Greenland’s largest glaciers could melt faster than warming predictions at worst, according to new research

Greenland’s three largest glaciers – which contain enough ice water to raise global sea level by around 1.3 meters – could melt faster than even the worst-case warming forecast, according to research published Tuesday.

Until 2000, the main driver of sea level rise was the melting of glaciers and the expansion of ocean water as it warmed.

But over the past two decades, the world’s ice sheets atop Greenland and Antarctica have become the main source of sea level rise.

A team of researchers based in Denmark and Britain used historical images and a range of other data to estimate the amount of ice lost by Greenland’s Jakobshavn Isbrae, Kangerlussuaq Glacier and Helheim Glaciers in the 20th century.

They found that Jakobshavn Isbrae lost more than 1.5 trillion tons of ice between 1880 and 2012, while Kangerlussuaq and Helheim lost 1.4 trillion and 31 billion tons between 1900 and 2012, respectively.

Melting ice has already contributed more than eight millimeters to global sea level, the researchers wrote.

Shfaqat Abbas Khan, a researcher at the Technical University of Denmark, said using photographs taken before the satellite era was another tool to help recreate the ice loss of the last century.

“Historical measurements in the 19th and 20th centuries can hide important information that can significantly improve our future projections,” he said.

The United Nations Climate Science Advisory Committee, the IPCC, has predicted sea level rise from all sources to be between 30-110 centimeters by 2100, depending on emissions.

Under the IPCC’s high-emissions path, known as RCP8.5, nothing is done to curb carbon pollution throughout the 21st century, leading to a climate that is more than three degrees Celsius warmer than levels pre-industrial.

Models run under RCP8.5 for the three glaciers featured in Tuesday’s study predict sea level rise of 9.1–14.9mm by 2100.

But the paper, published in Nature Communications, pointed out that the temperature rise of the high-emission path was more than four times greater than in the 20th century, when the three glaciers had already added 8mm to the seas.

“The worst case scenario is underestimated. Ice loss can be three to four times greater than previously predicted for the glaciers considered in this study,” Khan said.

A Nature study published in September found that if greenhouse gas emissions continued unabated, the ice sheets in Greenland lose about 36 trillion tons this century – enough to raise the global waterline by about 10 centimeters.