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.

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.

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.

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.

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.

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.

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 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.