Changes in thermal conditions in the northern part of the Mazovia (central Poland) between the late 19th and early 21st centuries

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The study uses two air temperature datasets: newly found and digitised dataset from a period 1881–1895 and a dataset from a nearby Institute of Meteorology and Water Management – National Research Institute (IMGW-PIB) weather station from a period 1951–2010. No statistically significant changes in mean daily air temperature (Tmean) were found between 1881–1895 and 1951–1980. The increase in Tmean of ca. 1.5°C was found between 1881–1895 and 1981–2010. As Płońsk is a small town this increase can be considered as unbiased by the Urban Heat Island intensification. The largest shift in the cumulative empirical distribution function of Tmean between both studied time periods was noted for the summer in the interval of values from 17.6 to 20.0°C and for the winter in the interval of values from 0.1 to 2.5°C The longest spells of days with a statistically significant warming were identified in mid-January (increase of at least 5.0°C between 13 and 16 January), late March – early April and in the first half of August (the longest spell of ten consecutive days). A significant reduction in a duration of the thermal winter (a reduction of 25 days) and extending of the summer (an increase of 17 days) were detected as well as the shift in the timing of transitional seasons. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1 Introduction Multi-year meteorological data sets, dating back to the 19th century and even earlier periods, make it possible to determine climate trends and oscillations from the end of the Little Ice Age to the present (Nordli et al. 2014 ; Pospieszyńska and Przybylak 2019 ). They also allow us to estimate the magnitude of modern warming (Piotrowicz 2009 ; Bryś and Bryś 2010 ; Kolendowicz et al. 2019 ). However, we should remember that today the longest operating weather stations are usually located in the urban areas while they were located in the suburban or rural areas in the 19th century. Therefore, the air temperature data sets may have a systematic bias caused by urbanization of the surrounding of the observational sites. The urbanization effect is believed to contribute 10% at best to the global land averaged air temperature centennial trend (Hartmann et al. 2014 ). This urbanization effect was, however, proved to be stronger in some regions by newer researches (Tysa et al. 2019 ; Zhang et al. 2021 ). Thus, meteorological data sets dating back to the 19th century and originating from small towns and villages are of a specially high value in the studies of the modern warming. In the case of central and eastern Poland, measurement series from stations operating as part of the so-called Warsaw network have an important but underestimated role in understanding the climatic conditions of the late 19th century. Meteorological measurements were performed from 1886 and sub-daily and daily data were collected from over a dozen weather stations located across the former Kingdom of Poland (also known as Congress Poland) and regions today located in Ukraine and Belarus. In 1910 the network comprised over 60 stations (Spostrzeżenia meteorologiczne… 1913). The weather data collected there were published in periodicals in the 19th century and at the beginning of the 20th century, especially in the Pamiętnik Fizyograficzny (1881,…,1913). Only a small part of these datasets was actually used in scientific studies. They included the first climate-related monographs of Poland (Romer 1912 ; Merecki 1915 ; Gorczyński and Kosińska 1916 ), and also contemporary studies of centennial changes of air temperature and precipitation in Warsaw and Łódź (Boryczka et al. 2000 ; Kożuchowski and Marciniak 1987 ; Siedlecki and Pawlak, 2004 ; Wibig et al. 2004 ). In this paper we assessed the changes in air temperature in Płońsk in the period between the end of the 19th century and the beginning of the 21st century. Płońsk is a small town with a population of ca. 21,500 people, located in the northern Mazovia region, central Poland. We focused our study not only on the annual, seasonal and monthly air temperature values but we also analysed changes in Tmean in consecutive days of a year, which has not been done in Polish Climate Change studies yet. 2 Data and methods The raw data taken into account in this study consisted of sub-daily values of air temperature obtained from two weather stations: Płońsk, Warsaw network station and Poświętne, station of the Institute of Meteorology and Water Management – National Research Institute (IMGW-PIB) (Fig. 1 ). The data were used to calculate the mean daily air temperature (Tmean). Tmean values were then used to compare the thermal conditions in the northern part of Mazovia region at the end of the 19th century to those in the second half of the 20th century and the beginning of the 21st century. In addition, mean annual air temperature data obtained from the Astronomical Observatory in Warsaw for the period 1826–1900 (after: Gorczyński and Kosińska 1916 ) were used in the study to assess the degree to which thermal conditions in the Mazovia region in the period 1881–1985 were typical in the context of the longer period 1826–1900. Air temperature data obtained from the Warsaw weather station for the period 1881–1895 were also used in the present study for the assessment of the homogeneity of the air temperature data set collected at Płońsk. sources: a) Mapa Szczegółowa Polski WIG, Pas 38, Słup 31, 1933, based on Russian mapping from 1885, from the MAPSTER website ( http://igrek.amzp.pl ), b) Topographic Map (WMS) ( https://www.geoportal.gov.pl ) The weather station in Płońsk was established ten years before the Warsaw network started to gather meteorological data (in 1875) at the initiative of a physician and amateur astronomer, Jan Walery Jędrzejewicz (Kowalczyk 1888 ). Jędrzejewicz died in December 1887 and new measurements were carried out by a new local physician – Leon Rutkowski – from January of the following year. He and his assistants carried out measurements intermittently until 1904. The results of these observations were published as monthly summaries in a journal called the Pamiętnik Fizyograficzny (1882,..., 1910). This study used a data set from the period 1881–1895 when the data were the most complete and of the highest quality. Missing data were found for individual days and two longer periods: in December 1887 and in June 1889 (a total of 67 days, 1.2% of all days in the surveyed period). The location of the station did not change during that period. However, the measurements were carried out at this point by two observers, which could affect the homogeneity of the data series. A median test was used to assess whether the annual mean air temperature values from the years 1881–1887 and 1888–1895 could be considered as coming from the same statistical population. The use of data from a relatively short, 15-year observation period also prompted us to check whether the thermal conditions in the years analysed differed remarkably from those noted in the Mazovia region in the entire 19th century. Air temperature for the weather station at Poświętne (φ − 52°38’N, λ − 20°23’E, h − 101 m a.s.l.) was obtained from the IMGW-PIB Public Data Portal ( https://danepubliczne.imgw.pl ). The study used data from 1951–1980 and 1981–2010 periods. The data set for the 1981 − 1980 time period was complete. In the time period 1981–2010 missing data were found in June 1989 and from April to July 2009; a total of 152 days of missing data, representing 1.4% of all days in the study period. At the Płońsk weather station measurements were carried out three times per day at times close to the so-called Mannheim hours – at 7:00 AM, 1:00 PM, and 9:00 PM local time. The Tmean was calculated according to the following formula: Tmean = (T 7 AM + T 1 PM + 2 · T 9 PM ) / 4 (1) Until 1970 measurements at the Poświętne weather station were taken at 7:00 AM, 1:00 PM, and 9:00 PM local time, the same as at the Płońsk weather station in the 19th century. The Tmean was also calculated in the same way. After 1970 the measurement times were changed to 6:00 AM, 12:00 PM, and 6:00 PM UTC, and the method of calculating the Tmean was changed twice. Since 1996 minimum and maximum temperatures (TN and TX) have been used in the calculation of Tmean. Thermometers used in the 19th century to measure TN and TX at the weather stations of the Warsaw network were unreliable, and the TN and TX series lacked much data. It was therefore not possible to calculate the Tmean for Płońsk for the 19th century according to contemporary methodologies. Instead, the value of Tmean for Poświętne after 1970 was recalculated using sub-daily air temperature data for 6:00 AM, 12:00 PM, and 6:00 PM UTC, and the formula was used until 1970. This made it possible to obtain a homogenous Tmean data set for both of the studied periods. The different methods of calculating Tmean are not the sole reason that could make it difficult to compare the data series from Płońsk and Poświętne from the late 19th century and the second half of the 20th and the beginning of the 21st centuries. The compared air temperature datasets come from two different sites. The station in Płońsk was established at the astronomical observatory of Jędrzejewicz, in the meadows in the River Płonka valley, on the north-eastern edge of the town (Jędrzejewicz 1882 ) (Fig. 1 A). Thermometers were placed in an open box protected from rain and snow by a zinc sheet. The box hung on the north-east wall of the observatory, which protected thermometers from direct sunlight. The mercury bulbs of the thermometers were affixed at 4.6 m above ground level (Jędrzejewicz 1880 ). The present-day weather station operating at Poświętne is located at a distance of approx. 1.0-1.2 km from the previous station. It is located on the outskirts of modern-day Płońsk similarly to the historical weather station. This is because the town has expanded and today buildings are located on both sides of the Płonka River valley (Fig. 1 B). Therefore, the location of the weather station has changed, but its surroundings remain similar. The station established in Płońsk by Jędrzejewicz was located in a river valley; the station operating at Poświętne is located in a flat area outside of it. Although both stations were established within different forms of relief, it is worth noting that the Płonka Valley is small and shallowly incised. The elevation difference between the two weather stations is only about 5 m. Differences in thermal conditions at these two points that may result from orographic effects are therefore assumed to be inconsiderable. Air temperature measurements performed at Poświętne in the period 1951–2010 were taken in an instrument shed at a standard height of 2 m above ground level, i.e., at a lower height than measurements taken in the 19th century. However, the thermal gradient above a height of 2 m above ground level is smaller than that in the surface layer. It was therefore assumed that the difference in the height of the thermometers did not strongly affect the readings taken off the thermometers. The comparison of thermal conditions in the area of Płońsk in the 1881–1895 time period and in the periods 1951–1980 and 1981–2010 made use of mean values (daily, monthly, annual), and the annual range of air temperature. Box plots of the mean monthly air temperature were prepared as well as histograms of the empirical distribution and empirical cumulative distribution function plots. The latter two were generated for each given meteorological season separately: winter (Dec-Feb), spring (Mar-May, summer (Jun-Aug) and autumn (Sep-Nov). The statistical significance of the differences found in mean values was tested using Student’s t-test or the Mann-Whitney U-test when the data distribution deviated significantly from the normal distribution. The normality of the tested distributions was checked using the Shapiro-Wilk test. The duration of thermal seasons (winter, early spring, spring, summer, autumn, early winter) was also compared for the time periods 1881–1895 and 1981–2010. The dates of thermal season onset were defined using three threshold values of air temperature proposed by Merecki for Central Europe (1915), namely 0.0°C, 5.0°C, and 15.0°C. The annual cycle of air temperature was smoothed out due to the occurrence of non-periodic fluctuations in Tmean, making it difficult to unambiguously indicate the day on which Tmean had exceeded a given threshold value. Values of the multiannual Tmean for subsequent days of the year were replaced with values calculated using harmonic analysis (Fortuniak et al. 1998 ). Calculated smoothed values of the mean air temperature for subsequent days of the year took into account the zero harmonic (A 0 ), i.e. annual mean air temperature and first (fundamental) harmonic. A calculation was performed for a 365-day series of Tmean using the formula: x’ ( t i ) = A 0 + A 1 cos (2 π f t i ) + B 1 cos (2 π f t i ), (2) where: x’ ( t i ) – air temperature calculated from the model for each consecutive day of the year t i (1…365), A 0 – mean annual air temperature, f – 1/365, A 1 i B 1 – Fourier coefficients: $$\:{A}_{1}=\:\frac{2}{n}\sum\:_{i=1}^{n}T({t}_{i})\text{c}\text{o}\text{s}(2\pi\:f{t}_{i}),\:{B}_{1}=\:\frac{2}{n}\sum\:_{i=1}^{n}T\left({t}_{i}\right)\text{s}\text{i}\text{n}\left(2\pi\:f{t}_{i}\right)$$ where: T ( t i ) – multiannual Tmean for consecutive days of the year. After determining the average length of the thermal seasons in the two time periods analysed, the difference in their length was calculated. 3 Results The first step was to answer the question whether the change of the observer at the Płońsk weather station at the end of the 19th century caused inhomogeneity of the analysed data set. The results of the median test (χ 2 = 0.4464, p = 0.833) indicate that there is no basis for rejecting the null hypothesis H 0 , that both samples have the same median of mean annual air temperature. Therefore, the dataset of air temperature at Płońsk from the whole time period 1881–1895 was found to be statistically homogenous and the variability of thermal conditions in this period was considered to result only from the variation of climate controls. Next, the authors answered the question whether the thermal conditions in 1881–1895 differed remarkably from those in the Mazovia region throughout the 19th century. The mean annual air temperature in Warsaw in the 15-year period 1881–1895 equalled 7.3°C, the same as in the longer 1826–1900 time period (Fig. 2 ). The first 15-year period 1826–1840 was slightly cooler, with a mean annual air temperature of only 6.9°C (Table 1 ). However, an analysis of variance ( F = 0.7730, p = 0.546) does not allow us to reject the null hypothesis H 0 , stating that the differences in mean annual air temperature in Warsaw in the 15-year sub-periods of the longer 1826–1900 time period are not statistically significant. Table 1 Mean annual air temperature (°C) during 15-year periods at the Warsaw Astronomical Observatory weather station from 1826 to 1900 Periods 1826–1840 1841–1855 1856–1870 1871–1885 1885–1900 Mean annual air temperature 6.9 7.2 7.4 7.4 7.4 In the northern part of the Mazovia region Tmean in the years 1981–2010 (Poświętne station) was remarkably higher than Tmean in 1881–1895 at Płońsk. The warming equalled 1.5°C (Table 2 ). A statistically significant increase in air temperature between the end of the 19th century and the end of the 20th and the beginning of the 21st century was found in the majority of months. It was not found only in February, September, November and December. The largest increase in Tmean occurred in January and March, by 2.3°C, and of at least 2.0°C in April and August. Table 2 Mean monthly and annual air temperature in the northern part of the Mazovia region in the years: A – 1881–1895 (Płońsk) and B – 1981–2010 (Poświętne); statistically significant differences are bolded Data set Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year A -4.1 -2.7 0.7 7.3 14.0 16.9 19.0 17.4 13.5 7.6 2.3 -1.7 7.5 B -1.8 -0.8 3.0 9.3 15.4 18.0 20.3 19.5 14.1 8.8 3.2 -0.6 9.0 B-A 2.3 p = 0.035 1.9 p = 0.09 2.3 p < 0.01 2.0 p < 0.01 1.4 p < 0.01 1.1 p = 0.01 1.3 p = 0.02 2.1 p < 0.01 0.6 p = 0.28 1.2 p = 0.02 0.9 p = 0.145 1.1 p = 0.07 1.5 p < 0.01 The larger increase in air temperature in the winter months than in the summer months did not result in a significant reduction in the mean annual range of air temperature. It was 24.8°C in the period 1881–1895 and 24.6°C in the period 1981–2010. What did change, however, was the ratio of the mean air temperature in spring and autumn. Autumn tended to be warmer than spring by an average of 0.3°C at the end of the 19th century. Today it is cooler than spring by an average of 0.5°C. This difference is not statistically significant at the p ≤ 0.05, but these changes can suggest a shift towards a more continental climate in Poland in recent years compared with the late 19th century. The coldest day of the year occurred in the first half of January in both studied periods. In the 1881–1895 time period it was two days – 14 and 15 January with a Tmean of -6.8°C. In 1981–2010 the coldest day of the year was 8 January with an average Tmean of -2.8°C. The warmest day of the year at the end of the 19th century occurred on 16 July (20.2°C) and in the 1981–2010 time period it was observed two weeks later. On 31 July and 2 August the average Tmean was 21.5°C. It can also be seen that an outstanding feature of the annual cycle of the air temperature in both studied time periods is a cooling in mid-June (Fig. 3 b). Today, the average Tmean in the northern part of the Mazovia region is higher than that at the end of the 19th century on 90% of the days of the year. This increase was at least 1.0°C on 67% of the days of the year. The largest increase of at least 5.0°C in Tmean was found between 13 and 16 January (Fig. 3 b). Although the increase in Tmean occurred for most of the days of the year and it was quite large, it was not statistically significant for many days, which results from a high variability of Tmean on a given day from year to year. A statistically significant ( p ≤ 0.05) increase in Tmean was found only on 18% of the days of the year. These were usually single days or two-day spells and accounted for 42% of the 64 significantly warmer days of the year. The longest spell of days for which a significant increase in Tmean was identified in the 1981–2010 period compared to the 1881–1895 period is 10-days long (1–10 August). However, if one or two days with a statistically insignificant increase in air temperature are assumed not to interrupt such a period, then the longest spell would be 20 days (30 July – 18 August). Seven-day spells of days with a significant increase in Tmean were observed in mid-January (12–18 January) and late March – early April (30 March – 5 April), while three-day spells were identified in early May and late September. The average Tmean is the same during 5 days of the year today compared to the end of the 19th century. In addition, Tmean is today lower than at the end of the 19th century on 33 days (9% of all days of the year). None of these differences are statistically significant yet. Analysis of order statistics of Tmean values confirms an ongoing warming in the study area in all months. An increase in lower and upper quartiles, median as well as maximum values of Tmean was noted in all months (Table 3 , Fig. 4 ). Only minimum Tmean values in the winter months (December-February) and in April did not increase. Table 3 Order statistics (minimum, lower quartile, median, upper quartile, maximum) for Tmean in the northern part of the Mazovia region in the years: A – 1881–1895 (Płońsk) and B – 1981–2010 (Poświętne) Data set Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Minimum A -21.8 -17.0 -16.7 -2.5 2.8 7.9 10.4 10.3 2.4 -3.9 -14.9 -16.3 B -25.4 -20.8 -14.3 -3.6 3.8 9.4 11.6 11.2 3.6 -1.7 -13.8 -17.9 B-A -3,6 -3.8 2.4 -1.1 1.0 1.5 1.2 0.9 1.2 2.2 1.1 -1.6 Lower quartile A -7.7 -5.7 -2.2 4.1 11.1 14.4 16.6 15.2 11.1 4.7 -0.2 -3.5 B -5.1 -3.7 0.3 6.1 12.3 15.1 17.6 17.2 11.7 5.9 0.3 -3.3 B-A 2.6 2.0 2.5 2.0 1.2 0.7 1.0 2.0 0.6 1.2 0.5 0.2 Median A -2.4 -1.8 1,6 6.6 14.4 16.9 19.0 17.0 13.4 7.8 2.8 -0.8 B -0.5 -0.1 2,9 9.3 15.3 18.0 20.2 19.7 13.8 9.0 3.7 0.2 B-A 1.9 1.7 1.3 2.7 1.2 1.1 1.2 2.7 0.4 1.2 1.0 1.0 Upper quartile A 0.5 0,7 4.0 10.4 16.9 19.2 21.4 19.5 16.0 10.6 5.6 1.4 B 2.4 2.4 6.0 12.2 18.7 20.8 22.8 21.9 16.3 11.9 6.5 2.6 B-A 1.9 1.7 2.0 1.8 1.8 1.6 1.4 2.4 0.3 1.3 0.9 1.2 Maximum A 4.7 7.8 12.6 18.2 26.9 25.8 28.2 27.2 22.2 17.3 10.4 8.8 B 10.6 11.8 15.1 23.4 27.0 29.6 31.1 31.0 23.3 20.4 13.0 10.6 B-A 5.9 4.0 2.5 5.2 0.1 3.8 2.9 3.8 1.1 3.1 2.6 1.8 Although the average air temperature in winter in the northern Mazovia region is now higher than at the end of the 19th century, periods of severe cold for several days still occur, such as during the winters of 1986/1987, 1996/1997, and 2005/2006. The likelihood of extremely cold air temperature was higher in the years 1981–2010 than in the 1881–1895 time period. The empirical distributions of Tmean in individual seasons differed for the two studied periods. The empirical distribution of Tmean was bimodal (except in autumn) at the end of the 19th century, while it was unimodal in the 1981–2010 period, with spring, summer and autumn having a slightly lower modal value than that in the years 1881–1895, but falling into the intervals of higher values. It is also apparent in each season of the year that the 1881–1895 period features a higher frequency of low Tmean values and lower frequency of higher Tmean values compared to the 1981–2010 time period (Fig. 5 ). The largest difference between the cumulative empirical distribution function for both studied time periods was noted for the summer in the interval of values from 17.6 to 20.0°C and for the winter in the interval of values from 0.1 to 2.5°C (Fig. 6 ). The differences between thermal conditions in 1881–1895 and 1981–2010 are bigger compared to differences between thermal conditions in 1881–1895 and 1951–1981. The mean monthly Tmean values were the same in April and August in 1881–1895 and 1951–1981. Tmean increased in the months from October to January and in March, and it was lower in May, July, and September in the time period 1951–1980 compared with the years 1881–1895. The said differences did not exceed 0.9°C and they were statistically insignificant (Table 4 ). A statistically significant ( p ≤ 0.05) change in Tmean identified in the 1951–1980 period compared to the 1881–1895 was found only on 3% of the days of the year (Fig. 3 a). Of these, all but one three-days spell of days were single days. This three-days spell of days with a significant decrease in Tmean was observed in late June and early July (29 June − 1 July). Therefore, it may be concluded that the increase in air temperature occurred only from the 1980s onwards. Table 4 Mean monthly and annual air temperature values for the northern part of the Mazovia region in the years: A – 1881–1895 (Płońsk) and B – 1951–1981 (Poświętne) and the differences between them Data set Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year A -4.1 -2.7 0.7 7.3 14.0 16.9 19.0 17.4 13.5 7.6 2.3 -1.7 7.5 B -3.5 -2.8 1.2 7.3 13.1 17.1 18.2 17.4 13.0 8.0 3.2 -0.9 7.6 B-A 0.6 p = 0.51 -0.1 p = 0.10 0.5 p = 0.59 0.0 p = 0.98 -0.9 p = 0.10 0.2 p = 0.55 -0.8 p = 0.11 0.0 p = 0.92 -0.5 p = 0.27 0.4 p = 0.40 0.9 p = 0.10 0.8 p = 0.17 0.1 p = 0,72 The increase in air temperature between 1881–1895 and 1981–2010 also manifested itself in a change in the duration of thermal seasons, especially summer and winter. The duration of these two seasons was similar in the northern part of the Mazovia region at the end of the 19th century. Thermal winter lasted an average of 99 days and summer 102 days. Today, thermal summer lasts 119 days (an increase of 17 days) and winter lasts only 74 days. Early spring and early winter have drawn out by 4 days (Table 5 ). Table 5 Average duration of thermal seasons (number of days) in the northern part of the Mazovia region in the years: A – 1881–1895 (Płońsk) and B – 1951–1981 (Poświętne) and the differences between them Data set Winter Early spring Spring Summer Autumn Early winter A 99 28 53 102 54 29 B 74 32 54 119 53 33 B-A -25 4 1 17 -1 4 All transitional seasons have shifted by several days. Today, thermal early spring starts on average 15 days earlier and ends 11 days earlier than at the end of the 19th century (Fig. 7 ). 4 Discussion & conclusions The observed changes in Tmean in the northern part of the Mazovia region between the end of the 19th century and the end of the 20th and the beginning of the 21st centuries are similar to those determined in other regions of Poland and Central Europe (Piotrowicz 2007 ; Rebetez and Reinhard 2008 ; Brazdil et al. 2012; Nordli et al. 2014 ; Urban and Tomczyński 2017 ; Kolendowicz et al. 2019 ; Pospieszyńska and Przybylak 2019 ). The observed warming was approximately 1.5 ± 0.4°C in these areas. As the air temperature trend in Toruń, Poznań, Wrocław and Kraków, i.e. Polish cities with a population of 200 000 or more, is similar to that in Płońsk, we conclude that an urbanization contribution to the observed warming is small in Poland. Zhang et al. ( 2021 ) also found that the urbanization effect on global trends in mean air temperature is small in Europe and it is the strongest in East Asia. In other European regions, e.g. northern and southern Europe, the increasing trend in mean annual air temperature was somewhat weaker. For example, the air temperature increased by 0.9°C in Finland between 1909 and 2008 (Tietäväinen et al. 2010 ), by 0.7–1.6°C in Iceland between 1871 and 2001 (Hanna et el. 2004), and by 0.6°C in Athens (1890–2009) (Founda 2011 ). The observed increase in air temperature in the northern part of the Mazovia region varied seasonally. The highest increase occurred in spring; in March and April the air temperature increase at Płońsk exceeded 2.0°C. A similar pattern was found both at weather stations located close to the studied area, e.g. in Toruń or Poznań, and in other regions of Central Europe. In the Czech Republic, the increase in air temperature between 1882 and 2010 ranged between 1.3°C (autumn) to 1.9°C (summer) (Brazdil et al. 2012). Statistically significant warming at the end of the 20th and beginning of the 21st centuries compared to the end of the 19th century observed in Płońsk dataset in most cases results from a significant increase in air temperature on particular days of the year. We found several spells of such days which has been done in Polish climate change studies for the first time. An increase in the lower and upper quartile, median as well as minimum and maximum Tmean values was also found for Płońsk for selected months. These results correspond to results obtained in Poznań. The warming manifested itself there not only in an increase in the arithmetic mean but also in lower and upper quartiles, especially in August (Kolendowicz et al. 2019 ). The trend in the duration of the thermal seasons varies much more in different regions of Europe than the trend in mean annual air temperature. In Toruń, as in Płońsk, the duration of the summer increased significantly (by an average of 18 days in 2001–2010 compared with 1871–1880), while winter shortened (by 29 days) (Pospieszyńska and Przybylak 2019 ). The duration of transitional seasons did not change significantly, similar to Płońsk and the dates of their occurrence also shifted. An increase in the length of summer (by 11 days) and autumn (by 5 days) and shortening of winter and spring (by 4 days) were noted in Tartu (Estonia) between 1891 and 2003 (Kull et al. 2008 ). A shortening of winter was observed at many Eastern European localities between 1881 and 1995 (Jaagus et al. 2003 ) and ranged from a few days to more than 30 days. In contrast, no significant trends in the duration of summer were detected there. The duration of spring increased at selected weather stations, e.g. in Kyiv by 10.4 days. It should be noted that differences in trends in the duration of thermal seasons can result from differences in the method of the delimitation of seasons in the studies mentioned above. The increase in air temperature in the northern part of the Mazovia region has been pronounced only since the 1980s. Tmean was not higher in the 1951–1980 period than that in the period 1881–1985. This conclusion confirms the results of other research studies focused on the assessment of long-term air temperature trends in Poland and in other European countries (Gjelten et al. 2014 ; Hanna et al. 2004 ; Kolendowicz et al. 2019 ; Labudová et al. 2015 ). An increase in Tmean was noted for Poznań in the time period 1848–2016. However, no trend was identified for the sub-period 1902–1987, while in 1987–2016 the air temperature increase was as high as 1.4°C (Kolendowicz et al. 2019 ). The spatially averaged air temperature in Slovakia was almost the same in the 1961–1990 time period as that in 1931–1960. A large increase in air temperature was only noted in the 1991–2014 time period (Labudová et al. 2015 ). An increase in air temperature was observed in the town of Ås (southern Norway) in the 1930s, and since the late 1970s (Gjelten et al. 2014 ). The 1960s were a relatively cool period. Many other weather stations in northern Europe showed a negative air temperature trend for the time period 1931–1960 (e.g. Stockholm in Sweden and Reykjavik and Grimsey in Iceland) or no trend at all (e.g. Copenhagen in Denmark, Torshavn in the Faroe Islands) (Hanna et al. 2004 ). An important issue when comparing meteorological datasets from quite distant time periods is always to answer the question whether, and to what extent, the obtained results could be affected by differences in methods of measurement and data processing. In the case of this study the questions are whether the data from the weather stations at Płońsk and Poświętne describe well the thermal conditions in the northern Mazovia region and to what extent air temperature datasets from these stations could be affected by changing the location of the weather station. Access to metadata is crucial in detecting potential inhomogeneities. The weather station in Poświętne was established in 1923 and from the start of its operation carried out measurements in accordance with the methodology used by IMGW-PIB and its predecessors. Therefore, the metadata are known and easily accessible. In the case of the weather station established by Jędrzejewicz in Płońsk in the 19th century the metadata were published in the journal Pamiętnik Fizyograficzny and in other periodicals of that time (Jędrzejewicz 1880 , 1882 ; Uwagi o … 1904). The exposure mode of thermometers in the 19th century was different from that used today. The 19th century standard was to place thermometers on the north (shaded, not sunny) wall of a building. This is how thermometers were placed in Płońsk, on the north-east wall of Jedrzejewicz’s astronomical observatory, at a height 4.6-5.0 m above ground level. At the weather station in Poświętne, thermometers were exposed in a Stevenson screen standing in an open area, 2.0 m above ground level. A comparison of air temperature measurements using different modes of thermometer exposure were carried in the UK (Parker 1994 ). The results of the study show a lower diurnal temperature range measured on the north wall of the building compared to measurements in the Stevenson screen. However, the annual Tmean values were similar regardless of the location of the thermometers. The air temperature measured on the north wall of the said building and in the Stevenson screen also hardly differed in Denmark. The average differences in mean monthly air temperature did not exceed 0.1°C. Slightly larger differences were found in Iceland where the higher air temperature was found on the north wall of the said building during the summer months (Nordli et al. 1997 ). This is due to the location of these stations close to the northern Arctic Circle where the sun almost never sets in summer and it can illuminate the north walls of buildings both in the morning and evening. However, this is not an issue at the latitude of Poland. Tmean values can be also affected by the method of their calculation, as shown by Harris and Pedersen ( 1995 ), Urban ( 2010 ) and Kuśmierek-Tomaszewska et al. ( 2013 ). In the 19th century, the Tmean value was calculated at the Płońsk site as a weighted arithmetic mean according to Formula 1. The measurement hours, i.e. 7:00 AM, 1:00 PM, and 9:00 PM were determined at the local mean time of the Plońsk meridian 20°22’E. A similar method of calculating Tmean was used at climatological weather stations of IMGW-PIB until 1970, i.e. also at the weather station in Poświętne (Płońsk). Later, the methods of Tmean calculation changed twice. Today, Tmean is calculated as the arithmetic mean of the TX, TN, T 7 AM UTC and T 6 PM UTC . The method of Tmean calculation used at the IMGW-PIB weather stations since 1995 gives results up to a few tenths of a °C lower depending on the month analysed compared to the methodology used prior to 1970 (Urban 2010 ; Kuśmierek-Tomaszewska et al. 2013 ). Thus, the same methodology (that used until 1970) was applied to the entire dataset in order to reduce as much as possible the impact of changes in the Tmean calculation on the compared air temperature values. This procedure reduced any potential inhomogeneity in the data, although it probably did not remove it completely, due to the fact that the timing of the measurements had changed after 1970 to 6:00 AM, 12:00 PM, and 6:00 PM UTC. While the timing of the morning and midday Tmean observations are similar today to that used at the end of the 19th century, the evening Tmean observation time is now approximately 2 hours earlier. The impact of this key change on the compared Tmean values is likely to be small in the colder half of the year when evening measurements both in 1881–1895 and 1981–2010 were carried out already after sunset. In the summertime, 6:00 PM UTC falls in the evening, while 9:00 PM at Płońsk local mean time (around 7:50 PM UTC) is already nighttime. Tmean values in summer months in the 1981–2010 time period used in this study may therefore be slightly overestimated with respect to data from the late 19th century. However, this issue requires further in-depth study using data from nearby weather stations run by the IMGW-PIB, where measurements are now made hourly. In conclusion, it needs to be said that a key issue in the study of climate change is information on data quality. Information on the quality of data as well as on the measurement and data processing methods makes it possible to detect and sometimes eliminate inhomogeneity of meteorological datasets, which has been done to a considerable extent in the case of the Tmean data from Płońsk and its surroundings. Declarations Author Contribution K.J. and E.Ż. contributed to the study conception and design. K.J. and T.B. contributed to material preparation and data collection. Analysis were performed by K.J. and E.Ż. The first draft of the manuscript was written by K.J. and it was commented and supplemented E.Ż. and T.B. All authors read and approved the final manuscript. Data Availability Digitized Tmean data set from the Płońsk weather station (1881-1895 period) that was published in Pamiętnik Fizyograficzny (1882-1910) is stored in the repository of the Section of Climatology of the Faculty of Geography and Regional Studies University of Warsaw and is available from the corresponding author on reasonable request. References Brázdil R, Zahradníček P, Pišoft P, Štěpánek P, Bělínová M, Dobrovolný P (2012) Temperature and precipitation fluctuations in the Czech Republic during the period of instrumental measurements. Theor Appl Climatol 110:17–34. https://doi.org/10.1007/s00704-012-0604-3 Boryczka J, Stopa-Boryczka M, Lorenc H, Kicińska B, Skrzypczuk J (2000) Atlas współzależności parametrów meteorologicznych i geograficznych w Polsce. Prognozy zmian klimatu Warszawy, Book 14. Warsaw University, Warszawa Bryś K, Bryś T (2010) Reconstruction of the 217-Year (1791–2007) Wrocław Air Temperature and Precipitation Series. Bull Geogr Phys Geogr Ser 3:121–171. https://doi.org/10.2478/BGEO-2010-0007 Fortuniak K, Kożuchowski K, Papiernik Ż (1998) Roczny rytm klimatu Polski i jego sezonowe osobliwości. Prz Geogr 70:283–304 Founda D (2011) Evolution of the air temperature in Athens and evidence of climatic change. Adv Build Energy Res 5:7–41. https://doi.org/10.1080/17512549.2011.582338 Gjelten HM, Nordli Ø, Grimenes AA, Lundstad E (2014) The Ås temperature series in southern Norway – homogeneity testing and climate analysis. Bull Geogr Phys Geogr Ser 7:7–26. https://doi.org/10.2478/bgeo-2014-0001 Gorczyński W, Kosińska S (1916) O temperaturze powietrza w Polsce. Pamiętnik Fizyograficzny 23:1–262 Hanna E, Jónsson T, Box JE (2004) An analysis of Icelandic climate since the nineteenth century. Int J Climatol 24:1193–1210. https://doi.org/doi:10.1002/joc.1051 Harris SA, Pedersen JH (1995) Comparison of three methods of calculating air temperature from electronic measurements. Z Geomrphol 39:203–210. http://doi.org/doi: 10.1127/zfg/39/1995/203 Hartmann DL, Klein Tank AMG, Rusticucci M, Alexander L, Brönnimann S, Charabi Y, Dentener F, Dlugokecky E, Eastwrling D, Kaplan A, Soden B, Thorne P, Wild M, Zhai PM (2014) Observations: Atmosphere and Surface. In: Stocker TF, Qin D, Plattner G-K, Tingor M, Allen SK, Boschung J, Nauels A, Xia Y, Bex V, Midgley PM (eds) Climate Change 2013: The Physical Science Basis. Cambridge University Press, Cambridge, pp 159–254 Jaagus J, Truu J, Ahas R, Aasa A (2003) Spatial and temporal variability of climatic seasons on the East European Plain in relation to large-scale atmospheric circulation. Clim Res 23:111–129. https://doi.org/doi:10.354/cr023111 Jędrzejewicz JW (1880) Spostrzeżenia meteorologiczne z lat 1875, 1876 i 1877 zebrane przez Dra Jędrzejewicza w Płońsku. Przyroda i Przemysł 2:13–15 Jędrzejewicz JW (1882) Obserwatorium astronomiczne D-ra Jędrzejewicza w Płońsku. Tygodnik Powszechny 30:468–470 Kolendowicz L, Czernecki B, Półrolniczak M, Taszarek M, Tomczyk MA, Szyga-Pluta K (2019) Homogenization of air temperature and its long-term trends in Poznań (Poland) for the period 1848–2016. Theor Appl Climatol 136:1357–1370. https://doi.org/10.1007/s00704-018-2560-z Kowalczyk J (1888) Wiadomość o obserwatorium w Płońsku i o pracach Jana Jędrzejewicza w dziedzinie astronomii i meteorologii. Prace Matematyczno-Fizyczne 1:113–118 Kożuchowski K, Marciniak K (1987) Zmiany temperatury powietrza w Europie Środkowej od 1781 roku. Geogr J 58:173–189 Kull A, Kull A, Jaagus J, Kuusemets V, Mander Ü (2008) The effects of fluctuating climatic conditions and weather events on nutrient dynamics in a narrow mosaic riparian peatland. Boreal Environ Res 13:243–263 Kuśmierek-Tomaszewska R, Żarski J, Dudek S (2013) Porównanie średniej dobowej temperatury powietrza obliczonej na podstawie różnych procedur pomiarowych. Infrastruktura i Ekologia Terenów Wiejskich 2:109–121 Labudová L, Faško P, Ivaňáková G (2015) Changes in climate and changing climate regions in Slovakia. Morav Geogr Rep 23:70–81. https://doi.org/10.1515/mgr-2015-0019 Linderholm HW, Walther A, Chen D (2008) Twentieth-century trends in the thermal growing season in the Greater Baltic Area. Clim Change 87:405–419. https://doi.org/10.1007/s10584-007-9327-3 Merecki R (1915) Klimatologia ziem polskich. Gebethner & Wolf, Warszawa Nordli PØ, Alexandersson H, Frich P, Førland EJ, Heino R, Jónsson T, Tuomenvirta H, Tveito OE (1997) The effect of radiation screens on Nordic time series of mean temperature. Int J Clim 17:1667–1681. https://doi.org/10.1002/(sici)1097-0088(199712)17:153.0.co;2-d Nordli Ø, Hestmark G, Benestad RE, Isaksen K (2014) The Oslo temperature series 1837–2012: homogeneity testing and temperature analysis. Int J Clim 35:3486–3504. https://doi.org/10.1002/joc.4223 Pamiętnik F, Znatowicz B, Wróblewski W (1881) Kulwieć K, Warszawa Parker DE (1994) Effects of changing exposure of thermometers at land stations. Int J Clim 14:1–31. https://doi.org/10.1002joc.3370140102 Piotrowicz K (2007) Temperatura powietrza. In: Matuszko D (ed) Klimat Krakowa w XX wieku. Kraków, IGiGP UJ Piotrowicz K (2009) The Occurrence of Unfavorable Thermal Conditions on Human Health in Central Europe and Potential Climate Change Impact: An Example from Cracow, Poland. Environ Manag 44:766–777 Pospieszyńska A, Przybylak R (2019) Air temperature changes in Toruń (central Poland) from 1871 to 2010. Theor Appl Climatol 135:707–724. https://doi.org/10.1007/s00704-018-2413-9 Rebetez M, Reinhard M (2008) Monthly air temperature trends in Switzerland 1901–2000 and 1975–2004. Theor Appl Climatol 91:27–34. https://doi.org/10.1007/s00704-007-0296-2 Romer E (1912) Klimat Ziem Polskich. Encyklopedia Polska, Vol. 1: Geografia fizyczna Ziem Polskich i charakterystyka fizyczna ludności. Akademia Umiejętności, Kraków Siedlecki M, Pawlak W (2004) Sumy miesięczne opadów atmosferycznych w Łodzi w latach 1903–2003. Acta Geogr Lodziensia 89:73–86 Spostrzeżenia meteorologiczne, dokonane w r (1913) 1909 i 1910 na stacyach meteorologicznych sieci warszawskiej. Pamiętnik Fizyograficzny 21:1–155 Szyga-Pluta K, Tomczyk A, Piotrowicz K, Bednorz E (2023) Patterns in the multiannual course of growing season in Central Europe since the end of the 19th century. Questiones Geographicae 42:59–74 Tietäväinen H, Tuomenvirta H, Venäläinen A (2010) Annual and seasonal mean temperatures in Finland during last 160 years based on gridded temperature data. Int J Clim 30:2247–2256. https://doi.org/10.1002/joc.2046 Tysa SK, Ren G, Qin Y, Zhang P, Ren Y, Jia W, Wen W (2019) Urbanization effect in regional temperature series based on a remote sensing classification scheme of stations. J Geophys Res Atmos 124:10 646–10661. https://doi.org/10.1029/2019JD030948 Urban G (2010) Ocena wybranych metod obliczania średniej dobowej, miesięcznej i rocznej wartości temperatury powietrza (na przykładzie Sudetów Zachodnich i ich przedpola). Opera Corcontica 47:23–34 Urban G, Tomczyński K (2017) Air temperature trends at Mount Śnieżka (Polish Sudetes) and solar activity, 1881–2012. Acta Geogr Slov 57:33–44. http://dx.doi.org/10.3986/AGS.837 Uwagi o stacyach Sieci Warszawskiej (1904) Pamiętnik Fizyograficzny 18:1–11 Wibig J, Fortuniak K, Kłysik K (2004) Rekonstrukcja serii temperatury powietrza w Łodzi z okresu 1903–2000. Acta Geogr Lodziensia 89:19–31 Zhang P, Ren G, Qin Y, Zhai Y, Zhai T, Tysa SK, Xue X, Yang G, Sun X (2021) Urbanization effect on estimate of global trends in mean and extreme air temperature. J Clim 34:1923–1945. https://doi.org/10.1175/JCLI-D-20-0389.1 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 27 Jan, 2026 Read the published version in Theoretical and Applied Climatology → Version 1 posted Editorial decision: Revision requested 10 Sep, 2025 Reviews received at journal 10 Sep, 2025 Reviews received at journal 29 Jul, 2025 Reviewers agreed at journal 26 Jul, 2025 Reviewers agreed at journal 25 Jul, 2025 Reviewers agreed at journal 24 Jul, 2025 Reviewers invited by journal 24 Jul, 2025 Editor assigned by journal 13 Jul, 2025 Submission checks completed at journal 13 Jul, 2025 First submitted to journal 11 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7101735","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":491567166,"identity":"2b412e8a-ea15-48ac-85db-4cf354319334","order_by":0,"name":"Krzysztof Jarzyna","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA60lEQVRIiWNgGAWjYBACCQaGBAiLv/kAiGJsAOIDxGmROJYA08JASAsM5BgQp0WygeHh54o/h/P4G858k+ZhsJHdcID3AF4t0gwMyZJneA4XSxzu3QbUkma84QBfAl4tckC/SDZIHE5sOHB2m3QOw+HEDQd4DAhpSf7ZYHA4cf6BnGdALf8JawE6LE2yIQFkeA4bUMsBwlokmxnSLBsOpCduvHHM2PqPQbLxzMME/CJxvCf5ZsMf68R555sf3pxRYSfbd7z34AN8WhiYeRKAZDOUZwAWwasBCNhBrqhDFiGoZRSMglEwCkYYAADUZ1EyPJ8cEwAAAABJRU5ErkJggg==","orcid":"","institution":"University of Warsaw","correspondingAuthor":true,"prefix":"","firstName":"Krzysztof","middleName":"","lastName":"Jarzyna","suffix":""},{"id":491567168,"identity":"27bb299f-536d-41c1-a5a9-6752878873c1","order_by":1,"name":"Elwira Żmudzka","email":"","orcid":"","institution":"University of Warsaw","correspondingAuthor":false,"prefix":"","firstName":"Elwira","middleName":"","lastName":"Żmudzka","suffix":""},{"id":491567171,"identity":"86c9abd9-0f99-4f28-8d7f-4b4862da2c3c","order_by":2,"name":"Tytus Berbeć","email":"","orcid":"","institution":"Institute of Soil Science and Plant Cultivation","correspondingAuthor":false,"prefix":"","firstName":"Tytus","middleName":"","lastName":"Berbeć","suffix":""}],"badges":[],"createdAt":"2025-07-11 12:38:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7101735/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7101735/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00704-026-06023-2","type":"published","date":"2026-01-27T15:58:56+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":87761417,"identity":"60aec59d-e250-4eee-91eb-2dc6c08a7a43","added_by":"auto","created_at":"2025-07-28 16:59:41","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":315168,"visible":true,"origin":"","legend":"\u003cp\u003eLocation of the weather stations included in the study (black triangles on maps): a) in the 19\u003csup\u003eth\u003c/sup\u003e century and b) present-day\u003c/p\u003e\n\u003cp\u003esources: a) Mapa Szczegółowa Polski WIG, Pas 38, Słup 31, 1933, based on Russian mapping from 1885, from the MAPSTER website (http://igrek.amzp.pl), b) Topographic Map (WMS) (\u003ca href=\"https://www.geoportal.gov.pl/\"\u003ehttps://www.geoportal.gov.pl\u003c/a\u003e)\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7101735/v1/c971d851c024b4130ad88984.jpg"},{"id":87761419,"identity":"7c24cdff-4dcf-4f0d-a880-8e11f75517f1","added_by":"auto","created_at":"2025-07-28 16:59:41","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":64481,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of the mean annual Tmean at the Warsaw Astronomical Observatory weather station in the years 1826-1900 and at Płońsk in the years 1881-1895\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7101735/v1/f85670f97f5840496ce334ab.jpg"},{"id":87762436,"identity":"9d10c2a9-cc89-45a2-892f-04274b1c3330","added_by":"auto","created_at":"2025-07-28 17:15:41","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":171832,"visible":true,"origin":"","legend":"\u003cp\u003eAnnual cycle of Tmean in the northern part of the Mazovia region: a) comparison of periods 1881-1895 and 1951-1980, b) comparison of periods 1881-1895 and 1981-2010; shaded belts shows at least two-days long periods with statistically significant increase or decrease in Tmean\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7101735/v1/2a87dbfb54f2d2e1a4117bba.jpg"},{"id":87761743,"identity":"b17f24b3-4dff-46a1-bc3d-1d9c34a1f459","added_by":"auto","created_at":"2025-07-28 17:07:41","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":54262,"visible":true,"origin":"","legend":"\u003cp\u003eOrder statistics (minimum, lower quartile, median, upper quartile, maximum) for Tmean in individual months in the northern part of the Mazovia region in the years 1881-1895 (Płońsk) and 1981-2010 (Poświętne)\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7101735/v1/77e89d5b0be5cd45879c105c.jpg"},{"id":87761421,"identity":"b6b5f196-7cc0-41cf-9713-ef3f3cd54617","added_by":"auto","created_at":"2025-07-28 16:59:41","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":107145,"visible":true,"origin":"","legend":"\u003cp\u003eEmpirical distribution of Tmean in individual seasons in the northern part of the Mazovia region in the years 1881-1895 (Płońsk) and 1981-2010 (Poświętne)\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7101735/v1/3e614d0f0422c699a1fdfe4f.jpg"},{"id":87761422,"identity":"08006448-0ad9-4fbc-be1c-bfa7738ed961","added_by":"auto","created_at":"2025-07-28 16:59:41","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":135281,"visible":true,"origin":"","legend":"\u003cp\u003eCumulative empirical distribution function plots of Tmean in individual seasons in the northern part of the Mazovia region in the years 1881-1895 (Płońsk) and 1981-2010 (Poświętne)\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7101735/v1/7c3f0b771b4ffbed00de393f.jpg"},{"id":87761423,"identity":"d17e0d71-d94d-4937-9019-32a8fc5d97c0","added_by":"auto","created_at":"2025-07-28 16:59:41","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":126484,"visible":true,"origin":"","legend":"\u003cp\u003eThermal seasons in the northern part of the Mazovia region in the years: a) 1881-1895 (Płońsk) and b) 1951-1981 (Poświętne)\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7101735/v1/5851d01340316f9d6f546ccc.jpg"},{"id":101690832,"identity":"a1a56be9-efe3-4174-8807-2a22db6c242b","added_by":"auto","created_at":"2026-02-02 16:09:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1828557,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7101735/v1/8bbd6b65-335f-4381-ba3d-6e959435528d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Changes in thermal conditions in the northern part of the Mazovia (central Poland) between the late 19th and early 21st centuries","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eMulti-year meteorological data sets, dating back to the 19th century and even earlier periods, make it possible to determine climate trends and oscillations from the end of the Little Ice Age to the present (Nordli et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Pospieszyńska and Przybylak \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). They also allow us to estimate the magnitude of modern warming (Piotrowicz \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Bryś and Bryś \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Kolendowicz et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). However, we should remember that today the longest operating weather stations are usually located in the urban areas while they were located in the suburban or rural areas in the 19th century. Therefore, the air temperature data sets may have a systematic bias caused by urbanization of the surrounding of the observational sites. The urbanization effect is believed to contribute 10% at best to the global land averaged air temperature centennial trend (Hartmann et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). This urbanization effect was, however, proved to be stronger in some regions by newer researches (Tysa et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Zhang et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Thus, meteorological data sets dating back to the 19th century and originating from small towns and villages are of a specially high value in the studies of the modern warming.\u003c/p\u003e\u003cp\u003eIn the case of central and eastern Poland, measurement series from stations operating as part of the so-called \u003cem\u003eWarsaw network\u003c/em\u003e have an important but underestimated role in understanding the climatic conditions of the late 19th century. Meteorological measurements were performed from 1886 and sub-daily and daily data were collected from over a dozen weather stations located across the former Kingdom of Poland (also known as Congress Poland) and regions today located in Ukraine and Belarus. In 1910 the network comprised over 60 stations (Spostrzeżenia meteorologiczne\u0026hellip; 1913). The weather data collected there were published in periodicals in the 19th century and at the beginning of the 20th century, especially in the Pamiętnik Fizyograficzny (1881,\u0026hellip;,1913). Only a small part of these datasets was actually used in scientific studies. They included the first climate-related monographs of Poland (Romer \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1912\u003c/span\u003e; Merecki \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1915\u003c/span\u003e; Gorczyński and Kosińska \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1916\u003c/span\u003e), and also contemporary studies of centennial changes of air temperature and precipitation in Warsaw and Ł\u0026oacute;dź (Boryczka et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Kożuchowski and Marciniak \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Siedlecki and Pawlak, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Wibig et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2004\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn this paper we assessed the changes in air temperature in Płońsk in the period between the end of the 19th century and the beginning of the 21st century. Płońsk is a small town with a population of ca. 21,500 people, located in the northern Mazovia region, central Poland. We focused our study not only on the annual, seasonal and monthly air temperature values but we also analysed changes in Tmean in consecutive days of a year, which has not been done in Polish Climate Change studies yet.\u003c/p\u003e"},{"header":"2 Data and methods","content":"\u003cp\u003eThe raw data taken into account in this study consisted of sub-daily values of air temperature obtained from two weather stations: Płońsk, \u003cem\u003eWarsaw network\u003c/em\u003e station and Poświętne, station of the Institute of Meteorology and Water Management \u0026ndash; National Research Institute (IMGW-PIB) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The data were used to calculate the mean daily air temperature (Tmean). Tmean values were then used to compare the thermal conditions in the northern part of Mazovia region at the end of the 19th century to those in the second half of the 20th century and the beginning of the 21st century.\u003c/p\u003e\u003cp\u003eIn addition, mean annual air temperature data obtained from the Astronomical Observatory in Warsaw for the period 1826\u0026ndash;1900 (after: Gorczyński and Kosińska \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1916\u003c/span\u003e) were used in the study to assess the degree to which thermal conditions in the Mazovia region in the period 1881\u0026ndash;1985 were typical in the context of the longer period 1826\u0026ndash;1900. Air temperature data obtained from the Warsaw weather station for the period 1881\u0026ndash;1895 were also used in the present study for the assessment of the homogeneity of the air temperature data set collected at Płońsk.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003esources: a) Mapa Szczeg\u0026oacute;łowa Polski WIG, Pas 38, Słup 31, 1933, based on Russian mapping from 1885, from the MAPSTER website (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://igrek.amzp.pl\u003c/span\u003e\u003cspan address=\"http://igrek.amzp.pl\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e), b) Topographic Map (WMS) (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.geoportal.gov.pl\u003c/span\u003e\u003cspan address=\"https://www.geoportal.gov.pl\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eThe weather station in Płońsk was established ten years before the \u003cem\u003eWarsaw network\u003c/em\u003e started to gather meteorological data (in 1875) at the initiative of a physician and amateur astronomer, Jan Walery Jędrzejewicz (Kowalczyk \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1888\u003c/span\u003e). Jędrzejewicz died in December 1887 and new measurements were carried out by a new local physician \u0026ndash; Leon Rutkowski \u0026ndash; from January of the following year. He and his assistants carried out measurements intermittently until 1904. The results of these observations were published as monthly summaries in a journal called the Pamiętnik Fizyograficzny (1882,..., 1910). This study used a data set from the period 1881\u0026ndash;1895 when the data were the most complete and of the highest quality. Missing data were found for individual days and two longer periods: in December 1887 and in June 1889 (a total of 67 days, 1.2% of all days in the surveyed period). The location of the station did not change during that period. However, the measurements were carried out at this point by two observers, which could affect the homogeneity of the data series. A median test was used to assess whether the annual mean air temperature values from the years 1881\u0026ndash;1887 and 1888\u0026ndash;1895 could be considered as coming from the same statistical population. The use of data from a relatively short, 15-year observation period also prompted us to check whether the thermal conditions in the years analysed differed remarkably from those noted in the Mazovia region in the entire 19th century.\u003c/p\u003e\u003cp\u003eAir temperature for the weather station at Poświętne (φ \u0026minus;\u0026thinsp;52\u0026deg;38\u0026rsquo;N, λ \u0026minus;\u0026thinsp;20\u0026deg;23\u0026rsquo;E, h \u0026minus;\u0026thinsp;101 m a.s.l.) was obtained from the IMGW-PIB Public Data Portal (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://danepubliczne.imgw.pl\u003c/span\u003e\u003cspan address=\"https://danepubliczne.imgw.pl\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). The study used data from 1951\u0026ndash;1980 and 1981\u0026ndash;2010 periods. The data set for the 1981\u0026thinsp;\u0026minus;\u0026thinsp;1980 time period was complete. In the time period 1981\u0026ndash;2010 missing data were found in June 1989 and from April to July 2009; a total of 152 days of missing data, representing 1.4% of all days in the study period.\u003c/p\u003e\u003cp\u003eAt the Płońsk weather station measurements were carried out three times per day at times close to the so-called \u003cem\u003eMannheim hours\u003c/em\u003e \u0026ndash; at 7:00 AM, 1:00 PM, and 9:00 PM local time. The Tmean was calculated according to the following formula:\u003c/p\u003e\u003cp\u003eTmean = (T \u003csub\u003e7 AM\u003c/sub\u003e + T \u003csub\u003e1 PM\u003c/sub\u003e + 2 \u0026middot; T \u003csub\u003e9 PM\u003c/sub\u003e) / 4 (1)\u003c/p\u003e\u003cp\u003eUntil 1970 measurements at the Poświętne weather station were taken at 7:00 AM, 1:00 PM, and 9:00 PM local time, the same as at the Płońsk weather station in the 19th century. The Tmean was also calculated in the same way. After 1970 the measurement times were changed to 6:00 AM, 12:00 PM, and 6:00 PM UTC, and the method of calculating the Tmean was changed twice. Since 1996 minimum and maximum temperatures (TN and TX) have been used in the calculation of Tmean.\u003c/p\u003e\u003cp\u003eThermometers used in the 19th century to measure TN and TX at the weather stations of the \u003cem\u003eWarsaw network\u003c/em\u003e were unreliable, and the TN and TX series lacked much data. It was therefore not possible to calculate the Tmean for Płońsk for the 19th century according to contemporary methodologies. Instead, the value of Tmean for Poświętne after 1970 was recalculated using sub-daily air temperature data for 6:00 AM, 12:00 PM, and 6:00 PM UTC, and the formula was used until 1970. This made it possible to obtain a homogenous Tmean data set for both of the studied periods.\u003c/p\u003e\u003cp\u003eThe different methods of calculating Tmean are not the sole reason that could make it difficult to compare the data series from Płońsk and Poświętne from the late 19th century and the second half of the 20th and the beginning of the 21st centuries. The compared air temperature datasets come from two different sites. The station in Płońsk was established at the astronomical observatory of Jędrzejewicz, in the meadows in the River Płonka valley, on the north-eastern edge of the town (Jędrzejewicz \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1882\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). Thermometers were placed in an open box protected from rain and snow by a zinc sheet. The box hung on the north-east wall of the observatory, which protected thermometers from direct sunlight. The mercury bulbs of the thermometers were affixed at 4.6 m above ground level (Jędrzejewicz \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1880\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe present-day weather station operating at Poświętne is located at a distance of approx. 1.0-1.2 km from the previous station. It is located on the outskirts of modern-day Płońsk similarly to the historical weather station. This is because the town has expanded and today buildings are located on both sides of the Płonka River valley (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). Therefore, the location of the weather station has changed, but its surroundings remain similar. The station established in Płońsk by Jędrzejewicz was located in a river valley; the station operating at Poświętne is located in a flat area outside of it. Although both stations were established within different forms of relief, it is worth noting that the Płonka Valley is small and shallowly incised. The elevation difference between the two weather stations is only about 5 m. Differences in thermal conditions at these two points that may result from orographic effects are therefore assumed to be inconsiderable.\u003c/p\u003e\u003cp\u003eAir temperature measurements performed at Poświętne in the period 1951\u0026ndash;2010 were taken in an instrument shed at a standard height of 2 m above ground level, i.e., at a lower height than measurements taken in the 19th century. However, the thermal gradient above a height of 2 m above ground level is smaller than that in the surface layer. It was therefore assumed that the difference in the height of the thermometers did not strongly affect the readings taken off the thermometers.\u003c/p\u003e\u003cp\u003eThe comparison of thermal conditions in the area of Płońsk in the 1881\u0026ndash;1895 time period and in the periods 1951\u0026ndash;1980 and 1981\u0026ndash;2010 made use of mean values (daily, monthly, annual), and the annual range of air temperature. Box plots of the mean monthly air temperature were prepared as well as histograms of the empirical distribution and empirical cumulative distribution function plots. The latter two were generated for each given meteorological season separately: winter (Dec-Feb), spring (Mar-May, summer (Jun-Aug) and autumn (Sep-Nov).\u003c/p\u003e\u003cp\u003eThe statistical significance of the differences found in mean values was tested using \u003cem\u003eStudent\u0026rsquo;s t-test\u003c/em\u003e or the Mann-Whitney \u003cem\u003eU-test\u003c/em\u003e when the data distribution deviated significantly from the normal distribution. The normality of the tested distributions was checked using the Shapiro-Wilk test.\u003c/p\u003e\u003cp\u003eThe duration of thermal seasons (winter, early spring, spring, summer, autumn, early winter) was also compared for the time periods 1881\u0026ndash;1895 and 1981\u0026ndash;2010. The dates of thermal season onset were defined using three threshold values of air temperature proposed by Merecki for Central Europe (1915), namely 0.0\u0026deg;C, 5.0\u0026deg;C, and 15.0\u0026deg;C.\u003c/p\u003e\u003cp\u003eThe annual cycle of air temperature was smoothed out due to the occurrence of non-periodic fluctuations in Tmean, making it difficult to unambiguously indicate the day on which Tmean had exceeded a given threshold value. Values of the multiannual Tmean for subsequent days of the year were replaced with values calculated using harmonic analysis (Fortuniak et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). Calculated smoothed values of the mean air temperature for subsequent days of the year took into account the zero harmonic (A\u003csub\u003e0\u003c/sub\u003e), i.e. annual mean air temperature and first (fundamental) harmonic. A calculation was performed for a 365-day series of Tmean using the formula:\u003c/p\u003e\u003cp\u003e\u003cem\u003ex\u0026rsquo;\u003c/em\u003e(\u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e)\u0026thinsp;=\u0026thinsp;\u003cem\u003eA\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eA\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e cos (2 π \u003cem\u003ef t\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e)\u0026thinsp;+\u0026thinsp;\u003cem\u003eB\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e cos (2 π \u003cem\u003ef t\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e), (2)\u003c/p\u003e\u003cp\u003ewhere:\u003c/p\u003e\u003cp\u003e\u003cem\u003ex\u0026rsquo;\u003c/em\u003e(\u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e) \u0026ndash; air temperature calculated from the model for each consecutive day of the year \u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e (1\u0026hellip;365),\u003c/p\u003e\u003cp\u003e\u003cem\u003eA\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e \u0026ndash; mean annual air temperature,\u003c/p\u003e\u003cp\u003e\u003cem\u003ef\u003c/em\u003e \u0026ndash; 1/365,\u003c/p\u003e\u003cp\u003e\u003cem\u003eA\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e i \u003cem\u003eB\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e \u0026ndash; Fourier coefficients:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{A}_{1}=\\:\\frac{2}{n}\\sum\\:_{i=1}^{n}T({t}_{i})\\text{c}\\text{o}\\text{s}(2\\pi\\:f{t}_{i}),\\:{B}_{1}=\\:\\frac{2}{n}\\sum\\:_{i=1}^{n}T\\left({t}_{i}\\right)\\text{s}\\text{i}\\text{n}\\left(2\\pi\\:f{t}_{i}\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ewhere:\u003c/p\u003e\u003cp\u003e\u003cem\u003eT\u003c/em\u003e(\u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e) \u0026ndash; multiannual Tmean for consecutive days of the year.\u003c/p\u003e\u003cp\u003eAfter determining the average length of the thermal seasons in the two time periods analysed, the difference in their length was calculated.\u003c/p\u003e"},{"header":"3 Results","content":"\u003cp\u003eThe first step was to answer the question whether the change of the observer at the Płońsk weather station at the end of the 19th century caused inhomogeneity of the analysed data set. The results of the median test (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.4464, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.833) indicate that there is no basis for rejecting the null hypothesis H\u003csub\u003e0\u003c/sub\u003e, that both samples have the same median of mean annual air temperature. Therefore, the dataset of air temperature at Płońsk from the whole time period 1881\u0026ndash;1895 was found to be statistically homogenous and the variability of thermal conditions in this period was considered to result only from the variation of climate controls.\u003c/p\u003e\u003cp\u003eNext, the authors answered the question whether the thermal conditions in 1881\u0026ndash;1895 differed remarkably from those in the Mazovia region throughout the 19th century.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe mean annual air temperature in Warsaw in the 15-year period 1881\u0026ndash;1895 equalled 7.3\u0026deg;C, the same as in the longer 1826\u0026ndash;1900 time period (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The first 15-year period 1826\u0026ndash;1840 was slightly cooler, with a mean annual air temperature of only 6.9\u0026deg;C (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). However, an analysis of variance (\u003cem\u003eF\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.7730, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.546) does not allow us to reject the null hypothesis H\u003csub\u003e0\u003c/sub\u003e, stating that the differences in mean annual air temperature in Warsaw in the 15-year sub-periods of the longer 1826\u0026ndash;1900 time period are not statistically significant.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMean annual air temperature (\u0026deg;C) during 15-year periods at the Warsaw Astronomical Observatory weather station from 1826 to 1900\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePeriods\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1826\u0026ndash;1840\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1841\u0026ndash;1855\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1856\u0026ndash;1870\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1871\u0026ndash;1885\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1885\u0026ndash;1900\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean annual air temperature\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e7.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eIn the northern part of the Mazovia region Tmean in the years 1981\u0026ndash;2010 (Poświętne station) was remarkably higher than Tmean in 1881\u0026ndash;1895 at Płońsk. The warming equalled 1.5\u0026deg;C (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). A statistically significant increase in air temperature between the end of the 19th century and the end of the 20th and the beginning of the 21st century was found in the majority of months. It was not found only in February, September, November and December. The largest increase in Tmean occurred in January and March, by 2.3\u0026deg;C, and of at least 2.0\u0026deg;C in April and August.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMean monthly and annual air temperature in the northern part of the Mazovia region in the years: A \u0026ndash; 1881\u0026ndash;1895 (Płońsk) and B \u0026ndash; 1981\u0026ndash;2010 (Poświętne); statistically significant differences are bolded\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"14\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eData set\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJan\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFeb\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMar\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eApr\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMay\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eJun\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eJul\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eAug\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eSep\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u003cp\u003eOct\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c12\"\u003e\u003cp\u003eNov\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c13\"\u003e\u003cp\u003eDec\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c14\"\u003e\u003cp\u003eYear\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-4.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-2.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e7.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e14.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e16.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e19.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e17.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e13.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e7.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e2.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e-1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e\u003cp\u003e7.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-1.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e9.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e15.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e18.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e20.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e19.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e14.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e8.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e3.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e-0.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e\u003cp\u003e9.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB-A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e2.3\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ep =\u003c/em\u003e\u003c/p\u003e\u003cp\u003e0.035\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e2.3\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e \u0026lt;\u003c/p\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e2.0\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e \u0026lt;\u003c/p\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e1.4\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e \u0026lt;\u003c/p\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e\u003cb\u003e1.1\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e\u003cb\u003e1.3\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e\u003cb\u003e2.1\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e \u0026lt;\u003c/p\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e0.6\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e\u003cb\u003e1.2\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e0.9\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.145\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e1.1\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e\u003cp\u003e\u003cb\u003e1.5\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e \u0026lt;\u003c/p\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe larger increase in air temperature in the winter months than in the summer months did not result in a significant reduction in the mean annual range of air temperature. It was 24.8\u0026deg;C in the period 1881\u0026ndash;1895 and 24.6\u0026deg;C in the period 1981\u0026ndash;2010.\u003c/p\u003e\u003cp\u003eWhat did change, however, was the ratio of the mean air temperature in spring and autumn. Autumn tended to be warmer than spring by an average of 0.3\u0026deg;C at the end of the 19th century. Today it is cooler than spring by an average of 0.5\u0026deg;C. This difference is not statistically significant at the p\u0026thinsp;\u0026le;\u0026thinsp;0.05, but these changes can suggest a shift towards a more continental climate in Poland in recent years compared with the late 19th century.\u003c/p\u003e\u003cp\u003eThe coldest day of the year occurred in the first half of January in both studied periods. In the 1881\u0026ndash;1895 time period it was two days \u0026ndash; 14 and 15 January with a Tmean of -6.8\u0026deg;C. In 1981\u0026ndash;2010 the coldest day of the year was 8 January with an average Tmean of -2.8\u0026deg;C. The warmest day of the year at the end of the 19th century occurred on 16 July (20.2\u0026deg;C) and in the 1981\u0026ndash;2010 time period it was observed two weeks later. On 31 July and 2 August the average Tmean was 21.5\u0026deg;C. It can also be seen that an outstanding feature of the annual cycle of the air temperature in both studied time periods is a cooling in mid-June (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eToday, the average Tmean in the northern part of the Mazovia region is higher than that at the end of the 19th century on 90% of the days of the year. This increase was at least 1.0\u0026deg;C on 67% of the days of the year. The largest increase of at least 5.0\u0026deg;C in Tmean was found between 13 and 16 January (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). Although the increase in Tmean occurred for most of the days of the year and it was quite large, it was not statistically significant for many days, which results from a high variability of Tmean on a given day from year to year. A statistically significant (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;0.05) increase in Tmean was found only on 18% of the days of the year. These were usually single days or two-day spells and accounted for 42% of the 64 significantly warmer days of the year. The longest spell of days for which a significant increase in Tmean was identified in the 1981\u0026ndash;2010 period compared to the 1881\u0026ndash;1895 period is 10-days long (1\u0026ndash;10 August). However, if one or two days with a statistically insignificant increase in air temperature are assumed not to interrupt such a period, then the longest spell would be 20 days (30 July \u0026ndash; 18 August). Seven-day spells of days with a significant increase in Tmean were observed in mid-January (12\u0026ndash;18 January) and late March \u0026ndash; early April (30 March \u0026ndash; 5 April), while three-day spells were identified in early May and late September.\u003c/p\u003e\u003cp\u003eThe average Tmean is the same during 5 days of the year today compared to the end of the 19th century. In addition, Tmean is today lower than at the end of the 19th century on 33 days (9% of all days of the year). None of these differences are statistically significant yet.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAnalysis of order statistics of Tmean values confirms an ongoing warming in the study area in all months. An increase in lower and upper quartiles, median as well as maximum values of Tmean was noted in all months (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Only minimum Tmean values in the winter months (December-February) and in April did not increase.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eOrder statistics (minimum, lower quartile, median, upper quartile, maximum) for Tmean in the northern part of the Mazovia region in the years: A \u0026ndash; 1881\u0026ndash;1895 (Płońsk) and B \u0026ndash; 1981\u0026ndash;2010 (Poświętne)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"13\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eData set\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJan\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFeb\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMar\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eApr\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMay\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eJun\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eJul\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eAug\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eSep\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u003cp\u003eOct\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c12\"\u003e\u003cp\u003eNov\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c13\"\u003e\u003cp\u003eDec\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"13\" nameend=\"c13\" namest=\"c1\"\u003e\u003cp\u003eMinimum\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-21.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-17.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-16.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-2.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e7.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e10.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e10.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e2.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e-3.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e-14.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-16.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-25.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-20.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-14.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-3.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e11.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e11.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e3.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e-1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e-13.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-17.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB-A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-3,6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-3.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-1.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e2.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e1.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-1.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"13\" nameend=\"c13\" namest=\"c1\"\u003e\u003cp\u003eLower quartile\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-7.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-5.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-2.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e11.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e14.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e16.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e15.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e11.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e4.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e-0.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-3.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-5.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-3.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e12.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e15.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e17.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e17.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e11.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e5.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-3.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB-A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e2.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e0.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"13\" nameend=\"c13\" namest=\"c1\"\u003e\u003cp\u003eMedian\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-2.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-1.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1,6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e14.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e16.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e19.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e17.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e13.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e7.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-0.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2,9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e9.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e15.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e18.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e20.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e19.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e13.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e9.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e3.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e0.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB-A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e2.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"13\" nameend=\"c13\" namest=\"c1\"\u003e\u003cp\u003eUpper quartile\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0,7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e16.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e19.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e21.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e19.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e16.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e10.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e5.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e1.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e18.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e20.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e22.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e21.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e16.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e11.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e6.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e2.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB-A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e2.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"13\" nameend=\"c13\" namest=\"c1\"\u003e\u003cp\u003eMaximum\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e12.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e18.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e26.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e25.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e28.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e27.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e22.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e17.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e10.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e8.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e15.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e23.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e27.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e29.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e31.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e31.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e23.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e20.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e13.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e10.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB-A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e3.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e2.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e3.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e1.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e3.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e1.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eAlthough the average air temperature in winter in the northern Mazovia region is now higher than at the end of the 19th century, periods of severe cold for several days still occur, such as during the winters of 1986/1987, 1996/1997, and 2005/2006. The likelihood of extremely cold air temperature was higher in the years 1981\u0026ndash;2010 than in the 1881\u0026ndash;1895 time period.\u003c/p\u003e\u003cp\u003eThe empirical distributions of Tmean in individual seasons differed for the two studied periods. The empirical distribution of Tmean was bimodal (except in autumn) at the end of the 19th century, while it was unimodal in the 1981\u0026ndash;2010 period, with spring, summer and autumn having a slightly lower modal value than that in the years 1881\u0026ndash;1895, but falling into the intervals of higher values. It is also apparent in each season of the year that the 1881\u0026ndash;1895 period features a higher frequency of low Tmean values and lower frequency of higher Tmean values compared to the 1981\u0026ndash;2010 time period (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe largest difference between the cumulative empirical distribution function for both studied time periods was noted for the summer in the interval of values from 17.6 to 20.0\u0026deg;C and for the winter in the interval of values from 0.1 to 2.5\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe differences between thermal conditions in 1881\u0026ndash;1895 and 1981\u0026ndash;2010 are bigger compared to differences between thermal conditions in 1881\u0026ndash;1895 and 1951\u0026ndash;1981. The mean monthly Tmean values were the same in April and August in 1881\u0026ndash;1895 and 1951\u0026ndash;1981. Tmean increased in the months from October to January and in March, and it was lower in May, July, and September in the time period 1951\u0026ndash;1980 compared with the years 1881\u0026ndash;1895. The said differences did not exceed 0.9\u0026deg;C and they were statistically insignificant (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). A statistically significant (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;0.05) change in Tmean identified in the 1951\u0026ndash;1980 period compared to the 1881\u0026ndash;1895 was found only on 3% of the days of the year (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). Of these, all but one three-days spell of days were single days. This three-days spell of days with a significant decrease in Tmean was observed in late June and early July (29 June \u0026minus;\u0026thinsp;1 July). Therefore, it may be concluded that the increase in air temperature occurred only from the 1980s onwards.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMean monthly and annual air temperature values for the northern part of the Mazovia region in the years: A \u0026ndash; 1881\u0026ndash;1895 (Płońsk) and B \u0026ndash; 1951\u0026ndash;1981 (Poświętne) and the differences between them\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"14\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eData set\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJan\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFeb\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMar\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eApr\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMay\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eJun\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eJul\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eAug\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eSep\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u003cp\u003eOct\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c12\"\u003e\u003cp\u003eNov\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c13\"\u003e\u003cp\u003eDec\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c14\"\u003e\u003cp\u003eYear\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-4.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-2.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e7.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e14.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e16.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e19.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e17.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e13.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e7.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e2.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e-1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e\u003cp\u003e7.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-3.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-2.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e7.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e13.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e17.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e18.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e17.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e13.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e8.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e3.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e-0.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e\u003cp\u003e7.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB-A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.6\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.1\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.0\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-0.9\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.2\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e-0.8\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e0.0\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e-0.5\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e0.4\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e0.9\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e0.8\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e\u003cp\u003e0.1\u003c/p\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e =\u003c/p\u003e\u003cp\u003e0,72\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe increase in air temperature between 1881\u0026ndash;1895 and 1981\u0026ndash;2010 also manifested itself in a change in the duration of thermal seasons, especially summer and winter. The duration of these two seasons was similar in the northern part of the Mazovia region at the end of the 19th century. Thermal winter lasted an average of 99 days and summer 102 days. Today, thermal summer lasts 119 days (an increase of 17 days) and winter lasts only 74 days. Early spring and early winter have drawn out by 4 days (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eAverage duration of thermal seasons (number of days) in the northern part of the Mazovia region in the years: A \u0026ndash; 1881\u0026ndash;1895 (Płońsk) and B \u0026ndash; 1951\u0026ndash;1981 (Poświętne) and the differences between them\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eData set\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWinter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eEarly spring\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eSpring\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eSummer\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eAutumn\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eEarly winter\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e102\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e29\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e119\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e33\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB-A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAll transitional seasons have shifted by several days. Today, thermal early spring starts on average 15 days earlier and ends 11 days earlier than at the end of the 19th century (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e"},{"header":"4 Discussion \u0026 conclusions","content":"\u003cp\u003eThe observed changes in Tmean in the northern part of the Mazovia region between the end of the 19th century and the end of the 20th and the beginning of the 21st centuries are similar to those determined in other regions of Poland and Central Europe (Piotrowicz \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Rebetez and Reinhard \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Brazdil et al. 2012; Nordli et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Urban and Tomczyński \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Kolendowicz et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Pospieszyńska and Przybylak \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The observed warming was approximately 1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4\u0026deg;C in these areas. As the air temperature trend in Toruń, Poznań, Wrocław and Krak\u0026oacute;w, \u003cem\u003ei.e.\u003c/em\u003e Polish cities with a population of 200 000 or more, is similar to that in Płońsk, we conclude that an urbanization contribution to the observed warming is small in Poland. Zhang et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) also found that the urbanization effect on global trends in mean air temperature is small in Europe and it is the strongest in East Asia.\u003c/p\u003e\u003cp\u003eIn other European regions, e.g. northern and southern Europe, the increasing trend in mean annual air temperature was somewhat weaker. For example, the air temperature increased by 0.9\u0026deg;C in Finland between 1909 and 2008 (Tiet\u0026auml;v\u0026auml;inen et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), by 0.7\u0026ndash;1.6\u0026deg;C in Iceland between 1871 and 2001 (Hanna et el. 2004), and by 0.6\u0026deg;C in Athens (1890\u0026ndash;2009) (Founda \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe observed increase in air temperature in the northern part of the Mazovia region varied seasonally. The highest increase occurred in spring; in March and April the air temperature increase at Płońsk exceeded 2.0\u0026deg;C. A similar pattern was found both at weather stations located close to the studied area, e.g. in Toruń or Poznań, and in other regions of Central Europe. In the Czech Republic, the increase in air temperature between 1882 and 2010 ranged between 1.3\u0026deg;C (autumn) to 1.9\u0026deg;C (summer) (Brazdil et al. 2012). Statistically significant warming at the end of the 20th and beginning of the 21st centuries compared to the end of the 19th century observed in Płońsk dataset in most cases results from a significant increase in air temperature on particular days of the year. We found several spells of such days which has been done in Polish climate change studies for the first time.\u003c/p\u003e\u003cp\u003eAn increase in the lower and upper quartile, median as well as minimum and maximum Tmean values was also found for Płońsk for selected months. These results correspond to results obtained in Poznań. The warming manifested itself there not only in an increase in the arithmetic mean but also in lower and upper quartiles, especially in August (Kolendowicz et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe trend in the duration of the thermal seasons varies much more in different regions of Europe than the trend in mean annual air temperature. In Toruń, as in Płońsk, the duration of the summer increased significantly (by an average of 18 days in 2001\u0026ndash;2010 compared with 1871\u0026ndash;1880), while winter shortened (by 29 days) (Pospieszyńska and Przybylak \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The duration of transitional seasons did not change significantly, similar to Płońsk and the dates of their occurrence also shifted. An increase in the length of summer (by 11 days) and autumn (by 5 days) and shortening of winter and spring (by 4 days) were noted in Tartu (Estonia) between 1891 and 2003 (Kull et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). A shortening of winter was observed at many Eastern European localities between 1881 and 1995 (Jaagus et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) and ranged from a few days to more than 30 days. In contrast, no significant trends in the duration of summer were detected there. The duration of spring increased at selected weather stations, e.g. in Kyiv by 10.4 days. It should be noted that differences in trends in the duration of thermal seasons can result from differences in the method of the delimitation of seasons in the studies mentioned above.\u003c/p\u003e\u003cp\u003eThe increase in air temperature in the northern part of the Mazovia region has been pronounced only since the 1980s. Tmean was not higher in the 1951\u0026ndash;1980 period than that in the period 1881\u0026ndash;1985. This conclusion confirms the results of other research studies focused on the assessment of long-term air temperature trends in Poland and in other European countries (Gjelten et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Hanna et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Kolendowicz et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Labudov\u0026aacute; et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). An increase in Tmean was noted for Poznań in the time period 1848\u0026ndash;2016. However, no trend was identified for the sub-period 1902\u0026ndash;1987, while in 1987\u0026ndash;2016 the air temperature increase was as high as 1.4\u0026deg;C (Kolendowicz et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The spatially averaged air temperature in Slovakia was almost the same in the 1961\u0026ndash;1990 time period as that in 1931\u0026ndash;1960. A large increase in air temperature was only noted in the 1991\u0026ndash;2014 time period (Labudov\u0026aacute; et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). An increase in air temperature was observed in the town of \u0026Aring;s (southern Norway) in the 1930s, and since the late 1970s (Gjelten et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). The 1960s were a relatively cool period. Many other weather stations in northern Europe showed a negative air temperature trend for the time period 1931\u0026ndash;1960 (e.g. Stockholm in Sweden and Reykjavik and Grimsey in Iceland) or no trend at all (e.g. Copenhagen in Denmark, Torshavn in the Faroe Islands) (Hanna et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2004\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eAn important issue when comparing meteorological datasets from quite distant time periods is always to answer the question whether, and to what extent, the obtained results could be affected by differences in methods of measurement and data processing. In the case of this study the questions are whether the data from the weather stations at Płońsk and Poświętne describe well the thermal conditions in the northern Mazovia region and to what extent air temperature datasets from these stations could be affected by changing the location of the weather station.\u003c/p\u003e\u003cp\u003eAccess to metadata is crucial in detecting potential inhomogeneities. The weather station in Poświętne was established in 1923 and from the start of its operation carried out measurements in accordance with the methodology used by IMGW-PIB and its predecessors. Therefore, the metadata are known and easily accessible. In the case of the weather station established by Jędrzejewicz in Płońsk in the 19th century the metadata were published in the journal Pamiętnik Fizyograficzny and in other periodicals of that time (Jędrzejewicz \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1880\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1882\u003c/span\u003e; Uwagi o\u003cem\u003e\u0026hellip;\u003c/em\u003e 1904).\u003c/p\u003e\u003cp\u003eThe exposure mode of thermometers in the 19th century was different from that used today. The 19th century standard was to place thermometers on the north (shaded, not sunny) wall of a building. This is how thermometers were placed in Płońsk, on the north-east wall of Jedrzejewicz\u0026rsquo;s astronomical observatory, at a height 4.6-5.0 m above ground level. At the weather station in Poświętne, thermometers were exposed in a Stevenson screen standing in an open area, 2.0 m above ground level. A comparison of air temperature measurements using different modes of thermometer exposure were carried in the UK (Parker \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). The results of the study show a lower diurnal temperature range measured on the north wall of the building compared to measurements in the Stevenson screen. However, the annual Tmean values were similar regardless of the location of the thermometers. The air temperature measured on the north wall of the said building and in the Stevenson screen also hardly differed in Denmark. The average differences in mean monthly air temperature did not exceed 0.1\u0026deg;C. Slightly larger differences were found in Iceland where the higher air temperature was found on the north wall of the said building during the summer months (Nordli et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). This is due to the location of these stations close to the northern Arctic Circle where the sun almost never sets in summer and it can illuminate the north walls of buildings both in the morning and evening. However, this is not an issue at the latitude of Poland.\u003c/p\u003e\u003cp\u003eTmean values can be also affected by the method of their calculation, as shown by Harris and Pedersen (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1995\u003c/span\u003e), Urban (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) and Kuśmierek-Tomaszewska et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). In the 19th century, the Tmean value was calculated at the Płońsk site as a weighted arithmetic mean according to Formula 1. The measurement hours, i.e. 7:00 AM, 1:00 PM, and 9:00 PM were determined at the local mean time of the Plońsk meridian 20\u0026deg;22\u0026rsquo;E. A similar method of calculating Tmean was used at climatological weather stations of IMGW-PIB until 1970, i.e. also at the weather station in Poświętne (Płońsk). Later, the methods of Tmean calculation changed twice. Today, Tmean is calculated as the arithmetic mean of the TX, TN, T \u003csub\u003e7 AM UTC\u003c/sub\u003e and T \u003csub\u003e6 PM UTC\u003c/sub\u003e. The method of Tmean calculation used at the IMGW-PIB weather stations since 1995 gives results up to a few tenths of a \u0026deg;C lower depending on the month analysed compared to the methodology used prior to 1970 (Urban \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Kuśmierek-Tomaszewska et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Thus, the same methodology (that used until 1970) was applied to the entire dataset in order to reduce as much as possible the impact of changes in the Tmean calculation on the compared air temperature values. This procedure reduced any potential inhomogeneity in the data, although it probably did not remove it completely, due to the fact that the timing of the measurements had changed after 1970 to 6:00 AM, 12:00 PM, and 6:00 PM UTC. While the timing of the morning and midday Tmean observations are similar today to that used at the end of the 19th century, the evening Tmean observation time is now approximately 2 hours earlier. The impact of this key change on the compared Tmean values is likely to be small in the colder half of the year when evening measurements both in 1881\u0026ndash;1895 and 1981\u0026ndash;2010 were carried out already after sunset. In the summertime, 6:00 PM UTC falls in the evening, while 9:00 PM at Płońsk local mean time (around 7:50 PM UTC) is already nighttime. Tmean values in summer months in the 1981\u0026ndash;2010 time period used in this study may therefore be slightly overestimated with respect to data from the late 19th century. However, this issue requires further in-depth study using data from nearby weather stations run by the IMGW-PIB, where measurements are now made hourly.\u003c/p\u003e\u003cp\u003eIn conclusion, it needs to be said that a key issue in the study of climate change is information on data quality. Information on the quality of data as well as on the measurement and data processing methods makes it possible to detect and sometimes eliminate inhomogeneity of meteorological datasets, which has been done to a considerable extent in the case of the Tmean data from Płońsk and its surroundings.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eK.J. and E.Ż. contributed to the study conception and design. K.J. and T.B. contributed to material preparation and data collection. Analysis were performed by K.J. and E.Ż. The first draft of the manuscript was written by K.J. and it was commented and supplemented E.Ż. and T.B. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eDigitized Tmean data set from the Płońsk weather station (1881-1895 period) that was published in Pamiętnik Fizyograficzny (1882-1910) is stored in the repository of the Section of Climatology of the Faculty of Geography and Regional Studies University of Warsaw and is available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBr\u0026aacute;zdil R, Zahradn\u0026iacute;ček P, Pišoft P, Štěp\u0026aacute;nek P, Běl\u0026iacute;nov\u0026aacute; M, Dobrovoln\u0026yacute; P (2012) Temperature and precipitation fluctuations in the Czech Republic during the period of instrumental measurements. 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J Clim 34:1923\u0026ndash;1945. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1175/JCLI-D-20-0389.1\u003c/span\u003e\u003cspan address=\"10.1175/JCLI-D-20-0389.1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"theoretical-and-applied-climatology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"taac","sideBox":"Learn more about [Theoretical and Applied Climatology](https://www.springer.com/journal/704)","snPcode":"704","submissionUrl":"https://submission.nature.com/new-submission/704/3","title":"Theoretical and Applied Climatology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7101735/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7101735/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe paper examines changes in thermal conditions in Płońsk (central Poland) between the end of the 19th century and the beginning of the 21st century. The study uses two air temperature datasets: newly found and digitised dataset from a period 1881\u0026ndash;1895 and a dataset from a nearby Institute of Meteorology and Water Management \u0026ndash; National Research Institute (IMGW-PIB) weather station from a period 1951\u0026ndash;2010. No statistically significant changes in mean daily air temperature (Tmean) were found between 1881\u0026ndash;1895 and 1951\u0026ndash;1980. The increase in Tmean of ca. 1.5\u0026deg;C was found between 1881\u0026ndash;1895 and 1981\u0026ndash;2010. As Płońsk is a small town this increase can be considered as unbiased by the Urban Heat Island intensification. The largest shift in the cumulative empirical distribution function of Tmean between both studied time periods was noted for the summer in the interval of values from 17.6 to 20.0\u0026deg;C and for the winter in the interval of values from 0.1 to 2.5\u0026deg;C The longest spells of days with a statistically significant warming were identified in mid-January (increase of at least 5.0\u0026deg;C between 13 and 16 January), late March \u0026ndash; early April and in the first half of August (the longest spell of ten consecutive days). A significant reduction in a duration of the thermal winter (a reduction of 25 days) and extending of the summer (an increase of 17 days) were detected as well as the shift in the timing of transitional seasons.\u003c/p\u003e","manuscriptTitle":"Changes in thermal conditions in the northern part of the Mazovia (central Poland) between the late 19th and early 21st centuries","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-28 16:59:37","doi":"10.21203/rs.3.rs-7101735/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-10T12:14:50+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-10T11:47:49+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-29T09:58:40+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"97847709772676569674580045716143764083","date":"2025-07-26T19:54:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"162401414211063796093971411915895433214","date":"2025-07-25T06:45:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"267594224521300305633568829081060515767","date":"2025-07-24T10:47:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-24T08:12:18+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-13T22:03:12+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-13T22:02:05+00:00","index":"","fulltext":""},{"type":"submitted","content":"Theoretical and Applied Climatology","date":"2025-07-11T12:27:02+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"theoretical-and-applied-climatology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"taac","sideBox":"Learn more about [Theoretical and Applied Climatology](https://www.springer.com/journal/704)","snPcode":"704","submissionUrl":"https://submission.nature.com/new-submission/704/3","title":"Theoretical and Applied Climatology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"66c8e13b-ba65-4f75-94cd-3047aa8d74d3","owner":[],"postedDate":"July 28th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-02T16:06:29+00:00","versionOfRecord":{"articleIdentity":"rs-7101735","link":"https://doi.org/10.1007/s00704-026-06023-2","journal":{"identity":"theoretical-and-applied-climatology","isVorOnly":false,"title":"Theoretical and Applied Climatology"},"publishedOn":"2026-01-27 15:58:56","publishedOnDateReadable":"January 27th, 2026"},"versionCreatedAt":"2025-07-28 16:59:37","video":"","vorDoi":"10.1007/s00704-026-06023-2","vorDoiUrl":"https://doi.org/10.1007/s00704-026-06023-2","workflowStages":[]},"version":"v1","identity":"rs-7101735","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7101735","identity":"rs-7101735","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}