We investigate the link between warm-temperature extremes in Europe and the persistence of large-scale atmospheric-circulation patterns for both winter and summer, along with some possible physical mechanisms connecting the two. We assess atmospheric persistence, leveraging concepts from dynamical systems theory, and reconcile this approach with the more conventional meteorological views of persistence. We find that wintertime warm spells are partly associated with persistent zonal advection at the surface level but display no statistically significant persistence anomaly in the mid-troposphere. For summertime heatwaves, we find a weak yet significant link to anomalously persistent circulation patterns in the mid-troposphere, while there are few significant persistence anomalies of the surface circulation pattern. We further find no evidence of a strong warm-temperature advection signal. This suggests that other radiative and dynamical processes, for example sensible heating and adiabatic warming, as well as local effects, could play a more important role than large-scale warm-temperature advection for these events. We thus argue that persistent atmospheric configurations are not a necessary requirement for warm-temperature extremes and that the results depend to a considerable extent on region and tropospheric level.

Extreme temperatures can cause severe disruptions to society, from negative health consequences to infrastructure damage. Accurate and timely weather forecasts contribute to minimise these detrimental effects, by supporting early warning systems. In this context, information on the expected performance of the forecasts is valuable. Here, we investigate whether there is a relationship between the persistence of atmospheric circulation patterns in the Euro-Atlantic sector and forecast skill for temperatures and temperature extremes in Europe. We first apply an objective method to compute the persistence of large-scale atmospheric patterns to European Centre for Medium-range Weather Forecasts (ECMWF) sub-seasonal retrospective forecasts. We find that the forecasts successfully predict atmospheric persistence up to timescales of approximately two weeks. We next investigate the relationship between the persistence of an atmospheric state and the practical predictability of temperature in terms of the error in surface temperature forecasts. The relationship between the two varies depending on season and location. Nonetheless, in a number of cases atmospheric persistence provides potentially valuable information on the practical predictability of temperature. We specifically highlight the cases of wintertime temperature forecasts up to 3 weeks lead time and wintertime cold spells up to roughly two weeks lead time.

Europe is a heatwave hotspot: numerous temperature records have been broken in recent summers, and roughly 60,000 and 50,000 heat-related deaths occurred in the summers of 2022 and 2023, respectively. With recent summers, like that of 2022, projected to become the new norm, there is a pressing need to further develop heat-health warning systems to help society adapt to a warming climate. Here, we forecast heat-related mortality by applying a statistical epidemiological framework to temperature forecasts extending up to two weeks in advance. Focusing on two recent and exceptional summers in Europe, namely 2022 and 2023, we evaluate the skill of the daily heat-related mortality forecasts, and assess its association with temperature. For most of Europe, milder temperatures, close to the minimum mortality temperature, are associated with more skilful heat-related mortality forecasts. However, some of the hottest regions in Europe instead showed enhanced forecast skill associated with higher temperatures. This suggests that heat-related mortality forecasts can provide valuable information in European regions associated with high levels of heat-related mortality. Consequently, we advocate for local health authorities to include information from forecasts of heat-related mortality in their heat warning systems.

Heat poses a critical risk to human health around the world. Recent work has investigated how anthropogenic climate change can modulate atmospheric circulation patterns, finding that circulation patterns increasing in frequency are associated with high temperatures in Europe. Here, we investigate the role of these changes in the dynamics of the atmosphere for European heat-related mortality. We find that dynamical changes have reinforced the thermodynamic warming trend, and are associated with increased heat-related mortality in northern and central continental Europe. Furthermore, dynamical changes appear to have played an important role for the extreme temperatures of the European summer of 2003, and the associated heat-related mortality. We thus highlight the importance of considering the role of changes in atmospheric circulation patterns when investigating the role of climate change for heat events and their impacts. Furthermore, we argue that heat action plans should consider the possibility of record-shattering heat events, where dynamical changes contributing to anomalously high temperatures could coincide with the peak of the seasonal temperature cycle, as seen in 2003.