Ice field in Northern Patagonia
Photo: MARTIN BERNETTI / AFP
Climate change is exacerbating the pace: due to global warming, global glacier melt has accelerated significantly over the past 20 years.
According to an international study published in the journal Nature, the glaciers lost an average of 267 billion tons (gigatons) of ice per year between 2000 and 2019, but most of them in the past five years.
The melting ice is now contributing more than 20 percent to the rise in sea levels.
With the lost gigatons of ice, Switzerland could have been submerged six meters under water every year, explained the ETH Zurich, whose researchers were involved in the study, for the sake of clarity.
According to the study, almost all of the world's 220,000 glaciers are affected by the melt, with a few exceptions.
Usually, apart from the polar ice caps, only a few hundred of them are under constant observation.
"There are many regions that we didn't know how they would develop," says lead author Romain Hugonnet.
It hits glaciers in Alaska, Iceland or the Alps in particular.
The high mountain glaciers of the Pamir, Hindu Kush and Himalayas are also losing a lot of ice.
“The situation in the Himalayas is particularly worrying.
The great rivers such as the Ganges, Brahmaputra and Indus are fed to a large extent by glacial melt water in the dry season.
The increase in meltwater is currently acting like a buffer for the people in the region, ”says a statement from ETH.
However, if the Himalayan glaciers continue to shrink at an increasing rate, populous countries such as India or Bangladesh could face water or food shortages in a few decades.
Billions of tons of ice are disappearing
For their study, Hugonnet and his colleagues analyzed half a million previously largely unused satellite images.
In this way, according to their own statement, they succeeded in “the first complete inventory of glacier melt in the world”.
According to Hugonnet, who conducts research at ETH Zurich and the University of Toulouse, this has accelerated significantly: Whereas between 2000 and 2004 it was an average of 227 billion tons per year, the decline from 2015 to 2019 was an average of 298 billion tons per year .
The conclusions of the study coincided with the assessments of the Intergovernmental Panel on Climate Change (IPCC), but are much more precise, said Hugonnet.
This applies in particular to the effects of glacier melt on sea level rise.
The new, more geographically accurate data could also help plan adaptation strategies in densely populated areas, where glaciers play an important role in agriculture and water supplies, Hugonnet said.
In the short term, the melting glaciers could compensate for the water shortage in some regions such as India or the Andes.
But once the peak is exceeded, the amount of water would decrease rapidly until there was nothing left, warned the researcher.
In a few areas, to the surprise of the researchers, the melting rate slowed between 2000 and 2019.
This was the case, for example, on the east coast of Greenland, Iceland and Scandinavia.
The study attributes this to a weather anomaly in the North Atlantic.
From 2010 to 2019, this caused higher local precipitation and lower temperatures, which slowed down the ice shrinkage.
According to the ETH, the results of the study will now be included in the next IPCC status report.
joe / AFP