This graph shows the change in sea level since 1880. Sea level rose more than 18 centimeters during the 20th Century. The data used to make this graph come from 23 tide gauges. The thick black line is an average.
Click on image for full size
Courtesy of Robert A. Rohde/Global Warming Art Project

Climate Change and Sea Level Rise

Sea level is creeping higher each year as the Earth warms.  As sea level continues to rise, there are many low coastal areas worldwide where homes, towns and cities are in danger of being flooded

Currently, global sea level is rising about 3 mm per year (about 1/8 inch.)  Scientists are still trying to pin down exactly how much sea level rise we can expect during the 21st Century. The Intergovernmental Panel on Climate Change estimates 18-59 centimeters (7-23 in) of sea level rise. If an ice sheet were to slide into the ocean, that estimate would be much higher. 

How does global warming cause sea level to rise? There are two reasons.  First, when climate warms, water that is on land in glaciers and ice sheets melts and makes its way down rivers to the ocean.  Second, as seawater warms, the water molecules move further apart which makes the water take up more space.  Scientists suspect that more than half of sea level rise today is due to warmed and expanded sea water.

Many people live in coastal areas around the world. Rising sea level could cause their homes to flood and their land to erode.  Seawater could get into their drinking water and farms could become flooded. Many countries are looking for ways to protect the places where people live from rising seas.

Last modified May 2, 2011 by Jennifer Bergman.

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