Anthropogenic sea-level rise (SLR) is predicted to impact, and, in many cases, displace, a large proportion of the population via inundation and heightened SLR-related hazards. With the global coastal population projected to surpass one billion people this century, SLR might be among the most costly and permanent future consequences of climate change. In this Review, we synthesize the rapidly expanding knowledge of human mobility and migration responses to SLR, providing a coherent roadmap for future SLR research and associated policy. While it is often assumed that direct inundation forces a migration, we discuss how mobility responses are instead driven by a diversity of socioeconomic and demographic factors, which, in some cases, do not result in a migration response. We link SLR hazards with potential mechanisms of migration and the associated governmental or institutional policies that operate as obstacles or facilitators for that migration. Specific examples from the USA, Bangladesh and atoll island nations are used to contextualize these concepts. However, further research is needed on the fundamental mechanisms underlying SLR migration, tipping points, thresholds and feedbacks, risk perception and migration to fully understand migration responses to SLR.

International audienc

It is plausible that the impacts of climate change will render certain nation-states uninhabitable before the close of the century. While this may be the fate of a small number of those nation-states most vulnerable to climate change, its implications for the evolution of statehood and international law in a “post-climate” regime is potentially seismic. I argue that to respond to the phenomenon of landless nationstates, international law could accommodate an entirely new category of international actors. I introduce the Nation Ex-Situ. Ex-situ nationhood is a status that allows for the continued existence of a sovereign state, afforded all of the rights and benefits of sovereignty amongst the family of states, in perpetuity. In practice this would require the creation of a government framework that could exercise authority over a diffuse people. I elaborate on earlier calls to use a political trusteeship system to provide the framework for an analogous structure. I seek to accomplish two quite different but intimately related tasks: first, to define and justify the recognition of deterritorialized nation-states, and, second, to explain the trusteeship arrangement that will undergird the ex-situ nation. In doing so, I introduce the notion of a post-climate era, in which the very structure of human systems—be they legal, economic, or socio-political—are irrevocably changed and ever-changing.

As states, cities, tribes, and private interests cope with climate damages and seek to increase preparedness and resilience, they will need to navigate myriad choices and options available to them. Making these choices in ways that identify pathways for climate action that support their development objectives will require constructive public dialogue, community participation, and flexible and ongoing access to science- and experience-based knowledge. In 2016, a Federal Advisory Committee (FAC) was convened to recommend how to conduct a sustained National Climate Assessment (NCA) to increase the relevance and usability of assessments for informing action. The FAC was disbanded in 2017, but members and additional experts reconvened to complete the report that is presented here. A key recommendation is establishing a new nonfederal “climate assessment consortium” to increase the role of state/local/tribal government and civil society in assessments. The expanded process would 1) focus on applied problems faced by practitioners, 2) organize sustained partnerships for collaborative learning across similar projects and case studies to identify effective tested practices, and 3) assess and improve knowledge-based methods for project implementation. Specific recommendations include evaluating climate models and data using user-defined metrics; improving benefit–cost assessment and supporting decision-making under uncertainty; and accelerating application of tools and methods such as citizen science, artificial intelligence, indicators, and geospatial analysis. The recommendations are the result of broad consultation and present an ambitious agenda for federal agencies, state/local/tribal jurisdictions, universities and the research sector, professional associations, nongovernmental and community-based organizations, and private-sector firms.

As one of the lowest-lying island nation states in the world, the Republic of the Marshall Islands is vulnerable to sea level rise, flooding and the associated impacts on soil and water salinity. Persistent drought is further affecting agricultural production and access to drinking water, and heat stress is increasingly common. The number of Marshallese people residing in the USA has increased rapidly from 6650 in 2000 to an estimated 30,000 in 2018. While we know that climate change is already affecting the Marshall Islands and that there are significant migration flows, we do not know to what extent people already migrate because of climate change. This paper addresses this gap and presents findings from interdisciplinary fieldwork in the Marshall Islands and destination areas in the USA. The research team conducted a survey (N = 278), focus group discussions, expert interviews and a geo-spatial analysis of flood extent and migration rates to study the relationship between climatic events, ecosystem services and migration. The results show that respondents primarily cite education, health care, work and family visits as migration drivers, and only few mention climate impacts or environmental change. However, respondents do identify impacts of climate change on their livelihoods, health and safety, and the study finds significant correlations between climate impacts, trends in ecosystem services and migration propensities at household level. Furthermore, 62% of Marshallese respondents in the USA indicated that climate change affects their decision to return to Marshall Islands in the future.Climatic Change

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This article explores so-called ‘loss and damage’ as well as the emerging legal infrastructure that seeks to address it. The article concludes by identifying some of the deep points of contention in the international discourse on loss and damage, particularly regarding compensation, and considerations for a successful resolution of the impasse that loss and damage has produced.

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