Sea levels might rise 2 metres for each degree of warming

Under a business-as-usual scenario, temperatures are expected to rise by four degrees compared to pre-industrial times by the end of the century. Photo: flickr.com Phillip C cc by

Prehistoric data has been used to simulate possible sea levels over the next two millenia.

In the long term, we can expect more than two metres of sea-level rise per degree of global warming, a study published in the Proceedings of the National Academy of Sciences shows. Thermal expansion of seawater is the main reason for the 0.2 metres the oceans have risen so far. The melting of the large ice sheets in Greenland and Antarctica has only contributed to around 10 per cent of the global sea-level rise, since these systems respond significantly slower to higher temperatures. “The problem is: once heated out of balance, they simply don’t stop,” says Anders Levermann, lead author of the study.

The research team managed to simulate what will happen to sea levels over the next two millennia, by combining data on prehistoric sea levels with a physical model. “The Antarctic computer simulations were able to simulate the past five million years of ice history, and the other two ice models were directly calibrated against observational data – which in combination makes the scientists confident that these models are correctly estimating the future evolution of long-term sea-level rise,” says Peter Clark, co-author of the study.

Under a business-as-usual scenario, temperatures are expected to rise by four degrees compared to pre-industrial times by the end of the century. “Continuous sea-level rise is something we cannot avoid unless global temperatures go down again,” concludes Levermann. “Thus we can be absolutely certain that we need to adapt. Sea-level rise might be slow on time scales on which we elect governments, but it is inevitable and therefore highly relevant for almost everything we build along our coastlines, for many generations to come.”

Sources: Potsdam Institute for Climate Impact Research, Press release 15 July 2013

The multimillennial sea-level commitment of global warming. By Anders Levermann et al. Published in Proceedings of the National Academy of Sciences (online edition), vol. 110 no. 34  

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