Climate Change Science | Effects | Environmental | Sea level rise

Sea level rise from climate change

Sea level rises as a result of global warming for two reasons:

• The expansion of water as it gets warmer causes sea level to rise; and
• The warming of the atmosphere causes ice to melt, releasing additional liquid water into the oceans.

The chart below shows the historic sea level rise, as calculated by satellite sea level calculations produced by the NASA Goddard Space Flight Center. Based on this data, NASA estimate sea level is rising by 3.4mm per annum at current rates of warming.

Historic sea level measurements

Data shows that melting ice from the Greenland ice cap is the largest contributor to sea level rises. In addition to melting of the Greenland and Antartic ice sheets, smaller ice caps and glaciers around the world are showing signs of accelerated retreat, also contributing to sea level changes.

The video below shows historic changes in Arctic sea ice

Understanding the sea level changes that are attributable to global warming is not straightforward - various other naturally occurring factors can contribute to sea level changes which need to be considered as part of any measurements:

• Regional cyclical patterns, such as El Nino (see here cause period changes in sea levels
• changes to the earth's basin in response to loading of ice (e.g. post glacial rebound), altering the shape of ocean basins
• responses to variations in precipitation and evaporation driven by weather conditions and seasons, leading to changing volumes of water stores (e.g. land stores such as lakes, rivers and ice; atmospheric stores in water vapour; and the ocean stores) within the water cycle.

NASA has more information at this link.