Loss of glaciers faster than expected

How will our glaciers change during the 21st century? In a new study whose findings are published in Science (5 January), an international team1 , including scientists from the CNRS and Université Toulouse III–Paul Sabatier, has demonstrated a loss of glacial mass greater than earlier projected—and specifically, 11% to 44% higher than estimates used in the most recent IPCC report. Small glaciers (<1 km²) predominate on our planet, and they are the most impacted by mass loss. In the scenario where global warming is limited to 1.5 °C, 49% of the world’s glaciers, the majority of the small ones , are expected to disappear by 2100, prompting a 9-cm sea level rise. The largest glaciers would also be affected but would not disappear. If, on the other hand, temperatures rise by 4 °C, neither small nor large glaciers will be spared: 83% would disappear and there would be a 15.4-cm sea level rise. To reach their conclusions, the team of scientists relied on the observations of a study that quantified widespread, accelerated glacial mass loss around the world between 2000 and 2019. These earlier data allowed them to calibrate their mathematical model, developed especially for the work presented in their publication, for each and every one of the 215 thousand glaciers on Earth. The model also accounts for processes not previously represented, such as mass loss due to iceberg calving and the effect of a layer of debris on the surface of a glacier. Shrinkage of the greatest glaciers, like those in Alaska, the Canadian Arctic, and around Antarctica, key to future sea level rise, may still be limited if we implement measures to mitigate global warming.

• 1In France, this study incluted scientists from the Laboratoire d’étude en géophysique et océanographie spatiales (CNRS/CNES/IRD/Université Paul Sabatier Toulouse III)