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E. Linacre |
7/'98 |
Temperature measurements since 1792 at Cracow provide the longest record in Poland (1). Continuous readings started earlier elsewhere, e.g. in 1719 at Berlin, 1743 at St Petersburg, 1755 at Basel, 1756 at Stockholm, 1757 at Paris, 1763 at London, 1764 at Edinburgh, 1768 at Geneva, 1771 at Prague, 1775 at Vienna, and 1779 at Warsaw (2). Most of these were coordinated in 1795 to form what was known as the ‘Florence grid’.
The annual mean values at Cracow varied in parallel with the average of values from Prague, Warsaw and Vienna (1). All show a fall during the 1820’s, followed by a gradual rise until the present. The rise at Cracow was about 1.8 K. En route there were fluctuations with a period of about 11 years.
An analysis of monthly mean temperatures at Cracow during 1826-1990 shows useful persistence between February and March average temperatures, and, to a lesser extent, a correlation between those of May and July (3). Annual mean values show some periodicity of about 8 years.
Annual means at Cracow have risen from 7.6° C in 1826-55, to 8.1° C in 1886-1915, to 9.0° C in 1961-90, i.e. a total rise of 1.4 K (3). This century, Cracow temperatures rose above the averages of three adjacent small towns from -0.3 K in 1890 to +1.0 K in 1990, i.e. 1.2 K. The latter increase is attributed to the growth of Cracow into a large industrial centre. At the three adjacent small towns, there is no perceptible trend in annual mean temperatures during the last century.
Records of the length of the snout of the Grosser Aletsch glacier in Switzerland over the past thousand years show maximum extensions around the years 1120, 1350, 1620, 1870, i.e. with a periodicity of about 250 years (2). More recently there has been a retreat by about 3 km.
References
(1) Trepinska, J., Z. Ustrnul & L. Kowanetz 1997. Variability of the air temperature in central Europe in the years 1792-1995. Geographica Polonica, 70, 43-52.
(2) Trepinska, J. 1992. Thermic fluctutaions in Poland and in Europe - from the Little Ice Age till the contemporary warming. Paper to the 5th Symposium on the Protection of Forest Ecosystems, p 13-22.
(3) Kozuchowski, K., J. Trepinska and J. Wibig 1994. The air temperature in Cracow from 1826 to 1990: persistence, fluctuations and the urban effect. Internat. J. Climatology, 14, 1035-49.