New research findings have suggested that the accelerated pace of global warming may be nearing the tipping point as shown in the observed increasing vulnerability of the Greenland ice sheet.

Scientists from the Potsdam Institute for Climate Impact Research (PIK) and the Universidad Complutense de Madrid warned in their report that the vast Greenland ice sheet could have been thinning at an alarming faster rate and reversing that trend may prove difficult.

Beyond 1.6 degrees Celsius (or 2.9 degrees Fahrenheit) the sheets that accumulated for millions of years could start melting, with the whole process set to be completed over the next 50,000 years, the Spanish and German scientists said.

The report was published Monday by the journal Nature Climate Change.

Prior to the publication of the report, experts have estimated that global temperature increase of at least 3.1 degrees Celsius from the pre-industrial level would induce the sheet's gradual melting, which when completed could swamp low-lying cities around the world.

According to Bloomberg, seven metres (or 23 feet) of water would swallow key cities around the world, based on estimates that were provided by the United Nations.

But that eventuality would not come until some thousand of years, the report said, though it added the gap from point A to B will be significantly reduced the moment that the mercury starts ticking up.

Basing on computer-generated climate models that were previously employed to predict the growth and shrinkage pattern of the Greenland ice sheet, the report claimed that by the time global temperature had surged by four degrees, melting will be completed within 8000 years.

Double that temperature and man will only have to wait another 2000 years before the sheets would totally melt away, with the incredible acceleration, the report said, mainly attributed to the sheets' inability to grow back during the course of the melting period.

Presently, scientists have determined that industrial activities since the 18th century were largely responsible for global temperature spike of 0.8 degree, suggesting that Earth is still a long way before it begins losing the Greenland ice sheet.

But mankind cannot rest on this notion, according to study lead author Alexander Robinson, who cautioned: "We might already be approaching the critical threshold."

"The more we exceed the threshold, the faster it melts," Robinson told Bloomberg.

And what was lost may not be recovered at all, according to Andrey Ganopolski of PIK, explaining that "our study shows that under certain conditions the melting of the Greenland ice sheet becomes irreversible."

"If the global temperature significantly overshoots the threshold for a long time, the ice will continue melting and not regrow - even if the climate would, after many thousand years, return to its pre-industrial state," the PIK researcher told Agence France Presse (AFP) on Monday.