Coastal regions, particularly some low-lying river deltas, have very high population densities. It is estimated that in excess of 150 million people live within 1 metre of high tide level, and 250 million within 5 metres of high tide1,2. Also, there are billions of dollars invested in coastal infrastructure immediately adjacent to the coast (Figure 6C.1). Sea-level rise
contributes to coastal erosion and inundation of low-lying coastal regions - particularly during extreme sea-level events - and saltwater intrusion into aquifers, deltas and estuaries. These changes have impacts on coastal ecosystems, water resources, and human settlements and activities. Regions at most risk include heavily populated deltaic regions, small islands, especially atolls (islands formed of coral, Figure 6C.2), and sandy coasts backed by major coastal developments.
Sea-level rise is a central element in detecting, understanding, attributing and correctly projecting climate change. During the 20th century, the oceans have stored well over 80 per cent of the heat that has warmed the earth. The associated thermal expansion of the oceans, together with changes in glaciers and ice caps, will likely dominate 21st century sea-level rise. However, on longer time scales, the ice sheets of Greenland and Antarctica have the largest potential to contribute to significant changes in sea level.
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