the extraordinary ones have increased.

Interdisciplinary frameworks for studying natural hazards and their temporal trends have an important potential in data generation for risk assessment, land use planning, and therefore the sustainable management of resources. This paper focuses on the adjustments required because of the wide variety of scientific fields involved in the reconstruction and characterisation of flood events for the past 1000 years. The aim of this paper is to describe various methodological aspects of the study of flood events in their historical dimension, including the critical evaluation of old documentary and instrumental sources, flood-event classification and hydraulic modelling, and homogeneity and quality control tests. Standardized criteria for flood classification have been defined and applied to the Isère and Drac floods in France, from 1600 to 1950, and to the Ter, the Llobregat and the Segre floods, in Spain, from 1300 to 1980. The analysis on the Drac and Isère data series from 1600 to the present day showed that extraordinary and catastrophic floods were not distributed uniformly in time. However, the largest floods (general catastrophic floods) were homogeneously distributed in time within the period 1600–1900. No major flood occurred during the 20th century in these rivers. From 1300 to the present day, no homogeneous behaviour was observed for extraordinary floods in the Spanish rivers. The largest floods were uniformly distributed in time within the period 1300–1900, for the Segre and Ter rivers.

Daily meteorological records for Barcelona, Spain, start unofficially in 1780. The records are of very good quality, although the metadata are far from complete. This study gives the general characteristics of the daily instrumental records, details of the data sources together with the reconstruction of the daily and monthly pressure series. In the second part of this paper, a separate time series made up of three (deterministic, periodic and random) components is analysed, and a methodological approach based on the cumulative deviation from the mean is then used to homogenize the monthly pressure series. Published in 2001 by John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Monthly grid-point pressure data are reconstructed from station records of pressure for Europe since 1780. The region encompasses 35–70oN to 30oW–40oE. 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. Copyright © 1999 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

There are concerns that recent climate change is altering the frequency and magnitude of river floods in an unprecedented way 1 . Historical studies have identified flood-rich periods in the past half millennium in various regions of Europe 2 . However, because of the low temporal resolution of existing datasets and the relatively low number of series, it has remained unclear whether Europe is currently in a flood-rich period from a long-term perspective. Here we analyse how recent decades compare with the flood history of Europe, using a new database composed of more than 100 high-resolution (sub-annual) historical flood series based on documentary evidence covering all major regions of Europe. We show that the past three decades were among the most flood-rich periods in Europe in the past 500 years, and that this period differs from other flood-rich periods in terms of its extent, air temperatures and flood seasonality. We identified nine flood-rich periods and associated regions. Among the periods richest in floods are 1560-1580 (western and central Europe), 1760-1800 (most of Europe), 1840-1870 (western and southern Europe) and 1990-2016 (western and central Europe). In most parts of Europe, previous flood-rich periods occurred during cooler-than-usual phases, but the current flood-rich period has been much warmer. Flood seasonality is also more pronounced in the recent period. For example, during previous flood and interflood periods, 41 per cent and 42 per cent of central European floods occurred in summer, respectively, compared with 55 per cent of floods in the recent period. The exceptional nature of the present-day flood-rich period calls for process-based tools for flood-risk assessment that capture the physical mechanisms involved, and management strategies that can incorporate the recent changes in risk.

Reliable and complete knowledge of the historical floods is necessary for understanding the extreme hydrological dynamics of the rivers, their natural variability and anthropic changes. In this work we reconstruct the most important floods of the Ebro basin during the last 400 years in different areas of the basin. The analysis is based on four different areas: the Ebro River at Zaragoza, the Cinca River at Fraga, the Segre River at Lleida, and the Ebro River near its mouth at Tortosa. Based on a documentary research, we have first obtained relevant information about the initial conditions (rainfall duration and distribution, snow cover influence) and the maximum flood heights that allow to reconstruct the maximum peak flows by using hydraulic models and to calculate the subbasins contributions. The results show four main types of extreme floods: a) those affecting simultaneously all the subbasins with the highest peak discharges (Ebro at Tortosa in 1787: 0.15 m 3  s -1  km -2 ); b) those originated at the western basin, upstream from Zaragoza, with an Atlantic origin, presenting moderate maximum peak flows, caused by persistent winter rainfall and where snowmelt significantly contributes to the flood; c) those originating at the central Pyrenean subbasins, with Mediterranean origin, occurring, with high peak discharges. These mainly occur during autumn as a consequence of rainfalls of different duration (between 3 days and 1 month), and without significant snow thawing and d) finally, less frequent but very intense flash floods events centered in the Lower Ebro area with low peak flows. In terms of frequency, two different periods can be distinguished: from 1600 until 1850, the frequency of events is low; since 1850 the frequency of events is clearly higher, due to an increase of the climatic variability during last stages of the Little Ice Age. From the 1960's reservoirs construction modifies discharges regime., (Copyright © 2018 Elsevier B.V. All rights reserved.)