The three largest glaciers in Greenland – which hold enough frozen water to lift global sea levels some 1.3m – could melt faster than even the worst-case warming predictions, research published on November 17 showed.
Until 2000, the main driver of sea level rise was melting glaciers and the expansion of ocean water as it warms.
But over the last two decades, the world’s ice sheets atop Greenland and Antarctica have become the single largest source of sea level rise.
A team of researchers based in Denmark and Britain used historical images and a host of other data to estimate how much ice had been lost from Greenland’s Jakobshavn Isbrae, Kangerlussuaq Glacier and Helheim Glaciers in the 20th century.
They found that Jakobshavn Isbrae lost more than 1.5 trillion tonnes of ice between 1880-2012, while Kangerlussuaq and Helheim lost 1.4 trillion and 31 billion tonnes from 1900-2012, respectively.
The ice melt has already contributed more than 8mm to global sea levels, the researchers wrote in a paper published in Nature Communications.
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 last century’s ice loss.
The UN’s climate science advisory panel, the IPCC, has forecast sea level rise from all sources of between 30-110cm by 2100, depending on emissions.
Under the IPCC’s high emissions pathway, known as RCP8.5, nothing is done to curb carbon pollution throughout the 21st century, leading to a climate more than 3C hotter than pre-Industrial levels.