Under the "worst case" scenario, global mean sea-level is expected to rise almost one metre by the year 2100, affecting more than 140 million people in China and Bangladesh alone, with large local differences due to tides, wind and atmospheric pressure patterns, changes in ocean circulation, vertical movements of continents etc.
There is evidence to indicate that sea levels may rise over the next 50 years, sufficiently to radically change the boundaries between coastal nations, to cause some island countries (such as the Maldives) to disappear, and to change the shapes and strategic importance of international waterways. Global estimates based on the period 1881-1980 indicate a rate of sea level increase of approximately 1mm per year. It is also estimated that by 2030 sea level will be rising at about 4mm or 5mm a year. 50 million people could be made homeless by flooding caused by rising sea levels in Bangladesh and Egypt.
Climate change, resulting in sea-level rise and flooding or erosion of low-lying coastal areas and lagoons, will have serious adverse impacts on ecosystems, water resources, coastal zones and human settlements, particularly in the countries of Western and Central Africa, the Nile Delta and the Indian Ocean island states.
In 2017 it was reported that five tiny Pacific islands in the Solomon Island archipelago had disappeared due to rising seas and erosion, a discovery thought to be the first scientific confirmation of the impact of climate change on coastlines in the Pacific, according to Australian researchers. The missing islands, ranging in size from 1 to 5 hectares (2.5-12.4 acres) were not inhabited by humans. But six other islands in the archipelago had large swaths of land washed into the sea and on two of those, entire villages were destroyed and people forced to relocate.