Research from a Swiss-based global monitoring network found that due to global warming, the world’s glaciers were melting five times as fast as they were in mid-20th century, especially in Central Europe, the Caucasus, much of North America and New Zealand.
Glaciers lost more than 9,000 billion tons of ice since 1961, raising water levels by 27 millimeters worldwide, said an international research team led by the University of Zurich that studied how glacial ice melt and melting ice sheets in Greenland and the Antarctic were causing sea levels to rise.
The biggest contributors to rising global sea levels were the glacial losses in Alaska, Patagonia and Arctic regions. Major ice losses also were found in the European Alps, Caucasus and New Zealand, but due to the smaller size of their glaciers, they had a lesser role in causing global sea levels to rise.
The study published this week in the journal Nature showed glaciers were losing 369 billion tons a year of snow and ice — more than half of it in Alaska and the continental United States. That means they were shrinking 18 percent faster than scientists measured in 2013. The main influence on shrinking glaciers was warmer-than-normal summer temperatures.
Sea-level rise has been caused by the warming oceans, primarily, but the study also found that glacial melt was responsible for more than a quarter of the annual rise.
The research team combined glaciological field observations with geodetic satellite measurements, which digitally measure the Earth’s surface and provide data on fluctuating ice thickness. That let them reconstruct the changes in ice thickness among more than 19,000 glaciers worldwide, far more than any previous study.
Satellite analyses were compared with a database from the Zurich-based World Glacier Monitoring Service, or WGMS, an international organization that builds on work begun in 1894 when an International Glacier Commission was created at the Sixth International Geological Congress in Zurich. That commission evolved into the current International Association of Cryospheric Sciences.
“By combining these two measurement methods and having the new comprehensive dataset, we can estimate how much ice has been lost each year in all mountain regions since the 1960s,” glaciologist Michael Zemp, director of WGMS, said in a statement.
“The glaciological measurements made in the field provide the annual fluctuations, while the satellite data allows us to determine overall ice loss over several years or decades,” he said.
Only Asia’s glaciers stay the course
The fastest-shrinking glaciers were in central Europe, the Caucasus, western Canada, the U.S. Lower 48 states, New Zealand and close to the tropics. They were losing more than 1 percent of their mass each year, a rate that would likely cause their disappearance by the end of this century.
Due to local climate conditions, southwestern Asia was the only area where glaciers were not shrinking.
Researchers initially focused on how climate change affected ice ages. The most detailed information was for the Alps and Scandinavia, where long and uninterrupted records have been kept. In recent decades, WGMS collected standardized observations about how glaciers fluctuate — their changes in mass, volume, area and length of glaciers with time — and how surface ice changes.
Last October, the Nobel Prize-winning U.N. panel on climate change reported that even the most optimistic scenarios for lowering global greenhouse gases in line with the 2015 Paris Agreement on climate change will have serious repercussions for the planet and future generations.
The Paris accord committed the world to “holding the increase in the global average temperature to well below 2 degrees Celsius above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 degrees C. above pre-industrial levels.”
The United Nations’ Intergovernmental Panel on Climate Change, or IPCC, said limiting the global average temperature increase to 1.5 degrees C., rather than 2 degrees C., would avert 150 million premature deaths over the 21st century, but to do so the global economy must become “carbon neutral” by 2050.
It said that a half-degree C. less of warming would cause 0.1 meters less in sea-level rise and halve the number of people who would lack fresh water. Substantially fewer heatwaves and droughts would result, it said, and the world’s coral reefs might survive.
Since the world has already warmed by 1 degree C. from pre-industrial levels, even the most favorable scenarios mean only a difference of a half-degree.