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The article presents the current state of knowledge on climate change in Poland (Central Europe) in the first half of the last millennium (1001-1500). To this end, it employs all available quantitative climate reconstructions created in the last two decades and four new reconstructions using three dendrochronological series and an extensive database of historical source data on weather conditions. The growth of conifers in lowland and upland Poland depends on the temperature in the cold season, especially in February and March. All available reconstructions based on dendrochronology date represent this time of the year. Summer temperatures were reconstructed using biological proxies and documentary evidence. The latter, however, is limited to the 15th century only. Winter temperature was used as the proxy for annual temperature proxies instead of the more usual use of summer temperature. The Medieval Warm Period (MWP; also called the Medieval Climate Anomaly [MCA]) occurred in Poland probably from the late 12th century to the first halves of the 14th or 15th centuries. All the analysed quantitative reconstructions suggest that the MWP in Poland was comparable to or warmer than the current temperature (1951-2000). The coldest conditions in the entire study period were noted in the first half of the 11th century (both winter and summer) and the second half of the 15th century (only winter). The greatest climate continentality occurred in the 15th century. Good agreement was found between the reconstructions of Poland's climate and many reconstructions available for Europe. [ABSTRACT FROM AUTHOR]

Based on three drought indices (SPI, SPEI, Z-index) reconstructed from documentary evidence and instrumental records, the summers of 1531–1540 were identified as the driest summer decade during the 1501–2015 period in the Czech Lands. Based on documentary data, extended from the Czech scale to central Europe, dry patterns of various intensities (represented, for example, by dry spells, low numbers of precipitation days, very low rivers, and drying-out of water sources) occurred in 1532, 1534–1536, 1538, and particularly 1540, broken by wetter or normal patterns in 1531, 1533, 1537, and 1539. Information relevant to summer droughts extracted from documentary data in central Europe was confirmed in summer precipitation totals from a multi-proxy reconstruction for Europe by Pauling et al. (2006) and further by self-calibrated summer Palmer Drought Severity Index (PDSI) reconstruction from tree ring widths in Old World Drought Atlas (OWDA) by Cook et al. (2015). The summer patterns described are consistent with the distribution of sea level pressure deviations from a modern reference period. Summer droughts were responsible for numerous negative impacts, such as bad harvests of certain crops, reduction and lack of water sources, and frequent forest fires, while in the wetter summers central Europe was affected by floods. However, there are no indications of severe impacts of a multi-country or multi-year effect. Reconstructions based on documentary data indicate that the summers of 1531–1540 constitute the driest summer decade in central Europe for the past five centuries between 1501 and 2010 CE. [ABSTRACT FROM AUTHOR]

The history of drought occurrence in Poland in the last millennium is poorly known. To improve this knowledge we have conducted a comprehensive analysis using both proxy data (documentary and dendrochronological) and instrumental measurements of precipitation. The paper presents the main features of droughts in Poland in recent centuries, including their frequency of occurrence, coverage, duration, and intensity. The reconstructions of droughts based on all the mentioned sources of data covered the period 996–2015. Examples of megadroughts were also chosen using documentary evidence, and some of them were described. Various documentary sources have been used to identify droughts in the area of Poland in the period 1451–1800 and to estimate their intensity, spatial coverage, and duration. Twenty-two local chronologies of trees (pine, oak, and fir) from Poland were taken into account for detecting negative pointer years (exceptionally narrow rings). The delimitation of droughts based on instrumental data (eight long-term precipitation series) was conducted using two independent approaches (Standard Precipitation Index, SPI, calculated for 1-, 3-, and 24-month timescales, and a new method proposed by authors). For delimitation of droughts (dry months), the criteria used were those proposed by McKee et al. (1993) and modified for the climate conditions of Poland by Łabędzki (2007). More than 100 droughts were found in documentary sources in the period 1451–1800, including 17 megadroughts. A greater than average number of droughts were observed in the second halves of the 17th century and the 18th century in particular. Dendrochronological data confirmed this general tendency in the mentioned period. Analysis of SPI (including its lowest values, i.e. droughts) showed that the long-term frequency of droughts in Poland has been stable in the last two or three centuries. Extreme and severe droughts were most frequent in the coastal part of Poland and in Silesia. Most droughts had a duration of 2 months (about 60 %–70 %) or 3–4 months (10 %–20 %). Frequencies of droughts with a duration of 5-or-more months were lower than 10 %. The frequency of droughts of all categories in Poland in the instrumental period 1722–2015 was greatest in winter, while in the documentary evidence (1451–1800) droughts in this season are rarely mentioned. The occurrence of negative pointer years (a good proxy for droughts) was compared with droughts delimited based on documentary and instrumental data. A good correspondence was found between the timing of occurrence of droughts identified using all three kinds of data (sources). [ABSTRACT FROM AUTHOR]

• A total of 166 floods were recorded in the study period. The greatest number (102, i.e. 61.4%) was noted in the 15th century. • Floods were registered most often for the Vistula River basin (84 cases). Significantly fewer floods (69) were observed in the Oder River basin. • The "above average or supra-regional floods" category was most common (77 cases) in Poland in the period 1001–1500 according to the classification of Brázdil et al. (2006). • The main reason for floods in Poland in the 11th–15th centuries was the three sub-types of rain (47.6%, 79 cases). Documentary evidence is increasingly being recognized as a precious source for assessing flood records. We have used this type of proxy data to identify the occurrence of floods in Poland from the 11th to the 15th centuries. In addition, we estimated the intensity of each flood event using the best-known classifications for Europe (Barriendos and Coeur, 2004; Brázdil et al., 2006) and assessed their origin based on modified Lambor's (1954) criteria. The database of floods in Poland contains 166 occurrences in the study period. Most occurred in the 15th century (61.4%). Of the studied regions, Silesia and the Baltic Coast and Pomerania regions were the two most affected by flood events, each accounting for 33–34% of instances. Based on the Brázdil et al. (2006) classification, 77 of the recorded floods are above-average or supra-regional. Also, the indexation of floods based on Barriendos and Coeur (2004) demonstrated that 99 were extraordinary flood events. Rain and its subtypes were the leading causes of floods, with 79 records (47.6%). Flood occurrence in Poland exhibited good spatial coherency with neighboring countries. The updated and most complete inventory of floods in medieval Poland that we present here with a detailed analysis of their frequency, intensity and origin, improves the existing knowledge about this phenomenon in Central Europe. The results of this study, similarly to many other previous studies, also confirm the great capacity for documentary evidence to provide valuable and reliable information about flood records for the pre-instrumental period. [ABSTRACT FROM AUTHOR]