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Risk science in the age of climate change

Extreme weather events, rising sea levels, avalanches - these are just some of the hazards that place the question of risk at the heart of the debate on resilience and adaptation to climate change.

Risk science in the age of climate change

© NASA

Publication date: 14/06/2023

Press, Research

Related teams :
Volcanic Systems

Related themes : Natural Hazards

Over the next few years, as part of the France 2030 Irima (2) research programme (1) launched on 22 May 2023, the research sector will be helping to consolidate knowledge about the hazards and risks that our societies are facing and will face in the era of global change.

Aldo Sottolichio (3), Xavier Bertin (4), Nicolas Eckert (5) and Anne Le Friant (6) describe the risks studied by national research teams that include scientists from CNRS-Insu. Magali Reghezza (7) explains the issues surrounding risk science.

Panneau d'alerte sur l'érosion dunaire, à l'entrée de la plage de Biscarrosse © Cyril FRESILLON/EPOC/CNRS Images

As a preliminary, it is useful to define the concept of risk here. Risk is a dangerous situation resulting from the simultaneous presence of a potentially damaging event (hazard) and elements (8) (issues) that are both exposed and vulnerable. For example, for the same hazard (tsunami), coastal areas are not exposed to the same risk depending on the density of the population living there. As long as the threat has not been identified, the risk does not exist for societies, and is therefore not the subject of any preventive action. A distinction is made between the so-called “real” risk (the objectified threat) and the “perceived” risk (the threat as assessed by individuals), bearing in mind that there is often a discrepancy between the two. Risk can be over- or underestimated, depending on a number of factors (9).

Among the major risks now facing our societies, the impacts of climate change occupy a central place. In its 2022 report, the French High Council for the Climate stressed that France is not ready to face up to the risks of climate change. In France, we are exposed to both slow-onset hazards (rising sea levels, reduced snow cover, collapse of biodiversity) and extreme events (hot, dry, wet), the frequency, intensity, duration and earliness of which are increasing in a climate that is changing and will continue to change until carbon neutrality is achieved (10). Added to this are the induced, composite or systemic risks: health risks (physical and mental health), technological risks, risks to agriculture, tourism and industry, economic and financial risks, social risks, etc.

The next few years will be crucial for improving risk science (11), taking into account the complexity of certain territories, such as the French overseas territories, where risks are superimposed and the so-called “cascade” effect (one risk can lead to another). Depending on the area, so-called “natural” hazards (see box) such as erosion, cyclones or landslides give rise to different risks.

Let’s take a look at coastal, mountain and overseas risks, and the challenge of developing risk sciences in these areas.

Coastal risks: erosion and flooding

The coast is particularly exposed to hazards linked to meteorological and climatic causes. It is also exposed to risks because a large proportion of the world’s population lives there, and this trend is set to continue over the coming decades.

Erosion refers to the loss of territory due to excessive energy from currents or waves, which release sediment (sand, gravel, etc.) or erode cliffs, changing the shoreline, often resulting in a retreat of the coastline. Coastal risks are complex to study because of the overlapping time scales involved: there are cyclical phenomena (tides, seasons) resulting in slow, gradual change over the long term. These cycles are superimposed on rapid and extreme phenomena that accelerate or counteract long-term trends. Moreover, coastlines react not only to the intensity of hydrodynamic agents (typically waves), but also to the input of sediment, which is necessary to compensate for losses through erosion. A beach that receives a lot of sand, even if it is exposed to waves, will not necessarily retreat.

Riprap installed on the Lacanau-Océan beach on the Aquitaine coast. Riprap is an active, hard-hitting method of combating erosion, which pushes back the coastline to the point of endangering some homes. © Cyril FRESILLON/EPOC/CNRS Images

On the other hand, sediment accumulated over several years on an estuarine mudflat can be evacuated in a matter of hours by a storm. As far as erosion is concerned, trends are accumulating: on coasts with a sediment deficit, violent waves during storms are enough to modify the coastline, which is gradually and chronically retreating over several years.

It is important to understand that climate change aggravates existing phenomena. For example, flooding (13) can be either a slow event linked to rising sea levels or a sinking coastline (14), or a rapid event due to a meteorological (15) or tectonic phenomenon (tsunami, fault movement, etc.). These phenomena have always existed, but with climate change, sea level rise is accelerating and marine submersions will be more frequent. In the tropical ocean, cyclones develop in warm waters (above 27°C), so a warming climate is likely to lead to more violent storms (16). It is also leading to the development of cyclones in unusual (non-tropical) areas in Europe (e.g. storm Leslie to the west of Portugal in 2018 or Lorenzo in 2019 to the west of the Bay of Biscay). The Mediterranean may also be affected, as in August 2022.

Society’s demand, which is the focus of the Irima research programme, is to predict how the coastline will evolve in the context of climate change. Overall, the coastline is retreating almost across the board, but scientists want to work in a multidisciplinary way to improve modelling and thus better predict events. To this end, they need to acquire a better understanding of physical phenomena (wave physics, the response of the coastline to its waves, etc.) and the connection between these phenomena and climatology, not forgetting the societal aspect with adaptation processes.

Mountain risks

Mountain areas are characterised by physical constraints such as slopes and altitude gradients, which affect the land and have consequences for its occupation and attractiveness (tourism, industry, energy, transport, etc.). Spatial planning (and therefore the issues at stake) is constantly evolving as a result of changing practices and development. It is also one of the areas where climate change is most visible through the rapid modification of glaciers, snow cover and the hydrological cycle, and the changes to landscapes that also depend on changes in society.

Avalanche des Lanches from the north face of Bellecote on 25/02/1995, which buried half a dozen chalets © Inrae

Avalanches, rock falls, landslides, glacial and periglacial hazards (17) and floods are the main hazards (often combined in the form of cascading phenomena). They are highly variable over time (depending on climate change), with consequences that are themselves variable, depending on the combined changes in society. As with coastal risks, there are several timeframes to be taken into account when studying risks: the gradual melting of glaciers, for example, is a background signal that scientists are able to predict precisely, and which can change not only the long-term context of the area but also the conditions for the appearance of sudden and rapid phenomena.

These have major immediate consequences (collapse of seracs, sudden flooding due to the rupture of a water pocket, etc.). For example, climate change has a major influence on avalanches.

At low or very low altitudes, the risks are reduced, while at high altitudes avalanche activity may increase or at least be maintained with the amplification of precipitation extremes. Similarly, the release and transport of sediments linked to the retreat of glaciers can be destructive in valleys. As part of the Irima PEPR, the aim is to gain a better understanding of all the physical and social dimensions of mountain risks, from processes to risk assessment and decision-making, by specifically targeting the knowledge gaps that prevent effective risk assessment and mitigation. The aim is to characterise the dynamics of changes in risks and their components over the long term, and to develop methods for taking them into account in risk mapping and management over different time horizons and under different climate scenarios. Particular attention is also being paid to the cascading risks associated with the degradation of permafrost, glacial retreat and the reduction in seasonal snow cover.

Overseas risks

Subject to cyclones, earthquakes and volcanic events (Lesser Antilles, Mayotte, Reunion, etc.), the overseas territories are special risk areas. They are also island territories where risk management is complex, not only because of the remoteness of the heavy resources available in mainland France, but also because of the concentration of the population on the coasts, and because of local building practices, sometimes strongly influenced by the origins of the original populations. All these specific features need to be taken into account when working on earthquake risks: these are triggered by seismic activity or volcanic activity, which can change rapidly (for example, the recent change in the alert status of Montagne Pelée (18)), so vigilance must always be adapted to these rapid changes. Overseas risks have increased as a result of climate change and human pressure, particularly from tourism, which has increased the number of hazards near the coast. The intensification of cyclones and rising sea levels will be major challenges over the coming decades. In this context, identifying the time scales associated with the emergence of chronic submersions will enable us to build adaptation trajectories for island communities in the outermost regions.

In the Irima research programme, one of the challenges of the Overseas axis is to identify new signals for studying natural hazards and the associated human impact on large spatio-temporal scales (e.g. seismic and volcanic cycles or cyclone cyclicity). We hope that these new signals will make it possible, for example, to identify new precursors of certain telluric events. This improved knowledge of phenomena will enable us to develop integrative risk management strategies tailored to overseas and intertropical areas, capable of dealing with the extreme consequences of cascading events leading to multiple risks (earthquakes, eruptions, instabilities, tsunamis, floods, etc.).

Carcasses destroyed by Hurricane Irma on the Grandes Cayes ecosite on the island of Saint-Martin © Cyril FRESILLON / LGP / CNRS Images

For example, hazard maps for volcanic eruptions or simulations of damage caused by tsunamis could help the authorities in their various crisis or development plans. Holistic, integrated models of complex processes that take account of the uncertainties in climate change projections are essential to develop.

PEPR Irima: the challenge of risk science

The three examples of risk presented demonstrate the particular importance of climate change and its consequences for the study of risk. Research work in different scientific fields provides a better understanding of natural phenomena and the vulnerabilities of socio-ecosystems, and can make a major contribution to anticipating risks for the most exposed and vulnerable populations and areas, as well as contributing to mitigation, adaptation and resilience policies.

The aim of the Irima research programme is to formalise risk science in France in the context of global, anthropogenic and climate change. The aim is not only to study a range of natural hazards to improve risk prediction, particularly extreme events, but also to analyse the way in which vulnerable areas and populations are managed. Studies will also be carried out to rethink risk analysis frameworks and policies, in particular cascading or interrelated risks, which are exacerbated by climate change. Bringing together researchers from different disciplines (geologists, oceanographers, geophysicists, modellers, geographers, sociologists, historians, etc.) is a unique opportunity to produce new knowledge and scientific expertise relevant to public action.

To find out more

About the research programmes:

The PEPR programmes are part of the France 2030 investment plan. Their aim is to build or consolidate French leadership in scientific fields that are linked or likely to be linked to technological, economic, societal, health or environmental change and that are considered priorities at national or European level.

About the Irima research programme :

For more information on the Irima research programme, carried out in collaboration with BRGM and Grenoble Alpes University.

Industrial accidents, natural disasters… society and risk | CNRS Le journal

On risks :

Notes

  1. Priority Exploratory Research Programme (PEPR) on integrated risk management for more resilient societies in an era of global change. PEPRs are part of the France 2030 investment plan. They aim to build or consolidate French leadership in scientific fields that are linked or likely to be linked to technological, economic, societal, health or environmental change and that are considered priorities at national or European level.
  2. Coordinated by BRGM (Gilles Grandjean), CNRS-INSHS (Soraya Boudia) and Grenoble Alpes University (Didier Georges). Find out more about Irima (see box).
  3. Lecturer at the University of Bordeaux in the Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC – OASU) laboratory. Supervising bodies: CNRS / University of Bordeaux / Bordeaux Polytechnic Institute / EPHE.
  4. CNRS researcher at the Littoral, Environment and Societies Laboratory (LIENSs) Supervising bodies: CNRS / La Rochelle University.
  5. Inrae researcher at the Institute of Environmental Geosciences (IGE – OSUG) Supervising bodies: CNRS / INRAE / IRD / UGA. Co-leader of the Environmental Risks TEP of the ALLENVI alliance.
  6. CNRS researcher at the Institut de Physique du Globe de Paris (IPGP) Supervising bodies: CNRS / IPG.
  7. ENS-PSL lecturer-researcher at the Physical Geography: Ancient and Current Environments Laboratory (LPG) Boards: CNRS / Université Panthéon-Sorbonne / Université Paris-est Créteil Val-de-Marne.
  8. The issues at stake are diverse in nature: people, socio-ecosystems, socio-technical systems, production systems, infrastructures, goods, etc.
  9. Risk representations vary according to age, socio-economic level, level of education, profession, experience, family and social background, beliefs and values, as well as scientific uncertainties, available models and calculation capacities, socio-political priorities and the resources available to deal with them, etc.
  10. Even if anthropogenic disturbances will still have consequences years after carbon neutrality has been achieved.
  11. The risk sciences have a long history, with multiple fields of study and highly internationalised domains: disaster risk reduction (DRR), disaster studies, vulnerability studies, resilience studies, as well as all approaches based on hazards.
  12. River mouth
  13. When the sea level exceeds the natural barriers to submersion (pebble banks, dunes, etc.) or artificial barriers (dykes).
  14. For reasons of overloading of city buildings, as in the case of New York, or overloading of sediment, as in the case of the Mississippi delta.
  15. A storm with wind and swell or simply a strong swell without a cyclone.
  16. In 2017, there were three category 5 cyclones in the Caribbean.
  17. The reduction in the surface area of glaciers is causing instability in glacial and periglacial zones. Periglacial hazards can be characterised by the sudden flow of water stored in these areas, ice breaking off the glacier or the melting of alpine permafrost.
  18. Surveillance of the site was upgraded to the yellow volcanic alert level in 2020, i.e. heightened scientific vigilance, due to a resurgence of low-intensity seismic activity. This watch is still in place in 2023.
  19. Climate change is perceived by the majority of French people, even if the level of climate scepticism remains high compared with our European neighbours. In 2022, 62% of French people were aware that climate change would require major lifestyle changes.
  20. 100% for the last decade
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