June 27, 2017

expert reaction to research on rate of sea level rise

Publishing in Nature Climate Change, scientists looked at the rate of global mean sea level rise from 1993 to 2004.

Prof Sir Brian Hoskins, Chair of the Grantham Institute at Imperial College London, said:

“A big question in climate science has been whether the rise in global sea level rise is accelerating. Now there is strong evidence that this is indeed the case in a recent 20 year period, and that the main cause is the reduction in mass of the Greenland Ice Sheet.

“This is a major warning to us about the dangers of a sea level rise that will continue for many centuries even after global warming is stopped. The Paris agreement target of limiting the temperature rise to less than 2°C, with an aspiration of 1.5°C provides the best chance of minimising this impact of global warming that will inevitably threaten many coastal cities around the world.”

Prof. Andrew Shepherd, Director of the Centre for Polar Observation and Modelling at the University of Leeds, said:

“Even with decades of measurements, it’s hard to be sure whether there has been a steady acceleration in the rate of global sea level rise during the satellite era, because the change is so small.  Ice losses from Greenland have played a particularly strong role, but they reached a new high during the warm summer of 2012, and it’s still too soon to disentangle that single event from all the other changes that have taken place.”

Prof. Robert Nicholls, Co-Leader of the Tyndall Centre’s Cities and Coasts Research Programme at the University of Southampton, said:

“I think this result is entirely consistent with expectations. If sea-level rise had not accelerated then that would suggest there was something wrong with our expectations of accelerated sea-level rise. Let’s remember that 2 mm/yr of global sea level rise results in 20 cm of sea-level rise over a century. If sea-level rise continues to accelerate at 0.5 mm/yr/decade as this paper estimates the total rise in sea level from 1990 to 2100 will be about 60 cm. So this is very consistent with the middle estimates in AR5.

“The fact that the processes that drive this change are different to AR5 is interesting — if sea-level rise due to thermal expansion catches up then we might see more. So possibly this is suggesting sea level could be at the high end.”

Prof. Peter Wadhams, Professor of Ocean Physics at the University of Cambridge, said:

“This result is important because the Intergovernmental Panel on Climate Change makes a very conservative projection of total sea level rise by the end of the century (60-90 cm) based on the idea that the RATE of sea level rise remains constant. Yet there is convincing evidence, including accelerating losses of mass from Greenland and Antarctica, that the rate is actually increasing, and increasing exponentially.

“After a few decades this makes a major difference to the total rise, which most scientists now expect to be well over a metre by the end of the century. By sticking to the lower figure, IPCC is betraying all those who live in coastal low lying areas (like Bangladeshi farmers) as well as policy makers responsible for protection of cities.”

 * ‘The increasing rate of global mean sea-level rise during 1993–2014’ by Xianyao Chen et al. was published in Nature Climate Change on Monday 26 June.

Declared interests

Prof. Peter Wadhams: I deal with this question in my book “A Farewell to Ice”