Habitability of low-lying socio-ecological systems under a changing climate

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 Group II’s contribution to the Fifth and Sixth Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC, AR5, and AR6). Focusing on low-lying coastal socio-ecological systems (LCS) and acknowledging that attempts to define “severe” climate risk have been problematic at the level of global syntheses, we argue for a more place- and people-based framing relating to “habitability under a changing climate.” We summarize habitability in terms of five habitability pillars: land, freshwater, food, settlement and infrastructure, and economic and subsistence activities; we acknowledge social and cultural factors (including perceptions, values, governance arrangements, human agency, power structures) as critical underlying factors rather than as separate pillars. We further develop the habitability framing and examine climate risk to future human health and habitability for three climate “hotspot” archetypes (arctic coasts, atoll islands, densely populated urban areas). Building on the IPCC AR6 framing of severe climate risks, we discuss three key parameters describing severe climate risks in LCS: the point of irreversibility of changes, physical and socio-ecological thresholds, and cascading effects across various habitability dimensions. We also highlight the variability of severe risk conditions both between coastal archetypes and within each of them. Further work should consist of refining the case study framing to find the right balance between capturing context-specificities through real-world local case studies and commonalities derived from more generic archetypes. In addition, there is a need to identify appropriate methods to assess irreversibility, thresholds, and cascading effects, and thus severe climate risks to habitability

Framing and Context of the Report

The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides policymakers with regular assessments of the scientific basis of human-induced climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the most comprehensive and up-to-date assessment of the observed and projected changes to the ocean and cryosphere and their associated impacts and risks, with a focus on resilience, risk management response options, and adaptation measures, considering both their potential and limitations. It brings together knowledge on physical and biogeochemical changes, the interplay with ecosystem changes, and the implications for human communities. It serves policymakers, decision makers, stakeholders, and all interested parties with unbiased, up-to-date, policy-relevant information. Chapter 1: This special report assesses new knowledge since the IPCC 5th Assessment Report (AR5) and the Special Report on Global Warming of 1.5ºC (SR15) on how the ocean and cryosphere have and are expected to change with ongoing global warming, the risks and opportunities these changes bring to ecosystems and people, and mitigation, adaptation and governance options for reducing future risks. Chapter 1 provides context on the importance of the ocean and cryosphere, and the framework for the assessments in subsequent chapters of the report. All people on Earth depend directly or indirectly on the ocean and cryosphere. The fundamental roles of the ocean and cryosphere in the Earth system include the uptake and redistribution of anthropogenic carbon dioxide and heat by the ocean, as well as their crucial involvement of in the hydrological cycle. The cryosphere also amplifies climate changes through snow, ice and permafrost feedbacks. Services provided to people by the ocean and/or cryosphere include food and freshwater, renewable energy, health and wellbeing, cultural values, trade and transport. {1.1, 1.2, 1.5} Sustainable development is at risk from emerging and intensifying ocean and cryosphere changes. Ocean and cryosphere changes interact with each of the United Nations Sustainable Development Goals (SDGs). Progress on climate action (SDG 13) would reduce risks to aspects of sustainable development that are fundamentally linked to the ocean and cryosphere and the services they provide (high confidence1 ). Progress on achieving the SDGs can contribute to reducing the exposure or vulnerabilities of people and communities to the risks of ocean and cryosphere change (medium confidence). {1.1} Communities living in close connection with polar, mountain, and coastal environments are particularly exposed to the current and future hazards of ocean and cryosphere change. Coasts are home to approximately 28% of the global population, including around 11% living on land less than 10 m above sea level. Almost 10% of the global population lives in the Arctic or high mountain regions. People in these regions face the greatest exposure to ocean and cryosphere change, and poor and marginalised people here are particularly vulnerable to climate-related hazards and risks (very high confidence). The adaptive capacity of people, communities and nations is shaped by social, political, cultural, economic, technological, institutional, geographical and demographic factors. {1.1, 1.5, 1.6, Cross-Chapter Box 2 in Chapter 1} Ocean and cryosphere changes are pervasive and observedfrom high mountains, to the polar regions, to coasts, and intothe deep ocean. AR5 assessed that the ocean is warming (0 to700 m: virtually certain2; 700 to 2,000 m: likely), sea level is rising(high confidence), and ocean acidity is increasing (high confidence).Most glaciers are shrinking (high confidence), the Greenland andAntarctic ice sheets are losing mass (high confidence), sea ice extent inthe Arctic is decreasing (very high confidence), Northern Hemispheresnow cover is decreasing (very high confidence), and permafrosttemperatures are increasing (high confidence). Improvementssince AR5 in observation systems, techniques, reconstructions andmodel developments, have advanced scientific characterisationand understanding of ocean and cryosphere change, including inpreviously identified areas of concern such as ice sheets and AtlanticMeridional Overturning Circulation (AMOC). {1.1, 1.4, 1.8.1}Evidence and understanding of the human causes of climatewarming, and of associated ocean and cryosphere changes,has increased over the past 30 years of IPCC assessments (veryhigh confidence). Human activities are estimated to have causedapproximately 1.0ºC of global warming above pre-industrial levels(SR15). Areas of concern in earlier IPCC reports, such as the expectedacceleration of sea level rise, are now observed (high confidence).Evidence for expected slow-down of AMOC is emerging in sustainedobservations and from long-term palaeoclimate reconstructions(medium confidence), and may be related with anthropogenic forcingaccording to model simulations, although this remains to be properlyattributed. Significant sea level rise contributions from Antarctic icesheet mass loss (very high confidence), which earlier reports did notexpect to manifest this century, are already being observed. {1.1, 1.4}Ocean and cryosphere changes and risks by the end-of-century(2081?2100) will be larger under high greenhouse gas emissionscenarios, compared with low emission scenarios (very highconfidence). Projections and assessments of future climate, oceanand cryosphere changes in the Special Report on the Ocean andCryosphere in a Changing Climate (SROCC) are commonly basedon coordinated climate model experiments from the Coupled ModelIntercomparison Project Phase 5 (CMIP5) forced with RepresentativeConcentration Pathways (RCPs) of future radiative forcing. Currentemissions continue to grow at a rate consistent with a high emissionfuture without effective climate change mitigation policies (referredto as RCP8.5). The SROCC assessment contrasts this high greenhousegas emission future with a low greenhouse gas emission, highmitigation future (referred to as RCP2.6) that gives a two in threechance of limiting warming by the end of the century to less than 2oC above pre-industrial. {Cross-Chapter Box 1 in Chapter 1} Characteristics of ocean and cryosphere change include thresholds of abrupt change, long-term changes that cannot be avoided, and irreversibility (high confidence). Ocean warming, acidification and deoxygenation, ice sheet and glacier mass loss, and permafrost degradation are expected to be irreversible on time scales relevant to human societies and ecosystems. Long response times of decades to millennia mean that the ocean and cryosphere are committed to long-term change even after atmospheric greenhouse gas concentrations and radiative forcing stabilise (high confidence). Ice-melt or the thawing of permafrost involve thresholds (state changes) that allow for abrupt, nonlinear responses to ongoing climate warming (high confidence). These characteristics of ocean and cryosphere change pose risks and challenges to adaptation. {1.1, Box 1.1, 1.3} Societies will be exposed, and challenged to adapt, to changes in the ocean and cryosphere even if current and future efforts to reduce greenhouse gas emissions keep global warming well below 2ºC (very high confidence). Ocean and cryosphere-related mitigation and adaptation measures include options that address the causes of climate change, support biological and ecological adaptation, or enhance societal adaptation. Most ocean-based local mitigation and adaptation measures have limited effectiveness to mitigate climate change and reduce its consequences at the global scale, but are useful to implement because they address local risks, often have co-benefits such as biodiversity conservation, and have few adverse side effects. Effective mitigation at a global scale will reduce the need and cost of adaptation, and reduce the risks of surpassing limits to adaptation. Ocean-based carbon dioxide removal at the global scale has potentially large negative ecosystem consequences. {1.6.1, 1.6.2, Cross-Chapter Box 2 in Chapter 1} The scale and cross-boundary dimensions of changes in the ocean and cryosphere challenge the ability of communities, cultures and nations to respond effectively within existing governance frameworks (high confidence). Profound economic and institutional transformations are needed if climate-resilient development is to be achieved (high confidence). Changes in the ocean and cryosphere, the ecosystem services that they provide, the drivers of those changes, and the risks to marine, coastal, polar and mountain ecosystems, occur on spatial and temporal scales that may not align within existing governance structures and practices (medium confidence). This report highlights the requirements for transformative governance, international and transboundary cooperation, and greater empowerment of local communities in the governance of the ocean, coasts, and cryosphere in a changing climate. {1.5, 1.7, Cross-Chapter Box 2 in Chapter 1, Cross-Chapter Box 3 in Chapter 1} Robust assessments of ocean and cryosphere change, and the development of context-specific governance and response options, depend on utilising and strengthening all available knowledge systems (high confidence). Scientific knowledge from observations, models and syntheses provides global to local scale understandings of climate change (very high confidence). Indigenous knowledge (IK) and local knowledge (LK) provide context-specific and socio-culturally relevant understandings for effective responses and policies (medium confidence). Education and climate literacy enable climate action and adaptation (high confidence). {1.8, Cross-Chapter Box 4 in Chapter 1} Long-term sustained observations and continued modelling are critical for detecting, understanding and predicting ocean and cryosphere change, providing the knowledge to inform risk assessments and adaptation planning (high confidence). Knowledge gaps exist in scientific knowledge for important regions, parameters and processes of ocean and cryosphere change, including for physically plausible, high impact changes like high end sea level rise scenarios that would be costly if realised without effective adaptation planning and even then may exceed limits to adaptation. Means such as expert judgement, scenario building, and invoking multiple lines of evidence enable comprehensive risk assessments even in cases of uncertain future ocean and cryosphere changes.Fil: Abram, Nerilie. Australian National University; AustraliaFil: Gattuso, Jean Pierre. Centre National de la Recherche Scientifique; FranciaFil: Prakash, Anjal. Teri School Of Advanced Studies; IndiaFil: Cheng, Lijing. Chinese Academy Of Science; ChinaFil: Chidichimo, María Paz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: Crate, Susan. George Mason University; Estados UnidosFil: Enomoto, H.. National Polar Agency; JapónFil: Garschagen, M.. Technische Universitat München; AlemaniaFil: Gruber, N.. Swiss Federal Institute of Technology Zurich; SuizaFil: Harper, S.. University Of Alberta. Faculty Of Agricultural, Life And Environmental Sciences. Departament Of Agricultural, Food And Nutritional Science.; CanadáFil: Holland, Elisabeth. University Of South Pacific; FiyiFil: Kudela, Raphael Martin. University of California at San Diego. Scripps Institution of Oceanography; Estados UnidosFil: Rice, Jake. University of Toronto; CanadáFil: Steffen, Konrad. Swiss Federal Institute for Forest, Snow and Landscape Research; SuizaFil: Von Schuckmann, Karina. Mercator Ocean International; Franci

Assessment of building damage and risk under extreme flood scenarios in Shanghai

This article presents a flood risk assessment for Shanghai, which provides an indication of what buildings (including residential, commercial, office, and industrial) will be exposed to flooding and its damage. Specifically, this assessment provides a risk assessment that buildings may face after construction. To achieve the flood risk assessment on buildings, we developed an integrated flood model and collected data on building shape and number of floors, land use, and construction costs for different building types in Shanghai. The extreme compound flood scenarios (1/200-, 1/500-, 1/1000-, and 1/5000-year floods) and building metadata were aggregated using a risk analysis chain. According to the damage for different flood scenarios, the average annual loss (AAL) can be calculated and is referred to as building flood risk. The AAL of residential, commercial, office, and industrial buildings is USD 12.3, 2.5, 3.7, and 3.4 million, respectively. Among the 15 (non-island) districts in Shanghai, Pudong has the highest AAL. The risk analysis chain developed in this study can be reproduced for other megacities. The results provide a clear picture for future building flood risks which links directly to disaster risk management, which implies the extent of flood risk in building types, sub-districts, and districts related to the Shanghai Master Plan. This assessment takes into consideration future climate change scenarios, information for scenario-based decision making, and a cost–benefit analysis for extreme flood risk management in Shanghai. We also discussed different potential adaptation options for flood risk management.</p

Understanding human vulnerability to climate change: A global perspective on index validation for adaptation planning

Climate change is a severe global threat. Research on climate change and vulnerability to natural hazards has made significant progress over the last decades. Most of the research has been devoted to improving the quality of climate information and hazard data, including exposure to specific phenomena, such as flooding or sea-level rise. Less attention has been given to the assessment of vulnerability and embedded social, economic and historical conditions that foster vulnerability of societies. A number of global vulnerability assessments based on indicators have been developed over the past years. Yet an essential question remains how to validate those assessments at the global scale. This paper examines different options to validate global vulnerability assessments in terms of their internal and external validity, focusing on two global vulnerability indicator systems used in the WorldRiskIndex and the INFORM index. The paper reviews these global index systems as best practices and at the same time presents new analysis and global results that show linkages between the level of vulnerability and disaster outcomes. Both the review and new analysis support each other and help to communicate the validity and the uncertainty of vulnerability assessments. Next to statistical validation methods, we discuss the importance of the appropriate link between indicators, data and the indicandum. We found that mortality per hazard event from floods, drought and storms is 15 times higher for countries ranked as highly vulnerable compared to those classified as low vulnerable. These findings highlight the different starting points of countries in their move towards climate resilient development. Priority should be given not just to those regions that are likely to face more severe climate hazards in the future but also to those confronted with high vulnerability already

A people-centred perspective on climate change, environmental stress, and livelihood resilience in Bangladesh

The Ganges–Brahmaputra delta enables Bangladesh to sustain a dense population, but it also exposes people to natural hazards. This article presents findings from the Gibika project, which researches livelihood resilience in seven study sites across Bangladesh. This study aims to understand how people in the study sites build resilience against environmental stresses, such as cyclones, floods, riverbank erosion, and drought, and in what ways their strategies sometimes fail. The article applies a new methodology for studying people’s decision making in risk-prone environments: the personal Livelihood History interviews (N = 28). The findings show how environmental stress, shocks, and disturbances affect people’s livelihood resilience and why adaptation measures can be unsuccessful. Floods, riverbank erosion, and droughts cause damage to agricultural lands, crops, houses, and properties. People manage to adapt by modifying their agricultural practices, switching to alternative livelihoods, or using migration as an adaptive strategy. In the coastal study sites, cyclones are a severe hazard. The study reveals that when a cyclone approaches, people sometimes choose not to evacuate: they put their lives at risk to protect their livelihoods and properties. Future policy and adaptation planning must use lessons learned from people currently facing environmental stress and shocks

IPCC reasons for concern regarding climate change risks

The reasons for concern framework communicates scientific understanding about risks in relation to varying levels of climate change. The framework, now a cornerstone of the IPCC assessments, aggregates global risks into five categories as a function of global mean temperature change. We review the framework's conceptual basis and the risk judgments made in the most recent IPCC report, confirming those judgments in most cases in the light of more recent literature and identifying their limitations. We point to extensions of the framework that offer complementary climate change metrics to global mean temperature change and better account for possible changes in social and ecological system vulnerability. Further research should systematically evaluate risks under alternative scenarios of future climatic and societal conditions

Enhancing the relevance of Shared Socioeconomic Pathways for climate change impacts, adaptation and vulnerability research

This paper discusses the role and relevance of the shared socioeconomic pathways (SSPs) and the new scenarios that combine SSPs with representative concentration pathways (RCPs) for climate change impacts, adaptation, and vulnerability (IAV) research. It first provides an overview of uses of social–environmental scenarios in IAV studies and identifies the main shortcomings of earlier such scenarios. Second, the paper elaborates on two aspects of the SSPs and new scenarios that would improve their usefulness for IAV studies compared to earlier scenario sets: (i) enhancing their applicability while retaining coherence across spatial scales, and (ii) adding indicators of importance for projecting vulnerability. The paper therefore presents an agenda for future research, recommending that SSPs incorporate not only the standard variables of population and gross domestic product, but also indicators such as income distribution, spatial population, human health and governance