Alexandre K. Magnan

• PhD & Habilitation
• Senior Researcher at Cawthron Institute

The completion of the Sixth Assessment Cycle of the Intergovernmental Panel on Climate Change (IPCC) provides a unique opportunity to understand where the world stands on climate-change-related risks to natural and human systems at the global level, as well as for specific regions and sectors. Since its Third Assessment Report (AR3), released 2 dec...

Coastal cities are at the frontlines of climate change impacts, resulting in an urgent need for substantial adaptation. To understand whether, and to what extent, cities are on track to prepare for climate risks, this paper systematically assesses the academic literature to evaluate evidence on climate change adaptation in 199 coastal cities worldw...

The completion of the Sixth Assessment Cycle of the Intergovernmental Panel on Climate Change (IPCC) provides a unique opportunity to understand where the world stands on climate change-related risks to natural and human systems, at the global level as well as for specific regions and sectors. Since its Third Assessment Report, released two decades...

S’adapter au changement climatique, est-ce s’y résigner ? Longtemps soutenu, le discours ne résiste pas à l’examen. Ni à la nécessaire complémentarité des stratégies, entre adaptation et atténuation.

Climate change will push the planet worryingly close to its boundaries, across all latitudes and levels of development. One question therefore is the extent to which climate change does (and will) severely affect societies' livelihoods, health, well-being, and cultures. This paper discusses the "severe climate risks" concept developed under Working...

This Policy Brief proposes a modus operandi for the Global Goal on Adaptation (GGA) framework, in close connection with the development of the Paris Agreement's Global Stocktake (GST), and with a focus on combining policy and scientific expert judgments instead of exclusively relying only on a quantitative indicator basis. Its conclusions can infor...

Assessing progress and gaps in climate adaptation is a key policy concern, and also raises scientific challenges around which metrics should be used and who should assess progress. A structured expert judgement using local case studies shows that, for coastal areas, today’s global adaptation is halfway to achieving the full adaptation potential.

The state of progress towards climate adaptation is currently unclear. Here we apply a structured expert judgement to assess multiple dimensions shaping adaptation (equally weighted): risk knowledge, planning, action, capacities, evidence on risk reduction, long-term pathway strategies. We apply this approach to 61 local coastal case studies cluste...

Background Ocean-related options (OROs) to mitigate and adapt to climate change are receiving increasing attention from practitioners, decision-makers, and researchers. In order to guide future ORO development and implementation, a catalogue of scientific evidence addressing outcomes related to different ORO types is critical. However, until now, s...

There are now serious concerns about the growing risk of shortfalls in open-ocean fish stocks, and the effects on economic imperatives to access the remaining stocks, global-scale inflation and resulting inequalities in access to marine proteins for the most deprived people in society, as well as fractured regional and international relationships b...

This report explores 10 transboundary climate risks of global importance. The assessments take a deep dive into how transboundary climate risks impact local livelihoods, and critical sectors such as finance, health and global supply chains (e.g. agricultural commodities and manufacturing components). Each chapter explores, for a given transboundary...

Transboundary climate risks are risks induced by climate change that cross national borders. They do not only move from one country to its immediate neighbours: they also leap across entire regions and continents, transmitting risks to countries and people many thousands of miles away from the initial point of impact. These countries and individual...

Title: The added-value of expert judgment-based approaches to assess adaptation efforts (GAP-Track) This chapter discusses a method to assess climate adaptation progress.

Islands are at the center of discourses on climate change. Yet despite extensive work on diverse island systems in a changing climate, we still lack an understanding of climate change-related responses amongst islands and what shifting from what might be called “tinkering” (perhaps heat warnings) to “transformational” adaptation (perhaps relocation...

Atoll islands face increasing coastal risks (coastal erosion and marine flooding) due to climate change, especially sea-level rise. To face increasing coastal risks, various adaptation options are considered by atoll countries and territories, including in particular hard protection (preferred option to date), Nature-based Solutions (increasingly u...

More international incentives and coordination are needed

Sea level rise (SLR) will increase adaptation needs along low-lying coasts worldwide. Despite centuries of experience with coastal risk, knowledge about the effectiveness and feasibility of societal adaptation on the scale required in a warmer world remains limited. This paper contrasts end-century SLR risks under two warming and two adaptation sce...

This paper discusses whether existing coastal risk reduction policies in French Polynesia—a French Overseas Territory with a high degree of political autonomy—(i) consider current and future coastal risks from climate variability and change, and (ii) are designed to evolve as new knowledge on climate change emerges. The analysis relies on the study...

This report presnets the results of the pilot phase (2021) of the GAP-Track (Global Adaptation progress Tracker). See https://www.iddri.org/en/project/assessing-global-progress-climate-adaptation-gap-track-2021.

Little knowledge exists on the cascading implications of coastal migration across borders and, as a result, there is limited work on enhancing adaptive migration and relocation when relevant. Putting in place a governance framework and relevant policy tools (across scales and planned over time) to anticipate and prepare for migration from or to coa...

Assessing global progress on human adaptation to climate change is an urgent priority. Although the literature on adaptation to climate change is rapidly expanding, little is known about the actual extent of implementation. We systematically screened >48,000 articles using machine learning methods and a global network of 126 researchers. Our synthe...

The three recent Special Reports of the IPCC provide an opportunity to understand overarching climate risk, as they cover a wide diversity of risks to natural and human systems. Here we develop a scoring system to translate qualitative IPCC risk assessments into risk scores that, when aggregated, describe global risk from climate change. By the end...

Le niveau des mers et des océans monte. Or, une élévation de plusieurs dizaines de centimètres supplémentaires à l’horizon des prochaines décennies se traduira par une augmentation considérable du niveau des risques pour la plupart des littoraux du monde. Il existe des moyens d’anticiper ce défi, qui vont d’interventions menées à l’échelle planétai...

The shrinking solution space for adaptation calls for long-term dynamic planning starting now

Maintaining coral reef ecosystems is a social imperative, be cause so many people depend on coral reefs for food production, shoreline protection, and livelihoods. The survival of reefs this century, however, is threatened by the mounting effects of climate change. Climate mitigation is the foremost and essential action to prevent coral reef ecosys...

We present the first systematic, global stocktake of the academic literature on human adaptation. We screen 48,316 documents and identify 1,682 articles that present empirical research documenting human efforts to reduce risk from climate change and associated hazards. Coding and synthesizing this literature highlights that the overall extent of ad...

Recent assessments of future risk to atoll habitability have focused on island erosion and submergence, and have overlooked the effects of other climate‐related drivers, as well as differences between ocean basins and island types. Here we investigate the cumulative risk arising from multiple drivers (sea‐level rise; changes in rainfall, ocean–atmo...

https://www.unenvironment.org/resources/adaptation-gap-report-2020

Small islands are widely used to illustrate vulnerability to climate change and the urgency to adapt because they are facing its impacts at an accelerated rate. The ability to anticipate and plan for climate risks-especially from marine flooding and coastal erosion induced by hurricanes, storms and sea-level change-is significantly tied to idiosync...

The effectiveness, feasibility, duration of effects, co-benefits, disbenefits, cost effectiveness and governability of four ocean-based negative emissions technologies (NETs) are assessed in comparison to eight other ocean-based measures. Their role in revising UNFCCC Parties' future Nationally Determined Contributions is discussed in the broad con...

This study assesses changes in coastal risk reduction and adaptation-labelled responses in Mauritius Island since the 1960s. Using research documents, interviews, field observations, image analysis, and case studies, it analyses evolutions in public and private stakeholders’ strategies, and the levers and barriers at play. Based on 60 beach sites,...

Coastal areas host a significant part of the world population and of humankind’s adaptation needs in the face of effects of climate change, especially sea-level rise and ocean warming and acidification. Atoll islands illustrate frontline situations due to their biophysical (low elevation, small land area, 360°-exposure to waves, limited natural res...

Purpose of Review -- This paper discusses three scientific frontiers that need to be advanced in order to support decision-makers and practitioners in charge of operational decisions and action on the design and implementation of concrete adaptation policies and actions. These frontiers refer to going beyond the (1) incremental vs. transformational...

Context : It is now widely accepted that the climate is changing, and that societal responses will need to be rapid and comprehensive to prevent the most severe impacts. A key milestone in global climate governance is to assess progress on adaptation. To-date, however, there has been negligible robust, systematic synthesis of progress on adaptation...

The Intergovernmental Panel on Climate Change (IPCC) reports provide policy-relevant insights about climate impacts, vulnerabilities and adaptation through a process of peer-reviewed literature assessments underpinned by expert judgement. An iconic output from these assessments is the burning embers diagram, first used in the Third Assessment Repor...

Several ocean-based measures are available to reduce both climate change and its impacts on the open-ocean and coastal ecosystems, suggesting that the international community working on the ocean, from institutions to the private sector, can play a significant role in both adaptation and mitigation. All measures have limitations and tradeoffs. Desp...

In Mauritius island in the Indian Ocean, as in most low-lying coastal areas and Small Island Developing States in particular, coastal risks affect community livelihood, economic prosperity and the degradation of natural ecosystems. Risks of coastal erosion and marine flooding result both from climate-related ocean changes and anthropogenic drivers...

Based on the study of nine atolls of the Tuamotu Archipelago, French Polynesia, this article assesses the anthropogenic disturbances that disrupt atoll island natural dynamics and thereby undermine the ability of these islands to naturally adjust to climate-related pressures. It more specifically investigates to what extent the existing legal frame...

Recent assessments of future risk to atoll habitability have focused on island erosion and submergence, and have overlooked the effects of other climate-related drivers, as well as differences between ocean basins and island types. Here we investigate the cumulative risk arising from multiple drivers (sea-level rise; changes in rainfall, ocean-atmo...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Most studies addressing the future of atoll islands focused on ocean-climate drivers of risk, especially sea-level rise, and disregarded the role of local human disturbances. However, the future habitability of these countries will critically depend on the response of inhabited and exploited islands to ocean-climate pressures. Here, using the Maldi...

This Working Paper proposes to measure progress in climate change adaptation at the global level, for example through the development of new indicators using new technologies. This approach—the Global Adaptation Progress Tracker (GAP-Track)—involves both scientific and political challenges: in particular, which indicators (need to be innovative to...

Ocean and cryosphere changes already impact Low-Lying Islands and Coasts (LLIC), including Small Island Developing States, with cascading and compounding risks. Disproportionately higher risks are expected in the course of the 21st century. Reinforcing the findings of the IPCC Special Report on Global Warming of 1.5°C, vulnerable human communities,...

This is the Summary for Policy Makers of the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate, as approved by the IPCC member countries at the Plenary in Monaco, 25 September 2019.

Tropical cyclone (TC) impacts on small islands can be divided into four main categories that are common to both low‐lying atoll islands and high mountainous islands. This chapter investigates both the impacts of and the stakeholders' responses to TC Bejisa, which, in January 2014, affected Saint‐Paul, the second most populated municipality of Reuni...

The unique coping capacities and other attributes that Pacific island nations have been developing for centuries have sustained them in the face of an enormous range of local and global challenges. These include climate change-related hazards, and especially tropical cyclones and high-wave incidents that notably generate landslides and river and co...

Relative sea-level rise and the influence of vertical land motion at Tropical Pacific Islands (Supplementary material)

French coastal policies have recently put greater emphasis on the need to better inform coastal populations about coastal risks in the context of climate change, in particular in French overseas territories that are nationally recognized as hotspots. It is therefore critical to further assess local populations' knowledge and perceptions of climate-...

This handbook is currently in development, with individual articles publishing online in advance of print publication. At this time, we cannot add information about unpublished articles in this handbook, however the table of contents will continue to grow as additional articles pass through the review process and are added to the site. Please note...

This study investigates the relative sea–level changes and the influence of vertical land movements at South Western Tropical Pacific Islands. The dataset consists of tide gauge records, remote satellite altimetry observations and GPS records. After evaluating the uncertainties and the nature of vertical land movements, we focus on the present and...

Sea level rise and extreme weather events threaten the livelihoods and possibly the long-term existence of whole island nations. While the media, policy, and often scientific arenas essentially focus their attention on Small Island Developing States (SIDS), which are widely recognised as hotspots of global climate change, the situation of the numer...

This paper characterizes the current exposure of people leaving on the low-lying atoll reef islands to the risk of marine inundation induced by various sea-related hazards (i.e. cyclones, distant swells and local storms). It offers one of the rare scientific studies that go beyond the general assertion on atoll populations’ exposure to sea-related...

Cet article représente l’une des rares études scientifiques cherchant à dépasser le discours général sur l’exposition des populations des atolls face aux risques liés à la mer, en l’occurrence ici à la submersion marine, en mesurant concrètement le degré réel d’exposition actuelle des populations et en observant les stratégies locales de protection...

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The Paris Agreement target of limiting global surface warming to 1.5–2°C compared to pre-industrial levels by 2100 will still heavily impact the ocean. While ambitious mitigation and adaptation are both needed, the ocean provides major opportunities for action to reduce climate change globally and its impacts on vital ecosystems and ecosystem servi...

This Policy Brief summarises the main findings of The Ocean Solutions Initiative (http://www.obs-vlfr.fr/~gattuso/tosi_products.php) that assessed the potential of 13 ocean-based measures. The Ocean Solutions Initiative is an endeavour by a group of 18 ocean experts across natural and social sciences to assess the potential of 13 ocean-based measur...

The study of recent past trajectories of vulnerability to climate-related hazards allows for highlighting the prevailing environmental and anthropogenic drivers that operated over the last fifty to sixty years and given latency phenomena in social systems, therefore have the potential to continue driving a system's vulnerability in the coming decad...

Mataiva Atoll (French Polynesia) has a 25km² entirely reticulated lagoon, a quite unique coral structure in the world. Mataiva lagoon is also rich in phosphate. The project of exploiting it arose in the 1970s, and in the 1980s international companies engaged a dialogue with the Government of French Polynesia to get authorisations. Public meetings w...

This work organizes into a coherent storyline four intertwined dimensions of the study of societal vulnerability to climate change: (i) the Trajectory of Vulnerability (ToV) approach; (ii) the minimization of the risk of maladaptation and the identification of inescapable solutions to adaptation; (iii) the development of chain of impacts and of ris...

This brief from SEI, IDDRI and ODI finds that a transboundary view of climate risk creates opportunities for international cooperation on adaptation. This brief asserts that the critical importance of adaptation is still under-valued in international negotiations. Specifically, the view that adaptation is a local problem is holding back ambition to...

Cet article démontre l'intérêt d'une approche de la résilience des territoires par la reconstruction de « chaînes d'impacts » d'événements passés. Proposé au Ministère de l'Ecologie comme composante du référentiel national d'adaptation au changement climatique [ONERC, 2012], ce concept a fait l'objet d'applications à des cyclones tropicaux ayant to...

Climate change poses an existential threat to Small Island Developing States (SIDS). They have played a leading role in raising awareness of climate change on the international stage and advocating for strong climate action, notably through the Alliance of Small Island States (AOSIS). Despite their heterogeneity, they succeeded in building a common...

This article advocates for a dynamic and comprehensive understanding of vulnerability to climate‐related environmental changes in order to feed the design of adaptation future pathways. It uses the trajectory of exposure and vulnerability ( TEV ) approach that it defines as ‘storylines of driving factors and processes that have influenced past and...

Cette étude présente les résultats de la reconstruction de 6 trajectoires de vulnérabilité des littoraux de quatre communes de l’île de la Réunion (sud-ouest de l’océan Indien). La période couverte est 1950-2011 et définit des trajectoires dites « courtes ». Les résultats montrent l’importante contribution des facteurs anthropiques (aménagement du...

This paper highlights the high variability of the nature and severity of the impacts of Tropical Cyclone Bejisa (January 2014, category 3) along the 20-km-long beach–dune systems of the western coast of Reunion Island. Erosional impacts were reported on 17 out of 26 topographic transects, while nine transects exhibited accretion. Sediment loss and...

Full text available here: - http://science.sciencemag.org/content/sci/352/6291/1280.full.pdf?ijkey=36Jvi2YzN8cJ2&keytype=ref&siteid=sci - http://science.sciencemag.org/content/352/6291/1280.full?ijkey=36Jvi2YzN8cJ2&keytype=ref&siteid=sci

Full text available here: http://rdcu.be/iigT.

This paper reviews the current theoretical scholarship on maladaptation and provides some specific case studies—in the Maldives, Ethiopia, South Africa, and Bangladesh—to advance the field by offering an improved conceptual understanding and more practice‐oriented insights. It notably highlights four main dimensions to assess the risk of maladaptat...

The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) states that climate change and ocean acidification are altering the oceans at a rate that is unprecedented compared with the recent past, leading to multifaceted impacts on marine ecosystems, associated goods and services, and human societies. AR5 underlined key unce...

• The ocean moderates anthropogenic climate change by absorbing signi cant parts of the heat and CO2 that accumulate in the atmosphere. The ocean also receives all water from melting ice. • This regulating function happens at the cost of profound alterations of the ocean’s physics and chemistry, especially leading to ocean warming and acidi cation,...

The oceans moderate global warming, which in turn has major effects on their ecosystems. Within the framework of the Oceans 2015 Initiative, some 20 researchers from across the world have analysed the risks of impact on marine and coastal ecosystems. They warn that safeguarding our oceans must be a priority of the United Nations Climate Change Conf...