Global Sea Level Rise | Blue Earth Systems

Key takeaways

Greenhouse gases from human activities are warming the planet, and the ocean absorbs about 90 percent of that heat.
Global sea level is rising because warming water expands and melting land ice adds water to the ocean.
Sea level is rising about twice as fast today as it was in the early 1990s.

Global sea level rise is linked to climate change

For more than a century, burning coal, oil and gas has added carbon dioxide and other greenhouse gases to the atmosphere. These gases trap heat, and about 90 percent of that extra heat ends up in the ocean. When seawater warms it expands and takes up more space, so sea level rises. This is called thermal expansion.

The rest of the rise comes from land ice. Mountain glaciers and the great ice sheets of Greenland and Antarctica are losing ice to melting and to faster flow into the sea. The water they release adds directly to the ocean.

The two main causes of global sea level rise. Shares are approximate for the period since 2005, based on the ocean mass and steric height records on our Vital Signs pages.

How fast is it rising?

It took about 90 years, from 1902 to 1992, for global sea level to rise 10 cm. It has risen by roughly the same amount again in only the past three decades. Today the ocean is rising at about … mm per year, compared with about … mm per year in 1993.

Sea ice versus land ice. Melting sea ice, such as the floating ice of the Arctic Ocean, barely changes sea level because it already displaces its own weight of water. Land ice is different. Glaciers and ice sheets sit on land, so when they melt or slide into the ocean they add new water and raise sea level.

See the record

The satellite record of global sea level is updated as new data arrive.

Global mean sea level

Satellite altimetry since 1993

Rise since 1993

…mm

Monthly12 month mean

Dive deeper

The sea level budget

Scientists check their understanding by adding up the individual contributions and comparing the total with the rise measured by satellites. This accounting is called the sea level budget. Since 2005, gravity satellites show the ocean gaining mass at about … mm per year, and Argo floats show the upper ocean expanding at about … mm per year. Their sum agrees with the total measured by altimeters to within a few tenths of a millimeter per year, with the remainder mostly explained by warming of the deep ocean below 2000 m.

Where the added water comes from

Greenland loses about … gigatonnes of ice per year, adding about … mm per year to sea level.
Antarctica loses about … gigatonnes per year, adding about … mm per year.
Mountain glaciers worldwide add roughly another 0.6 to 0.8 mm per year.
Water stored on land in soils, lakes, aquifers and reservoirs varies from year to year. Pumping groundwater adds to the ocean, while filling reservoirs holds water back.

Why the rate wobbles

Global sea level does not rise in a perfectly smooth line. El Niño and La Niña move heat and water around the planet. During La Niña, extra rain over South America, Southeast Asia and Australia stores water on land and global sea level can stall or even fall for a few months. During El Niño that water returns to the ocean and sea level jumps. Big volcanic eruptions, such as Pinatubo in 1991, can also cool the ocean for a few years. Scientists remove these effects to reveal the underlying acceleration.

Rise over longer time scales

Tide gauge records and geological evidence show that global sea level was nearly stable for about two thousand years before the late 1800s. The rise since then is faster than at any time in at least the last 3,000 years. The ocean and ice sheets respond slowly to warming, so the rise already under way will continue for centuries even if warming stops.