THE world’s glaciers are disappearing faster than scientists thought, with two-thirds of them projected to melt out of existence by the end of the century at current climate change trends, according to a new study.

The study in Thursday’s journal Science examined all of the globe’s 215,000 land-based glaciers — not counting those on ice sheets in Greenland and Antarctica — in a more comprehensive way than past studies.  

Projected ice loss by 2100 ranges from 38.7 trillion metric tons to 64.4 trillion tons, depending on how much the globe warms and how much coal, oil and gas is burned, the study said.

The study calculates that all that melting ice will add anywhere from 3.5 inches in the best case to 6.5 inches in the worst case to the world’s sea level, 4 per cent to 14 per cent more than previous projections.

A 4.5-inch sea-level rise from glaciers would mean more than 10 million people around the world would be living below the high-tide line, who otherwise would be above it, said sea level rise researcher Ben Strauss, CEO of Climate Central. 

In a worst-case scenario of several degrees of warming, 83 per cent of the world’s glaciers would likely disappear by the year 2100, study authors said.

But if the world can limit future warming to just a few more tenths of a degree and fulfil international goals then slightly less than half the globe’s glaciers will disappear, said the study. 

The world is now on track for a 2.7°Celsius temperature rise since pre-industrial times, which by the year 2100 means losing 32 per cent of the world’s glacier mass, or 48.5 trillion metric tons of ice as well as 68 per cent of the glaciers disappearing. 

“For many small glaciers it is too late,” said study co-author Regine Hock, a glaciologist at the University of Alaska Fairbanks and the University of Oslo in Norway. 

“However, globally our results clearly show that every degree of global temperature matters to keep as much ice as possible locked up in the glaciers.”

Experts say the loss of glaciers is about more than rising seas.

It also means shrinking water supplies, more risk from flood events due to melting glaciers and about losing historic ice-covered spots from Alaska to the Alps to even near Mount Everest’s base camp.