Global warming: irreversible damage to glaciers if temperatures rise by more than 1.5°C
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Two United Nation reports published on Monday warn that global warming exceeding 1.5 degrees Celsius will have “irreversible” consequences for the Earth’s glaciers, sea ice and frozen surfaces. They call for action to be taken “as quickly as possible”.
Exceeding the 1.5-degree threshold of global warming compared with pre-industrial levels – the most ambitious target of the Paris Agreement in 2015 – “will lead to significant – and often irreversible – consequences within the cryosphere and the polar oceans”, that is to say, “the regions of the planet characterised by the presence of snow, ice and frozen ground”, states one of the reports.
This will lead to melting glaciers and sea ice, thawing permafrost, and an accelerated rise in sea levels. The repercussions will be manifold and will increase the risk of flooding, economic and ecological damage, as well as water shortages and hazards in mountainous areas.
Some impacts are already visible, such as the loss of 20% of Switzerland’s glacial mass, the report highlights. And even though the 1.5-degree target remains relevant, it is already “too high” for the cryosphere, whose “safe temperature” is closer to 1 degree, or even lower.
‘Very slow’ recovery
Global warming has already reached 1.37 degrees compared with pre-industrial levels. And according to the European Copernicus network, the 1.5-degree threshold could be exceeded by around 2030.
“To limit […] the damage caused by ice loss in the polar and mountainous regions of the globe […] temperatures must be brought well below 1.5 degrees as quickly as possible”, explains James Kirkham, lead author of one of the reports, published a week before COP31, where countries are due to discuss measures to tackle global warming.
+ Swiss glaciers lost 20% of their volume in five years
“Every additional fraction of a degree and every year spent above this threshold will lead to more devastating consequences,” he insists.
Scientists are particularly warning of the risks of crossing certain tipping points. They stress that, even if global warming is brought back below 1.5 degrees, “recovery will be very slow”.
Thus, in the case of the ice caps, bringing global warming back below the average threshold of 1.5 degrees “will not, however, undo the consequences of the warming experienced during the period when the threshold was exceeded”, warns Chen Zhao, a glaciologist specialising in Antarctica and a contributor to the reports.
‘Glimpses of hope’
Nevertheless, a few “glimpses of hope” remain: some glaciers could partially recover if global warming quickly falls back below an average threshold of 1.5 degrees, or even 1 degree. Arctic sea ice could also benefit.
“But, unfortunately, the timeline for this recovery is far from linear compared to that of the decline. It could take several decades, or even centuries,” explained Matthew England, an oceanographer and climatologist at the University of New South Wales.
The second report shows that a temperature rise exceeding 2.8 degrees Celsius, which were to persist into the next century, would have significant consequences. Sea levels could thus rise by up to 5 cm per year by 2150, compared with the current rate of 0.45 cm. The thawing of permafrost could also release as much CO₂ each year as the United States – the world’s second-largest polluter – currently emits.
‘Tsunami from the mountains’
A worst-case scenario that is not so unlikely: according to a recent UN report, even if countries met their climate commitments, the world is heading for warming of around 2.6 degrees Celsius by 2100.
“A temporary overshoot of 1.5 degrees does not mean that the Paris Agreement’s targets are irrelevant. On the contrary, it makes them even more urgent,” notes Mr Kirkham. And “sufficient and immediate political ambition”, particularly in terms of reducing fossil fuel use, “can still significantly reduce the damage to the cryosphere and its consequences” for people and the planet.
“The decisions taken over the next few years will determine the extent of the damage,” emphasises Gunjan Silwal, a Nepalese glacier researcher, in a statement, pointing out that “the tragedy in Nepal is just a foretaste”.
This “mountain tsunami”, caused by the collapse of a glacier and a section of a mountain peak in the north of the country – which scientists attribute to global warming – left more than 1,500 people dead and 5,000 missing in August.
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Translated from German, reviewed by an English Department journalist.
