Pre-industrial temperature variability on the Swiss Plateau derived from the instrumental daily series of Bern and Zurich

Abstract

Abstract. We describe the compilation of two early instrumental daily temperature series from Bern and Zurich, Switzerland, starting from 1760 and 1756, respectively. The series are a combination of numerous small segments from different observers at different locations within and outside the two cities that are converted to modern units and homogenized. In addition, we introduce a methodology to estimate the errors affecting daily and monthly mean values derived from early instrumental observations. Given the frequent small data gaps, we merge the two daily series into a more complete series representing the central Swiss Plateau. We finally compare the homogenized monthly series with other temperature reconstructions for Switzerland. We find significant differences before 1860, pointing to biases that might affect some of the most widely used instrumental data sets. In general, the homogenization of temperature measurements at the transition between the early instrumental and national weather service eras remains a problematic issue in historical climatology and has significant implications for other fields of climate research.

A 258-year-long data set of temperature and precipitation fields for Switzerland since 1763

“…The resampled temperature fields were further improved with data assimilation, and the resampled precipitation fields were bias corrected with quantile mapping. Extending a daily reconstruction for Switzerland as far back as the end of the 18th century was possible because of the data rescue efforts of CHIMES and follow-up projects (Brugnara et al, 2020b;Pfister et al, 2019;Brugnara et al, 2022).…”

“…Systematic measurements of meteorological data in Switzerland only started in the 1860s with the establishment of the national weather service (Hupfer, 2019;Begert et al, 2005). To reconstruct weather in the late 18th and early 19th century, we, therefore, relied on data that have been rescued by various initiatives (Brugnara et al, 2020b;Pfister et al, 2019;Camuffo and Jones, 2002;Klein Tank et al, 2002;Füllemann et al, 2011;Brugnara et al, 2022). Such early instrumental data are challenging to work with because common measurement standards had not yet been developed when the observations were recorded.…”

“…Only break points that were significant without metadata were considered since only very few metadata are available. For Bern, Zurich, Basel, and Geneva homogenized series were used which are based on various short series (Brugnara et al, 2022;.…”

“…The 258-year-long reconstructions should reproduce daily weather and long-term variability in temperature and precipitation over Switzerland. We assess this long-term variability by comparing the field mean of our data set to other data sets covering the same or similar periods (Valler et al, 2022;Casty et al, 2005;Brugnara et al, 2022;MeteoSwiss, 2021c). These data sets consist either of only observations, statistical reconstructions based on proxy data and observations, or reanalyses.…”

The weather diaries of the Kirch family: Leipzig, Guben, and Berlin, 1677–1774

“…London (Cornes et al, 2012b), Zwanenburg/DeBilt, shorter series from Nuremberg, Basel, Geneva, Zurich and Bern (e.g., Brugnara et al, 2022), St. Peterburg, Uppsala, and several Italian series from the IMPROVE project (Camuffo and Jones, 2002), among others (see inventory by Brönnimann et al, 2019). However, also other, non-instrumental weather diaries may be a good resource for comparisons, including those from Nuremberg (Brönnimann, 2023), Wroclaw (Przybylak, and Pospieszyńska, 2010), Gdansk (Filipiak et al, 2019) or Zurich (see weather diaries in EURO- CLIMHIST, Pfister et al, 2017).…”