Due to global warming, sea levels will rise for two reasons. First, as temperatures increase, large amounts of ice in the polar caps will melt, increasing the volume of water in the oceans. Second, material tends to expand when it is heated, which is called thermal expansion. So if the Earth's average temperature increases, the water in the ocean will expand, contributing to rising sea levels. One major effect of rising sea levels is that coastal areas will experience more flooding, especially from storm surges during hurricanes or typhoons.