Poland’s climate in the medieval period

Knowledge about the climate before AD 1500 (e.g. for the medieval period) is very limited for many areas of the world, including central Europe. The paper presents the latest state of knowledge on the climate of Poland (Central Europe) in the period 1001–1500. This is achieved using: i) quantitative climate reconstructions published in the past two decades, ii) three new reconstructions exploiting dendrochronological data, iii) one reconstruction based exploiting an updated and augmented database of historical source data on weather conditions. The annual growths of coniferous trees in lowland and upland Poland is highly dependent on the temperature at the end of winter and the beginning of spring, especially February and March. All available reconstructions based on dendrochronological data represent mainly this time of the year. A limited number of reconstructions exist for summer. They are based on biological proxies and documentary evidence, the latter being limited to the 15th century only. In Poland, annual mean temperature correlates with winter temperature more closely than with summer temperature. Winter temperatures can thus be used as annual proxies. The Medieval Warm Period (MWP; also called the Medieval Climate Anomaly) is estimated to have occurred in Poland from the late 12th century to the first half of either the 14th or 15th century. Analysis of all available quantitative reconstructions suggest that the MWP in Poland was comparable to or warmer than the current temperature (1951–2000). The first half of the 11th century (both winter and summer) and the second half of the 15th century (only winter) were the coldest periods in the Middle Ages. Very limited knowledge exists about the wetness of the seasons in Poland. Information is available only from documentary evidence and mainly for the 15th century. Weather notes describing precipitation conditions are most plentiful for summer and then for winter. A very limited number exists for the transitional seasons.             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 the area of Europe. The work was supported by the National Science Centre, Poland project No. 2020/37/B/ST10/00710.