EARTH'S sea levels should be 30 feet higher than they are – and dramatic melting in Antarctica may soon plug the gap, scientists warn.

They say that global temperatures today are the same as they were 115,000 years ago, a time when modern humans were only just beginning to leave Africa.

4 This graph shows what parts of the UK and Europe are at risk from a seal level rise of 5 metres (16ft)

Research shows that during this time period, known as the Eemian, scorching ocean temperatures caused a catastrophic global ice melt.

As a result, sea levels were 20-30ft higher than they are today.

But if modern ocean temperatures are the same as they were during the Eemian, that means our planet is "missing" a devastating sea rise.

If oceans were to rise by just six feet, large swathes of coastal cities would find themselves underwater, turning streets into canals and completely submerging some buildings.

4 Recent research uncovered preserved moss in the Arctic Circle. It had remained frozen in ice for 115,000 years until that ice retreated last month Credit: Gifford Miller/University of Colorado Boulder/INSTAAR

Large parts of London and Kent would be submerged, while Portsmouth, Cambridge and Peterborough wouldn't fair much better.

Scientists think that sea levels made this jump 115,000 years ago because of a sudden ice collapse in Antarctica.

The continent's vulnerable West Antarctic ice sheet – which is already retreating again today – released a lot of sea level rise in a hurry.

"There's no way to get tens of meters of sea level rise without getting tens of meters of sea level rise from Antarctica," said Dr Rob DeConto, an Antarctic expert at the University of Massachusetts.

Rising sea levels – what's the problem? Here's what you need to know... The global sea level has been gradually rising over the past century

Sea levels rise due to two main reasons

The first is thermal expansion – as water gets warmer, it expands

The second is melting ice on land, adding fresh water into seas

This has a cyclical effect, because melting ice also warms up the planet (and oceans), causing more even ice to melt and boosting thermal expansion

It's currently rising at a rate of around 0.3cm per year

The sea is huge, so that might sound harmless

But rising sea levels can have a devastating effect over time

Low-lying coastal areas can disappear completely, even putting areas of the UK at risk

It can also mean sea storms and tsunamis can have a more devastating effect, reaching further in-land than they would have previously

There's also an increased risk of flooding

His team created state of the art computer models that showed how Antarctic ice responded to warm ocean temperatures during the Eemian.

They showed that two processes, called marine ice cliff collapse and marine ice sheet instability, rapidly melted the West Antarctic ice sheet.

They exposed thick glaciers that formed part of the ice sheet to the ocean, meaning the ice blocks floated out to sea more quickly.

Here they quickly melted, adding thousands of tonnes of water to the world's oceans.

4 Dubbed the 'world's most dangerous glacier', the Thwaites glacier in Antarctica is under threat from rising temperatures

Scientists warn that if ice shelves in Antarctica undergo similar processes, it could spell disaster for Earth.

Combined with melting in Greenland, we could see sea levels rise much as six feet in total this century.

In the next century, ice loss would get even worse.

"What we pointed out was, if the kind of calving that we see in Greenland today were to start turning on in analogous settings in Antarctica, then Antarctica has way thicker ice, it's a way bigger ice sheet, the consequences would be potentially really monumental for sea level rise," Dr DeConto said.

4 Baffin Island (pictured) is part of Canada, and much of it sits in the Arctic Circle. Much of its ice is retreating due to rising temperatures Credit: Tyler Olson / Fotolia

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Last month, Nasa warned that Antarctica's Thwaites glacier could collapse within decades and "sink cities" after its discovered a 1,000-foot doomsday cavity lurking below the ice block.

If sea levels rise by just six feet, then parts of Europe could "disappear", according to some scientists.

And check out this sea level "doomsday" simulator if you'd like to know whether your home would be wiped out by rising oceans.

Are you worried about climate change? Let us know in the comments!

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