Sea levels have risen faster than expected in the last 20 years as a result of global warming and other factors, according to new research.
The study claims that estimates for sea level rises between 1901 and 1990 were too high due to incomplete records.
But from 1990 to 2010, sea levels were correctly predicted to be rising faster than ever before.
This caused a discrepancy in which the slower sea level rise seen in the last century caused the increase in recent years to appear even more rapid.
The study was carried out by scientists at Harvard University in Massachusetts.
Incomplete records from previous estimates of global sea-level rise in the 20th Century had been overestimated by as much as 30 per cent, they say.
And the new figures suggest that in the past two decades, since 1990, the rate of sea-level rise has accelerated more quickly than previously believed.
Since 1990 global sea levels have risen by about 3mm (0.12 inches) annually as the ice caps and glaciers melt because of rising temperatures.
Previous estimates had placed sea-level rise at between 1.5mm and 1.8mm (0.06 and 0.07 inches) annually from 1901 to 1990 - but now that figure is thought to be closer to just 1.2mm (0.05 inches).
RISING SEA LEVEL ESTIMATES
Previous estimates had placed sea-level rise at between 1.5mm and 1.8mm (0.06 and 0.07 inches) annually from 1901 to 1990.
But, now that figure is thought to be closer to just 1.2mm (0.05 inches).
When looking at the more recent figures, from 1990 and 2010, they found the estimates and the actual rising levels more closely matched - at around 3mm (0.12 inches) per year.
The slower sea level rise seen in the last century causes a discrepancy.
And this gap in the figures makes the increase in recent years appear even more rapid.
Scientists claim that the rate of increase in rising sea levels has, therefore, been underestimated by about 0.6mm (0.02 inches), overall.
The slower sea level rise seen in the last century causes a discrepancy.
And this gap in the figures makes the increase in recent years appear even more rapid.
Scientists claim that the rate of increase in rising sea levels has, therefore, been underestimated by about 0.6mm (0.02 inches), overall.
Dr Eric Morrow in the Department of Earth and Planetary Sciences said: 'What this paper shows is that sea-level acceleration over the past century has been greater than had been estimated by others. It's a larger problem than we initially thought.
'Another concern with this is that many efforts to project sea-level change into the future use estimates of sea level over the time period from 1900 to 1990.
'If we've been overestimating the sea level change during that period, it means that these models are not calibrated appropriately, and that calls into question the accuracy of projections out to the end of the 21st century.'
Dr Carling Hay, from the same department, added: 'Scientists now believe that most of the world's ice sheets and mountain glaciers are melting in response to rising temperatures.
'Melting ice sheets cause global mean sea level to rise. Understanding this contribution is critical in a warming world.'
The study published in Nature noted estimates of sea-level rise are created by dividing the world's oceans into sub-regions, and gathering records from tide gauges - essentially yard-sticks used to measure ocean tides - from each area.
But tide gauges don't include large areas of oceans and most detailed coastal records only began in the 1950s.
Dr Hay said: 'We know the sea level is changing for a variety of reasons.
'There are ongoing effects due to the last ice age, heating and expansion of the ocean due to global warming, changes in ocean circulation, and present-day melting of land-ice, all of which result in unique patterns of sea-level change.
'These processes combine to produce the observed global mean sea-level rise.
'We are looking at all the available sea-level records and trying to say that Greenland has been melting at this rate, the Arctic at this rate, the Antarctic at this rate, and so on.
'We then sum these contributions and add in the rate that the oceans are changing due to thermal expansion to estimate a rate of global mean sea-level change.'
To their surprise, previous estimates of sea-level rise over most of the 20th century were too high.
Dr Hay added: 'We expected that we would estimate the individual contributions, and that their sum would get us back to the 1.5 to 1.8 millimetres (0.06 to 0.07 inches) per year that other people had predicted.
'But the math doesn't work out that way. Unfortunately, our new lower rate of sea-level rise prior to 1990 means that the sea-level acceleration that resulted in higher rates over the last 20 years is really much larger than anyone thought.'
WHICH COUNTRIES WILL SUFFER MOST FROM CLIMATE CHANGE?
Climate change experts have released a map of the world revealing how prepared different countries are to cope with the effects of climate change (shown above).
In the map 192 countries are ranked by their ‘vulnerability’ and ‘readiness’, producing an overall score on their fate, ranging from bad (zero) to excellent (100).
The results reveal that Scandinavian countries and the UK are among the most likely to survive - but areas of sub-Saharan Africa will be hardest hit.
The maps were created by London-based company The Eco Experts, using data from the University of Notre Dame in Indiana, known as the ND-Gain Index.
They took into account location, terrain, pollution rates and national resources when calculating which countries would be most affected.
Countries like Norway, Sweden, Finland and Denmark score well on the scale.
But places like Central America, Africa and India all appear at risk from natural disaster - and are poorly equipped to cope, said The Eco Experts.
Jon Whiting, of The Eco Experts warned: ‘Hurricanes, earthquakes, blizzards, droughts and flooding are all real dangers for some of these areas, and this is compounded by a lack of national strategy to counteract the effects.’
Burundi, Chad, Sudan and the Democratic Republic of Congo produced some of the lowest scores, meaning these countries will be the biggest victims of weather disasters.