Stefan Muthers

Background In the midst of the emerging climate crisis, healthcare providers lack locally validated, disease-specific surveillance models. Stroke, a significant contributor to the global disease burden, has been linked to climate change. Therefore, we developed and benchmarked machine learning (ML) models based on locoregional weather systems to forecast the number of daily acute ischemic stroke (AIS) admissions. Methods AIS patients diagnosed between 2015 and 2021 at the tertiary University Medical Center (UMC) Mannheim, Germany were extracted from the local data integration center and geospatially matched to weather data from the German Weather Service (DWD) based on the clinic’s, patients’ home and closest tower’s locations at the time of admission. Statistical- (Poisson), boosted generalized additive model (GAM), support vector machines (SVR), and tree-based models including random forest (RF) and extreme gradient boosting (XGB) were evaluated in regression settings within time-stratified nested cross-validation setup (training-validation: 2015-2020, test set: 2021) to predict the number of daily AIS admissions. Findings The cohort included 7,914 AIS patients (4,244 male, 53·6%). XGB showed the best test performance with lowest mean absolute error (MAE) of 1·21 cases/day. Maximum air pressure was identified as the top predictive variable. Shapley additive explanations analyses revealed that temperature extremes of extended cold-(lag-3 minimum temperature <-2 °C; minimum perceived temperature <-1·4 °C) and hot stressors (lag-7 minimum temperature >15 °C), as well as stormy conditions (lag-1 and lag-2 maximum wind gust >14 m/s and speed >10·4 m/s), increased stroke incidences substantially with distinct seasonal associations. Interpretation ML models can sufficiently forecast AIS admissions based on weather patterns allowing for improved resource allocation and preparedness.

Heat Health Warning System (HHWS) provide information for general public and public health. In Germany, weather Forecast is used to predict heat episodes, which are associated with negative health impacts. Therefore, a heat balance model of the human body and an extracted equivalent temperature (Perceived Temperature) is applied. Thresholds for strong and extreme heat stress based on thermal perception classification are used and build the first approach of the HHWS. Furthermore, the threshold of strong heat stress includes a short term adaptation component and considers the previous thermal stress conditions of the last 30 days. The second step includes nocturnal conditions, based on forecasted minimum air temperature or a simulated maximum indoor temperature for typical houses. The indoor temperature is calculated also based on a urban heat model for cities with a population over 100.000 inhabitants. Both criteria are important for the decision about warnings for the present and next days. Warnings are generated by daily weather forecast automatically and are additionally confirmed or adjusted by a biometeorological forecaster. The warning is valid on county level considering several elevation classes. The heat warning is available as a map on the internet and registered users can receive information by a daily newsletter. A specific smartphone app is also available for general use. The main target groups are the public, nursing homes and ministries of the federal states and other authorities. The HHWS with his regional differentiation of heat stress warnings is also part of the heat health action plans in Germany. HHWS is main part of the Heat action Plans in Germany.

Der Zusammenhang zwischen sommerlichen Hitzeperioden und der Zunahme der Sterbefälle wurde in den letzten Jahren weltweit und auch für Deutschland in zahlreichen Studien belegt. In Deutschland stand dabei überwiegend die Gesamtmortalität im Mittelpunkt. Weniger bekannt ist, wie sich die hitzebedingte Sterblichkeit in einzelnen Diagnosegruppen verhält. In der vorgestellten Untersuchung haben wir den Einfluss von Hitzeperioden auf das Auftreten von Todesfällen infolge von ischämischen Herzerkrankungen (ICD-10 I20-I25) und chronischen Erkrankungen der unteren Atemwege (ICD-10 J40-J47) untersucht. Die retrospektive Analyse basiert auf Daten der Jahre 2001-2015 für mehrere Regionen in Deutschland. Die Todesursachengruppe ischämischen Herzerkrankungen liegt bei Frauen und Männern mit 12.6% bzw. 15.2% auf Rang eins in der Todesursachenstatistik. Bei den chronischen Krankheiten der unteren Atemwege gibt es größere Unterschiede zwischen den Geschlechtern. Bei Männern belegt sie mit 4.3% der Fälle Rang 3, bei Frauen mit 3.3% Rang 7 (alle Zahlen jeweils für das Jahr 2015). Das Mortalitätsrisiko sowohl aufgrund von Atemwegserkrankungen als auch von ischämischen Herzerkrankungen steigt oberhalb von ca. 18°C Tagesmitteltemperatur stark an und erreicht eine Zunahme der Mortalität um bis zu 40 % an sehr heißen Tagen (Tagesmittel > 26°C). Die Mortalität aufgrund von chronischen Atemwegserkrankungen ist mit 4.4% pro °C durch einen steileren Anstieg stärker betroffen, als die Mortalität infolge von ischämischen Herzerkrankungen mit 3.5% pro °C. In einem zweiten Schritt wurden die Ergebnisse der retrospektiven Analyse auf Projektionen zur zukünftigen Entwicklung des Klimas in Deutschland angewandt. Für beide Diagnosegruppen zeigt sich ein Anstieg der hitzebedingten Sterblichkeit, die mit der zunehmenden Häufigkeit von Hitzewellen (mind. drei aufeinanderfolgende Tage mit Lufttemperatur > langjährigen 95. Perzentil) einhergeht. Die Anzahl Hitzewellentage wird für Deutschland von aktuell 13 Tagen (1981 – 2010) bis 2021 – 2050 auf ca. 23 Tage (identisch für RCP 4.5 und RCP 8.5), am Ende des Jahrhunderts sogar auf 31 bzw. 54 Tage steigen (RCP 4.5 bzw. RCP8.5). Zusätzlich zur Häufigkeit zeigen sowohl die Dauer als auch die Intensität der Hitzeperioden eine signifikante Zunahme. Die Mortalität während Hitzeperioden steigt vor allem in Abhängigkeit mit ihrer Dauer und verstärkt die zu erwartende Mortalitätszunahme. Die erzielten Ergebnisse betonen den Bedarf geeigneter gesundheitlicher Präventionsmaßnahmen und eine deutliche Verstärkung von Klimaschutzmaßnahmen, um die hitzebedingten Auswirkungen der erwarteten Klimaänderungen so gering wie möglich zu halten.

Links between springtime Arctic stratospheric ozone anomalies and anomalous surface weather in the Northern Hemisphere have been found recently. Stratospheric ozone thus provides valuable information which may help to improve seasonal predictability. However, the extent and causality of the ozone-surface climate coupling remain unclear and many state-of-the-art forecast models lack any representation of ozone feedbacks on planetary circulation.We investigate the importance of the ozone-surface climate coupling with two Chemistry Climate Models, contrasting simulations with fully interactive ozone against prescribed zonally averaged climatological ozone under fixed present-day boundary conditions. We focus on springtime Arctic ozone minima and compare subsequent surface patterns in runs with and without interactive ozone, thus rendering a detailed and physically-based quantification of the stratospheric ozone impact on surface climate possible.  All model simulations show a connection between Arctic ozone minima and a positive phase of the Arctic Oscillation in the month after the depletion in spring. Runs with interactive ozone chemistry show an amplified surface response and a 40% stronger Arctic Oscillation index after ozone depletion. This amplified Arctic Oscillation goes along with enhanced positive surface temperature anomalies over Eurasia. Moreover, composite surface patterns after spring ozone minima in model simulations with interactive ozone show a better agreement with composites in reanalysis data compared to runs with prescribed ozone.Mechanisms whereby stratospheric ozone affects both the stratospheric and tropospheric circulation are explored. These include the reduction of short-wave heating over the pole due to ozone loss, thus amplifying stratospheric temperature anomalies and allowing for an intensification of the polar vortex with subsequent impacts on wave propagation and the stratospheric meridional circulation. This suggests that ozone is not only passively responding to stratospheric dynamics, but actively feeds back into the circulation. Following these results, stratospheric ozone anomalies actively contribute to anomalous surface weather in spring, emphasizing the potential importance of interactive ozone chemistry for seasonal predictions.

Die Zunahme von Wetter- und Klimaextremen durch den voranschreitenden Klimawandel ist zunehmend mit gesellschaftlichen Beeinträchtigungen und ökonomischen Kosten verbunden. Eine umfassende Quantifizierung und nutzerspezifische Kommunikation dieser sozioökonomischen Klimafolgen an politische und privatwirtschaftliche Entscheider ist für die Vermeidung möglicher Folgen oder eine adäquate Anpassung unerlässlich. Eine Abschätzung sozioökonomischer Klimafolgen erfordert (i) Daten zur klimatischen Gefährdung, (ii) Informationen zur räumlichen Exposition sozioökonomischer Größen, (iii) Annahmen zur ihrer Sensitivität, als auch (iv) eine Maschinerie, um diese Größen gekoppelt auszuwerten. Hierfür wird in diesem Vortrag die open-source python Plattform CLIMADA [1,2] vorgestellt und zur sozioökonomischen Folgenabschätzung durch Wetter- und Klimaextreme auf Deutschland angewendet. Am Beispiel von extremer Hitze wird demonstriert, wie projizierte klimatische Trends mit unterschiedlichen Szenarien für den demographischen Wandel auf sub-nationaler Skala wechselwirken und so die möglichen Auswirkungen (z.B. durch hitzebedingte Übersterblichkeit [3]) verstärkt werden könnten. Die Anwendung von CLIMADA ist nicht nur auf Klimaprojektionen beschränkt, sondern erlaubt eine räumlich aufgelöste und nahtlose Bereitstellung von sozioökonomischen Risiken und ökonomischen Schäden durch Wetter- und Klimaextreme von der Wettervorhersage bis zum Ende des Jahrhunderts.   Referenzen: [1] https://github.com/CLIMADA-project/climada_python [2] Aznar-Siguan, G. and Bresch, D. N., 2019: CLIMADA v1: a global weather and climate risk assessment platform, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-12-3085-2019 [3] an der Heiden, M. et al. Heat-related mortality. Deutsches Aerzteblatt Online, doi:10.3238/arztebl.2020.0603 (2020).

Background: Foehn describes a wind which occurs in areas with close proximity to mountains. The presence of foehn wind is associated with worsening health conditions. This study analyzes the correlation between a foehn typical circulation and the incidence for suffering a severe trauma. Methods: This is a retrospective, multicentre observational register study. The years from 2013 to 2016 were analyzed for the presence of foehn winds. A logistic regression analysis with the number of daily admitted trauma patients as the primary target value was performed in dependence of foehn winds. Southern Bavaria is a typical foehn wind region. Individuals were treated in 37 hospitals of Southern Bavaria which participate in the TraumaRegister DGU®, an international register that includes all severe trauma patients, mainly in Germany. We analyzed patients with an Injury Severity Score (ISS) of at least nine with admission to intensive care units or prior death in the emergency room. Results: 6215 patients were enrolled in this study. A foehn-typical circulation was present on 65 days (4.5%). 301 patients (5%) suffered a trauma with an ISS ≥ 9 on a foehn day. The mean ISS was 20.2 (9–75). On average, 4.3 patients (0–15 patients) were admitted on a daily basis due to a severe trauma. The multivariate regression analysis revealed a daily increase of 0.87 individuals (p = 0.004; 95% CI 0.23–1.47) on foehn days. During spring 1.07 patients (p = < 0.001; 95% CI 0.72–1.42), in summer 1.98 patients (p = < 0.001; 95% CI 1.63–2.32), in fall 0.63 (p = < 0.001; 95% CI 0.28–0.97) and on Saturdays, 0.59 patients (p = < 0.001; 95% CI 0.24–0.93) were additionally admitted due to severe trauma. Conclusion: Foehn winds are significantly associated with severe trauma in trauma centers of the TraumaNetzwerk DGU®.

Chronic respiratory and ischemic heart diseases are globally important parts of total mortality. This study focuses on the occurrence of mortality due to these disease groups in Germany and possible effects of the thermal environment. A retrospective analysis on the mortality rates of chronic lower respiratory diseases (CLRD) and ischemic heart diseases (IHD) at the regional level in Germany for the period 2001–2015 was done in combination with meteorological observations from the network of the German Meteorological Service. In order to control the mortality data for long-term and seasonal trends, a 365-day Gaussian low-pass filter with a filter response function was applied. The thermal environment was analysed using 2 m air temperature (T_a) and the human biometeorological index Perceived Temperature (PT). The relationship of the Relative Risk (RR) of mortality to the thermal environment is displayed as an exposure–response curve, with threshold values at which RR increases significantly towards higher and lower temperature values. CLRD mortality increases above 17.6 °C, at approximately 4.4%/°C (CI: ± 0.3). The increase of IHD mortality above the threshold of 18.8 °C is less steep, at 3.5%/°C (CI: ± 0.2). During hot periods, CLRD mortality increases by 19.9%, which is twice as much as IHD mortality, with an increase of 9.8%. However, cold days and cold periods affect IHD slightly more than CLRD. The results highlight the concerns of CLRD patients during hot days as well as heat waves. This could lead to better precautions being taken for respiratory patients, which are already established for cardiac patients in Germany.

Arctic stratospheric ozone has been shown to exert a statistically significant influence on Northern Hemispheric surface climate. This suggests that Arctic ozone is not only passively responding to dynamical variability in the stratosphere, but actively feeds back into the circulation through chemical and radiative processes. However, the extent and causality of the chemistry-dynamics coupling is still unknown. Since many state-of-the-art climate models lack a sufficient representation of ozone-dynamic feedbacks, a quantification of this coupling can be used to improve intra-seasonal weather and long-term climate forecasts.We assess the importance of the ozone-dynamics coupling by performing simulations with and without interactive chemistry in two Chemistry Climate Models. The chemistry-dynamics coupling was examined in two different sets of time-slice simulations: one using pre-industrial, and one using year-2000 boundary conditions. We focus on the impact of sudden stratospheric warmings (SSW) and strong vortex events on stratosphere-troposphere coupling, since these go along with strong ozone anomalies and therefore an intensified ozone feedback.  We compare the runs with and without interactive chemistry.For pre-industrial conditions, simulations without interactive ozone show a more intense and longer lasting surface signature of SSWs compared to simulations with interactive chemistry. Conversely, for year-2000 conditions, the opposite effect is found: interactive chemistry amplifies the surface signature of SSWs. Following these results, atmospheric CFC concentrations, which differ greatly in the pre-industrial and year-2000 runs, determine the sign of the ozone-circulation feedback, and thus have a strong impact on chemistry-climate coupling. Implications for modeling of stratosphere-troposphere coupling and future projections are discussed.

During intense heat episodes, the human population suffers from an increased morbidity and mortality. In order to minimize such negative health impacts, the general public and the public health authorities are informed and warned by means of an advanced procedure known as a “heat health warning system” (HHWS). It is aimed at triggering interventions and at taking preventive measures. The HHWS in Germany has been in operation since 2005. The present work is aimed at showing the updated structure of an advanced HHWS that has been developed further several times during its 15 years of operation. This is to impart knowledge to practitioners about the concept of the system. In Germany, dangerous heat episodes are predicted on the basis of the numerical weather forecast. The perceived temperature as an appropriate thermal index is calculated and used to assess the levels of heat stress. The thermo-physiologically based procedure contains variable thresholds taking into account the short time acclimatization of the people. The forecast system further comprises the nocturnal indoor conditions, the specific characteristics of the elderly population, and the elevation of a region. The heat warnings are automatically generated, but they are published with possible adjustments and a compulsory confirmation by the biometeorology forecaster. Preliminary studies indicate a reduction in the heat related outcomes. In addition, the extensive duration of the strongest heat wave in summer 2018, which lasted three weeks, highlights the necessity of the HHWS to protect human health and life.

After 2003, another hot summer took place in Western and Central Europe in 2015. In this study, we compare the characteristics of the two major heat waves of these two summers and their effect on the heat related mortality. The analysis is performed with focus on South-West Germany (Baden–Württemberg). With an additional mean summer mortality of +7.9% (2003) and +5.8% (2015) both years mark the top-two records of the summer mortality in the period 1968–2015. In each summer, one major heat wave contributed strongly to the excess summer mortality: In August 2003, daily mortality reached anomalies of +70% and in July 2015 maximum deviations of +56% were observed. The August 2003 heat wave was very long-lasting and characterized by exceptional high maximum and minimum temperatures. In July 2015, temperatures were slightly lower than in 2003, however, the high air humidity during the day and night, lead to comparable heat loads. Furthermore, the heat wave occurred earlier during the summer, when the population was less acclimated to heat stress. Using regional climate models we project an increasing probability for future 2003- and 2015-like heat waves already in the near future (2021–2050), with a 2015-like event occurring about every second summer. In the far future (2070–2099) pronounced increases with more than two 2015-like heat waves per summer are possible.