Glacier mass loss: past the point of no return

In the Paris Agreement, 195 member states of the United Nations Framework Convention on Climate Change have agreed to limit the rise in global average temperature to significantly below 2°C, if possible to 1.5°C above pre-industrial levels. This should significantly reduce the risks of climate change. What does this plan - if successful - mean for the evolution of glaciers? Climate researchers Ben Marzeion and Nicolas Champollion from the Institute of Geography at the University of Bremen and Georg Kaser and Fabien Maussion from the Institute of Atmospheric and Cryospheric Sciences at the University of Innsbruck have investigated this question by calculating the effects of compliance with these climate goals on the progressive melting of glaciers. Melting glaciers have a huge influence on the development of sea level rise. In our calculations, we took into account all glaciers worldwide - without the Antarctic and Greenland ice sheets and peripheral glaciers - and modelled them in various climate scenarios, explains Georg Kaser.

One kilogram of CO₂ emitted costs 15 kilograms of glacier ice

Whether the average temperature rises by 2 or only 1.5°C makes no significant difference for the development of glacier mass loss over the next 100 years. Around 36 percent of the ice still stored in glaciers today would melt even without further emissions of greenhouse gases. That means: more than a third of the glacier ice that still exists today in mountain glaciers can no longer be saved even with the most ambitious measures, says Ben Marzeion.

However, looking beyond the current century, it does make a difference whether the 2 or 1.5°C goal is achieved. Glaciers react slowly to climatic changes. If, for example, we wanted to preserve the current volume of glacial ice, we would have to reach a temperature level from pre-industrial times, which is obviously not possible. In the past, greenhouse gas emissions have already triggered changes that can no longer be stopped. This also means that our current behaviour has an impact on the long-term evolution of the glaciers - we should be aware of this, adds glaciologist Kaser. In order to make these effects tangible, the scientists have calculated that every kilogram of CO₂ that we emit today will cause 15 kilograms of glacier melt in the long term. Calculated on the basis of an average car newly registered in Germany in 2016, this means that one kilogram of glacier ice is lost every five hundred meters by car, clarifies Ben Marzeion.

This work was funded by the German Federal Ministry of Education and Research (grant 01LS1602A) and German Research Foundation (grant MA 6966/1-1), and supported by the former Austrian Federal Ministry of Science and Research as part of the UniInfrastrukturprogramm of the research platform Scientific Computing at the University of Innsbruck.