Temperature observations (1855-1884) made by Abraham Bredahl Rosenvinge of the Bakke Estate in Trondheim – a quality assessment

Abraham Bredahl Rosenvinge lived at the Bakke Estate in Trondheim. He started a series of consecutive observations, which he carried out three times a day from 1 April 1855 until 7 July 1884. The series ceased a few days before his death. The aim of the study is to investigate the quality of his observations, and decide whether they should be included in a homogenized, composite, long-term series of observations for Trondheim.

Several quality tests were performed. An inhomogeneity in evening observations in summer 1871 was detected, apparently caused by the construction of a new main building on the farm. However, this influenced the daily mean temperatures only in May and June, and by only 0.14 °C and -0.22 °C respectively. Temperature differences between Bakke and another station in Trondheim located at Our Lady’s Church indicated that none of the thermometers were out of calibration. The testing revealed that Rosenvinge’s observations should be included in a composite long-term series of observations rather than the alternative observations carried out at Our Lady’s Church.

Recent observations (1981-2010) at Værnes, 25 km east of Trondheim, were nominally 0.9°C warmer than at Bakke (1855-1884). The observation sites were judged equal, so temperature in Trondheim has increased about 1°C since Rosenvinge carried out his observations.