Global sea level rises and falls in response to changes in climate, tectonic processes, tides, atmospheric conditions, water density & volume, precipitation, and river flow. Sea levels rise during interglacial (warm) periods and fall during glacial (cold) periods. It is estimated that during the last glacial time, global sea level was 400 feet lower than it is today.

Similarly, sea ice changes in response to climate. During ice ages, glaciers and ice sheets are more abundant. During interglacial times, sea ice melts, contributing to global sea level rise.

In recent times, scientists have observed a rise in global sea level and a shrinking of global ice cover related to warming atmospheric temperatures. Earth's large ice sheets are melting at an alarming rate, which could have consequences for the human populations that live along the coast. For example, it is estimated that if the Eastern Antarctic Ice Sheet melts, global sea level will rise by approximately 200 feet.