IPCC Sea-Level Rise Scenarios Fall Short for At-Risk Coastal Cities

It turns out that the sea-level rise scenarios for high-risk coastal areas aren't good enough--at least according to new research. While the Intergovernmental Panel on Climate Change (IPCC) created these sea-level rise scenarios, researchers are now arguing that they don't provide the right information for coastal decision-making and management.

"Although the IPCC scenarios are a big step forward in understanding how the climate system works, these scenarios are not designed from the perspective of coastal risk management and, unfortunately, this is not spelled out clearly both within and beyond the IPCC reports," said Jochen Hinkel, the lead author of the new research, in a news release.

The scientists warn that IPCC scenarios are often inappropriate or incomplete for the management of high-risk coastal areas, since they exclude the potential for extreme sea-level rises. In fact, the scenarios only cover the central range of possible sea-level rise.

"Consider, for example, the situation of London, which is protected against coastal floods through the Thames Estuary Barrier," said Hinkel. "There was concern that rapid sea-level rise would not allow sufficient time to upgrade or replace the Thames Estuary Barrier because such large engineering tasks required 25 to 30 years for planning and implementation."

For this type of situation, the IPCC scenario range is not the right piece of information since there is a 0 to 33 percent probability of sea-level rise lying outside this range. Such a high residual risk isn't tolerable from the perspective of protecting major cities from sea-level rise.

"Ongoing work on projecting the central range of sea-level rise could be complemented with the development of high-end scenarios for different time horizons and correspond to different real-world coastal management decisions," said Robert Nicholls, co-author of the new study.

The findings are published in the journal Nature Climate Change.

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