Climate of Moscow at the end of Little Ice Age

Better understanding of current climate changes needs a full knowledge about regional specific of thermal conditions at the end of Little Ice Age. So, the earliest available meteorological data are important. First regular daily qualitative meteorological observations were taken in Moscow city from 1657 to 1675. Episodic short series of instrumental measurements were made there for the first time in 1731; regular daily measurements started in 1779 when one of Mannheim network stations was founded in Moscow.

         All known old data series of the air temperature T measurements in Moscow since 1779 were collected and analyzed. Mannheim station existed there from 1779 to 1797 but average values of T are available from issues of Ephemerides Societatis Meteorologicae Palatinae only for the period 1779–1792. High accuracy of measurements at Mannheim network is confirmed by high correlation co-efficient between monthly-averaged T values in Moscow and at closest stations (Warsaw and St. Petersburg): up to 0.82-0.84 on separate months.

         Different methodical questions (unknown location of the station, unknown conditions of thermometer installation, its height and shading, an accuracy of its calibration, etc.) were studied. As a result it was found that the most probable error due to thermometer installation close to the northern building wall is ±0.1÷0.2 ºС; the error of daily-averaged T due to unknown height of measurements is ±0.1 ºС; the calibration accuracy in Mannheim was about ±0.1 ºС. Thus, a total error of T on average of a day in the 18^th century was not higher than ±0.3÷0.4 ºС. Probably it was even less because separate components of the error may be multidirectional. For the first time mean-annual T in Moscow was received for 1783, and the most probable values were estimated for 1784 and 1785 using the data of the closest Mannheim station (Saint-Petersburg) for separate months with data gaps. The end of Little Ice Age manifeted at extremely low minimal values of T: up to –31 ˚R (–38.8 ˚С) in December 17^th, 1788. However, thermal conditions from June to September changed only a bit since the 18^th century till nowadays (differences are not statistically significant with the 0.95 confidence probability).  

         Later measurements in Moscow were renewed since 1808 and broken again in August of 1812 due to Napoleon’s invasion and terrible Moscow fire. For the first time unknown data series of everyday measurements which were made by Ivan Lange in 1816–1817 were found and studied. As is known the famous 1816 ‘Year Without a Summer’ was noted almost all over the World by extremely cold summer as probable result of Mount Tambora eruption in 1815. Nevertheless, it was found that summer of 1816 in Moscow was comparatively cool but not extremely cold: monthly-averaged T there was 15.7, 17.3 and 14.5 ˚С in June, July and August, respectively, and 15.8 ˚С on average of the summer. Thus, 1816 occupies only 27^th place among the coldest summers in the city during 216 years.

         Author is thankful to the memory of his late PhD student Ekaterina L. Vasilenko.