Science 321, 1340–1343 (2008)

Credit: SYAGCI, ISTOCKPHOTO

An increase in sea level of more than two metres by 2100 is implausible, conclude scientists, who say that sea level could rise 0.8 metres to two metres at most by then. The new study factors in the dynamic effects of glaciers and ice sheets on sea level, aspects that have been excluded from earlier model estimates owing to poor understanding of the processes.

W. Tad Pfeffer of the University of Colorado at Boulder and colleagues estimated the volume of ice that all glaciers and ice sheets worldwide could lose through ice melt and the release of icebergs into the ocean. The authors analyse sea-level rise under four model scenarios that variously assume a present-day rate of ice melt or a tenfold increase in ice melt from land throughout the century, in combination with steady or severe ice loss through the calving of glaciers to form icebergs. For sea level to rise more than two metres by 2100, the discharge of icebergs into the ocean would need to occur more rapidly than ever before observed, at rates that may not even be feasible.

Accurate forecasts of sea-level rise are needed, say the scientists, so that resources for adapting to climate change can be directed appropriately.