CL3.2.6

Climate and human populations can be said to make up a complex system with many possibilities for one component to impact another. Present day global warming is one example, yet examples are not limited to the Anthropocene but can also be found in the deep past.  The Laacher See Eruption (LSE) that occurred around 13,000 BP is one example of how climate, the environment and human palaeodemography interacted. Archaeological findings suggest the LSE potentially had strong and long-lasting impact on contemporary hunter-gatherer societies in some parts of Europe – in some sense the memory of the impact might even be considered infinite and hysteresis-like, since culture might have changed more permanently in the eruption’s wake. We investigated the climatic legacy of the LSE using computer-based models. This requires a model suite that deals with both physical, environmental, and demographical variables. For this we combine the MPI Earth System Model with a statistical model that estimates population densities and information on generation times in hunter-gatherer societies. This configuration allows us to estimate the size and duration of the impact the LSE had on climate variables and - via changes in the carrying capacity - palaeodemography. Our findings suggest that the palaeodemography of Late Glacial hunter-gatherer societies showed a memory of the initial environmental perturbation at a temporal scale exceeding that of the transient perturbation itself. The memory found in our models is, however, relatively short-lived, which could reflect the actual memory of the physico-social system, or limitations of our modelling approach. Further evaluation of the model against archaeological sites is needed to suggest what is the case.

How to cite: Andreasen, L., Riede, F., and Timmreck, C.: Modelling volcanically induced climatic perturbations and their impacts on palaeodemography around 13ka BP in Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3763, https://doi.org/10.5194/egusphere-egu22-3763, 2022.

Volcanism is one of the main natural climate forcings at annual to multi-decadal timescales. Therefore, this forcing is important to study Holocene climate variability. Our main objective is to examine the impact of volcanism on the climate in the 6^th century AD within the iLOVECLIM model and analyze the results with archeological data. We hypothesize that large volcanic eruptions around 536 AD and 540 AD contributed to cooling of the climate, resulted to the adversities of Late ancient societies throughout Europe, and caused a major environmental event in Iron Age Scandinavia.

In this work, we have made three groups of simulations with the iLOVECLIM model, representing the climate of 536 AD and 540 AD. Two scenarios include high and low volcanic activity forcing, while in the third scenario, volcanic forcing is absent. We applied a model version with dynamical downscaling to reach a spatial resolution that allows for a meaningful comparison with archeological data. We compared our model results with C14-dated archaeological records from Scandinavia to analyze the spatial intensity of land use during these time periods. An evaluation of the difference between these simulations will highlight the impact of the volcanic activity on early to mid-6^th century Scandinavia.

This study demonstrates the link between climate and volcanism during these periods and shows the advantage of combining the archaeological records with climate data to understand human-environment interactions. Future research that considers both climatological and archaeological data can benefit our understandings of the impact extreme natural events had on the environment, the climate and people.

How to cite: Arthur, F., Hatlestad, K., Löwenborg, D., Solheim, S., Loftsgarden, K., Lindholm, K.-J., Roche, D. M., and Renssen, H.: The impact of volcanism on the Holocene climate (536 AD and 540 AD) using the iLOVECLIM model and archaeological data within the Scandinavian Region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4138, https://doi.org/10.5194/egusphere-egu22-4138, 2022.

The mid-6^th century is an outstanding period in climate history featuring one of the coldest decades in the past 2000 years. It was triggered by the 536/540 CE volcanic double event, creating the strongest decadal volcanic forcing in the last two millennia. The centuries of the first millennium are characterized by great societal changes, including the ending of antiquity and the beginning of early medieval state formations, a process believed to have been reinforced by the LALIA and the Justinian Plague. However, less is known about causal relationships between global cooling, regional climate, and local societal changes in Scandinavia after this volcanic double event. Here we aim to improve this understanding by combining global climate and local growing-degree-day (GDD) modeling for southern Norway.

We use the PMIP4 past2k and the 6^th-7^th century (520-680 CE) MPI-ESM ensemble simulations, to analyze the atmospheric circulation and surface climate changes as a response to the 536/540 CE volcanic double event, focusing on Scandinavia. The ensemble mean reveals significant surface cooling up to 2K, accompanied by reduced precipitation up to 25% over Scandinavia during the growing season. However, single MPI-ESM model realizations show slight warming and increased precipitation reflecting different atmospheric circulation patterns over the years following the eruptions. Three sites are selected for the GDD model as a case study, representing different weather regimes in Southern Norway, which are then driven with the MPI-ESM ensemble data as input. The high-resolution data are compared to archaeological- and high-resolution pollen records, to shed more light on the climate, vegetation, and society impacts for southern Norway. We discuss the likely volcanic climate response over Scandinavia based on the model spread, atmospheric circulation change patterns, and the local archaeological and pollen records.

How to cite: van Dijk, E., Mørkestøl Gundersen, I., de Bode, A., Høeg, H., Loftsgarden, K., Iversen, F., Timmreck, C., Jungclaus, J., and Krüger, K.: Climate, vegetation, and society impacts in Scandinavia following the 536/540 CE volcanic double event, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11966, https://doi.org/10.5194/egusphere-egu22-11966, 2022.

Before its destruction by the Roman army in 146 BCE, Carthage was one of the largest cities on earth. Established on a site some 15 km from modern day Tunis in ca. 814, the ancient town developed into the first truly urban centre of northwestern Africa; eventually housing a population of over half a million within its environs. As the hegemon of a vast territorial and maritime domain stretching by the fourth century from Morocco in the west to Libya in the east, Carthage was also the first state in the Maghreb to face the challenges incumbent in administrating provinces of such pronounced environmental diversity as their rain-fed hinterland in northern Tunisia and the arid coastal region of Tripolitania in modern Libya. Today, the majority of agriculture in Tunisia remains centred on the north of the country which benefits from the fickle graces of a Mediterranean climate, and where food production is deeply connected with the spatial distribution of winter rains critical to the farming season. Further south, and inland, drought risk increases concomitant with higher temperatures and less rainfall.

In 396, the Carthaginians faced a major rebellion of the subaltern working population of the countryside – one of a series of six rebellions recorded in classical sources for the 250 years until the fall of the city. Acknowledging the role of climate in influencing rapid social and political change in the modern region – with the outbreak of the Arab Spring occurring in the water-stressed region of Sidi Bouzid in Tunisia in 2011, for example – this paper examines whether the timing of internal war in the Carthaginian state was influenced by volcanically induced climatic perturbations via impacts on the agro-economy. Made possible by the publication of a revised chronology of explosive volcanic eruptions over the past 2,500 years (Sigl et al. (2015)), preliminary statistical testing reveals a non-random correlation with the timing of internal war. Recognising the complexity of the linkages between climate and conflict in agriculturally based economies, it can be hypothesized that the non-uniform impact of climatic shocks across geographically and demographically diverse spaces, as well as social strata within regions, was a key driver of unrest by increasing competition for land and resources between more well off resilient communities and those surviving on subsistence (Vesco et al. (2021)).

How to cite: Hill, A., Ludlow, F., McGovern, R., Kostick, C., and Medenieks, S.: The societal impacts of volcanically induced climate forcing on Carthaginian (pre-Roman) northwestern Africa (396-146 BCE), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10498, https://doi.org/10.5194/egusphere-egu22-10498, 2022.

Ongoing research shows an association between volcanic eruptions, the resulting disruption of climatic and hydrological patterns, and socio-economic disturbance in ancient Egypt during the final three centuries BCE (Manning, Ludlow et al. 2017). The present paper explores how this paradigm can extend our understanding of Judaea in the 160s BCE, a decade marked by consecutive famines amid intense political and social upheaval, particularly the so-called Maccabaean Revolt against Seleucid rule. Making use of state-of-the-art ice-core evidence that identifies three substantial volcanic eruptions within that timespan, as well as modelling that sheds light on the likely climatic impacts of the eruptions, this paper puts forward explanations to supplement those based upon the ancient (literary) sources alone, suggesting that volcanic forcing was a critical factor in these significant events in Judaean history. 

            The Maccabaean rebellion and its aftereffects on Jewish identity politics in posterity cannot be overstated, yet heretofore the contribution of famine conditions (now plausibly linked to external climatic forcing) to this watershed period have hardly been taken into account. Mindful that studies claiming climatic pressures as primary catalysts of important human historical events have often proved overly simplistic, the interaction of other contemporaneous stressors is also examined. Correspondences with the Egyptian and Chinese data are observed here too, especially in relation to conditions surrounding the onset and cessation of military action, and interference in religious matters in order to control a predominantly Temple-managed resource management and taxation system.

How to cite: Medenieks, S.: The volcanic 'triple event' of the 160s BCE and the causes of famine in Judaea during the Maccabaean Revolt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10004, https://doi.org/10.5194/egusphere-egu22-10004, 2022.

TERRANOVA is a Marie Skłodowska-Curie Innovative Training Networks (H2020-MSCA-ITN) project (2019-2023) training 15 PhD students in a new learning initiative between Humanities and Science: Mapping past environments and energy regimes, rethinking human-environment interaction and designing land management tools for policy. TERRANOVA will produce an unprecedented atlas with layers of reconstructed and modelled land-use and vegetation dynamics, climate change and mega-fauna history in Europe from the Eemian (Last Interglacial) and the Holocene from the start up until the present day. This paper describes the intermediate results of two years of research into Atlas building. Communication and data exchange, as well as the process of atlas generation work flow, have been undertaken, including examples of datasets from deep history, ancient landscapes, energy regimes and climate scenarios. The atlas database implements state-of-the-art standards for increasing the interoperability of spatiotemporal datasets. It is currently formed by four main data types: Archaeological data, Climate data, Land cover data, and Megafauna (i.e. large mammals) distribution. The intermediate publication concludes with listing the next steps to stream the Terranova atlas as a tool for communicating the European history of environmental change, including support for future landscape management policies.

How to cite: Kluiving, S., Roche, D., Zapolska, A., Pearce, E., Svenning, J.-C., Hatlestad, K., Lindholm, K.-J., Nikulina, A., Scherjon, F., Martinez, A., Vella, E., Serge, M.-A., Mazier, F., Davoli, M., Arthur, F., Renssen, H., MacDonald, K., Roebroeks, W., and Fernandez, N.: TERRANOVA from the last and current Interglacial periods into the Anthropocene: an Atlas database drawing lessons from ancient land use for future European landscape management, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5465, https://doi.org/10.5194/egusphere-egu22-5465, 2022.

Human-triggered climate change is widely acknowledged as a salient challenge to societal sustainability and welfare. Yet, our understanding of how human social systems may react to future change scenarios remains largely incomplete. However, human societies are the result of a long history of changes and adaptations to changing climates and environments. Understanding how individuals and their cultures have reacted and adapted to environmental changes over history and what effects these changes have had on landscapes could help us to more effectively design transition strategies towards low carbon societies. Hunter-gatherer societies in Cantabrian Spain between the Last Glacial Maximum (ca. 20,000 BP) and the Agricultural Revolution during the Mid Holocene (ca. 6,000 BP) evolved within a context of strong climate and environmental changes, as well as through societal changes via the adoption of a sedentary economy. Energy Regimes is a time-independent and functional theoretical and analytical tool of past societies, useful to identify and document past transitions. Statistical tests and analyses were used on archaeological data to document proxies such as demography, mobility, societal complexity, economy and overexploitation. The results were interpreted in the framework of Energy Regimes to better understand the changes and adaptation of human societies leading to the Agricultural Revolution and beyond in the context of changing environment and climate. Finally, quantification of energy use was extrapolated from the data and compared to the framework of social-metabolism, a quantitative approach similar to Energy Regimes. This work is part of the TERRANOVA programme. TERRANOVA is a Marie Skłodowska-Curie Innovative Training Networks (H2020-MSCA-ITN) project between Humanities and Science, which aims to map past environments and energy regimes, and to rethink human-environment interaction and designing land management tools for policy.

How to cite: Martinez, A., Kluiving, S., Muñoz-Rojas, J., Borja Barrera, C., and Fraile Jurado, P.: Rethinking the Agrarian Transition through the lens of long-term history of subsistence strategies and use of energy and resources in Cantabrian Spain, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6454, https://doi.org/10.5194/egusphere-egu22-6454, 2022.

Abrupt climate changes and consequent environmental changes have been repeatedly suggested as driving factors behind the rise and collapse of prehistoric and historical communities. The Near East experienced several major rapid climate changes during the Holocene (10.2 k, 9.2 k, 8.2 k, 4.2 k, and 3.2 k events cal. year BP). The Anatolian Peninsula represents an excellent laboratory for investigating the long-term relationships between these experienced climatic trends and settlement strategies. In this article, based on the analysis of 234 archaeological settlements that were active between the Chalcolithic (c. 6000 BC) and the Iron Age (c. 2600 BC) identified during different surveys carried out in the Delice Valley, the settlement strategies in the region over a period of approximately 3500 years, We examine it in detail in the light of past climatic conditions.

While trying to understand in detail this complex and non-linear relationship network between landscape and society, we aim to answer the following questions. First; What is the relationship between the organization of social groups in the landscape and the climate? Could the strategies (adaptive behaviors and resistances) developed by communities against changing environmental conditions be reflected in organizational changes? Second; Are there differences in the distribution patterns of settlements throughout the landscape? Finally; What are the possible reasons why the research area is settled with low density in some periods?  In this study; From the spatial statistics modules of ArcGIS; We modeled the spatial distribution patterns of settlements in the Delice Valley using the Average Nearest Neighbor (ANN) and GrassGIS's r.geomorphon modules.

We modeled the Early-Middle Holocene climate of the Delice Basin using the Macrophysical Climate Model and CHELSA-TraCE21k outputs. The general situation of Delice Valley, which is derived from the paleoclimate model, shows that the region has an arid climate structure and these conditions were settled in the Early Holocene. Although there was no change in the paleoclimatic structure of Delice Valley during the Middle and Late Holocene periods, the presence of significant ups and downs is important. It seems that the Delice Valley was heavily occupied in the middle Holocene. However, the spatial distribution of the settlements differs from each other periodically. It is not possible to interpret the differences in these site preferences independently of the Middle Holocene river activity. It is certain that the severe rise and fall of precipitation in the Middle Holocene had an important role on the position of ancient communities in the topography and neighborhood relations. Severe peaks observed in precipitation values in the Chalcolithic period forced people to prefer ridges away from the main river bed and exhibit a dispersal distribution pattern. On the contrary, the changes seen in the middle levels in the Early Bronze Age allowed the invasion of the floodplain. Geography and climatic conditions illustrated the settlement strategies of people and the fact of how they organize themselves in the landscape in our model results.

Keywords; Early-Middle Holocene, Paleoclimate, GIS, Delice Valley, Settlement Strategies.

How to cite: Kocaklı, K. and Arıkan, B.: Settlement Distribution patterns as indicators of Climate conditions of the Middle-Late Holocene; A Case study on the Delice Valley (North-Central Anatolia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4491, https://doi.org/10.5194/egusphere-egu22-4491, 2022.

Understanding past societal responses to climate change requires proxy indicators of human population, climate and land-use change. We apply a range of proxies to a lake sediment core from Laguna Itzan, a cenote adjacent to the ancient Maya population centre of Itzan, in order to examine the response of the lowland Maya to climatic and environmental change, which remains poorly understood. By combining molecular proxies for population (faecal stanols) and biomass burning (polycyclic aromatic hydrocarbons or PAHs) with isotopic analyses of plant wax n-alkanes as proxies for vegetation change (δ¹³C) and palaeohydrology (δ²H), we show the complex interplay of environmental and societal changes over 3300 years.

Leaf wax hydrogen isotope records show that drought between ca. 750 and 900 CE, thought to have been responsible for societal collapse or transformation across the Maya lowlands, is not expressed in the catchment of Itzan. This likely reflects spatial variability in the magnitude and timing of climate change. Population decline at Itzan may have been a result of instability caused by drought from other areas as a result of military incursions or through climate migration/an influx of climate refugees, pressures between neighbouring polities, or disruptions to trade networks or regional food production systems.

Leaf wax carbon isotope ratios indicate brief intervals of intensive maize agriculture, generally associated with wet periods, but this expansion of maize agriculture is not long lasting, and often returns to baseline levels of C₄ plant abundance. In addition to the earlier presence of humans at this site than currently indicated in the Itzan archaeological record based on the abundance of faecal stanols, we infer cultivation of maize around 4000 year BP, and potentially earlier. Further, analysis of the distribution of polycyclic aromatic hydrocarbons suggests that fire in the catchment transitioned over the past 3500 years from intense fires associated with slash and burn, or swidden, agriculture to a less intense fire regime following initial land clearance.

Our data indicate that human population dynamics and patterns of land clearance for agriculture varied substantially throughout the sediment core record, and that palaeoclimatic change may have driven these patterns. 

How to cite: Keenan, B., Johnston, K., Breckenridge, A., and Douglas, P.: Climate linkages between fire, population, and agriculture in the Maya lowlands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1133, https://doi.org/10.5194/egusphere-egu22-1133, 2022.

This talk will outline how the immediate impact of climatic events on societies of the past can be identified and quantified more robustly by archaeological research using mollusc shell records.

Advances in data acquisition regarding speed and resolution promise improved access to this high-resolution climate archive, and thus an improved interdisciplinary palaeo-perspective. Different to most long-term climate archives, mollusc shells are often found on site and record temperature changes on a seasonal scale, allowing us to measure weather extremes on a resolution that a) would have been immediately noticeable by individuals and b) is essential to subsistence strategies. In particular, we hope to provide a better environmental backdrop to the question of the climatic impact on the Neolithic Dispersal along the Mediterranean coasts and verify extreme short-term events on site, should they have occurred.

We are employing an innovative way of acquiring sea surface temperature (SST) data using a combined approach of stable oxygen isotopes (δ¹⁸O) and LIBS-screening (Laser Induced Breakdown Spectroscopy), resulting in a lower quantity of δ¹⁸O values required per shell and, as a result, a higher quantity of sampled shells. Our improved data acquisition process enables us to use a high resolution (i.e. +1000 data points per shell record) as well as a high sample quantity (100s of shells) approach, that provides extensive coverage across entire site stratigraphies.

By sourcing our climate data from shell remains found in archaeological layers, we are able to directly compare archaeological information of that layer with the individual climate records, side-stepping the need of radiocarbon-dating either dataset extensively and instead using the shared stratigraphic position to infer temporal concurrence.

This high quantity and high resolution approach produces a combined natural and societal archive, that because of its size can more easily and robustly reveal links between society and the immediate climate change, extreme events and natural hazards it experienced.

How to cite: Hausmann, N., Theodoraki, D., Pinon, V., and Anglos, D.: A high-resolution, high-quantity approach to mollusc shell analysis and linking archaeological with climatic data., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4827, https://doi.org/10.5194/egusphere-egu22-4827, 2022.

The idea that warfare increases when societies are subject to stress from climate extremes is plausible and yet has not been definitively established. Were it to be so, then the possibility of outbreaks of warfare, particularly between nations capable of bringing about unprecedented levels of destruction, would be one of the greatest risks for those living in an age of extreme climate events. As a contribution to the contention that there is a connection between extreme climate events and outbreaks of warfare, this paper offers a case study of the fall of the Kingdom of Israel c. 720 BCE with the conquest of the city of Samaria by Assyria. Because of the religious significance of the event, the defeat of the ancient Kingdom of Israel has been a subject of considerable study, despite the paucity of the sources. Until now, there has been no exploration of the role of climate extremes in the events of the period, other than to reject the idea that climate had any impact on the issue, as one scholar has written: 'no specific impulses from a (sudden) change in climate would have influenced the course of events leading to the end of the kingdom.’

This paper will draw on recent ice-core data to connect the fact that there was a very significant volcanic eruption in 723 BCE with the political and military events of the years immediately following. It will argue that a severe drop in temperature had a powerful impact on societies with relatively frail resilience to such shocks and that the stress created by the volcanic climate event had a profound effect on the decision makers of the era, with disastrous consequences in the case of the Kingdom of Israel.

How to cite: Kostick, C.: A Case Study of Extreme Weather Shock and Warfare: The Fall of the Kingdom of Israel c.720 BCE, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10012, https://doi.org/10.5194/egusphere-egu22-10012, 2022.

The Astronomical Diaries and Related Texts from Babylonia (Volumes I-III) provide sub-daily precisely dated meteorological observations recorded by ṭupšūtu (Akkadian for scribes) who were expert astronomers conducting a programme of observation spanning many centuries. Thanks to their use of clay as a medium, 209 (known) tablets survived, were excavated, translated and published, providing a unique window into the climate in the first millennium BCE.

A focus of the Irish Research Council-funded CLICAB Project (Climates of Conflict in Ancient Babylonia) is on deriving historic climate data from the translated tablets. Information has therefore been categorised into 50 unique keys, 24 of which refer to meteorological and related phenomena. This has facilitated the extraction of over 230,000 rows of observational data. Initial findings afford insight into the impact that ruling elites (and changes in governing regimes) had on the recording of observations, and therefore the availability of data with which to analyse past climate; but also on how mitigation strategies were implemented to improve (not always successfully) daily life.  

For the Ancient Babylonians the ruling elite (of Babylonia or neighbouring regions) could act as a key facilitator in promoting socio-economic viability in an often challenging environment through for example, the division of land for food production, as noted in the diary which remarked that fields were given “in year 32 at the command of the king for sustenance for the people of Babylon” (April 273 BCE). 

However the monarch could also act as an obstacle to societal environmental resilience. An example presented in the diaries highlights the use of water as a tool of conflict in an attempt to take over the kingdom (119 BCE). The diaries record Euphrates River level heights which may provide a longer time series than is available for the contemporary period due to ongoing and contentious hydro-politics in the region today (Travis et al., forthcoming; Kirschner & Tiroch, 2012).

There is also abundant evidence of the climatic impacts from major explosive eruptions in the diaries, the dating of which is now known thanks to recently revised ice-core chronologies (Sigl. et al., 2015), e.g. “the cold became severe” from the 8th-15th January 247 BCE. The combination of precisely dated meteorological information and river levels, alongside evidence of volcanic induced perturbations, and historical or “event” data are a distinctive characteristic of the diaries. This combination enables a deeper understanding into societies of the First Millennium BCE and their adaptive capacity when faced with changing political regimes and climates.  

How to cite: McGovern, R., Kostick, Dr. C., Hill, A., Medenieks, S., and Ludlow, Dr. F.: Societal responses to political and climatic changes in Babylon in the First Millennium BCE., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10356, https://doi.org/10.5194/egusphere-egu22-10356, 2022.

The time taken by human societies to recover after extreme events is of widespread interest to archaeologists and anthropologists. To date, there has been no consistent, comparative study across prehistoric cultures to determine rates of recovery, their spatiotemporal variability, and the factors that affect outcomes. This talk will present a meta-analysis of palaeodemographic records that use archaeological radiocarbon dates as a proxy for prehistoric population history. It will initially draw on well-known case studies, with a view towards quantifying the geographical/biotic/cultural influences on societal recovery in the face of extreme events, as well as how different types of events may shape adaptive responses. In summary, the paper aims to advocate for rigorous and robust approaches towards past patterns of resilience, ideally ones that 1) focus on measurable, comparable properties of cultural dynamics, and 2) are linked more closely with interdisciplinary definitions of resilience, in order to enable large-scale syntheses of archaeological and anthropological data to inform future action.

How to cite: Riris, P.: Recovery & resilience of prehistoric societies after extreme events as viewed through palaeodemography, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13145, https://doi.org/10.5194/egusphere-egu22-13145, 2022.

Rockfall in high mountains is perceived to change more than other mass-wasting processes, presumably as a result of ongoing climate warming and the related, increasing degradation of permafrost. However, the systematic lack of longer-term observational records of rockfall largely hampers any in-depth assessment of how process activity may have been altered by a warming climate and its variability since pre-industrial times. Here, we present evidence that the ongoing climate warming in the Swiss Alps indeed controls rockfall activity from degrading permafrost, and that changes in rockfall frequency correlate significantly with warming air temperature since the 1880s. Using this dataset, we then look into rockfall risk by combining changes in process activity with socio-deconomic developments at the study site. We illustrate how rockfall risk has changed over the past 140 years and how it might change over the course of the 21st century. hile more rockfall and larger volumes occur nowadays as compared to the early 20th century, rockfall risk has increased mostly due to changes in exposure and vulberability and only partly due to changes in process activity itself.

How to cite: Stoffel, M., Corona, C., and Ballesteros, J.: Climate warming enhances rockfall activity from permafrost environments - but rockfall risk increases primarily due to larger exposure and vulnerability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2010, https://doi.org/10.5194/egusphere-egu22-2010, 2022.

Climate extremes impact ecosystems directly by imposing stress conditions and impairing normal functioning. Depending on its severity, recovery from a given event can take several years to decades, which results in compounding effects of recurrent extremes in time. Climate extremes can also have indirect impacts on ecosystems e.g., by increasing the hazard of concurrent disturbances, such as fires or insect outbreaks. The increased frequency or intensity of climate extremes due to anthropogenic climate change has, therefore, the potential to increase the likelihood of impact cascades.

Understanding the processes controlling ecosystem responses to and recovery from extreme events, and how temporally and/or spatially compounding events affect ecosystem dynamics is crucial to anticipate potential threats to ecosystem stability under a changing climate. Here, we will discuss challenges in quantifying direct and lagged impacts of extreme events on ecosystem functioning and present recent studies trying to overcome these challenges based on recent historical events. Finally, we will identify key needs in observations and methods to improve understanding on cascading ecological impacts from more frequent extreme events.

How to cite: Bastos, A., Yu, X., and de Brito, M. M.: Legacy effects and cascading impacts of climate extremes on ecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3036, https://doi.org/10.5194/egusphere-egu22-3036, 2022.

Ultimately, human societies rely on the existence of functioning global ecosystems. Thus, avoiding the collapse of global ecosystems should be among the highest priorities of climate mitigation and adaptation efforts. However, "protecting" ecosystems is a challenge much more complex than avoiding adverse effects on human infrastructures, societies, economies or lives. For instance, natural hazards such as wildfires or floods can play a *functional* role for ecosystems, with species requiring those events in their life-cycle. Therefore simply trying to avoid the at-first-sight devastating effects of natural hazards on ecosystems can be counter-productive, and even be damaging.  

Here we present a statistical study made with the open-source, probabilistic risk model CLIMADA [1] about the frequency and magnitude distribution of several natural hazards affecting global terrestrial ecosystems. The hazard modelling is based on historical data augmented with probabilistic methods, and thus can be interpreted as providing a snap-shot of "current conditions". This can then be used as a baseline to be contrasted with future projections of climate change and socio-economic development. Further, this baseline can inform studies on the functional and vital relationship between natural hazards and ecosystems, which are necessary to design appropriate protection measures.

CLIMADA: https://github.com/CLIMADA-project/climada_python 

[1] Aznar-Siguan, G. et al., GEOSCI MODEL DEV. 12, 7 (2019) 3085–97

How to cite: Kropf, C. M., Vaterlaus, L., and Bresch, D. N.: Impact of natural hazards on global ecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7884, https://doi.org/10.5194/egusphere-egu22-7884, 2022.

High concentrations of ground-level ozone (O₃) and elevated levels of air temperature both represent natural hazards and health-relevant events. Two natural hazards occurring at the same time and contributing to a severe human health risk are defined as compound events. Co-occurring and hence compound ozone and temperature events pose a significant health risk and can lead to an intensified health burden for the European population (e.g., Hertig et al. 2020). 

Previous studies already point to the fact that the relationship of underlying main drivers with one or both hazards, their linkage as well as projected future frequency shifts of compound occurrences show spatial and temporal variations (e.g., Otero et al. 2016; Jahn, Hertig 2020). There is also evidence that compound events become more frequent in Europe during the 21^st century due to climate change (e.g., Jahn, Hertig 2020; Hertig 2020). Consequently, recent and upcoming European protection and resilience strategies need to focus on region-specific current and future environmental and climatic conditions.

In our current contribution we focus on health-relevant compound events by jointly evaluating elevated ground-level ozone concentrations and air temperature levels at a regional scale in Europe. A regionalization based on cluster analysis divides the European domain into regions of coherent ozone and temperature characteristics and variability. Spatiotemporally varying meteorological conditions which strongly influence the occurrence of compound events in the regions are identified. For projections until the end of the twenty-first century, the output of eight Earth System Models (ESMs) from the sixth phase of the Coupled Model Intercomparison Project (CMIP6) is used.

The results from this study show the regional character of ozone and temperature patterns and variabilities as well as respective recent and future compound event occurrences. The results can be used as a basis for further research to adjust and specify current air pollution and climate change mitigation and adaption strategies.

Hertig, E. (2020) Health-relevant ground-level ozone and temperature events under future climate change using the example of Bavaria, Southern Germany. Air Qual. Atmos. Health. doi: 10.1007/s11869-020-00811-z

Hertig, E., Russo, A., Trigo, R. (2020) Heat and ozone pollution waves in Central and South Europe- characteristics, weather types, and association with mortality. Atmosphere. doi: 10.3390/atmos11121271

Jahn, S., Hertig, E. (2020) Modeling and projecting health‐relevant combined ozone and temperature events in present and future Central European climate. Air Qual. Atmos. Health. doi: 10.1007/s11869‐020‐009610

Otero N., Sillmann J., Schnell J.L., Rust H.W., Butler T. (2016) Synoptic and meteorological drivers of extreme ozone concentrations over Europe. Environ Res Lett. doi: 10.1088/ 1748-9326/11/2/024005

How to cite: Jahn, S. and Hertig, E.: Health-relevant, compound ozone and temperature events over Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2936, https://doi.org/10.5194/egusphere-egu22-2936, 2022.

Available evidence indicates Extreme Weather Event (EWE) frequency has increased significantly in the last ⁓ 70 years along a 0.5°C global temperature rise. As such, a major concern arising from global warming projections are the potential impacts of increasingly frequent and intense EWEs on public health and societal well-being. The substantial toll of EWEs on socio-economic and physical health is well understood. Yet, due to a range of methodological impediments, the impact EWEs on psychological health and well-being remain less certain. Within this context, this literature review aimed to provide an “empirical” baseline of the psychological and well-being impacts of individuals exclusively exposed to EWEs. Given the wide range of psychological and well-being metrics available in the literature, the review was grounded on a ‘holistic’ approach with the all-encompassing concept of “psychological impairment” adopted. Here, impairment data, or morbidity, was pooled at the level of key Diagnostic and Statistical Manual of Mental Disorders (DSM) psychological “Domains”, including PTSD, Anxiety and Depression. Morbidity data was also pooled at a “composite” (any impairment) category encompassing all employed DSM-based domains. Further, reported risk factors (p < 0.05) and pooled odds ratios (pOR) were extracted and calculated from each pertinent study. Overall, 59 peer-reviewed investigations accounting for 61,443 EWE-exposed individuals comprised the review dataset. A “composite” post-exposure pooled-prevalence rate of 23% was estimated along with values of 24% for depression and ⁓ 17% for both PTSD and anxiety. Notably, estimated pOR (1.9) indicate a > 90% likelihood of a negative psychological outcome or impaired well-being among exposed individuals. Methodologically, a prevalent lack of integration of “control” criterion among reviewed investigations was identified. In this context, pooled data collated can be considered more akin to “prevalence” rates rather than a finite metric of “incidence” linking EWE exposure and outcomes. Collation of reported risk factors indicate more pronounced impacts among individuals with higher levels of EWE exposure (14.5%) and socio-demographic traits which are often associated with vulnerable population sub-groups, including female gender (10%), lower socio-economic status (5.5%), and a lower education level (5.2%). Regionally, Asia exhibited the highest impairment rates which is tentatively attributed to a combination of high EWE frequency and population density. The findings of this study provide a quantitative evidence base which can be used to inform public health intervention strategies focusing on exposed populations in the aftermath of EWEs.

How to cite: Chique, C., Hynds, P., Nyhan, M., Lambert, S., Boudou, M., and O'Dwyer, J.: Impacts of Extreme Weather Events on Mental Health & Well-Being – Key Findings from a Global ‘Scoping’ Literature Review, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2304, https://doi.org/10.5194/egusphere-egu22-2304, 2022.

Heat waves have severe impacts on economy, ecosystems, and society. In many regions, hot temperature extremes are expected to become more frequent and intense in the future. It is not clear, however, to which extent Europeans perceive heat waves as important and potentially pressing issues, which may for example vary according to a region’s climatic conditions. We analyze and compare the response of societal attention and public health to heat waves across many European countries for the period 2010-2020. In particular, we consider Google search attention to heat waves (which summarizes relevant search requests with similar search terms and across languages), as well as related excess mortality and press mentions.

We explore several temperature-related variables in this context and find that societal attention and excess mortality are most strongly related to maximum temperatures. Further, these relationships exhibit a threshold behavior with a temperature above which the sensitivity of societal attention or excess mortality to temperature is clearly increased. Applying a piecewise regression analysis, we identify these temperature thresholds in the relationships of societal attention and mortality with temperature in each country. In general, we find higher temperature thresholds in countries with warmer climate. Thresholds vary strongly between relatively cold countries and are more similar across warmer countries. These results are consistent across Google search attention and mortality analyses, even though excess mortality tends to be less strongly related to temperature, as they are potentially affected by other factors.

The country-specific temperature thresholds identified from empirical data will further be used to study the countries’ preparedness for future climate conditions. In the next step, applying the thresholds to climate model projections, we will identify the expected annual number of relevant heat wave days and their trends until the end of the century. This allows us to identify regions and time periods with a high sensitivity to heat waves where improved management and adaptation are particularly important.

How to cite: Bogdanovich, E., Guenther, L., Reichstein, M., Brenning, A., Frank, D., Schäfer, M. S., Ruhrmann, G., and Orth, R.: Geographically varying temperature thresholds for societal attention and health impacts of heat waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5448, https://doi.org/10.5194/egusphere-egu22-5448, 2022.

In July 2021, an exceptional flood developed in the River Meuse and its tributaries. The high rainfall intensity lasted for several days in a number of sub-catchments in Belgium, Germany and the Netherlands, causing devastating floods. In the River Meuse itself, the peak discharge was highest since measurements started in 1911. The flood was particularly exceptional because floods normally occur in winter. During this flood, which lasted for 5 days only, flow velocities exceeded 5 m/s and unprecedented morphological changes occurred, especially in the permanently free flowing river section, referred to as the Common Meuse. In a section of 15 km long, more than 20 deep scour holes developed in the riverbed, some exceeding depths of 15 m. Morphological changes of this intensity and magnitude during extreme events are only sparsely reported in literature.

The objective of the study is to improve understanding of the processes causing high river morphodynamics under extreme floods, by focusing on the Common Meuse. Here, the riverbed surface is composed of gravel and the bed slope is five times steeper than the downstream channelized river. Post event field data were collected revealing the morphological changes in the riverbed from multibeam measurements, and floodplains deposition patterns from field surveys. We analyzed the volumes and composition of the floodplain deposits in relation to the riverbed material and morphological changes in the main riverbed.

Our analysis shows that breaching of the thin gravel layer on the riverbed caused the massive morphological changes. Analysis of historical data suggest that the main ingredients for thinning of the gravel layer on the riverbed are gradual channel incision up to 2 cm/yr, the vertical composition of the riverbed and altered flow conditions. Previous river training works, weirs and sediment mining created a supply-limited river system and an eroding trend. In the Meuse valley, several tectonic faults are found. In uplifting areas, known as horsts, the gravel layer on the riverbed is relatively thin, as the river continuously erodes the rising riverbed. Room for the River measures carried out since the 1995 flood event lowered flood levels, but also increased flow velocities in river reaches that were not or only marginally widened. A large portion of fine sediments released from the riverbed underneath the gravel layer was deposited in comparatively wide floodplains located further downstream. The curvature of the river, height of the banks and concentrated flow directed towards the floodplains appear to determine locations of the main sand deposits. The unprecendented morphological changes may have a decisive impact on the morphological trends as well as on stability of infrastructure and flood safety. With respect to the latter, the impact of the scour holes on the overall hydraulic resistance and thus peak water levels will be assessed. These morphological processes may occur more frequently in future, also in other river sections, requiring new river management strategies to avoid a catastrophe.

How to cite: Barneveld, H., Frings, R., and Hoitink, T.: Massive morphological changes during the 2021 summer flood in the River Meuse, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11253, https://doi.org/10.5194/egusphere-egu22-11253, 2022.

Temperature extremes and heat stress are some of the major impacts of changing climate, with adverse effects on human life and property. Literatures shows that the frequency and intensity of heatwave related hazards are increasing over the last few decades. In global scenario, heatwaves are arguably more hazardous to human lives compared to any other natural disasters. However, heatwave hazard mapping studies are not so profuse over the Indian region. Many regions of the Indian subcontinent have become highly sensitive to heatwaves as a result of the recent rise in temperature extremes. As the heatwave has an impact over an extended spatial region, efficient response and mitigation plan is not possible compared with other natural disasters. India, being the second largest in human population; leading to urbanization, growing intensity of vulnerable community and the anthropogenic influences indicates an urgent need for a well-developed heatwave hazard map to aid the mitigation and response measures. Anthropogenic factors influencing the climate change are one among the main causative parameter for heatwave hazards. The repercussion of these factors will be evidently reflected in the atmospheric patterns and hence the involvement of atmospheric parameters is considered. In this study, we develop a novel index-based heatwave hazard map for India. Along with the conventional method of using temperature, the atmospheric influencing factors is also considered to quantify the changes in heatwave hazard for the historical period and the near future heatwave conditions. The vulnerable community including the farmers, who are attempting to combat with the extreme temperature issues will be benefited with the developed heatwave hazard map.  

Keywords: Heatwave hazard map, Climate change, Frequency and intensity, India

How to cite: Shilin, A., Sudharsan, N., Mondal, A., Kalbar, P., and Karmakar, S.: An insight to heatwave hazard mapping over the Indian subcontinent, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11891, https://doi.org/10.5194/egusphere-egu22-11891, 2022.

Droughts manifest in different forms, such as meteorological droughts, agricultural droughts, and hydrological droughts. Due to common forcing factors or land-atmosphere interactions, droughts may co-occur with high-temperature extremes over global land areas. The concurrence of droughts and hot extremes (or CDHEs) has received increased attention in the past decade, owing to their amplified impacts on society and ecosystems. Changes in different forms of CDHEs under global warming have been evaluated at different regional scales. However, the investigation of linkages among different CDHEs is rather rare. In this study, we assessed the variation and connection among different CDHEs during the warm period at the global scale based on the Global Land Data Assimilation System (GLDAS). We found an increased frequency of different CDHEs in the past half-century over most regions. In addition, we also investigated their connection in the variability at different climate regimes. Results on the linkage among different compound events can provide valuable information for water resources management under global warming.

How to cite: Feng, S., Hao, Z., Hao, F., and Zhang, X.: Linkage among different compound drought-hot events at a global scale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4356, https://doi.org/10.5194/egusphere-egu22-4356, 2022.

Heat waves (HWs) rank among the most dangerous weather phenomena, with catastrophic impacts on societies and ecosystems. Since the beginning of the 21^th century, many regions worldwide have been experiencing unprecedented extreme heat episodes. The Mediterranean countries in particular, are very prominent and vulnerable to climate change and heat-related risk. During summer 2021, Greece faced one of the worst HWs in its modern history, with exceptionally high temperatures prevailing from July 28^th to August 6^th. The special characteristics and the rarity of this event have been highlighted and evaluated through the historical climatic record of the National Observatory of Athens (NOA), dating since the mid 19^th century.

The study analysed daily maximum (T_max), mean (T_mean) and minimum (T_min) air temperatures of the historical record, and estimated several indices of all HW episodes detected during the study period. The analysis showed that the HW of 2021 (HW2021) exceeded all previous records in a number of indices concerning the persistence, amplitude, mean intensity of HWs (based on T_mean and T_min thresholds), but also ‘cumulative heat’ (an index combining both intensity and duration of a HW). Specifically, HW2021 was found to be the longest HW ever recorded at NOA (since the mid 19^th century), with a total duration of 10 days. The amplitude of HW2021 (maximum temperature of the hottest day) was 43.9 ⁰ C, representing the second highest temperature ever recorded at NOA, following the absolute record value of 44.8 ⁰ C observed on June 26^th 2007.

The most prominent features of HW2021 include the maintenance of very high temperatures throughout the whole 24-hour period and especially the elevated nighttime temperatures, inherent to the additive effect of the urban heat island in the city of Athens. The values of 31.6 and 36.5 ⁰C for the daily minimum and mean temperatures respectively, represent the highest values ever recorded at NOA. National all-time temperature records were observed in other Greek stations, with maximum temperatures reaching up to 47 ⁰C.  The prolonged hot and dry conditions triggered the ignition of catastrophic wildfires in Greece, with dramatic environmental and economic loss.

How to cite: Founda, D., Katavoutas, G., Pierros, F., and Mihalopoulos, N.: The extreme heat wave of 2021 in Greece: intensity, duration, cumulative heat and all-time records on centennial scale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5319, https://doi.org/10.5194/egusphere-egu22-5319, 2022.

The Quasi-Biennal Oscillation (QBO) and the El Niño-Southern Oscillation (ENSO) largely modulate the zonal wind in the tropics. Previous studies showed that QBO phases produce changes in deep convection through an increase/decrease in the tropopause height over the tropics and subtropics. This study investigates the combined effects of QBO and ENSO on tropical cyclone (TC) activity by modulating tropopause height. We found that tropopause height increases over the Gulf of Mexico, the Caribbean region, and the Western North Atlantic Ocean during La Niña + QBOW, allowing deeper tropical convection to develop over those regions. As a consequence, TC activity over those regions is not only increased in number but also enhanced in intensity. Conversely, during El Niño + QBOE, most deep tropical convection is inhibited over those same regions due to the decrease in tropopause height over the subtropics. We conclude that QBO effects on TCs and deep convection should be studied in combination with ENSO. Since TCs are among the most dangerous natural hazards, causing severe economic losses and high mortality, this signal of the QBO+ENSO on TCs could be key for planning activities before the beginning of the season, which might help reduce disaster risk and economic impacts on society, enhancing resilience.

How to cite: Jaramillo, A., Dominguez, C., Raga, G., and Quintanar, A. I.: The Combined QBO and ENSO Influence on Tropical Cyclone Activity over the North Atlantic Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2083, https://doi.org/10.5194/egusphere-egu22-2083, 2022.

Preconditioned compound events are defined as events in which an underlying weather-driven or climate-driven precondition causes an increase in the impacts of a hazard. In state-of-the-art risk assessment studies, the dependencies and cross-correlations between multiple variables/processes are usually difficult to account for. However,  previous studies have shown that some of the most devastating extreme events in the past years occurred within a cascade of interdependent and interrelated hazards. This is particularly true in the case of initial hydrologic conditions for large scale pluvial events (Eg: European Floods – 2021). The lack of proper characterisation of the spatiotemporal patterns and impacts of antecedent soil moisture conditions on extreme precipitation events hinder our understanding of such high impact flooding events and subsequently the early warning and mitigation or reduction of severe impacts for the society. Hence with this critical research gap in mind, in the present work, we employ Event Coincidence Analysis (ECA) to identify and characterise the regions over which Precipitation extremes (P) occur over Soil Moisture extreme states (SM). Precursor coincidence rate calculates the fraction of such preconditioned SM-P events out of total P extremes. The datasets used include the E-OBS v24.0 gridded product for precipitation and GLEAM v3.5a for soil moisture modelled product. Our results indicate strong seasonal variations in such SM-P preconditioning over Europe. A significant shift in the magnitude and spatial extent of SM-P coupling is seen within the seasons for the various regions. Strong coincidence is seen for western and central Europe in winter, and the coincidence weakens in summer. For eastern Europe, stronger preconditioning is seen in the summer compared to the winter season. The observed trends over the study duration of 1980 to 2020 are in line with the historical climatological and meteorological patterns of the regions. We further made use of the timings of annual maximum discharge (Peak flood values) at a catchment scale from a European flood database to investigate how the seasonal and spatial variations in the timings of floods could be interpreted from the SM-P preconditioning perspective. Our results will aid in strengthening existing flood risk assessment initiatives while providing new avenues and implications for a better understanding and proper representation of preconditioned compound flooding events over Europe.

How to cite: Manoj J, A., Pérez Ciria, T., Chiogna, G., Salzmann, N., and Agarwal, A.: Investigating Spatial Patterns And Characteristics Of Preconditioned Compound Flooding Over Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10435, https://doi.org/10.5194/egusphere-egu22-10435, 2022.

In climate change, migration from sub-Saharan Africa (SSA) would affect socio-economic development in SSA and Europe. However, empirical evidence is unclear about the role of international migration in achieving sustainable development. This article first attempted to study the migration patterns and determinants between 1995 and 2020. Sustainability index and regression models were built to estimate the cascading effects of international migration on expatriates and asylum seekers in SSA or Europe and the feedback effects on SSA’s sustainable development. In particular, SSA asylum seekers into 14 European countries (EURO-14) were investigated for their push-pull factors and impacts on the socio-economic development of EURO-14. Results show that the international migration was primarily intra-SSA to low-income but high-population-density countries. Along with increased sustainability scores, international migration declined, but emigration rose. Climate extremes tend to affect migration and emigration but not universally. Dry extremes propelled migration, whereas wet extremes had an adverse effect. Hot extremes had an increasing but insignificant effect. SSA's international migration was driven by food insecurity, low life expectancy, political instability and violence, and high economic growth, unemployment and urbanization rates. The probability of emigration was mainly driven by high fertility. SSA's international migration promoted asylum seeking to Europe, with the diversification of origin countries and a motive for economic wellbeing. 1% more migration flow or 1% higher probability of emigration led to a 0.2% increase in asylum seekers from SSA to Europe. Large-scale international migration and recurrent emigration constrained SSA's sustainable development in terms of political stability, food security and health. Regarding the asylum seekers to Europe, political instability and violence of SSA were major pushing factors while high GDP per capita, low unemployment, and ageing populations of EURO-14 were major pulling factors. Development aid reduced the outflow from SSA, whereas common colonial language and migrant networks facilitated the immigration to the EURO-14. The immigration from SSA did not affect the political stability of EURO-14. In contrast, economic development was promoted by settled migrants but hampered by asylum seekers. Overall, climate change is one factor of many but not the dominant. It might gain more weight if climate change accelerates. These findings can inform policymakers of countries that continue to improve development aids, food security and political stability in SSA while promoting the integration and inclusion of immigrants in Europe for better migration management and planning towards sustainable development, besides mitigating climate change. 

How to cite: Li, Q. and Samimi, C.: Sub-Saharan Africa's international migration and sustainable development under climate change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11529, https://doi.org/10.5194/egusphere-egu22-11529, 2022.

Understanding and managing systemic risk is more important than ever due to our immense global connectivity (e.g., between sectors, such as food-health-water-energy, countries and continents, down to individuals). Despite the fact that the notion of systemic risk is several decades old, the term is used in diverse ways across different disciplines (e.g., financial systems, medicine, earth system sciences, disaster risk research and climate science). Triggered by the repercussions of the global financial crisis of the late 2000s, and more recently the COVID-19 pandemic, which are clear realization of systemic risk, the perception of systemic risk has often been focused on global and catastrophic or even existential risks.  Systemic risk, however, can be seen as a feature of systems at all possible scales (e.g., global, national, regional, local) with system boundaries varying depending on the context.

Addressing current societal challenges, such as climate change, in terms of systemic risk requires integrating different systems perspectives and fostering system thinking, while implementing key intergovernmental agendas, such as the Paris Agreement, the Sendai Framework for Disaster Risk Reduction and the Sustainable Development Goals.

Based on insights gained and knowledge collected from an expert workshop, literature review and expert elicitation, we give an integrated perspective of climate, environmental and disaster risk science and practice on systemic risk as summarized in a Briefing Note to the International Science Council. We provide an overview of concepts of systemic risk that have evolved over time and identify commonalities across terminologies and perspectives associated with systemic risk used in different contexts. Key attributes of systemic risk are outlined without prescribing a single definition, and information and data requirements are discussed that are essential for a better and more actionable understanding of the systemic nature of risk. Finally, the opportunities to connect research and policy for addressing systemic risk are highlighted.

How to cite: Sillmann, J., Christensen, I., Hochrainer-Stigler, S., Huang-Lachmann, J.-T., Juhola, S. K., Kornhuber, K., Mahecha, M., Mechler, R., Reichstein, M., Ruane, A. C., Schweizer, P.-J., and Williams, S.: Systemic risk from the perspective of climate, environmental and disaster risk science and practice, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10250, https://doi.org/10.5194/egusphere-egu22-10250, 2022.

Climate extremes have been shown to have adverse effects on various productive elements of the
economy such as labour productivity or agricultural yields, measurable at the macro-level as changes
in Gross Domestic Product (GDP). Estimates of these macroeconomic costs of climate change play an
important role in climate policy debates and decisions. However, current estimates differ vastly –
partly because it is unclear how resilient affected regions, sectors and communities are and how
persistently climate extremes can hence affect them. In this talk, I will give an overview of recent
findings in this research area. Specifically, I will present insights gained from a novel data set
comprising subnational GDP data from the past 40 years and more than 1500 regions worldwide.
Based on these granular data, we have empirically estimated historic temperature and precipitation
impacts at different time scales, from daily fluctuations and extremes to changes in the long-term
mean. In total, we have identified five separate impact channels – most of them have been
unaccounted for in previous assessments. Our findings show that economic output is strongly affected
by rainfall and temperature changes but that these effects display large spatial heterogeneity .
Whereas low-income, low-latitude regions are most vulner able to rising and erratic temperatures,
increases in the number of rainy days and extreme rainfall events are most harmful in wealth y,
industrialized countries. I will conclude by discussing implications for assessments of the costs of
climate change.

How to cite: Wenz, L.: Economic costs of climate extremes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13553, https://doi.org/10.5194/egusphere-egu22-13553, 2022.

Climate change is widely recognized as a major risk to societies and natural ecosystems but the cascading processes of impacts through complex and interconnected systems are poorly understood. In fact, the high end of the risk, i.e. where risks become existential, is poorly framed, defined and analyzed by science. This gap is at odds with the fundamental relevance of existential and systemic risks for humanity, and it also limits the ability of scientific communities to engage with the emerging debates and narratives about the existential dimension of climate change that have recently gained considerable traction.

In this contribution we address this gap by scoping and defining existential risks related to climate change. We first review the context of existential risks and climate change, as related to systemic risks and drawing on research in fields such as global catastrophic risks and the so-called “Reasons for Concern” in the reports of the Intergovernmental Panel on Climate Change. We also consider how existential risks are framed in the civil society climate movement and what we can learn in this respect from the COVID-19 crisis, which is also a primary learning space for better understanding for both, systemic and existential risks. We then develop a definition that distinguishes between a narrower scope of conditions that threaten survival and basic needs, and a broader scope of conditions that threaten a certain level of well-being, consisting of meeting acceptable living standards. Based on this, we define six dimensions of existential risks of climate change, including the mechanisms they unfold, the systems affected, the dimension and magnitude, the probability of occurrence, time horizon and speed, and the scale of the threat. Our contribution is intended to support further scientific analysis of existential and systemic risks as part of the full risk space associated with climate change. Considering the widespread lag in awareness and regulation related to systemic risks, the results of this study should make the risk space better defined, more tangible and hence more conducive to preventive action by policy.

How to cite: Huggel, C., Bouwer, L. M., Juhola, S., Mechler, R., Muccione, V., Orlove, B., and Wallimman-Helmer, I.: The existential space of climate change and systemic risks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4575, https://doi.org/10.5194/egusphere-egu22-4575, 2022.

We live in a complex world: today’s societies are interconnected in complex and dynamic socio-technological networks and have become more dependent on the services provided by critical facilities. In coming years, climate change is expected to exacerbate these trends. In this context, systemic risk assessment is a worldwide challenge that institutions and private individuals must face at both global and local scales. The aim of this work is to adapt the traditional risk assessment methodology to the concept of resilience in order to quantify disaster resilience of a complex system by means of the graph (i.e., the mathematical representation of the system element and connections). We showed that is necessary to adapt the traditional risk assessment to resilience concept considering that the consolidaded definition, provided by the United Nations General Assembly in 2017, includes two fundamental features of systemic risk: (1) resilience is a property of a system and not of single entities and (2) resilience is a property of the system dynamic response.

The methodology proposed represents the elements of the system and their connections (i.e., the services they exchange) with a weighted and redundant graph exposed to extreme weather events and societal systems: river and pluvial floods in urban area. The quantitative analysis of systemic risk is characterized by three activities: 1) assess the systemic properties in order to highlight the centrality of some elements; 2) show how each element can dynamically adapt to an external perturbation, taking advantage of the redundancy of the connections and the capacity of each element to supply lost services; 3) quantify the resilience as the actual reduction of the impacts of events at different return periods.

To illustrate step by step the proposed methodology and show its practical feasibility, we applied it to a pilot study: the city of Monza, a densely populated urban environment.

How to cite: Arosio, M., Cesarini, L., and Martina, M.: Quantitative analysis of systemic risk: from traditional collective risk assessment to resilience concept, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11089, https://doi.org/10.5194/egusphere-egu22-11089, 2022.

Farmers’ adaptation to climate change is a two-step process that involves perceiving stressors and identifying impacts to respond to variability and changes through specific actions and strategies. Hence, successful adaptation depends on how well changing climate is perceived, either from a ‘bottom-up’ pathway –where farmers observe and identify changes through past experience–, or by using a ‘top-down’ pathway –where changes are identified through climate records. A gap between both pathways tends to be related to farmers’ misperception. For example, as life experiences influence perception, farmers who have been directly affected by extreme climatic events tend to report that the probability of such event happening again is relatively high. Furthermore, as perception is in part a subjective phenomenon, therefore, different farmers in the same locality might construct different perceptions of climate change impacts even though they experience the same weather patterns. Consequently, increased attention has been put on combining the ‘civic science’ of farmers’ perceptions with the ‘formal science’ from meteorological reports to identify the (in)consistency between perceived and observed data and how this affect farmers’ resilience when facing climate change impacts. This contribution provides a review comparing farmers’ perception and climate observations to address a twofold research question: 1) Which extreme events and compound risks are perceived by farmers in contrast with observed data? And 2) How do past experiences and social-learning influence farmers’ resilience and their adaptive capacity? We analyze a portfolio of 147 articles collected from Scopus library catalogue since 2000. The bibliometrics analysis was coupled with the systematic review to 103 articles selected from the original portfolio. Comparison between perceived and observed changes were focus on what was changing (onset, duration or cessation regarding temperature and rainfall patterns) and how it was changing (amount, frequency, intensity or inter-annual variability). Results will be useful for managers, developers, and policymakers of climate adaptation strategies to be more in tune with farmers’ understandings of when and how weather is changing. Furthermore, the review could generate recommendations for the design, formulation, and implementation of adaptation policies that are better tailored to farmers’ perception at local conditions, being more efficient and conducive to risk analysis when facing climate change.

How to cite: Ricart, S., Gandolfi, C., and Castelletti, A.: Contrasting farmers’ perception of climate change and climatic data: How (in)consistency supports risk reduction and resilience?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-976, https://doi.org/10.5194/egusphere-egu22-976, 2022.

Bangladesh is considered a climate hot spot for its unique geography, high population, poor infrastructure, high inequality, corrupt governance system and heavily agriculture-reliant economy. Due to its physical location compounding extreme weather events like cyclones, floods, heat waves, extreme rainfall etc. are a yearly phenomenon and climate change is contributing to their increasing frequency and intensifying severity. The impacts of such natural hazards then start a cascading process within the interconnected sectors of the society and affect different dimensions of human security, leading to multiple system failures, where the poor are hit disproportionately. Plenty of research is done on climate change impacts in Bangladesh, but there is lack of aggregated research that combines this evidence and provides a comprehensive overview of the systemic risk. The objective of this study is to investigate the existing literature on how climate change along with interdependent dimensions of the societal system pose threat to different components of human security. The concept of human security used here is based on three pillars: freedom from fear, freedom from want and freedom to live in dignity. A systematic map approach is adopted to ensure minimal human and publication bias as opposed to a traditional review process. Standardized key terms were used to search literature in Web of Science and broad inclusion criteria were applied for screening relevant papers. Selected papers will go through a robust coding process to create an exhaustive database and yield the complex pathways of interaction between climate-related extreme weather events and human security in Bangladesh.

How to cite: Sultana, F., Petzold, J., and Scheffran, J.: Impacts of climate change on human security in Bangladesh: a systematic map, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11580, https://doi.org/10.5194/egusphere-egu22-11580, 2022.

Floods, heatwaves, and humid heat stress often lead to extreme consequences that threaten human health, economic stability, and resilience to natural and built environments. According to the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change, heat stress has steadily increased over the Indian subcontinent. Along with the increase in heat stress, the frequency of heavy precipitation and flood events has grown over multiple locations across South Asia. Most studies assessed trends in heatwave and dry spells over South Asia, emphasizing sensible heat (dry bulb temperature) only and mostly performed attribution and risk analyses considering one driver at a time. A few studies have presented a climate-informed pluvial flood risk model accounting for sensible heat flux, neglecting the influence of humidity. However, very few studies have explored the compound role of humid heat stress followed by extreme precipitation within a limited time window. Here we show the concurrence of humid heat stress (i.e., heatwave compounded by humidity, hereafter HHS) and peak rain events in major urban locations across climatologically disparate monsoon sub-regions of India using ground-based observations. The observational evidence reveals the cities across the western half of the country show positive dependence between humid heat stress and extreme precipitation, whereas those located over the eastern half showed negative correlations. Our findings suggest the role of moisture transport in amplifying precipitation intensity preconditioned by HHS. Further, our joint hazard assessment model identifies potential hotspots where the humid heat stress is likely to intensify the precipitation extremes and consequently have extreme impacts of consecutive disasters (close succession of heatwave and heavy rainfall) over densely populated urban locations. The derived insights provide a clear rationale for assessing heatwave-induced pluvial flood response in a multi-hazard framework, which has implications for climate adaptations, ensuring science-policy cooperation.  

How to cite: Pradhan, S. and Ganguli, P.: Multivariate Approach Reveals a Higher Likelihood of Compound Warm-wet Spells in Urban India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2647, https://doi.org/10.5194/egusphere-egu22-2647, 2022.

Tropical Cyclones (TCs) and Easterly Waves (EWs) are the most important phenomena in Tropical North America. Hydrometeorological hazards produced 45.5% of all disasters over Mexico during the 1900–2018 period. On average, TCs represent 86.5% of the annual cost of disasters in Mexico, and the main TC hazard is the extreme rainfall they produced. Thus, examining their future changes is crucial for adaptation and mitigation strategies. The Community Earth System Model drove a three-member regional model multi-physics ensemble under the Representative Concentration Pathways 8.5 emission scenario for creating four future scenarios (2020–2030, 2030–2040, 2050–2060, 2080–2090). These future climate runs were analyzed to determine changes in EW and TC features: rainfall, track density, contribution to seasonal rainfall, and tropical cyclogenesis. Our study reveals that a mean increase of at least 40% in the mean annual TC precipitation is projected over northern Mexico and southwestern USA. Slight positive changes in EW track density are projected southwards 10° N over the North Atlantic Ocean for the 2050–2060 and 2080–2090 periods. Over the Eastern Pacific Ocean, a mean increment in the EW activity is projected westwards across the future decades. Furthermore, a mean reduction by up to 60% of EW rainfall, mainly over the Caribbean region, Gulf of Mexico, and central-southern Mexico, is projected for the future decades. Tropical cyclogenesis over both basins slightly changes in future scenarios (not significant). We concluded that these variations could have significant impacts on regional precipitation. Thus, Mexico should be prepared to face more TC extreme rainfall events. Suggestions for how Mexico can meet the objectives of international risk agendas are discussed.

How to cite: Dominguez, C.: Future Changes in Tropical Cyclone and Easterly Wave Characteristics over Tropical North America, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-851, https://doi.org/10.5194/egusphere-egu22-851, 2022.

There is no uniform definition of heat waves and many climate indices can be derived from the surface temperature. When considering the impact of heat on human health, heat stress needs to be considered. Several indicators of heat stress have are commonly used, such as the Heat Index (HI), the Wet-Bulb Globe Temperature (WBGT) or the Wet-Bulb Temperature (Tw), all take into account the temperature and humidity. Each of these indices can be computed from non-linear empirical formula but they all use different scales which make results difficult to compare. Here we performed a comparative study using these 3 indices by defining corresponding levels of heat stress between the different metrics. We analyzed where sever, dangerous and deadly heat stress hazards will become more frequent, using climate model projections from CMIP6, and where the choice of the index makes a difference. For each index, we use a filtering techniques to remove models that cannot reproduce realistic extreme values during the current period (using a set of 4 different reanalyses as a reference). Following, we translated this risk in terms of country exposure and vulnerability, using population and GDP growth scenario.

We show that South and East Asia and Middle-East, as previously pointed out by many studies, are highly exposed to heat stress hazards. But more vulnerable countries with less resources for mitigation are also highlighted such as West Africa and Central and South America. For all these regions, about 20 to more than 50% of the population would be exposed to sever heat stress each year no matter the heat stress index chosen. European countries and USA will also be exposed several time per year to conditions of similar heat stress level than the 2003 heat wave. When going to more extreme hazards, especially when considering the “survivability threshold” of 35°C for Tw, different indices lead to more discrepancies in the results but similar regions can be identified as the most vulnerable.

How to cite: Freychet, N., Hegerl, G. C., Lord, N. S., Lo, E., Collins, M., and Mitchell, D.: Robust change in population exposure to heat stress risk with increasing global warming., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1099, https://doi.org/10.5194/egusphere-egu22-1099, 2022.

Climate extremes induced by global warming have remarkable impacts on water resources, agricultural production, and terrestrial ecosystems. Climatic model simulations provide useful information to analyze changes in extremes (e.g., droughts, heatwaves) under global warming for climate policies and mitigation measures. However, systematic biases exist in climate model simulations, which hinders accurate assessments of extremes changes. Bias correction methods have been employed to correct biases in climate variables (e.g., precipitation, temperature) in model simulations. Previous studies mostly focus on individual variables while the correction of inter-variable correlation (e.g., precipitation-temperature dependence) is still limited. Moreover, the concurrence of climate extremes (e.g., droughts and hot extremes), which is closely related to the dependence among contributing variables, may amplify the impacts. However, bias correction of the contributing variables of compound events is still limited but growing. In this study, we employ the multivariate bias correction (MBC) approach to correct the precipitation, temperature, and their dependence from CMIP6 simulations. We found that the MBC can improve the simulation of precipitation-temperature dependence and associated compound dry and hot events. This study can provide useful insights for improving model simulations of compound weather and climate extremes for impact studies and mitigation measures.

How to cite: Meng, Y. and Hao, Z.: Multivariate bias corrections of global compound dry and hot events in CMIP6 model simulations , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3424, https://doi.org/10.5194/egusphere-egu22-3424, 2022.

Weather conditions refer to the state of the atmosphere at a specific time in a specific place. Changes in weather conditions influence human well-being by affecting the productivity of ecosystems and the quality of life. Climate change can affect weather conditions by changing the trend, frequency and extreme values of meteorological elements such as temperature, precipitation and humidity. The changes in weather conditions caused by climate change have had a serious impact on human well-being and will continue in the future. Therefore, assessing the impact of future climate change on weather conditions is of great significance for addressing climate change and promoting global sustainable development. However, the commonly used assessment indicators only describe the changes of weather conditions and do not consider the population exposure and people’s perceptions to the changes of weather conditions, which limits the significance of the evaluation results in improving human well-being and promoting regional sustainable development. Thus, taking the weather preference index (WPI) as the evaluation index and combined with the scenario framework provided by the Scenario Model Intercomparison Project (ScenarioMIP), we evaluated the impact of global climate change on weather conditions under different scenarios from 2015 to 2100. First, we quantified global WPI from 1980 to 2015 based on global meteorological observation data. Then, combined with global climate model data, we analyzed global WPI from 2015 to 2100 under different scenarios. Finally, we used trend analysis to evaluate the impact of global climate change on weather conditions. We found that global weather conditions will deteriorate from 2015 to 2100, and the global average WPI will change at a rate of -0.05/10a. At the same time, we also found that more than 60% of the world's urban residents will live in regions with deteriorated weather conditions in the future. Under any scenario, there will still be 1.46 billion urban population living in regions with deteriorated weather conditions in 2100, accounting for 61.55% of the total urban population. Therefore, we suggest that countries should be as close to the narrative line of the green revival scenario (SSP1-2.6) as possible in the development process, and reduce greenhouse gas emissions by means of terminal emission control, the development of clean energy and the introduction of ultra-low emission technologies. On top of that, resilience to climate change needs to be improved by improving public infrastructure and living conditions.

How to cite: Fang, Z.: Will global climate change make people more comfortable? A scenario analysis based on the weather preference index, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8152, https://doi.org/10.5194/egusphere-egu22-8152, 2022.

We are approaching the 1.5°C temperature goal of the Paris agreement at a worrisome pace. Achieving this global temperature goal is physically still possible but would require drastic greenhouse gas emission reductions as well as the deployment of some level of carbon dioxide removal. Most scenarios that limit global warming to 1.5°C by the end of the century experiment an overshoot – a temporary exceedance of this level of global warming followed by a decrease in global mean temperature once global greenhouse gas emissions become net-negative in the second half of the century.

However, besides a number of well documented tipping points our understanding of the reversibility of climate impacts remains limited. It is indeed not well understood for which climate and sectoral impacts one can expect reversibility or not, and over which time scale it would occur.

Here we attempt to present an overview of changes that an overshoot would bring to the climate system. We analyze standard climate indicators as well as extreme event indicators in overshoot scenarios including the SSP119 and the SSP534 scenarios for a range of CMIP6 models. Comparing climate projections at a fixed warming level before and after global warming has peaked reveals significant differences in local climatic conditions, with precipitation pattern changes being particularly affected. This preliminary investigation will help to identify regions of interest for which the mechanisms that hinder reversibility could be analyzed in more depth in future research.

How to cite: Pfleiderer, P., Lejeune, Q., Schleussner, C.-F., and Sillmann, J.: Additional climate impacts of overshoot scenarios, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8717, https://doi.org/10.5194/egusphere-egu22-8717, 2022.

We explore the changes in climate extremes (heat stress, temperature and precipitation) as projected by the Sixth phase of the Coupled Model Intercomparison Project (CMIP6) multi-model ensemble under the ‘business as usual scenario’ (ssp585) for global warming levels from 1.0°C to 3.0°C, relative to pre-industrial levels in Sub-Saharan Africa. We focus on the 86 UNESCO-designated Biosphere Reserves located in sub-Saharan Africa, a region highly vulnerable to climate change, spanning monsoon, wet, dry and Mediterranean climate regions. Projected changes of temperature indices are significant at all warming levels across the five climate classes of Sub-Saharan Africa. Notably, absolute heat extreme indices are projected to increase more strongly than global mean temperature in monsoon  and in dry climate regions.
We found the strongest health risk to heat stress in the two monsoon and the rainy climate regions, and the lowest in the Mediterranean climate region. High risk of heat stress emerges at a global warming of 1.5°C in the northern hemisphere (NH) monsoon region, whereas only above a global warming level of 3°C in the SH monsoon and rainy climate regions. We find that limiting global mean temperature below 2.0°C reduces by a half the exposure to high levels of heat stress in the population in and around the Biosphere Reserves in Sub-Saharan Africa.
Finally, we investigated processes that might explain the differences in the regions. The NH monsoon class reaches high heat stress risks earlier, already at a global warming of 1.0°C, due to the compounding effects of temperature and humidity, as temperatures start from a warmer baseline and occur jointly with a significant increase in precipitation. While the rainy climate region also exceeds high risk thresholds, values of the different heat stress indices are highest overall in the SH monsoon region. Since the latter is a region projected to experience an intense drying, this suggests that the strong increase in heat extremes is caused by an amplification of land warming through land-atmosphere feedbacks.

How to cite: Maroini, A., Giannini, A., and Vogel, M.-M.: Understanding heat extremes in Sub-Saharan Africa: Projected changes in UNESCO Biosphere Reserves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10169, https://doi.org/10.5194/egusphere-egu22-10169, 2022.

Compound events are the extreme weather and climate events that result from a combination of physical processes (climatic drivers and extreme events) occurring across different temporal (successive) and spatial (simultaneous) scales. Further, multiple drivers with a complex chain of processes, conditional dependencies and extreme return periods of such events lead to severe socio-economic and environmental impacts. The quantification and predictions of such extreme events still need to be advanced with changing climate and global warming. In previous literature, it is documented that precipitation and temperature are the fundamental drivers of different climatic variations resulting in compound extreme events. In light of these perspectives, a Standardized Compound Extreme Event Index (SCEEI) is modelled in this study integrating the joint properties of Standardized Precipitation Index (SPI) and Standardized Temperature Index (STI) that are derived from precipitation and temperature; respectively employing the India Meteorological Department (IMD) data series. The Gaussian model-based multivariate technique is applied to derive SCEEI. The severity of drought and extreme temperature at an annual scale is analysed using SCEEI for two neighbouring river basins of Eastern India, i.e. Brahmani and Baitarani river basins for the study period of 1979-2018. The variations of the extreme events and their severity are further assessed at a multi-decadal scale. The trends of these compound events for different time scales are checked by the Mann-Kendall test followed by Sen’s slope estimator. The multi-decadal time scale is divided as D¹ (1979-1988), D² (1989-1998), D³ (1999-2008), and D⁴ (2009-2018). It is observed that SCEEI captures drought events along with extreme temperatures reasonably well than the individual index (SPI and STI). The outcomes of this study conclude that the multivariate approach is a reliable perspective to assess the severity of compound extreme events. The developed approach in this study is novel for monitoring the compound extreme event severity under the non-availability basin-scale hydrological data that is advantageous for several worldwide data scare river basins to purpose an adaptation strategy and achieve the Sustainable Development Goals (SDGs).

Keywords: Compound events; SCEEI; IMD; multi-decadal; Brahmani; Baitarani; SDGs

How to cite: Swain, S. S., Mishra, A., and Chatterjee, C.: Modelling of Compound Drought-Temperature Extreme Event Framework: A Multi-Decadal Perspective, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11369, https://doi.org/10.5194/egusphere-egu22-11369, 2022.