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Phenological data have become increasingly important as indicators of long-term climate change. Consequently, long-term homogeneity of the records is an important aspect. In this paper, we apply a breakpoint detection algorithm to the phenological series from the Swiss Phenology Network (SPN). A combination of three statistical tests is applied and different constraints are tested with respect to the choice of reference series. Breakpoint detection is only possible for a fraction of the series due to the shortness of some series and the lack of suitable reference series. Spring phases are more likely to be suitable than fall phases because of their higher spatial correlation. Out of nearly 3000 phenological series with at least 20 data points, only about 5% were found to be significantly inhomogeneous, although a visual validation indicates that many mid-sized breakpoints remained undetected. The detected breakpoints were compared with metadata and more than half of them could be attributed to a change of observer. [ABSTRACT FROM AUTHOR]

The evolution of mean annual minimum (TMIN) and maximum temperature (TMAX) on the Swiss Plateau shows distinct differences over the last 150 years. TMIN increased relatively steadily by about 3 °C. TMAX increased by only 1.5 °C with substantial decadal variability and hardly any increase until about 1940. However, in the most recent decades, TMAX trends are somewhat larger than TMIN trends. While most aspects of the TMIN evolution can be well explained by the global forcing and the modifying effects of the large-scale atmospheric flow alone, local sunshine duration (SD) information is crucial to explain major features of the TMAX series and the differences between TMIN and TMAX since about 1950. SD shows no clear trend until 1950, a decline from 1950 to 1980 and an increase since 1980 resembling the global dimming and brightening signal. TMAX is strongly influenced by SD and the TMAX evolution can be well reconstructed with local TMIN and SD. Strong TMAX declines are found from 1950 to the 1970s. TMIN shows no trend in this period. Between 1980 and about 2005, both TMIN and TMAX show strong increases caused by the greenhouse gas forcing, decreasing aerosols and probably also decreasing cloud cover. Since about 2005, the increases are weaker. The brightening has weakened and the warming effect of the continuously growing greenhouse gas forcing has additionally been reduced by cooling effects caused by large-scale atmospheric flow anomalies. The reasons for the considerable differences in the TMIN and TMAX evolution prior to 1950 remain unknown and further investigations are needed to shed more light on this disparity. [ABSTRACT FROM AUTHOR]