Background The 2025 ice-rock avalanche that destroyed the Swiss Alpine village of Blatten in May 2025 represents an important example of high-altitude cascading risk. It also received wide media attention. This study analyses how the Blatten disaster was represented in Swiss news media, examining descriptions of the hazard cascade, disaster response strategies, dominant themes, and broader media frames. Using a corpus of 2,052 news articles, the study combines structured large language model extraction with human validation, topic modelling, and framing synthesis to analyse multilingual media coverage at scale. Results Swiss media consistently portrayed Blatten as a cascading high-mountain disaster involving rock slope failure, glacier collapse, debris flows, river damming, lake formation, and downstream flood risk. Coverage highlighted a broad portfolio of disaster risk management measures, including monitoring, early warning, evacuation, emergency interventions, financial assistance, insurance, reconstruction, and possible relocation. Topic modelling revealed that reporting extended well beyond the physical hazard to include community disruption, governance, funding, tourism, insurance, and long-term recovery. Framing analysis identified competing narratives in which successful emergency management coexisted with debates over reconstruction versus retreat, cultural identity, financial responsibility, and the future habitability of Alpine communities. Climate change emerged as an overarching but contested frame, appearing both as a driver of increasing mountain hazards and as the subject of scientific, political, and societal debate. Conclusions The Blatten disaster was represented not only as a cascading natural hazard but also as a catalyst for broader debates on climate change adaptation and the future of mountain communities. The findings demonstrate that media discourse extends beyond physical processes and emergency response to encompass governance, finance, cultural values, and place attachment. Integrating computational text analysis with qualitative framing provides a scalable approach for examining societal interpretations of disasters and can support interdisciplinary research on climate risks, disaster risk management, and long-term adaptation.

Compound hot–dry events have recently led to severe consequences globally, often triggering cascading impacts across ecological and socio-economic systems. Currently, most analyses of hot–dry extremes rely on short observational records or projections, limiting evaluation against pre-industrial variability—the climatic range to which many natural and human systems adapted over centuries. This makes it difficult to place impacts of the increased intensity and frequency of compound events in an appropriate context for examining adaptation needs.Here we leverage a unique data coverage in the Swiss Alps to quantify changes in summer mean climate and in compound hot–dry extremes and their associated return periods from 1600 to 2099 CE. Data used include multi-century temperature and atmospheric drought reconstructions from tree rings going back to 1600 CE, instrumental station records, and local-scale climate projections for 1981-2099.Copula-based modelling shows that summers classified as extreme in pre-industrial conditions have become common in today's climate and are expected to correspond to cold and wet conditions by the end of the century. Our analysis further shows that the hot–dry conditions witnessed in summer 2003—characterized by simultaneous positive temperature and vapor pressure deficit (VPD) anomalies of 5.3°C and 2.6 hPa relative to the pre-industrial mean, respectively—were unprecedented over at least the past 400 years and are projected to remain rare until the end of the century under RCP2.6. By contrast, they are likely to occur every 2-3 years under RCP4.5 and even to become colder and wetter than average by 2070-2099 under RCP8.5, since in the latter case, temperature and VPD anomalies are projected to exceed pre-industrial conditions by 10.4°C and 8.1 hPa in the extreme case (30-year return period).Without countermeasures, the consequences of these changes will include, among other things, dramatic losses in agricultural production and undesirable changes in forest ecosystem dynamics. Ultimately, our analysis suggests that rapid adaptation is necessary to avoid facing more frequent extreme heat and drought conditions than those observed under pre-industrial conditions. Under RCP8.5, in particular, socio-ecological systems will need to continuously adapt within 15 years to changes in the average climate to avoid facing high-impact hot-dry compound event frequencies higher than those experienced at any time over the past 400 years. Given that adaptation in mountain regions is currently not keeping up with the realized and projected climate impacts, as pointed out in several studies, we argue that the required speed of adaptation can pose substantial challenges for alpine societies.

Extreme El Niño events entail important socio-economic challenges, both in regions such as South America directly affected by their impacts and in regions around the world that are influenced by the associated teleconnections. Uncertainty remains about the ability of recent climate models to reproduce the characteristics and impacts of extreme El Niño events. In this study, we evaluate the ability of 32 CMIP6 models to simulate extreme El Niño events, focusing on their occurrence, their seasonal evolution, and the characteristics of the associated atmospheric moisture flux divergence. Our results reveal the reasonable performance of the CMIP6 ensemble in reproducing the observed anomalies and seasonal cycles of extreme El Niño events. The ensemble mean also captures the average temporal evolution and magnitudes of moisture flux anomalies, but fails to reproduce some important aspects of the associated spatial patterns. Most individual models have marked deficiencies in adequately simulating the seasonal cycle of atmospheric moisture flux divergence dynamics and reproducing a clear distinction between moderate and extreme events. The latter indicates that the atmospheric–ocean coupling and resulting precipitation anomaly patterns over Ecuador and northern Peru are still not correctly reproduced by the individual models. These deficiencies echo previous studies and underscore the limitations of current global climate models in providing reliable insights into the impacts of climate change on El Niño extremes and their consequences for regional atmospheric dynamics and precipitation. This work highlights the need for further research to improve model representations of extreme El Niño events and their associated impacts on vulnerable regions, thereby facilitating more effective risk management and adaptation measures.

Recent northward movement of polar jet has been linked with mid-latitude weather and climate anomalies, but distinguishing the natural variability and anthropogenic activity is hindered by a lack of long-term observations. Here we use tree ring oxygen records from the High Asia to reconstruct variability in the movement of the late spring High Asia Polar Jet (HAPJ) over the past six centuries. We find that the HAPJ has shown a gradually northward trend since 1600s, which have resulted in relatively wet conditions in the High Asia and southern west Asia from 1600s to late 1800s and recent decades. Combined with model results, we find the HAPJ is dominated by the phase changes of North Atlantic Oscillation and volcanic eruption at decadal to multi-decadal scales. At multi-decadal to centurial scales, solar activity is the largest contributor to HAPJ movement, while the contribution of increasing greenhouse gas is relatively small. These results highlight the importance of natural variability in HAPJ movements under the context of global warming.

Paleoclimatological field reconstructions are valuable for understanding hydroclimatic variability. While being similarly impactful on societies as temperature variability, hydroclimatic variability has still remained less in focus. However, reconstructing globally complete fields of climate variables lacks adequate proxy data from tropical regions like South America, limiting our understanding of past hydroclimatic changes in these areas. This study addresses this gap using low resolution climate archives, including speleothems, previously omitted from reconstructions. Speleothems record climate variations on decadal to centennial time scales and provide a rich dataset for the otherwise proxy data scarce region of tropical South America. By employing a multi-time scale Paleoclimate Data Assimilation approach, we synthesize climate proxy records and climate model simulations, capable of simulating water isotopologues in the atmosphere, to reconstruct 2000 years of South American climate. This includes surface air temperature, precipitation amount, drought index, isotopic composition of precipitation amount, and the intensity of the South American Summer Monsoon. The reconstruction reveals anomalous climate periods: a wetter and colder phase during the Little Ice Age (1500–1850 CE) and a drier, warmer period corresponding to the early Medieval Climate Anomaly (600–900 CE). However, these patterns are not uniform across the continent, with exceptions in northeastern Brazil and the Southern Cone, indicating regional variability. The anomalies are more pronounced than in previous reconstructions, but align with local proxy record studies, thus highlighting the importance of including speleothem proxies. The multi-timescale approach is essential for reconstructing multi-decadal and centennial climate variability. Despite methodological uncertainties regarding climate model biases and proxy record interpretations, this study marks a crucial first step in incorporating speleothems into climate field reconstructions, potentially enhancing insights into past hydroclimatic variability and hydroclimate projections.

Abstract Risiken für die Gesellschaft, die aufgrund einer Kombination von meteorologischen Extremereignissen ausgelöst und durch Prozesskaskaden verstärkt werden, sind schwierig zu analysieren und noch kaum erforscht, insbesondere auch im Kontext von Klimaanpassung. In diesem Beitrag stellen wir die Ergebnisse einer Fallstudie vor, deren Ziel es war, Wissenslücken und «blinde Flecken» in Bezug auf kombinierte Klimarisiken zu schliessen. In einer semiquantitativen Analyse wurde als Ausgangslage die Kumulation von zwei aufeinanderfolgenden sehr trockenen und warmen Jahreszeiten angenommen und die möglichen Auswirkungen auf den Schutzwald im Misox (GR) untersucht. In einer umfangreichen Befragung schätzten 29 Fachpersonen aus Praxis, Forschung und Verwaltung die Wahrscheinlichkeit für einen Verlust der Schutzfunktion in verschiedenen Gefährdungsszenarien ein. Die Ergebnisse zeigen, dass einzelne Gefahren, die durch das Extremereignis ausgelöst werden können (z.B. Trockenheit, Borkenkäferbefall, Sturm), die Schutzfunktion des Waldes wahrscheinlich nicht beeinträchtigen. In Szenarien, in denen Gefahren kombiniert auftreten, erwarten die meisten Fachpersonen zumindest einen teilweisen Verlust der Schutzfunktion. Sie favorisieren Massnahmen, welche die Waldstruktur durch Verbesserung der Verjüngung stärken, insbesondere eine Reduktion des Wildbestandes. Um die Widerstandsfähigkeit der alpinen Schutzwälder gegenüber dem Klimawandel zu gewährleisten, ist es von entscheidender Bedeutung, dass Anpassungsplanung und Präventionsmassnahmen das Risiko kombinierter Extremereignisse und der damit verbundenen Gefahren berücksichtigen, welche die Wälder durch kumulative und kaskadenartige Effekte bedrohen können.

The observed temperature record, which combines sea surface temperatures with near-surface air temperatures over land, is crucial for understanding climate variability and change1-4. However, early records of global mean surface temperature are uncertain owing to changes in measurement technology and practice, partial documentation5-8, and incomplete spatial coverage9. Here we show that existing estimates of ocean temperatures in the early twentieth century (1900-1930) are too cold, based on independent statistical reconstructions of the global mean surface temperature from either ocean or land data. The ocean-based reconstruction is on average about 0.26 °C colder than the land-based one, despite very high agreement in all other periods. The ocean cold anomaly is unforced, and internal variability in climate models cannot explain the observed land-ocean discrepancy. Several lines of evidence based on attribution, timescale analysis, coastal grid cells and palaeoclimate data support the argument of a substantial cold bias in the observed global sea-surface-temperature record in the early twentieth century. Although estimates of global warming since the mid-nineteenth century are not affected, correcting the ocean cold bias would result in a more modest early-twentieth-century warming trend10, a lower estimate of decadal-scale variability inferred from the instrumental record3, and better agreement between simulated and observed warming than existing datasets suggest2.

Climate change increases the frequency and severity of heat waves, which can negatively impact human health. Extreme heat can lead to heat stroke, dehydration, and other heat-related illnesses. Heatwaves are more severe for vulnerable populations such as older adults, young children, and people with pre-existing medical conditions. In this study, we analyze the occurrence of compound extreme heat-related mortality in five Swiss cities using neural networks.To define the excess mortality due to compound heat extremes (Hot day, Tmax>30oC, followed by a tropical night, Tmin>20oC) we compared mortality during the four hot summers of 2003, 2015, 2018, and 2019 with long-term average mortality rates (1981-2020). We trained long short-term memory (LSTM) neural networks on 40-year time series of maximum and minimum temperatures, hot day / tropical night compound events, and mortality in Basel, Bern, Geneva, Lugano, and Zürich. LSTM neural networks learn the important parts of the sequence seen so far and forget the less important ones. This makes these models predict with greater accuracy than traditional time series analysis methods.In general, we found that over the past 40 years, more than six percent of deaths were caused by compound extreme heat waves in the five Swiss cities. Geneva and Lugano are the most affected cities by compound heat, but the risk of heat-related mortality has decreased in these two regions over time, which could be a result of the action plans that exist in the Latin regions of Switzerland.We further used Switzerland's future climate model scenarios (CH2018), to predict mortality rates in Swiss cities in the near-future (2020–2050) and far-future (2070–2100). We projected that the number of people affected by mortality risks associated with heat could increase by three folds by the end of the century in most cities if no further adaptation is taken place.Our results show how important it is for governments, public health agencies, and individuals to be aware of the potential impacts of climate change on heat-related mortality and to take steps to mitigate and adapt to these impacts.

Extreme precipitation in the western tropical Andes have significant socio-economic impacts in northern Peru and Ecuador. Previous investigations have shown that high impact episodes were caused by atmospheric moisture flux convergence associated with strong El Niño events in the eastern Pacific Ocean, identifying two patterns: the one emerging during the 1982/1983 and 1997/1998 events, and the one emerging during the 2015/2016 event. In this contribution, we discuss the ability of CMIP6 global climate models to represent these two types of extreme El Niño events, by analyzing the associated atmospheric moisture transport patterns. Based on SST observations, we identified historical extreme El Niño events using the relative Niño34 index, an index recently proposed for addressing ENSO in a warming climate. We also use ERA5 to compare with the moisture flux of CMIP6. We compared 13 CMIP6 models with the historical record (1901-2014). We found the following: (1) six of the models simulated the two extremes El Niño patterns; (2) 62% of the models identify 4.5 extreme El Niño events; and (3) only 27% of the models represent the seasonality of the moisture flux convergence overestimating the moisture flux convergence branch located to the south (4° S) of its normal position (4° N). Our results provide a starting point to investigate the impacts of climate change and its impacts on atmospheric dynamics and associated extreme events at the regional level in tropical South America.

The interaction of multiple hazards across various spatial and temporal scales typically causes compound climate and weather extreme events. Compound concurrent hot day and night extremes that combine daytime and nighttime heat are of greater concern for health than individual hot days or hot nights. Continuous day and nighttime heatwaves can exacerbate human discomfort and therefore increase the risks of heat-related morbidity and mortality. However, little is known about the evolution of such events in the observed and projected climate. Four compound event types, namely (a) preconditioned, (b) multivariate, (c) temporally compounding, and (d) spatially compounding events were introduced in the literature that facilitates the selection of the proper approaches in the study of compound extreme events. The impact of a single or the combination of multiple types could shape more severe extreme events. In our study, we considered the temporally compounding and multivariate types and used climate observations (1981-2020) and high-resolution bias-corrected climate model scenarios of Switzerland (CH2018). Our analyses show that the average frequency and intensity of compound consecutive hot days and nights increase in five big cities of Switzerland until 2100 under RCP4.5. We projected 1.83 ± 0.07 (days decade−1) for Basel, 1.57 ± 0.1 (days decade−1) for Bern, 2.34 ± 0.13 (days decade−1) for Geneva, 2.55 ± 0.17 (days decade−1) for Lugano, and 1.93 ± 0.12 (days decade−1) for Zürich. Moreover, we found an increase in the intensity of summertime (April-October) compound hot extremes days and night in Basel (0.28 ± 0.03 °C decade−1), Bern (0.23 ± 0.02°C decade−1), Geneva (0.37 ± 0.04 °C decade−1), Lugano (0.4 ±0.07°C decade−1), and Zürich (0.44 ± 0.05°C decade−1).

Cumulative extreme events pose substantial risk to society and nature, as they can propagate through various socio-economic systems via process cascades. Adaptation to future climates requires estimations of the likelihood and possible combined impacts of cumulating meteorological/climatic extremes events. Due to the very rare occurrence of low probability events, such estimations remain challenging. In response to this knowledge gap, a collaborative effort of academic and government institutions at different administrative levels is undertaken. It aims at analysing the potential of such cumulative, complex risks and to suggest actions needed to manage them in Switzerland. The project is based on two case studies, which were developed in collaboration with stakeholders from science, policy making and practice at the national and sub-national level. The case studies assess rare but plausible combined risks of extreme drought events and other meteorological extremes, e.g. heat, as projected by the recently published Swiss Climate Scenarios CH2018. One case study is conducted in the alpine region of southern Grisons, the second one in the urban area of Basel. Currently, there are only limited approaches available to quantitatively model the manifold cascading effects that may propagate through natural and human systems after the occurrence of combined drought-related extremes. We therefore adapt methods from the field of civil protection and use expert knowledge to develop impact storylines and estimate probabilities and magnitudes of adverse effects on societies and ecosystems. To estimate the feasibility of a combined drought event leading to the loss of the protective function of forests in the southern Swiss Alps (case study 1), we developed an extensive expert survey. 29 experts from science, administration and practice provided quantitative estimates of drought thresholds and damage probabilities. The survey was split into a top-down and a bottom-up approach, allowing to characterize the possible impacts from two different angles and thereby also assess the robustness of the results. In contrast, urban areas consist of diverse interlinked systems with very different characteristics, which does not allow to assess impact cascades with a single expert survey. Instead, we used a three-step approach based on semi-quantitative storylines informed by literature and expert interviews. In a first step, experts for individual systems, such as water, transport or health were interviewed about possible weaknesses and blind-spots with regard to the trigger-event. Second, we characterized possible storylines of impact cascades using process diagrams along with quantitative estimates of drought related variables such as river discharge, air and water temperature. In a third step, the plausibility of these storylines was discussed once more with the experts. We report on the advantages and challenges of our approach compared to traditional modelling-based methods in light of transformative adaptation measures to future climates.

The interaction of multiple hazards across various spatial and temporal scales typically causes compound climate and extreme weather events. Compound concurrent hot day and night (CCHDNs) extremes that combine daytime and nighttime heat are of greater concern for health than individual hot days (HDs) or hot nights (HNs), even though their frequency is lower. We utilize a bottom-up exploratory approach to investigate how adaptation options and various unfolding future scenarios alleviate the impacts of the heatwaves and affect the frequency and intensity of CCHDNs. We use climate observations (1981–2020) and Switzerland's future climate model scenarios (CH2018) to analyze historical and future trends of the individual hot day followed by a hot night (HDNs, first metric), and the length and frequency of CCHDNs (second and third metrics) in the near-future (2020–2050) and far-future (2070–2100). Results show more frequent and lengthier HDNs in cities under all emission scenarios, notably significant under high emissions scenarios. The highest increase of HDNs occur in i) Lugano with 65.8 days (decade−1) in the historical period and 110 (371) days (decade−1) in near-future (far-future), ii) Geneva with historical 48 days (decade−1) to 108 (362) (decade−1), iii) Basel with 48–74 (217) days in the future, followed by iv) Bern with 15–44 (213) days and v) Zürich with 14–50 (217) days (decade−1) in the near-future and far-future, respectively. We consistently project that the CCHDNs in April–October become more likely and intense in all cities under all emission scenarios, with higher increases under the RCP8.5 scenario and after the 2050s. The frequency of compound extreme heatwaves (exceeding both historical thresholds of night and day temperatures) may increase by 3.5–7.8-fold and become 3.3–5.3-fold lengthier in all cities of Switzerland in the far-future. We find that the adaptation options targeting higher tolerance to increased minimum temperatures contribute more to reducing compound extreme events' frequency and intensity than adaptation options that address the maximum daily temperature.

The Little Ice Age (LIA), which lasted from about 1250 to 1860 AD, was likely the coldest period of the last 8000 years. Using new documentary data and analyses of alpine glacier fluctuations, the complex transition from the Medieval Climate Anomaly to the LIA and the ensuing high variability of seasonal temperatures, are described and interpreted for Europe. The beginning of the LIA was likely different in both hemispheres. The low temperature average of the LIA is primarily due to the high number of cold winters. Conversely many summers were warm and dry. Important triggers of the lower temperatures were, primarily, the numerous clusters of volcanic eruptions and the weak solar irradiance during the four prominent Grand Solar Minima: Wolf, Spörer, Maunder, and Dalton. The drop in temperature triggered the sea-ice–albedo feedback and led to a weakening of the Atlantic overturning circulation, possibly associated with a trend towards negative North Atlantic Oscillation indices. The statistics of extreme events show a mixed picture. Correlations with forcing factors are weak, and can only be found in connection with the “Years without a Summer”, which very often occurred after large volcanic eruptions.

Weather extremes can affect many different assets, sectors and systems of the human environment, including human security, health and well-being. Weather extremes that compound, such as heat and drought, and their interconnected risks are complex, difficult to understand and thus a challenge for risk analysis and management, because (in intertwined systems) impacts can propagate through multiple sectors. In a warming climate, extreme concurrent heat and drought events are expected to increase in frequency, intensity and duration, posing growing risks to societies. To gain a better understanding of compound extremes and associated risks, we analyze eight historical heat and drought extreme events in Europe, Africa and Australia. We investigated and visualized the direct and indirect impact paths through different sectors and systems together with the impacts of response and adaptation measures. We found the most important cascading processes and interlinkages centered around the health, energy and agriculture and food production sectors. The key cascades result in impacts on the economy, the state and public services and ultimately also on society and culture. Our analysis shows that cascading impacts can propagate through numerous sectors with far reaching consequences, potentially being able to destabilize entire socio-economic systems. We emphasize that the future challenge in research on and adaptation to concurrent extreme events lies in the integration of assets, sectors and systems with strong interlinkages to other sectors and with a large potential for cascading impacts, but for which we cannot resort to historical experiences. Integrating approaches to deal with concurrent extreme events should furthermore consider the effects of possible response and adaptation mechanisms to increase system resilience.

Büntgen et al. (2020) present a new reconstruction of extra-tropical summer temperatures based on updated versions of a large number of summer temperature sensitive tree-ring width chronologies from the Northern Hemisphere (NH), which cover the full Common Era (CE). This new dataset allows the authors to draw conclusions about NH temperature history and its relation to climate forcing, marking an important contribution to our understanding of past climate changes. While we have no issues with the main conclusions of B20, here we show that their comparison with PAGES 2k reconstructions is flawed: B20′s reconstruction focused on regional, summertime temperature, while the PAGES 2k reconstruction targeted global, annual mean temperature. For their reconstruction intercomparisons, B20 rescale all six tree-ring based reconstructions to their regional observational target but fail to do this same processing step with the PAGES 2k reconstructions. This inconsistent comparison leads B20 to incorrectly conclude that the PAGES 2k reconstructions severely lack variance and are therefore unreliable. In this contribution, we present a consistent comparison of the B20 and PAGES 2k reconstructions, and we highlight the importance of careful illustrations for interpreting scientific results both in the literature and in the public discussion. Our results show that, if more accurate methods for comparisons are applied, the temperature history and low-frequency amplitudes of the different proxy selection approaches and reconstruction products are not at odds, but actually consistent with the differences between their targets over the pre-industrial CE.