<Tr> <Td> </Td> <Td> The neutrality of this article is disputed . Relevant discussion may be found on the talk page . Please do not remove this message until conditions to do so are met . (August 2016) (Learn how and when to remove this template message) </Td> </Tr> <P> The rate of global mean sea - level rise (~ 3 mm / yr; SLR) has accelerated compared to the mean of the 20th century (~ 2 mm / yr), but the rate of rise is locally variable . Factors contributing to SLR include decreased global ice volume and warming of the ocean . On Greenland, the deficiency between annual ice gained and lost tripled between 1996 and 2007 . On Antarctica the deficiency increased by 75% . Mountain glaciers are retreating and the cumulative mean thickness change has accelerated from about − 1.8 to − 4 m in 1965 to 1970 to about − 12 to − 14 m in the first decade of the 21st century . From 1961 to 2003, ocean temperatures to a depth of 700 m increased and portions of the deeper ocean are warming . </P> <P> The Intergovernmental Panel on Climate Change (2007) projected sea level would reach 0.18 to 0.59 m above present by the end of the 21st century but lacked an estimate of ice flow dynamics calving . Calving was added by Pfeffer et al. (2008) indicating 0.8 to 2 m of SLR by 2100 (favouring the low end of this range). Rahmstorf (2007) estimated SLR will reach 0.5 to 1.4 m by the end of the century . Pielke (2008) points out that observed SLR has exceeded the best case projections thus far . These approximations and others indicate that global mean SLR may reach 1 m by the end of this century . However, sea level is highly variable and planners considering local impacts must take this variability into account . </P> <P> Global mean air temperature is increasing in relation to global warming . As a result, Earth's ice volume is decreasing and the heat content of the ocean is increasing . Global mean sea level is therefore rising, and the rate of rise has accelerated . Sea - level rise (SLR) presents challenges to coastal communities and ecosystems, and planners are engaged in assessing management options . Accordingly, it is desirable to have an estimate of SLR this century to properly design mitigation and adaptation strategies . An approximation of SLR by the end of the century will allow: 1) estimates of coastal erosion and changes in vulnerability to coastal hazards; 2) assessments of threats to coastal ecosystems; and 3) development of climate risk management policies . This paper reviews recent studies of global warming, sea - level observations, global ice volume, ocean heating, and estimates of SLR by the end of the 21st century . </P>

How much could sea level rise in the 21st century