Global sea levels rose faster in the 20th century than at any time in the previous 2,700 years, research has shown.
Without the global warming, sea levels might actually have fallen in the last 100 years, scientists believe.
Instead they are said to have increased by an average 14 centimetres between 1900 and 2000.
Without a rapid reduction in greenhouse gas emissions, worldwide sea levels are on course to rise by between 30cm and 120cm by the end of this century, it is claimed.
Even if the ambitious goals of the 2015 Paris Agreement to manage climate change are adopted, sea levels are still projected to rise by as much as 61cm.
The evidence is contained in two separate US and German research papers published in the journal Proceedings of the National Academy of Sciences. Both used new statistical approaches to assess sea level trends.
For the first, a US team led by Robert Kopp, from Rutgers University, analysed data from a host of geological indicators spanning almost 3,000 years.
The database included records from marshes, coral atolls and archaeological sites from 24 locations around the world.
The 20th century rise was extraodinary in the context of the last three decades
The results showed that global sea levels fell by about 7.6cm between the years 1000 and 1400, which coincided with a planetary cooling of around 0.2˚C. In contrast, today’s global temperature is about 1˚C higher than it was in the late 19th century.
Without global warming, it is likely that sea level change during the last century would have ranged between a fall of three centimetres and a rise of seven centimetres.
Kopp said: “The 20th century rise was extraordinary in the context of the last three millennia – and the rise over the last two decades has been even faster.”
The German study used a new prediction model that combined physics-based calculations of changes such as ice sheet melting and heat-induced expansion of sea water, and recorded data from observations made during the last century. Feeding the information into simulations for three greenhouse gas scenarios proposed by the Intergovernmental Panel On Climate Change revealed a rise in sea levels of between 30cm and 120cm by the year 2100.
This was broadly in line with the US study, which forecast a rise of between 52cm and 131cm if the world continues to rely heavily on fossil fuels.
Lead scientist Anders Levermann, from the Potsdam Institute for Climate Impact Research, said: “With all the greenhouse gases we already emitted, we cannot stop the seas from rising altogether, but we can substantially limit the rate of the rise by ending the use of fossil fuels.
“If the world wants to avoid the greatest losses and damages, it now has to rapidly follow the path laid out by the UN climate summit in Paris a few weeks ago.”
More than 600 million people live in vulnerable coastal areas less than 10 metres above sea level. Two-thirds of cities with populations of more than five million are located in these high-risk areas.
The US Environmental Protection Agency estimates that 26,000 square kilometres of land would be lost if global sea levels rise by 61cm.