Sea levels could rise faster than predicted, scientists warn
Future sea level rises could be twice as high as the latest estimates from the Intergovernmental Panel on Climate Change (IPCC), according to a new study by an international team of EU-funded scientists. Writing in the journal Nature Geoscience, the scientists, from the UK, Germany and the US, reveal that in the past, sea levels rose as fast as 1.6 metres per century. EU funding for the project came from the STOPFEN ('Sea level, temperature and ocean circulation, past and future. A European network') project, which was financed under the 'Improving human research potential and the socio-economic knowledge base' theme of the Fifth Framework Programme (FP5). There is a lot of debate regarding the extent of future sea level rises, with many scientists claiming that the IPCC's predictions are too low. Currently the IPCC predicts that sea levels will rise by between 18 and 59 centimetres by the end of this century. However, the IPCC itself notes that the upper values of the ranges should not be considered upper bounds for sea level rise, as the models used do not include uncertainties in climate-carbon cycle feedbacks or the effects of changes in ice sheet flow. 'The IPCC estimates mainly concern thermal expansion and surface ice melting, while not quantifying the impact of dynamic ice sheet processes,' said Professor Eelco Rohling of the University of Southampton. 'Until now, there have been no data that sufficiently constrain the full rate of past sea level rises above the present level.' To shed more light on future sea level changes, Professor Rohling and his colleagues went back in time to an era known as Marine Isotope Stage 5e, 124 to 119 thousand years ago. At that time, the Earth's climate was 2°Celsius warmer than it is today, and the melt-back of the Greenland and Antarctica ice sheets contributed to sea levels which were six metres higher than today. The researchers used a new method for sea level reconstruction to study the rate of sea level rise during this period. 'At that time, Greenland was 3 to 5°Celsius warmer than today, similar to the warming expected 50 to 100 years from now,' explained Professor Rohling. 'Our analysis suggests that the accompanying rates of sea level rise due to ice volume loss on Greenland and Antarctica were very high indeed. The average rate of rise of 1.6 metres per century that we find is roughly twice as high as the maximum estimates in the IPCC Fourth Assessment report, and so offers the first potential constraint on the dynamic ice sheet component that was not included in the headline IPCC values.'