Editing IPCC:AR6/WGII/Chapter-7 (section)

==== 7.3.2.1 Region-Specific Changes in Climatic Risks ====

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''As outlined in 7.2, the most common drivers of observed climate-related migration and displacement are extreme storms (particularly tropical cyclones), floods and droughts'' ( ''high confidence'' ) ''.'' The future frequency and/or severity of such events due to anthropogenic climate change are expected to vary by region according to future GHG emission pathways (Naik et al 2021; Regional Chapters, this report), with there being an increased potential for compound effects of successive or multiple hazards (e.g., tropical storms accompanied by extreme heat events ( [[#Matthews--2019|Matthews et al., 2019]] )). Table 7.2 summarises anticipated changes in future migration and displacement risks due to sudden-onset climate events by region (and by sub-regions for Africa and Asia, where climatic risks vary within the region).

'''Table 7.2 |''' Projected changes in sudden-onset climate events associated with migration and displacement by region.

{| class="wikitable"
|-
! '''Region'''

! '''Main directions of current migration flows (from [[#Abel--2014|Abel and Sander (2014)]] )'''

! '''Current climatic drivers of migration and displacement ( [[#7.2.6.1|Section 7.2.6.1]] )'''

! '''Expected changes in drivers (''' '''''including confidence statements''''' ''') from IPCC WGI 2021 Technical Summary, 4.3.1–4.3.2'''

|-
| Asia

| * East and Southeast Asia: within countries and between countries within same region.
* South and central Asia: within countries and between countries within same region; from south Asia to Middle East, North America, Europe.
* West Asia: within countries and between countries within the same region; to Europe

| Floods, extreme storms, extreme heat

| Increased risk of flooding in East, north, south and Southeast Asia due to increases in annual mean precipitation ( ''high confidence'' ) and extreme precipitation events in East, south, west central, north and Southeast Asia ( ''medium confidence'' ); uncertainty regarding future trends in cyclones (current trend = decreased frequency, increased intensity); higher average temperatures across region ( ''high confidence'' )

|-
| Africa

| * Within countries and between countries within the same region; to Europe and the Middle East

| Floods, droughts, extreme heat

| Decrease in total annual precipitation in northernmost and southernmost parts of Africa ( ''high confidence'' ); west-to-east pattern of decreasing-to-increasing annual precipitation in west Africa and east Africa ( ''medium confidence'' ); increased risk of heavy precipitation events that trigger flooding, across most parts of Africa ( ''medium confidence'' ); increased aridity and drought risks in north Africa, southern Africa and western parts of west Africa ( ''medium-high confidence'' )

|-
| Europe

| * Within countries and between countries in same region

| Floods

| Increased risk of floods across all areas of Europe except Mediterranean areas ( ''high confidence'' ); higher risks of drought and fire weather in Mediterranean areas ( ''high confidence'' )

|-
| North America

| * Within countries and between countries in same region

| Floods, tropical cyclones (US Atlantic and Caribbean coast), tornadoes, wildfires

| Increased frequency of heavy precipitation events across most areas ( ''high confidence'' ); tropical cyclones to become more severe ( ''medium confidence'' ); increased risk of drought and fire weather in central and western North America

|-
| Central and

South America

| * Within countries and between countries in same region; to North America, Europe

| Floods (Central and South America), extreme storms (Central America)

| Increases in mean annual precipitation and extreme precipitation events with higher risks of floods in most areas of South America ( ''medium confidence'' ); increased risk of droughts in northeastern and southern South America and northern Central America ( ''medium confidence'' ); tropical cyclones becoming more extreme ( ''medium confidence'' )

|-
| Australasia

| * Displacement within countries

| Wildfires

| Increases in fire weather across Australia and New Zealand ( ''medium confidence'' )

|-
| Small island states

| * Within and between countries in same region (e.g., Pacific Islands to Australia and New Zealand; Caribbean islands to USA)

| Extreme storms

| Potentially fewer but more extreme tropical cyclones ( ''medium confidence'' )

|}

''In low-lying coastal areas of most regions, future increases in mean sea levels will amplify the impacts of coastal hazards on settlements, including erosion, inland penetration of storm surges and groundwater contamination by salt water, and eventually lead to inundation of very low-lying coastal settlements'' ( ''high confidence'' ) ''( [[#Diaz--2016|Diaz, 2016]] ; [[#Hauer--2016|Hauer et al., 2016]] ; [[#Neumann--2015|Neumann et al., 2015]] ; [[#Rahman--2019|Rahman et al., 2019]] ; [[#IPCC--2019a|IPCC, 2019a]] )'' . Projections of the number of people at risk of future displacement by sea level rise range from tens of millions to hundreds of millions by the end of this century, depending on (a) the sea level rise scenario or RCP selected, (b) projections of future population growth in exposed areas and (c) the criteria used for identifying exposure. These latter measures can include estimates of populations situated within selected elevations above sea level (with 1 m, 2 m and 10 m being common parameters), populations situated in 1-in-100 year floodplains or populations in areas ''likely'' to be entirely inundated under specific RCPs ( [[#Neumann--2015|Neumann et al., 2015]] ; [[#Hauer--2016|Hauer et al., 2016]] ; [[#Merkens--2018|Merkens et al., 2018]] ; [[#McMichael--2020|McMichael et al., 2020]] ; [[#Hooijer--2021|Hooijer and Vernimmen, 2021]] ). As an illustrative example, an estimated 267 million people (error range = 197–347 million at 68% confidence level) worldwide lived within 2 m of sea level in 2020, 59% of whom reside in tropical regions of Asia ( [[#Hooijer--2021|Hooijer and Vernimmen, 2021]] ). At a 1 m increase in sea level and holding coastal population numbers constant, the number of people worldwide living within 2 m of sea level expands to 410 million (error range = 341–473 million). However, it is ''unlikely'' that coastal population growth rates will remain constant at global or regional scales in future decades. At present, coastal cities in many regions have relatively high rates of population growth due to the combined effects of in-migration from other regions and natural increase, with coastal areas of Africa having the highest projected future population growth rates ( [[#Neumann--2015|Neumann et al., 2015]] ; [[#Hooijer--2021|Hooijer and Vernimmen, 2021]] ; Box 7.5). Further complicating future estimates is that many large coastal cities are situated in deltas with high rates of subsidence, meaning that locally experienced changes in relative sea level may be much greater than sea level rise attributable to climate change, thereby further increasing the number of people exposed ( [[#Edmonds--2020|Edmonds et al., 2020]] ; [[#Nicholls--2021|Nicholls et al., 2021]] ).

Sea level rise is not presently a significant driver of migration in comparison with hazards assessed in [[#7.2.6|Section 7.2.6]] , but it has been attributed as a factor necessitating the near-term resettlement of small coastal settlements in Alaska, Louisiana, Fiji, Tuvalu and the Carteret Islands of Papua New Guinea ( [[#Marino--2015|Marino and Lazrus, 2015]] ; [[#Connell--2016|Connell, 2016]] ; [[#Hamilton--2016|Hamilton et al., 2016]] ; [[#Nichols--2019|Nichols, 2019]] ). In coastal Louisiana, communities tend to resist leaving exposed settlements until approximately 50% of available land has been lost ( [[#Hauer--2019|Hauer et al., 2019]] ). Movements away from highly exposed areas may have longer-term demographic implications for inland settlements ( [[#Hauer--2017|Hauer, 2017]] ), but this requires further study. Based on the available empirical evidence, sea level rise does not appear to currently be a primary motivation for international migration originating in small island states in the Indian and Pacific Oceans; rather, economic considerations and family reunification appear to be the dominant drivers ( [[#McCubbin--2015|McCubbin et al., 2015]] ; Stojanov and Du, 2016; [[#Heslin--2019|Heslin, 2019]] ; [[#Kelman--2019|Kelman et al., 2019]] ). However, climatic drivers of migration are anticipated to take on a much greater causal role in migration decisions in coming decades ( [[#Thomas--2020|Thomas et al., 2020]] ) and may discourage return migration to small island states ( [[#van%20der%20Geest--2020|van der Geest et al., 2020]] ). Even under best-case sustainable development scenarios, rising sea levels and associated hazards create risks of involuntary displacement in low-lying coastal areas and should be expected to generate a need for organised relocation of populations where protective infrastructure cannot be constructed (Horton and de Sherbinin, 2021; [[#Hamilton--2016|Hamilton et al., 2016]] ). In high emissions scenarios, low-lying island states may face the long-term risk of becoming uninhabitable, creating the potential for a new phenomenon of climate-induced statelessness ( [[#Piguet--2019|Piguet, 2019]] ; [[#Desai--2021|Desai et al., 2021]] ).

''Increased frequency of extreme heat events and long-term increases in average temperatures pose future risks to the habitability of settlements in tropical and subtropical regions, and may in the long term affect migration patterns in exposed areas, especially under high emissions scenarios'' ( ''medium agreement, low evidence'' ) ''.'' Greater research into the specific dynamics between extreme heat and population movements is required in order to make an accurate assessment of this risk. Recent studies suggest that future increases in average temperatures could expose populations across wide areas of the tropics and subtropics to ambient temperatures for extended periods each year that are beyond the threshold for human habitability ( [[#Pal--2016|Pal and Eltahir, 2016]] ; [[#Im--2017|Im et al., 2017]] ; [[#Xu--2020|Xu et al., 2020]] ). This effect would be amplified in urban settings where heat-island effects occur and create a heightened need for air conditioning and other adaptation measures. In addition to risks associated with average temperature changes, [[#Dosio--2018|Dosio et al. (2018)]] project that at 1.5°C warming, between 9% and 18% of the global population will be regularly exposed to extreme heat events at least once in five years, with the exposure rate nearly tripling with 2°C warming. How these changes in exposure to high temperatures will affect future migration patterns, particularly among vulnerable groups, will depend heavily on future adaptation responses (Horton and de Sherbinin, 2021). Multiple country-level studies assessed in Section 7.2 observe existing associations between extreme heat, its impacts on agricultural livelihoods and changes in rural-to-urban migration flows in parts of south Asia and sub-Saharan Africa. A study conducted in Indonesia, Malaysia and the Philippines suggests that an increased risk of heat stress would ''likely'' influence migration intentions of significant numbers of people ( [[#Zander--2019|Zander et al., 2019]] ).

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