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  . 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  the sea level rise scenario or RCP selected,  projections of future population growth in exposed areas and  the criteria used for identifying exposure. These latter measures can include estimates of populations situated within selected elevations above sea level , populations situated in 1-in-100 year floodplains or populations in areas likely to be entirely inundated under specific RCPs . As an illustrative example, an estimated 267 million people  worldwide lived within 2 m of sea level in 2020, 59% of whom reside in tropical regions of Asia . 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 . 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 . 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 .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report