Climate change: glaciers will only recover very slowly

Glaciers are disappearing as a result of global warming. In the Alps, for example, there are now only half as many as there were in the middle of the 19th century. Even if climate change is halted, it will take a very long time for the glaciers to recover, as researchers from Austria and the UK report.

The team led by Lilian Schuster from the University of Innsbruck and Fabien Maussion from the University of Bristol simulated the global development of glaciers up to the year 2500 under so-called overshoot scenarios. These are climate developments in which the temperature temporarily exceeds the target set in 2015 of limiting the temperature increase to 1.5 degrees Celsius. They have published the results in the scientific journal Nature Climate Change.

If this target is met, glaciers will retreat by around 35 percent. However, it currently seems unlikely that the 1.5 degree target will be met. “Current climate policies are heading towards around 3 degrees Celsius,” says Maussion.

The team has simulated such an overshoot scenario: In this, the temperature rises by 3 degrees by around 2150 and falls back to 1.5 degrees by 2300 – with delayed climate policies, this is a realistic development. “Such a world is significantly more damaging to glaciers than one in which the 1.5 degree limit is never exceeded.”

More freshwater, rising sea levels

In this scenario, glaciers will lose around 16 percent more mass by 2200 and around 11 percent more by 2500 than if the 1.5-degree target were met. If the glaciers melt, more freshwater will be available in the short term. However, the additional meltwater will contribute significantly to rising sea levels.

If temperatures fall again, the glaciers – that's the good news – will also recover. But not so fast: “Our models show that it would take many centuries or even millennia for large glaciers to recover after a 3-degree overshoot,” says Schuster, lead author of the study. “For smaller glaciers, such as those in the Alps, the Himalayas or the tropical Andes, recovery is conceivable by the year 2500 at the earliest – but not for future generations.”

On the other hand, the glaciers will benefit from a consistent climate policy, the researchers state: “Although it is becoming increasingly difficult to achieve the 1.5-degree target, our research results show that rapid reductions in greenhouse gas emissions still contribute to the long-term preservation of glaciers and their water runoff,” says Schuster. “Limiting warming to 1.5 degrees would preserve more than 10 percent more glacier mass compared to a temporary overshoot to 3 degrees by the year 2500.”

2025 is the International Year of Glacier Conservation. The team appeals to politicians and society to adhere to the target set in Paris in 2015: “A temporary overshoot of 1.5 degrees will cement glacier retreat for centuries. Much of this cannot be reversed, even if the climate cools later. The longer we wait to reduce emissions, the more we will burden future generations with irreversible consequences.”

(wpl)