Half of Earth’s glaciers will disappear by the end of the century, says study

The planet’s glaciers will liquefy much faster than scientists have predicted so far. Half of them will have disappeared by the end of this century, a quarter by 2050. This is the warning of a new study, published this week in the journal Science, which points to the acceleration of melting of the 215,000 glaciers already mapped around the world.

Conducted by 13 scientists, including Canadians, North Americans, Swiss, Norwegians, Austrians and French, the research used new observation data obtained from satellite images with an unprecedented degree of resolution. From these updated parameters, the researchers were able to recalibrate the model for calculating the melting of glaciers on Earth.

The results are up to 44% higher than the estimates used by the already alarming latest IPCC report, the UN Intergovernmental Panel on Climate Change. The new projection is that at least 104,000 glaciers will disappear from the world by 2100, half of them before 2050.

“Our study focused on the two extreme scenarios of global temperature rise and demonstrates that glaciers will lose about 30% of their mass if the thermometers register an increase of 1.5ºC and about 50% if they rise by 4ºC”, explains the glaciologist Etienne Berthier, 46, of the Laboratory of Studies in Geophysics and Space Oceanography at the University of Toulouse, France, and one of the authors of the study.

The 1.5ºC increase is the most ambitious goal of the Paris Agreement, adopted in 2015 by 195 countries, but it has been disregarded as a real possibility by a large part of the scientific community. Even so, the objective was reiterated in the Glasgow Agreement made during COP26, in 2021.

“The evolution of melting glaciers is dramatic. We want to communicate to global leaders that the situation is serious and that it is necessary to reduce the use of fossil fuels as much as possible.”

According to Berthier, the new satellite images for the last 20 years point to an unprecedented acceleration in the melting of glaciers. Between 2000 and 2019, this acceleration was 30% and these data made the model more realistic, says the researcher.

The study indicates that the first victims will be the smaller glaciers, of up to one square kilometer, which are more vulnerable, and those located at low and medium altitudes. Thus, the glaciers of the Andes and the tropics, such as Mount Kilimanjaro, in Tanzania, would be doomed in the shortest term, while those of the Caucasus, the Alps and the western United States should disappear later, by 2100.

Berthier recalls that in the Pyrenees, a region close to Toulouse, many small glaciers have already disappeared, closing ski resorts and other tourist attractions previously linked to the permanent presence of snow. “Many others, in this region, will disappear in 10 to 20 years. The fact that there is so little snow at the moment is a bad omen for next summer.”

“The main practical consequence of this rapid melting of glaciers is their contribution to the rise in sea levels. Added to the melting of the Greenland and Antarctica regions and the warming of the waters themselves, the liquefaction of glaciers should contribute to the rise in sea levels. between 60 and 90 centimeters by the end of the century,” he says.

“Glaciers alone will make sea levels rise by up to 15 centimeters. And that will compromise life in a good part of the planet’s coastal cities, such as those on the Brazilian coast, for example.”

A second consequence of accelerating glacier melt is that many glaciers function as what Berthier calls “water towers.” They hold frozen water during the winter months and, as the weather warms, they melt, providing water for 1.9 billion people worldwide.

“It’s a service that glaciers provide for humanity in the warmer months, precisely when water is needed the most, and there won’t be any more,” he points out.

The calculations of the study published in Science were improved, explains the glaciologist, from the inclusion of two processes previously discarded by the studies. The first is the melting of glaciers that end in lakes, rivers and seas, which promotes the rupture of larger blocks of ice, forming icebergs. The second is the accumulation of dust and other debris on the surface of glaciers, creating dark patches in the snow, which increase the rate of melting.

“All these factors contributed to our research finding greater and faster losses than previous studies”, explains Berthier.

He says he is skeptical about far-fetched projects for the preservation of glaciers, such as the use of roofs over glaciers to preserve them during the hottest months of the year or the arrangement of mirrors in space to reflect part of the sun’s rays.

“Covering the glaciers is something that only works on a very small scale, for example, on a snowy patch at a ski resort. It is impossible to cover an entire mountain”, he assesses. “Other projects seem risky to me because we don’t know what consequences they would have for nature, and some may be unexpected”, he adds.

“My choice today is for the reduction in the emission of greenhouse gases. In this field, there are interesting projects to capture these gases from the atmosphere for storage underground. Even so, they are proposals that are still impossible to be implemented on a global scale”, he says. “The safest and most efficient way to reduce global warming is still the reduction of the emission of these gases.”

_{The Planeta em Transe project is supported by the Open Society Foundations.}