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Wednesday, December 23, 2009

Jonathan T. Overpeck & Jeremy L. Weiss, PNAS 106 (2009), Projections of future sea level becoming more dire

Proceedings of the National Academy of Sciences, PNAS (December 22, 2009),Vol. 106, No. 51, pp. 21461-21462.

Projections of future sea level becoming more dire

Jonathan T. Overpeck* and Jeremy L. Weiss

University of Arizona, Tucson, AZ, U.S.A.

Few of the possible impacts of future climate change have captured more public attention than sea-level rise. Globally, sea-level rise has accelerated since the 19th century, driven primarily by the expansion of warmer oceans and melting glaciers, along with a modest transfer of water into the ocean from the Earth's polar ice sheets. The observed rate of sea-level rise has not been uniform around the globe because of regional factors, but there is no doubt that the average sea-level trend is upwards (1). Implications for the rates and magnitudes of future sea-level rise are less clear, and a new study in this issue of PNAS (2) provides useful insight into how sea level will change through this century and beyond.

There are two main types of sea-level information needed to inform the development of effective climate change policy. First are estimates of the sea-level rise expected in the relative near term, namely by the end of the century. Second are estimates of the sea-level rise that will occur further into the future over many centuries as ice sheets and oceans come into equilibrium with a warmer atmosphere.

The Fourth Assessment of the Intergovernmental Panel on Climate Change (IPCC) (1) was unable to provide a strong constraint on estimates of sea-level rise likely to occur by the end of this century. Their projection of 0.26- to 0.59-m sea-level rise by 2100 (under the business as usual A1FI greenhouse gas emissions scenario; ref. 1) represents a lower-bound estimate because it …

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