New Study Reveals Discrepancy Between Sea Level Rise Projections And Observations
Global analysis of local data finds most sea-level acceleration is not statistically significant and that projections may be biased upward.
A recent study published in the Journal of Marine Science and Engineering by Hessel G. Voortman and Rob De Vos compares local sea-level rise projections from the Intergovernmental Panel on Climate Change (IPCC) with observed data from tide gauges worldwide.
The findings suggest a notable difference between what’s projected and what’s being measured.
The study’s primary objective was to assess how local sea-level rise projections, first provided by the IPCC in 2021, align with actual observations. The researchers analyzed two global datasets: the Permanent Service for Mean Sea Level (PSMSL) and the Global Sea Level Observing System (GLOSS).
Limited Usable Data: The study found that less than 20% of the available data from both datasets was suitable for analysis. The usable data was also unevenly distributed globally, with locations in North America, Europe, and Japan being well-represented, while Latin America and Africa were severely under-represented.
No Significant Acceleration: In a striking discovery, approximately 95% of the suitable locations in both datasets showed no statistically significant acceleration in the rate of sea-level rise. This finding contrasts with the common assumption that a global, climate-driven acceleration is widespread.
Local Phenomena are the Cause: The study suggests that for the few locations (about 5%) where accelerated sea-level rise was detected, local, non-climatic factors are the most likely cause. These include:
- Geological processes, such as Glacial Isostatic Adjustment (GIA) where land is rising or falling in response to the melting of ancient ice sheets.
- Tectonic plate movements, which can cause sudden shifts or gradual changes in land elevation.
- Human activities, such as excessive groundwater extraction for urban development and mineral extraction, which can lead to significant land subsidence.
Projections May be Upwardly Biased: On average, the researchers found that the IPCC’s sea-level rise projections were biased upward by about 2 mm per year when compared to the observed rate in 2020.
This indicates that current projections may be conservative. The study recommends that designers of coastal infrastructure should conduct their own local analyses to compare them with projections.
The research highlights the importance of understanding local conditions, including geology, hydrology, and land use, when assessing and planning for sea-level changes. It also shows the need for more comprehensive, long-term sea-level data from underrepresented regions of the world.
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