Samuel Lüthi

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Lüthi

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Samuel

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0000-0003-2884-3467

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Publications1 - 9 of 9

Globally consistent assessment of economic impacts of wildfires in CLIMADA v2.2
Lüthi, Samuel; Aznar-Siguan, Gabriela; Fairless, Christopher; et al. (2021)
Geoscientific Model Development
In light of the dramatic increase in economic impacts due to wildfires over recent years, the need for globally consistent impact modelling of wildfire damages is ever increasing. Insurance companies, individual households, humanitarian organizations, governmental authorities, and investors and portfolio owners are increasingly required to account for climate-related physical risks. In response to these societal challenges, we present an extension to the open-source and open-access risk modelling platform CLIMADA (CLImate ADAptation) for modelling economic impacts of wildfires in a globally consistent and spatially explicit approach. All input data are free, public and globally available, ensuring applicability in data-scarce regions of the Global South. The model was calibrated at resolutions of 1, 4 and 10 km using information on past wildfire damage reported by the disaster database EM-DAT. Despite the large remaining uncertainties, the model yields sound damage estimates with a model performance well in line with the results of other natural catastrophe impact models, such as for tropical cyclones. To complement the global perspective of this study, we conducted two case studies on the recent megafires in Chile (2017) and Australia (2020). The model is made available online as part of a Python package, ready for application in practical contexts such as disaster risk assessment, near-real-time impact estimates or physical climate risk disclosure.
Rapid increase in the risk of heat-related mortality
Lüthi, Samuel; Fairless, Christopher; Fischer, Erich M.; et al. (2023)
Nature Communications
Heat-related mortality has been identified as one of the key climate extremes posing a risk to human health. Current research focuses largely on how heat mortality increases with mean global temperature rise, but it is unclear how much climate change will increase the frequency and severity of extreme summer seasons with high impact on human health. In this probabilistic analysis, we combined empirical heat-mortality relationships for 748 locations from 47 countries with climate model large ensemble data to identify probable past and future highly impactful summer seasons. Across most locations, heat mortality counts of a 1-in-100 year season in the climate of 2000 would be expected once every ten to twenty years in the climate of 2020. These return periods are projected to further shorten under warming levels of 1.5 °C and 2 °C, where heat-mortality extremes of the past climate will eventually become commonplace if no adaptation occurs. Our findings highlight the urgent need for strong mitigation and adaptation to reduce impacts on human lives.
From rigidity traps towards reparative disaster governance and management
Eriksen, Christine; Kirschner, Judith; Simon, Gregory L.; et al. (2025)
International Journal of Disaster Risk Reduction
Despite widespread critique, the established notion of sequential disaster management phases (mitigation, preparedness, response, recovery) continues to inform a standard set of policies and practices that lock people into rigid cycles of decision-making and action. In this paper, we refer to these as “rigidity traps.” Although expressed in different ways, rigidity traps result in the overarching effect of maintaining the broader conditions that shape disasters and they, in turn, proliferate the consequent impact. Awareness of rigidity traps, and the resulting processes and outcomes, is critical to avoid such traps. However, alternative disaster governance and management approaches are also needed in order to move on from the status quo. To this end, we build on work by scholars to deploy ‘the reparative’ as an analytical lens. Specifically, a reparative approach seeks to account for the wider historical and systemic conditions that organize and structure the ways disasters unfold, the consequences they bear, and their uneven effects across different people and places. We use this framing as a foundation to expand upon what a reparative approach might look like when applied to disaster governance and management. We do so by identifying a range of rigidity traps, which is followed by suggestions for alternative reparative approaches, including perspectives on how to institutionalise such approaches. While each example is grounded in either a particular place or type of hazard, the collection has been chosen due to their simultaneous relevance to a broader range of people, places and hazards.
The Heat is on - Impacts of Heat & Wildfires in a Rapidly Changing Climate
Lüthi, Samuel (2023)
Natural catastrophes affect societies by causing loss of human lives, by displacing people, by destroying infrastructure and cultural heritage, or by disturbing ecosystems and their services. Most natural catastrophes are a result of extreme climate conditions and are therefore strongly affected by the rapidly changing climate. In fact, the consequences of natural catastrophes are a key impact of climate change on societies. This thesis’ research and its applications are thus situated within the climate risk framework of the Intergovernmental Panel on Climate Changes (IPCC), where risk is a combination of the three components hazard, exposure and vulnerability. The hazard represents a physical event, such as a climate extreme. Exposures constitute the presence of assets or people that could be adversely affected by a hazard, while the vulnerability describes an exposure’s sensitivity or susceptibility to a given hazard. This framework is commonly applied to the assessment of impacts of natural catastrophes. However, in contrast to other climate extremes, wildfires and heatwaves received comparatively little attention in disaster risk research. Accordingly, the impact modelling capacities of these two climate extremes remained underdeveloped within climate impact research compared to other natural catastrophes such tropical cyclones or floods. This is in stark contrast with the impacts these two perils assert on the human and non-human environment. In this thesis, we therefore applied the IPCC’s climate risk framework to assess various aspects of the impacts of wildfires and extreme heat on society. The results are presented within the scope of three separate studies. The first study of this thesis introduces and describes a wildfire extension to the natural catastrophe risk modeling platform CLIMADA. In this extension, we use satellite data of past wildfires and overlap these with exposed assets to estimate economic damages. This allows us to model economic impacts from wildfires in a globally consistent yet spatially explicit fashion. All input data is free and globally available, ensuring applicability in data-scarce regions. Using this extension, we can produce damage estimates of past wildfires with a precision on the order of magnitude. This precision aligns with the impact estimates of other natural catastrophes such as tropical cyclones or floods. We complement the global perspective of the study with two case studies of recent mega fires in Chile (2017) and Australia (2020). The model is available open-source and lends itself for practical applications within disaster risk assessment and near real- time impact estimates of wildfires. In fact, it has been already picked up by the insurance industry. In the second study we shift the focus to assess the risk of heat-related mortality while using the same climate risk framework. In this interdisciplinary work, we combine large ensemble climate model data with empirical temperature-mortality relationships of 748 locations form 47 countries across the globe. We find that within most locations, heat-mortality levels of past extreme (1-in-100-year) seasons need to be expected every ten to twenty years, when assuming no adaptation. These return periods are projected to further shorten with increasing global temperatures and eventually to become commonplace in a world with 1.5◦C or 2 ◦C warming. Furthermore, heat-mortality levels of future extreme seasons are expected to double in a 1.5◦C world and nearly triple in a 2◦C world, as compared to extreme seasons of the climate in the year 2000, again assuming no adaptation. For this study, we could rely on the most expansive database on weather and health collected by the Multi-Country Multi-City (MCC) Collaborative Research Network which we combined with state-of-the-art approaches from climate science to quantify extreme seasons. The results of this study highlight a need to incorporate possible extreme scenarios into the planning of public health policies as we demonstrate that the experience from mortality impacts of past summer seasons underestimates the actual risk of heat-mortality in the current climate. Confronted with these findings, we assessed if countries adapt to heat, and if they do so fast enough. For our third study, we could rely again on the MCC mortality data to model changes in population’s vulnerability over time. Adequately displaying population’s adaptation to heat represents a key uncertainty in heat-mortality assessments of past trends and future projections. We therefore disentangled trends in heat-mortality by decomposing these into changes in hazard, exposure and vulnerability. We find that while changes in all three components are relevant, the absolute and relative importance differs strongly between the 23 countries for which the MCC network was able to collect long-term daily mortality data. In most countries, adaptation to heat happens fast and to a considerable extent. While adaptation could compensate for most of the increasing temperatures at the beginning of the 21st century, we report an increase of excess heat-mortality numbers as of 2015 in the majority of countries covered in our dataset. The findings of these study lay an empirical foundation to improve the representation of adaptation to heat in the assessment of past trends and future projections. This is crucial to validate the effectiveness of past adaptation measures or for designing targeted public health interventions. Overall, this thesis improves the climate impact modelling capabilities of the two natural catastrophes wildfire and extreme heat. Both extremes are modelled using the IPCC’s framework for assessing climate risk. They are integrated into the open-source natural catastrophe platform CLIMADA which eases the broader climate risk community to build upon the results of this thesis. The second and the third study could build upon a broad range of methods from environmental epidemiology, highlighting the importance of interdisciplinary research in climate impact science.
A natural hazard risk modelling approach to human displacement - frontiers & challenges
Meiler, Simona; Mühlhofer, Evelyn; Lüthi, Samuel; et al. (2025)
Environmental Research: Climate
Extreme weather is increasingly driving human displacement worldwide, a trend expected to worsen with climate change. Quantifying global displacement risk is thus crucial for assessing potential impacts and informing long-term strategies to build more resilient societies, and reducing this risk. One approach involves leveraging classic probabilistic risk modelling methods that hinge on the interplay of hazard, exposure, and vulnerability. Here, we present a methodological stocktaking of these natural-hazard risk models as applied to human displacement. Specifically, we present a globally consistent displacement risk model from multiple hazards under present-day and future conditions. We model population displacement from tropical cyclone winds, coastal floods, river floods, and droughts under present, optimistic, and pessimistic future climate conditions for the middle and end of the century, assuming constant exposure and vulnerability. Our results reveal that current displacement risk is on the order of 30 million annual average displacements (AAD). By 2100, global displacement risk could increase by 75% (157%) under optimistic (pessimistic) climate scenarios. While our risk model makes methodological advances through its global setup, utilisation of two risk frameworks and state-of-the-art datasets, we also highlight current challenges in displacement risk modelling. For instance, our approach primarily models displacement as the direct result of loss of homes from sudden-onset hazards. While we begin to incorporate indirect drivers, such as livelihood loss in river floods and droughts, the model still omits important social, political, and economic dimensions. Nevertheless, as our model adopts a modular design, continuous updates enable the inclusion of additional hazards, improved data, and integration of these broader dimensions. This stocktaking represents a concerted research effort, and our modelling framework may help inform global discussions in international climate negotiations, including those related to Loss and Damage, national action plans, policy development, and other climate adaptation strategies, provided appropriate data and context are applied.
Regional tropical cyclone impact functions for globally consistent risk assessments
Eberenz, Samuel; Lüthi, Samuel; Bresch, David N. (2021)
Natural Hazards and Earth System Sciences
Assessing the adverse impacts caused by tropical cyclones has become increasingly important as both climate change and human coastal development increase the damage potential. In order to assess tropical cyclone risk, direct economic damage is frequently modeled based on hazard intensity, asset exposure, and vulnerability, the latter represented by impact functions. In this study, we show that assessing tropical cyclone risk on a global level with one single impact function calibrated for the USA – which is a typical approach in many recent studies – is problematic, biasing the simulated damage by as much as a factor of 36 in the north West Pacific. Thus, tropical cyclone risk assessments should always consider regional differences in vulnerability, too. This study proposes a calibrated model to adequately assess tropical cyclone risk in different regions by fitting regional impact functions based on reported damage data. Applying regional calibrated impact functions within the risk modeling framework CLIMADA (CLIMate ADAptation) at a resolution of 10 km worldwide, we find global annual average direct damage caused by tropical cyclones to range from USD 51 up to USD 121 billion (value in 2014, 1980–2017) with the largest uncertainties in the West Pacific basin where the calibration results are the least robust. To better understand the challenges in the West Pacific and to complement the global perspective of this study, we explore uncertainties and limitations entailed in the modeling setup for the case of the Philippines. While using wind as a proxy for tropical cyclone hazard proves to be a valid approach in general, the case of the Philippines reveals limitations of the model and calibration due to the lack of an explicit representation of sub-perils such as storm surges, torrential rainfall, and landslides. The globally consistent methodology and calibrated regional impact functions are available online as a Python package ready for application in practical contexts like physical risk disclosure and providing more credible information for climate adaptation studies.
Extreme weather event attribution predicts climate policy support across the world
Cologna, Viktoria; Meiler, Simona; Kropf, Chahan M.; et al. (2025)
Nature Climate Change
Extreme weather events are becoming more frequent and intense due to climate change. Yet, little is known about the relationship between exposure to extreme events, subjective attribution of these events to climate change, and climate policy support, especially in the Global South. Combining large-scale natural and social science data from 68 countries (N = 71,922), we develop a measure of exposed population to extreme weather events and investigate whether exposure to extreme weather and subjective attribution of extreme weather to climate change predict climate policy support. We find that most people support climate policies and link extreme weather events to climate change. Subjective attribution of extreme weather was positively associated with policy support for five widely discussed climate policies. However, exposure to most types of extreme weather event did not predict policy support. Overall, these results suggest that subjective attribution could facilitate climate policy support.
A Reparative Paradigm for Thinking with Disasters
Simon, Gregory L.; O'Grady, Nathaniel; Grove, Kevin; et al. (2025)
The Geographical Journal
The field of disaster studies remains largely committed to a modernist spatio-temporal imaginary that persistently emphasises the singularity of a given disaster and often fails to account for the broader set of affairs in which disasters are situated and shaped, in turn leading to circumspect, uninventive and ineffective policy outcomes. In light of these trends, we argue for a paradigm shift in disaster research. In this commentary, we aim to advance studies on the governance and management of disasters by bringing these ongoing perspectives into conversation with recent debates on reparations and reparative thought. A reparative approach to disaster research contains at least three key elements. First, reparative disaster research encourages an explicit focus on relationality that pushes us to consider the intersecting spatial–historical processes and interconnected relationships comprising complex disasters. This relational approach expands our understanding of the dynamics that shape conditions of, and responses to, vulnerability and can engender a more transformative approach that animates and activates the forms of resistance. Second, a reparative approach acknowledges the capacity for disasters to destabilise established forms of disaster planning and infrastructure, thereby creating openings for more just and equitable forms of life in transformed contexts. This approach rejects ‘paranoid’ accounts suggesting that previous disaster outcomes will be automatically reproduced. Instead, it accommodates the possibility of alternative futures that might arise from disruptions in the present. Third, this approach has implications for how we approach disasters methodologically. Specifically, it urges us to reappraise the processes by which we undertake research in terms of fostering consistent and meaningfully collaborative relationships with communities in areas impacted by disasters.
The effectiveness of heat prevention plans in reducing heat-related mortality across Europe
Urban, Aleš; Huber, Veronika; Henry, Salomé; et al. (2025)
Environmental Research Letters
Heat-health warning systems and action plans, referred to as heat prevention plans (HPPs), are key public health interventions aimed at reducing heat-related mortality. Despite their importance, prior assessments of their effectiveness have yielded inconsistent results. The objective of this study is to systematically assess the effectiveness of HPPs in reducing heat-related mortality risk across Europe. We analysed daily mortality and mean temperature data from 102 locations in 14 European countries between 1990 and 2019. Using data from national experts, we identified the year of HPP implementation and categorised their development class. A three-stage analysis was conducted: (1) quasi-Poisson time series models were used to estimate location-specific warm-season exposure-response functions in 3 year subperiods; (2) mixed-effect meta-regression models with multilevel longitudinal structures were employed to quantify changes in pooled exposure-response functions due to HPP implementation, adjusted for long-term trends in heat-related mortality risks; and (3) the heat-related excess mortality due to HPP was calculated by comparing factual (with HPP) and counterfactual (without HPP) scenarios. Estimates are reported by country, region, and HPP class. HPP implementation was associated with a 25.2% [95% CI: 19.8% to 31.9%] reduction in excess deaths attributable to extreme heat, corresponding to 1.8 [95% CI: 1.3-2.4] avoided deaths annually per 100 000 inhabitants. This equates to an estimated 14 551 [95% CI: 10 118-19 072] total deaths avoided across all study locations following HPP implementation. No significant differences in HPP effectiveness were observed by European region or HPP class. Our findings provide robust evidence that HPPs substantially reduce heat-related mortality across Europe, accounting for temporal changes and geographical differences in risks. These results emphasise the importance of monitoring and evaluating HPPs to enhance adaptation to a warming climate.

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Samuel Lüthi

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