A new report by former NASA scientist James Hansen and 16 other experts says the already dire projections on rising sea levels are actually too optimistic, having underestimated the rate at which Earth's ice sheets will melt in response to warmer sea temperatures.

The researchers suggest glaciers in Greenland and Antarctica may melt as much as 10 times faster than what has previously been indicated by scientific modelling, which will result in drastic sea level rises occurring far earlier than had been anticipated.

How high and how quick? Hansen, a controversial figure who is widely regarded as a 'climate seer' of sorts for his previous efforts in trying to raise awareness of climate change, estimates seas could rise by 3 metres within just 50 years. Such an increase would put coastal cities and low-lying lands all around the world in dire jeopardy, with water ingress making them uninhabitable for all practical purposes.

"Parts of [our coastal cities] would still be sticking above the water," Hansen told Mark Hertsgaard at The Daily Beast, "but you couldn't live there."

The global consequences of such near-term changes in sea levels would be catastrophic and almost unimaginable outside of a Hollywood disaster movie. In a summary of the paper's findings circulated to journalists ahead of publication this week, Hansen and his team write:

"We conclude that continued high emissions will make multi-meter sea level rise practically unavoidable and likely to occur this century. Social disruption and economic consequences of such large sea level rise could be devastating. It is not difficult to imagine that conflicts arising from forced migrations and economic collapse might make the planet ungovernable, threatening the fabric of civilisation."

The researchers warn against accepting the conventional, 'safe' target of limiting global temperature rise to 2-degree Celsius, which they believe could be highly dangerous. 

It's important to note that the new research has not yet been peer-reviewed, as the researchers contend they wanted to make the study available as soon as possible in the lead-up to the United Nations Climate Change Conference in Paris later this year. When it's published in the online journal Atmospheric Chemistry and Physics later this week, an 'interactive public peer review' will take place, and the scientific community will have a chance to respond to what will almost certainly prove to be among this year's most controversial research.