A decades-long study has revealed that melting glaciers have contributed nearly 2cm to global sea level rise since the start of this century.

According to the research, glaciers worldwide lost a staggering 6.542 trillion tonnes of ice between 2000 and 2023, leading to an 18mm (0.7in) increase in sea levels. On average, they lost 273 billion tonnes of ice per year—an amount equivalent to 30 years of global water consumption.

The study, conducted by scientists from the University of Edinburgh and the University of Zurich, found that glaciers have lost approximately 5% of their total volume so far this century. The losses varied by region, with glaciers in the Antarctic and subantarctic islands shrinking by 2%, while those in central Europe lost a staggering 39%.

“These numbers are staggering. They serve as a reminder that things are changing fast in some regions,” said Prof Noel Gourmelen, the co-lead author of the study and personal chair of Earth observation at the University of Edinburgh’s school of geosciences.

A significant acceleration in ice loss was also observed, with 36% more ice melting between 2012 and 2023 compared to the previous decade.

“This is really important as it confirms the pace of glacier melting is accelerating over time,” said Prof Andrew Shepherd, head of the department of geography and environmental science at Northumbria University. “Even small amounts of sea level rise matter because it leads to more frequent coastal flooding. Every centimetre of sea level rise exposes another 2 million people to annual flooding somewhere on our planet.”

Beyond rising sea levels, glacier loss threatens freshwater supplies for remote and water-scarce communities.

“Around 2 billion people depend on meltwater from glaciers and so their retreat is a big problem for society,” said Shepherd. “It’s not just that we are losing them from our landscape, they are an important part of our daily lives.”

“Glaciers are also important for power generation,” said Gourmelen. “For instance, 70% of electricity in Iceland comes from hydropower. They rely on the water melt from glaciers to function. You have this in the Andes as well as parts of Europe, such as Switzerland.”

Published in the journal Nature, the study is part of the Glacier Mass Balance Intercomparison Exercise (Glambie), which synthesises data from field measurements and satellite observations.

After ocean warming, melting glaciers are the second-largest contributor to rising sea levels.

“This research is concerning because it predicts further glacier loss,” said Martin Siegert, professor of geosciences at the University of Exeter. “Two centimetres might not sound a lot, but this is the contribution from small glaciers – not the whole of the ice on the planet or that from Greenland and Antarctica.”

“Glaciers have a real impact,” says Gourmelen. “They are a biometer for climate change, so the findings are a measure of the impact climate change has had over the past 20 years.

“As we take action to try to mitigate this, following glacier activity will be a way of measuring our effectiveness in dealing with a changing climate.”