By Tim Radford
Many of the planet’s most scenic – and most valued – high-altitude landscapes are likely to look quite different within the next 80 years: the glaciers’ global melt will have left just bare rock.
By the century’s end, Europe’s famous Alps – the chain of snow- and ice-covered peaks that have become a playground of the wealthy and a source of income and pleasure for generations – will have lost more than nine-tenths of all its glacier ice.
And in the last 50 years, the world’s glaciers – in Asia, the Americas, Europe, Africa and the sub-Arctic mountains – have lost more than nine trillion tonnes of ice as global temperatures creep ever upwards in response to profligate combustion of fossil fuels.
And as meltwater has trickled down the mountains, the seas have risen by 27mm, thanks entirely to glacial retreat.
“Present mass-loss rates indicate that glaciers could almost disappear in some mountain ranges in this century”
In two separate studies, Swiss scientists have tried to audit a profit and loss account for the world’s frozen high-altitude rivers, and found a steady downhill trend.
Glacial ice is a source of security and even wealth: in the poorest regions the annual summer melt of winter snow and ice banked at altitude can guarantee both energy as hydropower and water for crops in the valleys and floodplains.
In wealthy regions, the white peaks and slopes become sources of income as tourist attractions and centres for winter sport – as well as reliable sources of power and water.
They made computer models of the annual flow of ice and its melting patterns and took 2017 as the reference year: a year when the Alpine glaciers bore 100 cubic kilometres of ice. And then they started simulating the future.
If humankind kept the promise made by 195 nations in Paris in 2015, to drastically reduce fossil fuel use, lower emissions of carbon dioxide, restore the forests and keep global warming to no more than 2°C above historic levels, then the stores of high ice would be reduced by more than a third over the next eight decades. If humankind went on expanding its use of fossil fuels at the present rates, then half of all the ice would be lost by 2050 and 95% by 2100.
But there will be losses in all scenarios: warming so far has seen to that. Ice reflects radiation and keeps itself cold, so change lags behind atmospheric temperature.
“The future evolution of glaciers will strongly depend on how the climate will evolve,” said Harry Zekollari, once of ETH and now at Delft University of Technology in the Netherlands, who led the research. “In the case of a more limited warming, a far more substantial part of the glaciers could be saved.”
The Alpine glaciers were made world-famous first by Romantic painters and poets of the 19th century, among them JMW Turner and Lord Byron. But their contribution to rising sea levels is, in a global context, negligible.
When Swiss researchers and their Russian, Canadian and European partners looked at the big picture, they found that the mass loss of ice from the mountains of Alaska, Canada, parts of Asia and the Andes matched the increasing flow of water from the melting Greenland ice cap, and exceeded the flow of melting water from the Antarctic continent.
Europe’s modest melt
They report in Nature that glaciers separate from the Greenland and Antarctic sheets covered 706,000 square kilometres of the planet, with a total volume of 170,000 cubic kilometres, or 40 centimetres of potential sea level rise.
And in the five decades from 1961 to 2016, according to careful study of satellite imagery and historic observations, the seas have already risen by 27mm as a consequence of increasing rates of glacial retreat. This is already between 25% and 30% of observed sea level rise so far.
Europe did not figure much in the reckoning. “Globally, we lose three times the ice volume stored in the entirety of the European Alps – every single year,” said Michael Zemp, a glaciologist at the University of Zurich.
He and his colleagues warn: “Present mass-loss rates indicate that glaciers could almost disappear in some mountain ranges in this century, while heavily glacierised regions will continue to contribute to sea level rise beyond 2100.”