July 21, 2026

expert reaction to study modelling impact of sea-level rise on UK coastal flood exposure to 2300

A modelling study published in Nature Communications looks at the impact of sea-level rise on UK coastal flood exposure.

Dr Joanne Williams, Expert in Sea-Level Extremes at The National Oceanography Centre (NOC), said:

“Care is needed in presenting this work, as it includes high end storylines. The paper also presents a “best plausible case” (B) storyline and one (A) they consider over-optimistic given current trajectories. Even if we were to achieve net-zero tomorrow, further sea-level rise will happen as it takes many years to stabilise the effects of an already warmer sea. But there is a great deal of variation between storylines as to how much time we will have to adapt. The high-end storylines are possibilities we need to consider, but they are still avoidable if society makes good decisions. It is useful to consider them, because it shows how expensive and challenging it will be if we do not act on climate, with very large areas at new risk. 

“It is good to see this paper uses more appropriate modelling of coastal flooding than the “assume everything below this height is wet” bathtub approach that is used in less careful studies.

“This work does not explicitly model flood defences. Lower levels of flooding are defensible, and there are many such examples in low lying parts of the UK, including in London. But to upgrade existing flood defence lines to the levels required by these high-end scenarios would be extremely challenging. Even existing flood defences take resources to build and maintain. 

“In the meantime, it is important for us to continue to carefully monitor sea-level rise so that we can detect any deviation from the expected changes and assess current and future flood risk for coastal communities.”

Prof Natasha Barlow, Technical Director – Coastal Resilience at Haskoning engineering consultancy, said:

“The authors use an approach that is well established in UK sea-level projections, based on the Met Office’s UKCP18 framework and a series of ‘storylines’. As such, the methodology is robust and widely accepted.

“The novelty of this work lies in extending projections to 2300, whereas most sea-level projections typically end at 2100. This does not challenge existing understanding but instead provides a longer-term perspective at a UK-specific scale.

“Such long-term perspectives are important for decision-making, particularly where adaptation to climate change will take time, or for major infrastructure and waste management projects that must consider timescales far beyond the increasingly close and somewhat arbitrary 2100 horizon.

“One limitation of the study, acknowledged by the authors, is that it does not account for coastal erosion or changes in sedimentation, such as the loss or development of coastal salt marshes resulting from sea-level rise (e.g. alongside the expanded Wash estuary the modelling predicts). These processes could significantly alter large sections of the coastline, leading to both losses of land and property, and opportunities for different forms of coastal use in the future.

“Modelling this far into the future inevitably involves uncertainties, particularly regarding the rate and extent of ice-sheet melt. The authors address this by focusing on a ‘H2’ worst-case scenario, which captures the upper range of uncertainty associated with potential runaway ice-sheet melting and are grounded in current scientific understanding.

“Some of the storylines are based on SSP5-8.5/RCP8.5. A recent modelling study¹ supporting the forthcoming IPCC AR7 concluded that this is no longer considered a plausible emissions pathway for the 21st century. While this is likely a reasonable position up to 2100, given current global climate commitments, runaway ice-sheet melt cannot be ruled out over longer timescales. The inclusion of these scenarios in this paper is therefore justified.”

¹ GMD – The Scenario Model Intercomparison Project for CMIP7 (ScenarioMIP-CMIP7)

Dr Rob Larter, Marine Geophysicist at the British Antarctic Survey, said:

“This study shows how the UK is likely to have to adapt to several metres of sea-level rise over coming centuries and presents a sobering analysis of how many additional people will be exposed to coastal flood risk as a result. Although there is no doubt that the increased rates of sea-level rise observed over the past three decades will continue or accelerate further, there is still considerable uncertainty about exactly how much sea level will rise by the end of the century. Looking beyond that, the uncertainties balloon further.

“The main reason for these uncertainties is imperfect knowledge of how ice-sheet instabilities could amplify the contributions from Antarctica and Greenland. The study explores the impact of potentially large contributions from these vast polar ice sheets through a ‘storylines’ approach. However, following assumptions made in the IPCC Sixth Assessment Report it implies that the storylines involving ice sheet instability that result in higher rates of sea-level rise are only applicable under a high warming scenario. The IPCC report suggested that the highest potential rates of sea-level rise it presented were only applicable in a high emissions and warming scenario because these rates were based on a model in which floating ice shelves around Antarctica, which buttress the ice sheet, only collapse after temperatures rise high enough to cause extensive melting on their surface. In contrast, observations over the past few years show that some ice shelves are in a state of terminal decline due to melting at their base alone, raising the possibility that such greatly increased rates of sea-level rise could occur even without a high warming scenario. Therefore, the higher impact storylines presented in this study need to be considered as genuine possibilities rather than unlikely scare stories.

“Major coastal defence infrastructure takes decades to plan and built. Therefore, decisions about which areas to ‘hold the line’ in, at least to the end of this century, need to made urgently so that planning can be accelerated to cost what will be needed and identify how it will be funded.”

* ‘Quantifying UK coastal flood exposure under future sea-level rise to 2300’ by M. Palmer et al was published in Nature Communications at 10am UK time Tuesday 21 July. 

Declared interests

Rob Larter: “I have no interests to declare other than my conviction that further research to understand ice-sheet instabilities is desperately needed.”

Natasha Barlow “is a Technical Director of Coastal Resilience at Haskoning, a global consultancy firm.  For 20 years previously she was an academic, including Professor of Environmental Change, at the University of Leeds and leader of the PALSEA (Paleo sea level and ice sheets) international working group.  Haskoning clients include public and private sector organisations seeking climate resilience solutions.  Her views expressed her are independent of any client or project.  She continues to publish peer reviewed academic papers on a range of research topics, alongside University researchers, and was the lead author on the marine and coastal section of the 2026 UK CCC Climate Change Risk Assessment Report (CCRA4).  She declares no interests in the Palmer et al. study.”

For all other experts, no reply to our request for DOIs was received.