Two Centuries of Air Temperature Observations in the City of Trento in the Alps (1816-2016)

Permanent observations of air temperature were initially established in Trento (a mid-sized city in the Italian Alps) in 1816, ad have been rather regularly performed since that year. However, observatories, observers and instruments have often changed in 200 years, resulting in shorter series of data recorded in a variety of sources. After a careful search for both published and unpublished data in various archives and libraries, the history of such observations has been documented in detail, thanks to a rich collection of meta-data concerning methods of observation, location of measurements and observers. Then a long record of monthly mean temperature data was obtained, as a composition of shorter time series from the various available sources. Also, by application of homogenization techniques, inhomogeneities have been detected and, as far as possible, related to changes occurred in either the observers, or the procedures, or the institutions recording the observations. The resulting homogeneous series was analyzed for regression, randomness and statistical significance, on both annual and seasonal bases. Regression analysis shows a significant positive trend in the annual mean temperatures. This is particularly remarkable in the last 30 years, in agreement with findings from other long series.