The glaciers worldwide shrink through climate change. Researchers have now investigated to what extent the ice masses recover if the 1.5-degree goal defined in the Paris climate agreement is only temporarily exceeded. The model -based analyzes showed: Even if the temperatures after a temporary warming fall by three degrees, for example, it would take many centuries for the glaciers to regenerate themselves – with serious consequences for the increase in sea level and drinking water supply.
Glaciers play an important role in the water supply in many parts of the world. Its meltwater irrigates fields and receives ecosystems, drives hydropower plants and supplies people with drinking water. However, due to climate change, these icy water storage tanks faster and faster. First of all, this decline in the glacier increases water availability, because a lot of ice is thawing in a short time and flows to the valley as a meltwater – a phenomenon called “Peak Water”. But the smaller the glaciers become, the less water they can release. Some glaciers have already exceeded this point.
When climate goals are exceeded
But how long does it take for the glaciers to regenerate again due to successful climate protection? A team led by Lilian Schuster from the University of Innsbruck examined this question using climate models. They simulated a so-called over-shoot scenario, in which the goal defined in the Paris climate agreement to limit global warming to 1.5 degrees Celsius compared to the pre-industrial level is temporarily exceeded. Only then lead to increased climate protection measures to reduce the temperature.
In the researcher’s model, the global average temperatures rose to three degrees Celsius above the pre-industrial level by 2150 and returned to the 1.5-degree level until 2300. In view of the current climate protection measures, this is realistic: “The current climate policy is heading to around three degrees Celsius,” explains Schuster’s colleague Fabien Maussion. “For glaciers, such a world is significantly more harmful than one in which the 1.5 ° C limit is never exceeded.”
Long -term water shortage
The results show that the glaciers in the simulated scenario lose about 16 percent more mass by 2200 than if the 1.5-degree goal is observed. Even if the global temperatures fall again, these losses cannot be compensated for for a long time. “Our models show that it would take many centuries or even thousands of years for large glaciers to recover after a three-degree Overshoot,” reports Schuster. “For smaller glaciers, for example in the Alps, in the Himalayas or in the tropical Andes, recovery is conceivable until 2500 at the earliest – but not for future generations.”
According to the researchers, this brings numerous problems. On the one hand, the melting glaciers ensure that the sea level rises by several meters. After the Peak Water phase has been exceeded, fewer melt water is also available. But the later regeneration of the glaciers further reduces water availability. Because water that is saved as a new ice in the glaciers is not available for other purposes. The research team describes this phenomenon as “trough water”, translated trough water. “Our study shows that about half of the catchment areas under consideration could experience such trough water phases after 2100,” says Schuster. There is a new potential for conflict here, because the long -term desirable cooling of the climate was worsened at short notice in some regions.
Appeal to politics
From the point of view of the researchers, it is all the more important to limit global warming in order to preserve as much as possible from the glaciers. “Although it is becoming increasingly difficult to achieve the 1.5-degree goal, our research results show that rapid emission reductions of greenhouse gases can still contribute to the long-term preservation of glaciers and their water drainage,” says Schuster.
Therefore, Schuster and her colleagues are addressing an urgent appeal to politics: “Reading on future carbon reducers instead of taking measures this decade will have unpredictable consequences,” they warn. “Our study underlines the urgency of a rapid reduction in emissions to limit the highlight of global warming to the lowest possible level. The longer we wait with the emission reduction, the more we burden future generations with irreversible consequences.”
Source: Lilian Schuster (University of Innsbruck, Austria) et al., Nature Climate Change, DOI: 10.1038/S41558-025-02318-W
