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11 hours ago
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Sea levels could be up to 4.9 feet (1.5 metres) higher than scientists previously thought, a new study has warned, putting millions more people at risk from rising oceans.
Earlier studies have relied on a rough estimate of the global sea level, which is actually far lower than the true water line in many places.
The new findings indicate sea levels could be around 11 inches (28 cm) higher than expected in the UK and between 3.2 ft and 4.9 ft (1-1.5 metres) higher in parts of Southeast Asia.
By comparison, 11 inches of increase is greater than the total sea level rise that has occurred since the beginning of the 20th century.
Scientists from Wageningen University in the Netherlands say that this 'blind spot' has meant the threat of sea level increase has been drastically underestimated.
Currently, the Intergovernmental Panel on Climate Change (IPCC) estimates that sea levels could rise by 3.2 ft (one metre) by 2100 if climate change is not slowed.
However, if the true sea level is already much higher than expected, 37 per cent more land and 68 per cent more people across the world will fall below the sea level than currently predicted.
That would mean 132 million more people's homes will be flooded by the rising waters.
Scientists say that global sea levels could rise up to 3.2 feet (one metre) higher than scientists previously thought, putting millions more homes underwater. Pictured: An illustration of how many more people could be affected by rising sea levels
The problem is that the real sea level measured by satellites is much higher than the assumed level used by scientific studies. This means small increases in sea level will have a bigger impact than expected because they are starting from a higher point
The problem stems from the fact that the overwhelming majority of studies on coastal erosion and threats measure land elevation relative to an assumed sea level known as a 'geoid model'.
This is essentially a mathematical prediction of where the sea level should sit based on the Earth's gravity and rotation.
Scientists compare this level with measurements of land elevation taken by satellites and work out how much more land would be covered with water if sea levels rose.
In their new study, published in the journal Nature, researchers analysed 385 pieces of peer-reviewed scientific literature from 2009 to 2025, and found that 90 per cent relied on these assumptions.
However, these geoid models don't take into account local factors that can affect the real sea level.
Co-author Dr Philip Minderhoud says: 'In reality, sea level is influenced by additional factors such as winds, ocean currents and seawater temperature and salinity.'
When compared with actual measurements of the sea surface taken by satellite, the geoid model often suggests that the sea level is much lower than it is in reality.
Depending on the geoid model used, previous studies underestimated the sea level by at least 9.4 inches (24 cm), with some discrepancies being as high as 25 feet (7.7 metres).
Previous research has underestimated how high sea levels already are in the UK by at least 11.8 inches (30 cm). This means sea level rise will lead to more damage than previously thought. Pictured: Red regions show areas that would be underwater with 4.26 feet (1.3 metres) of sea level rise
This means that the sea level is already much higher than most scientists think, making the risk of rising sea levels far more significant.
Professor Andrew Shepherd, Director of the Centre for Polar Observation and Modelling at Northumbria University, who was not involved in the study, says: 'Sea levels are much higher than we had thought.
'This means that 80 million people are living below sea level today, 50 million more than we had realised.'
If sea levels now increase by the amount estimated by the IPCC, it will be from a much higher starting point than previously thought.
This means millions more homes will be put underwater by the rising oceans.
Dr Matt Palmer, Science Fellow at the Met Office Hadley Centre and Associate Professor at the University of Bristol, says: 'The impacts of sea-level rise under climate change have been systematically underestimated.
'Put another way, we could see devastating impacts from coastal flooding earlier than expected from climate projections - particularly in the Global South.'
The Global South, especially Southeast Asia and the Indo-Pacific, is at greater risk because it has the biggest discrepancies between the geoid model and reality.
Southeast Asia will be the most affected since satellite measurements show that the real sea level is already about 4.9 ft (1.5 metres) higher than assumed by most risk assessments
In some places, satellite measurements show that the real sea level is already about 4.9 ft (1.5 metres) higher than assumed by most risk assessments.
In fact, Dr Minderhoud says that it was seeing this first-hand in Vietnam's Mekong Delta that first suggested the world's scientific models could be dramatically wrong.
He says: 'Here it was assumed in international impact assessments that the land would start to become inundated if sea level were to rise by 1.5 to 2 meters.
'But I could see that the surface water level, which stood in direct connection with the sea level, was already in many places within several decimetres [0.1 of a meter] of the land surface.'
In Southeast Asia, the researchers estimate that 96 per cent more people could be affected by a 3.2 feet (one metre) sea level increase than had been estimated.
Professor Jonathan Bamber, a researcher from the University of Bristol who was not involved in the study, says he is 'genuinely surprised by the results of this study'.
Professor Bamber adds: 'The wrong assumptions are made about what present-day sea level is, and it turns out that it has generally been underestimated in key sensitive coastal areas.
'This has important implications for impacts of future sea level rise in terms of the area and number of people potentially affected in low-lying areas such as South East Asia and the Nile Delta.'
