Modern Thermal Anomalies Within Former Polish Borders

W opracowaniu dokonano porównania częstości i rodzaju anomalii termicznych na historycznych ziemiach polskich na podstawie źródeł historycznych (X-XVI wiek) i danych pomiarowych (1951-2015). Stwierdzono odpowiednio 56 epizodów zimnych (głównie zimy) i 14 epizodów ciepłych (przeważnie lata) oraz 21 miesięcy anomalnie zimnych i 22 anomalnie ciepłe. Ich rozkład w czasie potwierdził znane z innych źródeł zmiany wiekowe klimatu w środkowej Europie, w tym szczególnie początek małej epoki lodowej (XV wiek) i nasilające się współczesne ocieplenie (od końca XX wieku).The study compares the frequency and type of thermal anomalies within former Polish borders (Fig. 1) using historical records (10th to 16th centuries) and data derived from actual measurements (1951-2015). Altogether 56 cold episodes (mainly winters, Table 1) and 14 warm episodes (mainly summers, Table 2) were identified, as well as 21 anomalously cold months and 22 anomalously warm months (Tables 3 and 4). The occurrence of strong disturbances in the annual air temperature profile in the form of exceptionally cold and exceptionally warm months and seasons is a natural feature of the European climate, especially in the central parts of the continent where the features of the dominant moderate climate involve transiency between maritime and continental influences. While their absolute frequency is low, the most frequent of such anomalies fall at the extreme ends of the spectrum, i.e. exceptionally cold winter months and exceptionally hot summer months. They even occur during long spells of an opposite type of climate, i.e. exceptionally hot summers during the Little Ice Age and exceptionally severe winters during the latest warming period. Despite this apparent paradox, the second conclusion that the study makes is an expected increase in the frequency of negative anomalies during cool periods and an analogous increase in positive anomalies during warm periods. This is evident in an increased number of severe winters during the early phase of the Little Ice Age, which is higher in comparison to that during the preceding period and during warm spells. The current warming period, especially the last 25 years, is marked by an exceptional dominance of hot and warm months both in comparison to the preceding period and to the number of anomalously cold months during the same warming period. The comparison made in this study of the frequency of anomalously cold and anomalously warm spells (months and seasons) recorded in historical sources (10th-16th c.) and noted from measurements (20th-21st c.) within former Polish borders has demonstrated that these spells correctly reflect longer-term climatic changes known from other sources