New research highlights that mountain glaciers across the globe will not recover for centuries - even if human intervention cools the planet back to the 1.5°C limit, having exceeded it.
The research, led by the University of Bristol in the UK and the University of Innsbruck in Austria in collaboration with colleagues from IIASA and Switzerland, presents the first global simulations of glacier change up to 2500 under so-called 'overshoot' scenarios, when the planet temporarily exceeds the 1.5°C limit up to 3°C before cooling back down.
The results, which have been published in Nature Climate Change, show that such a scenario could result in glaciers losing up to 16% more of their mass compared to a world that never crosses the 1.5°C threshold.
"Current climate policies are putting the Earth on a path close to 3°C. It's clear that such a world is far worse for glaciers than one where the 1.5°C limit is held," said corresponding author Fabien Maussion, Associate Professor in Polar Environmental Change at the University of Bristol. "We aimed to discover whether glaciers can recover if the planet cools again. It's a question many people ask - will glaciers regrow in our lifetime, or that of our children? Our findings indicate sadly not."
Rising global temperatures now indicate a significant chance of overshooting the Paris Agreement limits adopted a decade ago. For example, last year was the hottest year ever recorded on Earth and the first calendar year to exceed the 1.5°C mark.
The scientists assessed future glacier evolution under a strong overshoot scenario in which global temperatures continue rising to 3.0°C by around 2150, before falling back to 1.5°C by 2300 and stabilizing. This scenario reflects a delayed net-zero future, in which negative emission technologies like carbon capture are only deployed after critical warming thresholds have been exceeded.
The results show glaciers would fare much worse than in a world where temperatures stabilize at 1.5°C without overshooting, with an additional 16% of glacier mass being lost by 2200, and 11% more by 2500 - on top of the 35% already committed to melting even at 1.5°C. This extra meltwater eventually reaches the ocean, contributing to even greater sea-level rise.
The research used a pioneering open-source model developed at the University of Bristol and partner institutions, which simulates past and future changes in all of the world's glaciers, excluding the two polar ice sheets. It was combined with novel global climate projections produced by the University of Bern in Switzerland.
"Our models show it would take many centuries, if not millennia, for the large polar glaciers to recover from a 3°C overshoot. For smaller glaciers such as those in the Alps, the Himalayas, and the Tropical Andes, recovery won't be seen by the next generations but is possible by 2500," notes lead author, Lilian Schuster, a researcher at the University of Innsbruck.
Glacier meltwater in these mountain regions is vital to downstream communities - especially during dry seasons. When glaciers melt, they temporarily release more water, a phenomenon known as glacier 'peak water'.
"If glaciers regrow, they start storing water again as ice - and that means less water flows downstream. We call this effect 'trough water', in contrast to peak water. We found that roughly half of the basins we studied will experience some form of trough water beyond 2100. It's too early to say how much impact this will have, but our study is a first step toward understanding the many and complex consequences of climate overshoots for glacier-fed water systems and sea-level rise," Schuster adds.
This research was conducted as part of the EU-funded PROVIDE project, which investigates the impacts of climate overshoots on key sectors around the world.
"The glaciers of the future will bear witness to the consequences of our climate actions or inactions today. This is not a time of complacency. We need to slash emissions now and decisively on the race to net zero to avoid the worst consequences of climate change," concludes coauthor Carl-Friedrich Schleussner, who leads the Integrated Climate Impacts Research Group in the IIASA Energy, Climate, and Environment Program.
The projections for glaciers under climate change can also be explored on the PROVIDE Climate Risk Dashboard that is hosted by IIASA. Impacts of overshoot will also be a central topic at the international Overshoot Conference that will take place at IIASA in October 2025.
Adapted from a press release prepared by the University of Bristol. Read the original article here.
Reference
Schuster, L., Maussion, F., Rounce, D.R., Ultee, L., Schmitt, P., Lacroix, F., Frölicher, T.L., & Schleussner, C-F (2025). Irreversible glacier change and trough water for centuries after overshooting 1.5 °C. Nature Climate Change DOI: 10.1038/s41558-025-02318-w
