sea level could rise 2 m in the 21st century.
how much could sea level rise in the 21st century?
2 m
sea level rose by 6 cm during the 19th century and 19 cm in the 20th century. evidence for this includes geological observations, the longest instrumental records and the observed rate of 20th century sea level rise. for example, geological observations indicate that during the last 2,000 years, sea level change was small, with an average rate of only 0.0–0.2 mm per year. this compares to an average rate of 1.7 ± 0.5 mm per year for the 20th century. baart et al. (2012) show that it is important to account for the effect of the 18.6-year lunar nodal cycle before acceleration in sea level rise should be concluded. based on tide gauge data, the rate of global average sea level rise during the 20th century lies in the range 0.8 to 3.3 mm/yr, with an average rate of 1.8 mm/yr.
past sea level
the potential for major sea level rise depends mostly on a significant melting of the polar ice caps of greenland and antarctica, as this is where the vast majority of glacial ice is located. if all the ice on the polar ice caps were to melt away, the oceans of the world would rise an estimated . although previously it was thought that the polar ice caps were not contributing heavily to sea level rise (ipcc 2007), recent studies have confirmed that both antarctica and greenland are contributing a year each to global sea level rise. the thwaites glacier alone, in western antarctica is "currently responsible for approximately 4 percent of global sea level rise. it holds enough ice to raise the world ocean a little over 2 feet (65 centimeters) and backstops neighboring glaciers that would raise sea levels an additional 8 feet (2.4 meters) if all the ice were lost." the fact that the ipcc estimates did not include rapid ice sheet decay into their sea level predictions makes it difficult to ascertain a plausible estimate for sea level rise but a 2008 study found that the minimum sea level rise will be around by 2100. newer observations with nasa's ice-penetrating radar of operation icebridge confirm that sea level rise due to glacier melting is a credible threat.
retreat of glaciers since 1850