Global climate change impacts can already be tracked in many physical and biological systems; in particular, terrestrial ecosystems provide a consistent picture of observed changes. One of the preferred indicators is phenology, the science of natural recurring events, as their recorded dates provide a high-temporal resolution of ongoing changes. Thus, numerous analyses have demonstrated an earlier onset of spring events for mid and higher latitudes and a lengthening of the growing season. However, published single-site or single-species studies are particularly open to suspicion of being biased towards predominantly reporting climate change-induced impacts. No comprehensive study or meta-analysis has so far examined the possible lack of evidence for changes or shifts at sites where no temperature change is observed. We used an enormous systematic phenological network data set of more than 125 000 observational series of 542 plant and 19 animal species in 21 European countries . Our results showed that 78% of all leafing, flowering and fruiting records advanced (30% significantly) and only 3% were significantly delayed, whereas the signal of leaf colouring/fall is ambiguous. We conclude that previously published results of phenological changes were not biased by reporting or publication predisposition: the average advance of spring/summer was 2.5 days decade À1 in Europe. Our analysis of 254 mean national time series undoubtedly demonstrates that species' phenology is responsive to temperature of the preceding

We analyzed the leaf phenology of European beech (Fagus sylvatica) and its variation due to spatial and temporal climatic variability, using a modified data set of the phenological network in Slovenia. We used first leaf unfolding (LU) and general leaf colouring (LC) time series of 47 sites (altitudes from 55 to 1,050 m a.s.l.) and corresponding climate series (52 of precipitation and 38 of temperature) for the period 1955-2007, collected by the Environmental Agency of the Republic of Slovenia. Across the network in average, LU occurred from 14 April until 13 May, and LC from 3 October until 29 October. LU was delayed by 2.6 days and LC was promoted by 1.9 days when the altitude increased by 100 m. Year-to-year variation of LU was significantly correlated with March and April temperatures. March temperatures had a greater effect at lower elevations and April ones at higher elevations. LC was related to August and September temperatures, and occurred later if the temperatures were higher.Recently, March and April temperatures showed an increasing trend and LU occurred 1.52 days earlier per decade at 1,000 m a.s.l. but no significant shifts were observed at lower altitudes. August temperatures were also increasing but the trends of LC were not significant and were not clearly related to altitude. Our detailed subregional data from a relatively small area with high geographic variability showed that changes in climate affect phenological response, mainly leaf unfolding, to a greater degree at higher altitudes than at lower ones.

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Climate change is expected to exacerbate heat stress at the workplace in temperate regions, such as Slovenia. It is therefore of paramount importance to study present and future summer heat conditions and analyze the impact of heat on workers. A set of climate indices based on summer mean (Tmean) and maximum (Tmax) air temperatures, such as the number of hot days (HD: Tmax above 30 °C), and Wet Bulb Globe Temperature (WBGT) were used to account for heat conditions in Slovenia at six locations in the period 1981–2010. Observed trends (1961–2011) of Tmean and Tmax in July were positive, being larger in the eastern part of the country. Climate change projections showed an increase up to 4.5 °C for mean temperature and 35 days for HD by the end of the twenty-first century under the high emission scenario. The increase in WBGT was smaller, although sufficiently high to increase the frequency of days with a high risk of heat stress up to an average of a third of the summer days. A case study performed at a Slovenian automobile parts manufacturing plant revealed non-optimal working conditions during summer 2016 (WBGT mainly between 20 and 25 °C). A survey conducted on 400 workers revealed that 96% perceived the temperature conditions as unsuitable, and 56% experienced headaches and fatigue. Given these conditions and climate change projections, the escalating problem of heat is worrisome. The European Commission initiated a program of research within the Horizon 2020 program to develop a heat warning system for European workers and employers, which will incorporate case-specific solutions to mitigate heat stress.Electronic supplementary materialThe online version of this article (10.1007/s00484-018-1530-6) contains supplementary material, which is available to authorized users.

Knowledge of plant-weather relationships can improve crop management, resulting in higher quality and more stable crop yields. The annual timing of spring phenophases in mid-latitudes is largely a response to temperature, and reflects the thermal conditions of previous months. The effect of air temperature on the variability of hazelnut (Corylus avellana L.) phenophases (leafing, flowering) was investigated. Meteorological and phenological data for five cultivars were analysed over the periods 1969-1979 (P1) and 1994-2007 (P2) in Maribor, Slovenia. Phenological data series were correlated strongly to the temperature of the preceding months (R(2): 0.64-0.98) and better correlated to daily maximum and mean temperatures than to daily minimum temperatures. About 75% of phenophases displayed a tendency towards earlier appearance and a shorter flowering duration during P2, which could be explained by the significant temperature changes (+0.3°C/decade) from December to April between 1969 and 2007. An increase in air temperature of 1°C caused an acceleration in leafing by 2.5-3.9 days, with flowering showing higher sensitivity since a 1°C increase promoted male flowering by 7.0-8.8 days and female flowering by 6.3-8.9 days. The average rate of phenological change per degree of warming (days earlier per +1°C) did not differ significantly between P1 and P2. An estimation of chilling accumulation under field conditions during 1993-2009, between 1 November and 28 February, showed that all four of these months contributed approximately similar amounts of accumulated chilling units. The growing degree days (GDD) to flowering were calculated by an estimated base temperature of 2°C and 1 January as a starting date, given the most accurate calculations. In general, thermal requirements were greater in P2 than in P1, although this difference was not significant. Longer-time series data extended to other agricultural and wild plants would be helpful in tracking possible future changes in phenological responses to local climate.