In this chapter, we review the physical processes that affect the elevation of coastal settlements relative to the sea, and identify current and projected rates of change, describe the impacts of MSLR on coastal settlements and on small island states, provide rough estimates of the number of people exposed, identify options for in situ adaptation, describe common challenges in implementing planned relocations of communities at risk, with case studies from the Carteret Islands and Fiji, and conclude by reviewing the cascading risks faced in Bangladesh.

This chapter provides an introduction to climate-related migration and displacement in the distant and more recent past, an overview of the basic natural science processes behind anthropogenic climate change for readers that require one, a review of how the impacts of climate change in a general sense present risks to individuals, households and communities, and how vulnerability and adaptation shape these risks, a summary of the social science on how migration decisions are made and the general types of patterns and outcomes that emerge, and a consolidated picture of how climate hazards interact with non-climatic processes to shape migration and displacement.

The present chapter focuses on migration and displacement associated with events that are directly linked to hotter air temperatures and/or an associated lack of moisture experienced at local and regional scales: droughts, increased aridity, desertification, heat, and wildfires. With the exception of wildfires – which share many characteristics comparable to rapid-onset extreme weather events – the hazards assessed in the present chapter are gradual in their onset and impacts. Their impacts accumulate with each passing week, month, and/or year, steadily eroding the water, food and/or livelihood security of households and communities. The slow rate of onset allows exposed populations an opportunity to adjust and adapt through means that do not require changes to existing mobility practices and patterns, sometimes referred to as in situ adaptation responses. It is only after hot and/or dry conditions persist beyond a particular threshold of duration and/or severity that in situ adaptations no longer prove to be sufficient and changes in migration decision-making and outcomes emerge.

In this chapter, we review approaches to model climate-related migration including the multiple goals of modeling efforts and why modeling climate-related migration is of interest to researchers, commonly used sources of climate and migration data and data-related challenges, and various modeling methods used. The chapter is not meant to be an exhaustive inventory of approaches to modeling climate-related migration, but rather is intended to present the reader with an overview of the most common approaches and possible pitfalls associated with those approaches. We end the chapter with a discussion of some of the future directions and opportunities for data and modeling of climate-related migration.

This chapter reviews how climate change is projected to affect the frequency, severity and/or spatial distribution of tropical cyclones, severe storms that generate tornadoes, and floods; the factors that influence people’s exposure and vulnerability to such events; adaptation options for reducing displacement risks; and, common characteristics of migration and displacement across all categories of extreme weather events. We then focus on specific types of extreme weather and provide more detailed analyses and case studies of migration and displacement events associated with tropical cyclones, tornadoes, and floods.

Scholarly understanding of these topics has evolved rapidly over recent decades, yet there is still much we don’t know about the complex ways that climate change interacts with migration decisions. In this final chapter, we discuss a number of emerging issues and future research needs including: gendered dimensions of migration in the context of future climate change, how climate-related migration affects Indigenous populations and cultural heritage, the interplay between climate-related migration and human health, the impacts of climate-related migration on receiving communities, identification of critical thresholds in climate-migration connections, and unforeseeable climate-migration outcomes.

This chapter provides an overview of policymaking that is being done at international, regional, and national levels, highlighting some of the key processes and frameworks relevant to climate-related migration and displacement. We discuss the extent to which these policies respond adequately (or not) to the needs and complexity of the challenge. We also describe a range of actors that have been actively engaged in these policymaking processes and the nature of their influence on these processes. We assess the different levels of actors in descending order of scale, starting with an overview of international policy frameworks and processes and then moving through regional and national level processes and approaches. Although we assess each level separately, they should be viewed as a network or web of interconnected actors and processes that influence one another, even as they evolve.