Current Sea Level Rise

Current Sea Level Rise

Sea levels around the world are rising. Current sea-level rise potentially affects human populations (e.g., those living in coastal regions and on islands) and the natural environment (e.g., marine ecosystems). Between 1870 and 2004, global average sea levels rose 195 mm (7.7 in). From 1950 to 2009, measurements show an average annual rise in sea level of 1.7 ± 0.3 mm per year, with satellite data showing a rise of 3.3 ± 0.4 mm per year from 1993 to 2009, a faster rate of increase than previously estimated. It is unclear whether the increased rate reflects an increase in the underlying long-term trend.

Two main factors contributed to observed sea level rise. The first is thermal expansion: as ocean water warms, it expands. The second is from the contribution of land-based ice due to increased melting. The major store of water on land is found in glaciers and ice sheets.

Sea level rise is one of several lines of evidence that support the view that the climate has recently warmed. The global community of climate scientists confirms that it is very likely that human-induced (anthropogenic) warming contributed to the sea level rise observed in the latter half of the 20th century.

Sea level rise is expected to continue for centuries. In 2007, the Intergovernmental Panel on Climate Change (IPCC) projected that during the 21st century, sea level will rise another 18 to 59 cm (7.1 to 23 in), but these numbers do not include "uncertainties in climate-carbon cycle feedbacks nor do they include the full effects of changes in ice sheet flow". More recent projections assessed by the US National Research Council (2010) suggest possible sea level rise over the 21st century of between 56 and 200 cm (22 and 79 in).

On the timescale of centuries to millennia, the melting of ice sheets could result in even higher sea level rise. Partial deglaciation of the Greenland ice sheet, and possibly the West Antarctic ice sheet, could contribute 4 to 6 m (13 to 20 ft) or more to sea level rise.

Work by a team led by Veerabhadran Ramanathan of the Scripps Institution of Oceanography suggests that a quick way to stave off impending sea level rise is to cut emissions of short-lived climate warmers such as methane and soot.