As global temperatures rise, sea levels will also rise. The seawater expands as it warms. Water previously bound to mountain and polar glaciers melts and flow into the world’s seas. Much of the world’s population, especially the poorer people of the world, live at or close to sea level, areas vulnerable to the lethal combination of rising sea level and increasingly severe ocean storms. The rising water table along coastlines could also encourage the release of pathogens into septic systems and waterways. More than half the world’s people live within 35 miles of an ocean or sea. Areas at risk include developed coastal cities, towns and resort areas, saltwater marshes, coastal wetlands, sandy beaches, coral reefs, coral atolls, and river deltas. Sea levels have already risen 4 to 10 inches over the last century.