Global sea level could rise over three feet this century
Sea levels are already rising because of global warming. The current rate is roughly 1.2 inches per decade. The response of sea level to different scenarios of future warming is a question of major concern.
In its most recent major report, in 2007, the IPCC projected a sea level rise of 0.6 - 1.9 feet by 2100.[[Intergovernmental Panel on Climate Change. “IPCC Fourth Assessment Report: Working Group I Report 'The Physical Science Basis.”[Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)] Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. See table SMP.3., page 13 Summary for Policy Makers]] But that did not take into account what was acknowledged to be a likely increase in the disintegration of polar ice sheets — because the science in that area was poorly understood.
Several papers published since 2007 have greatly improved our understanding of the relation between ice sheets and sea level, both by looking at evidence from the past more closely[[Rahmstorf, S. “A Semi-Empirical Approach to Projecting Future Sea-Level Rise.” (PDF) Science, January 19, 2007.]] [[Rohling, E. J., K. Grant, C. H. Hemleben, M. Siddall, B. A. A. Hoogakker, M. Bolshaw, and M. Kucera. “High rates of sea-level rise during the last interglacial period.” (PDF) Nature Geoscience 1 (2007): 38-42.]] [[Grinsted, A, JC Moore, and J Svetlana. “Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD.” (Abstract) Climate Dynamics (2009).]] and by modeling the physics of ice sheet motion more accurately.[[Pfeffer, WT, JT Harper, and S O'Neel. “Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise.” (Abstract) Science 321, no. 5894 (September 5, 2008): 1340-1343.]] By the end of this century, most experts now think communities should plan for a total rise of at least three feet above current levels, although it could be as much as 6.6 feet (if we continue burning fossil fuels intensively, and the more pessimistic analyses are right) or as little as 1.6 feet (if we cut back significantly on CO2 and other greenhouse gases, and the most optimistic analyses are right). This range of sea level rise estimates will likely continue to change and potentially narrow with further research.
Among the consequences of significant sea level rise could be more frequent and damaging floods, threats to buildings and other infrastructure, inundation of low-lying islands and coastal cities, mass displacement of human populations and risks to ecosystems.