Nicolaus Copernicus University Centre for Climate Change Research

The database contains meteorological measurement data of air temperature in Wrocław from 1773 to 1781 converted from °F to °C. The observations were made by Johann Ephraim Scheibel in the area of the Gymnasium, which belonged to the Church of St. Elizabeth (central Wrocław). Measurements were taken three times a day: morning, midday, and evening; however, the detailed hours of observation are not known. The database also includes the daily average air temperature values, calculated as a weighted average from the three time points: (morning + midday + 2 × evening)/4. The original meteorological registers were published in the newspaper Oekonomische Nachrichten der Patriotischen Gesellschaft in Schlesien, issued in Wrocław from 1773 to 1781. In the years 1773–76, meteorological data were published in each weekly edition of the newspaper (usually seven days of observations ending on Thursday; the newspaper was issued on Saturday). From 1777 onwards, data were published for the entire month and in 3-month blocks in the last two years.

To check the probable biases in the calculation of MDATs, we assessed them using hourly air temperature data from Wrocław for the period 2013-2021. The values of the introduced corrections for the particular months are shown in Table 1. If the historical observations were made at times 6-7, 12-13, and 20-21 (formulas 7-10), then the biases are very small and on average do not exceed ±0.2°C (see mean 7-10, Table 1). On the other hand, maximum biases oscillate from 0.1 °C (December and January) to -0.5 °C (August to October).