“This paper finds something quite concerning; many of the projections have underestimated both what we are currently measuring and what we are likely to experience in the future. For Small Island Developing States (SIDS), that is far from a discrepancy. Because if the projections are conservative, then the policies, infrastructure standards and adaptation plans built on those projections are conservative also. And in our (SIDS) context, conservative does not mean safe. It means SIDS are further behind then currently believed.

“This is serious for Pacific SIDS: as parts of the western tropical and southwest Pacific have historically experienced rates of sea-level rise above the global average due to ocean dynamics. Sea level is not uniform, it shifts with currents, heat and gravity. So while globally the numbers can look one way, locally the lived experience is very different.

“The paper notes (in fig. 4) that compared to other regions, the Pacific shows lower exposure in aggregate terms. But we have to interrogate what “lower exposure” means. If exposure is measured by total population or absolute land area, then yes, small islands will appear smaller in the dataset. But proportionally? Existentially? Losing 1% of land in a large continental country is not the same as losing 1% of a small island state. In our context, that 1% could be an entire village or half a town, a burial ground, a freshwater lens and livelihood for subsistence survival.

“And this is where the implications move past adaptation planning. If projections and threshold triggers are too low, adaptation becomes reactive rather than anticipatory. You build a seawall for yesterday’s sea level. This brings soft and hard limits much earlier, compressing the window between ‘adaptable’ and ‘unavoidable loss’. This leaves residual risk higher than planners assume as countries will face greater losses than projected because hazard baselines are underestimated.

“Even with the levels and projections that are considered standard references, Pacific communities are already facing the impacts of sea-level rise. Right now, coastal erosion and saltwater intrusion is actively occurring in the Pacific. Sacred sites are already being relocated. People are already forced to leave their ancestral lands.

“If sea-level rise is happening faster than what is currently thought, then losses including non-economic losses are also happening faster than our planning and anticipatory frameworks assume or are equipped for. Non-economic loss and damage is rising quietly alongside the water, unavoidable losses will accumulate sooner and at greater scale. That directly affects discussions around Loss and Damage finance, responsibility and equity.

“While the study does not directly assess whether the underestimated projections feed into IPCC assessments, it does highlight something important. Many national policies rely heavily on frequently referenced sources like the IPCC as the global scientific benchmark. If the studies it uses are conservative and synthesise the same into reports, the true description of what the reality is has been severely limited as the panel operates on assessment cycles.

“For SIDS, that suggests we need to read the science carefully, especially like that of the Small Islands chapter, and ask whether we are planning for the median, or for the reality experienced on the ground.

“Can SIDS and coastal states only plan for the median of current models, or can they be aided to prepare for what is increasingly observable in front of them?”

"This study is a welcome addition to global sea‑level rise research. Many worldwide assessments rely on coarse resolution global satellite data. By using a more accurate and globally-consistent way of measuring coastal land elevation, the authors show that earlier global studies may have underestimated how many places are exposed to future sea‑level rise. This is an important improvement in our global understanding.

"However, global studies can only take us so far. They are not designed for local planning or decision‑making. While they can highlight global and regional differences, the impacts of sea level rise on coasts vary a lot from place to place, depending on factors like land sinking or rising (vertical land motion, often caused by tectonic factors), sediment movement, storm patterns, waves, and long‑term shoreline change patterns.

"For Aotearoa New Zealand and Pacific Island nations, high‑quality local data remains essential. New Zealand and Pacific Island nations need more investment in obtaining and maintaining accurate elevation datasets for both the coastal zone and the nearshore. New Zealand is already investing in high-quality local data. The New Zealand Coastal Change Database (coastalchange.nz) provides long‑term, nationally consistent coastal erosion rates that can be used to underpin local or regional coastal hazard and risk assessments.

"Other national research programmes are updating localised sea‑level rise projections with vertical land movement data, which will give communities more accurate information for regional and local planning. New Zealand and Pacific Island nations should prioritise local data for decision making about sea-level impacts."

"My quick read of the paper indicates that it won't affect Aotearoa as much because it focuses on the implications for the Global South, especially low-lying coastal areas in Southeast-Asia. Aotearoa has the Searise portal which accounts for the vertical land movement cited in the paper as one of the critical errors. In summary, we don't lack the information on the impacts of sea level rise on our coasts. Our impediment is more of a political nature, as in being more proactive in decisions to avoid further developing coastal areas at-risk of sea level rise and related coastal hazards such as erosion and inundation."