Recovery of the early period of long instrumental time series of air temperature in Padua, Italy (1716–2007)

The longest series of instrumental observations have a number of problems in the early period. This paper is focused on the recovery of early indoor and outdoor observations in Padua and their transformation in terms of a modern series. The Padua series was started by Giovanni Poleni with outdoor observations in 1716–1718, but soon, the readings passed indoors (1725–1764) to join the directives of the Royal Society, London. The indoor readings were recovered within the EU project IMPROVE, but it was necessary to transform indoor observations into outdoor ones, and this was possible thanks to the presence of simultaneous indoor and outdoor observations by Morgagni in Padua and Beccari in Bologna. These parallel series were also useful to fill a short gap. Another problem was to reconstruct the calibration of the Amontons thermometer, which changed when Poleni moved to a new house. Also the problem of the use of variable and/or different sampling times was solved making reference to the trend of the daily cycles in the different seasons and under diverse weather conditions. The data analysis has shown a trend that appears similar to the well-known results (IPCC 2007) for the last 160 yr but a less marked recent warming for winter and autumn. The 18th century was characterized by cold winters (culminated 1709 and 1740) and springs, and warm summers and autumns. A well-marked Bruckner cycle (35.8 yr), continually repeated and attenuated, is visible for the period 1716–1930. The wide time scale and the repetition of warmer and colder periods over two-thirds of the series noted in Padua and other Mediterranean stations may induce us to suppose that such cycles could continue in the future, at least on the local scale.