Even if humanity manages to reverse climate change and cool the Earth back down to the 1.5°C target, glaciers around the world are already on a path to centuries of continued melting.
New projections show that temporarily overshooting this limit—even up to 3°C—would lock in severe and irreversible glacier loss. Mountain ranges from the Alps to the Andes would see a major decline in ice mass, fueling long-term sea-level rise and disrupting critical water supplies for communities.
Global Glacier Crisis: No Quick Recovery
New research shows that mountain glaciers around the world are likely locked into centuries of decline, even if we manage to bring global temperatures back down to the 1.5°C target after exceeding it.
Led by scientists from the University of Bristol in the UK and the University of Innsbruck in Austria, the study is the first to model glacier changes worldwide all the way to the year 2500. The focus is on “climate overshoot” scenarios, where the planet temporarily warms well beyond the 1.5°C goal, reaching up to 3°C, before eventually cooling again.
Consequences of Climate Overshoot
Published on May 19 in Nature Climate Change, the findings reveal that overshooting the 1.5°C limit, even briefly, could cause glaciers to lose up to 16% more of their total mass compared to a world that never exceeds that threshold.
Dr. Fabien Maussion, co-author and Associate Professor in Polar Environmental Change at the University of Bristol, said the results are a clear warning. “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,” he explained.
“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.”
Record Heat and the 3°C Trajectory
Rising global temperatures now indicate a significant chance of overshooting of 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 climate 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 stabilising. 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.
Sea-Level Rise and Glacier Mass Loss
The results show glaciers would fare much worse than in a world where temperatures stabilise 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.
Long-Term Impacts on Mountain Glaciers
Lead author Dr. Lilian Schuster, a researcher at the University of Innsbruck, said: “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 Himalaya, and the Tropical Andes, recovery won’t be seen by the next generations but is possible by 2500.”
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’.
Dr. Schuster added: “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.”
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.
Irreversible Change and a Call to Action
Dr. Maussion said: “Overshooting 1.5°C, even temporarily, locks in glacier loss for centuries. Our study shows that much of this damage cannot simply be undone, even if temperatures later return to safer levels. The longer we delay emissions cuts, the more we burden future generations with irreversible change.”
Reference: “Irreversible glacier change and trough water for centuries after overshooting 1.5 °C” by Lilian Schuster, Fabien Maussion, David R. Rounce, Lizz Ultee, Patrick Schmitt, Fabrice Lacroix, Thomas L. Frölicher and Carl-Friedrich Schleussner, 19 May 2025, Nature Climate Change.
DOI: 10.1038/s41558-025-02318-w
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24 Comments
How can one be a professor of climate change? That’s like being a general of surrender or a doctor of misdiagnosis? One can be a climatologist and a professor but the name already states the opinion. Did we recover from the Maunder Minimum? Did we cool from the Roman Warm Period? I’m not losing sleep but I am also so scared of the new covid coming that it’s distracting me from the coming big melt
Nowhere in the article is any mention of “professor of climate change”.
That said, that human activities are changing the climate climate is now an established fact. There’s zero doubt about the core ideas. So, yes, it does make sense to study it.
It seems that your goal is to subtly discredit climate science. Your antiscience agenda is also evident at your dig about covid. But this is the issue: science is all about skepticism. So, you can surely join in, by proving the rest of the climate scientists wrong. That way, you won’t have to resort to twisting words. Go publish your papers. Become famous. Direct your indignation at people who actually study these things. Just don’t assume that scoffing is a substitute for actual scientific work.
“That said, that human activities are changing the climate climate [sic] is now an established fact. There’s zero doubt about the core ideas.”
The validity of an assertion such as you made does not stand on its own. There is lots of doubt if you care to look for it. However, I think the essence of your position is a misunderstanding of the problem. The question isn’t whether or not humans can affect the climate, but, rather, with all the interconnected feed back loops, to what extent do humans affect the net changes? Is the net effect actually significant and is it detrimental? Can you answer the question, “What is the optimal global average temperature and why?”
You say: Can you answer the question, “What is the optimal global average temperature and why?”
I do not know the optimal global average temperature.
But do you have a specific answer to your own question?
“I do not know the optimal global average temperature.”
Then why do you advocate to maintain the current temperature when it may be sub-optimal for humans and life in general?
One needs some standard to compare against to determine an optimal temperature. Geologic evidence suggests that during the Eocene in general, and the Paleocene-Eocene Thermal Optimum in particular, temperatures were probably about 10 deg C warmer than today. It was a time of abundance of plant and animal life, with great diversity in species, and included the ancestors of humans — primates. Based on that, both the diversity and abundance of life was greater when it was much warmer. If abundance and diversity is good, then it would be desirable to have a warmer Earth.
Currently, far more humans die from from cold exposure than heat. That would suggest that, presently, the optimum temperature would be close to an equal number of people dying from exposure to the elements. Inasmuch as it is easier to add clothes than remove clothes that aren’t being worn, it might not take much to even out the mortality rates. However, to optimize the climate for humans, it would again seem that warmer would be better.
Lastly, the abundance and diversity of life is far greater in warm areas. David Attenborough claimed that while the tropics only constitute about 2% of the surface of the Earth, 50% of the known species of life can be found in the tropics.
Therefore, whether one advocates for optimizing the environment for humans, or life in general, it seems that a warmer Earth would be better for both.
Clyde Spencer on May 30 says:
[I said] “I do not know the optimal global average temperature.”
Then why do you advocate to maintain the current temperature when it may be sub-optimal for humans and life in general?
If I don’t know the optimal temperature, then the right approach is to leave things alone. This is because the one thing we are absolutely sure about is that the current temperature is good for us – our numbers have skyrocketed in this temperature domain. Whereas if the temperatures rose (or fell), we wouldn’t know whether we are moving away from optimality or not, and therefore we wouldn’t know if we are causing harm to ourselves or not.
It’s like if you are in a small plane with just the pilot, and you discover that the pilot has passed out from drinking. You cannot fly the plane, but you notice that the autopilot light is on, and therefore the plane is flying level. Do you now disengage the autopilot? Then the plane will either gain or lose altitude – and one or the other might be better than the current situation. But should you try flying the plane when you don’t know how?
Climate is the same way. There are simply too many variables to know the effects. You seem to think that a warmer temperature is better for the planet. But your arguments are confused and simplistic.
Confused, because you say it is easy to add clothes (true), but then it would be better to err on the side of cooler earth and just add clothes. By your logic, shooting for a cooler earth would be safer.
Simplistic, because you ignore the feedback effects. What will kill us is not the 2C (or so) increase in average temperature, but the ripple effects of such a change.
For example, the extra greenhouse gases that gave us the 2C increase are not going away, and will stick with us. So, if we add no new greenhouse gases to the atmosphere then also the temperature will continue to rise. And, given that the rise in the last few decades has been steep, the temperature will likely continue to rise rapidly.
Another example – right now the ocean currents are set up to take heat away from the tropics towards the poles. We know that melting snow in the polar regions will disrupt this current because of the changing salinity of the melting polar waters. What will the effects be? There are models – and the models have scary predictions. You may say that the models are limited when the only testbed of such a model is the whole earth. And you would be right. But do you know any better? It’s thus best not to tinker with things on a global scale
Another example – you are right that the earth was warmer earlier (on average). We also had ice ages. Temperature change causes species to go away or to be on the brink of going away, and new species to come in and take its place. How do you know whether we will be one of the chosen ones to survive the climate change? Don’t let our technology lull you into complacency – the various species depend on each other – so our extinction or near extinction will be most likely dependent on the fates of other species that we have come to depend on. This suggests that we are very close to the optimal temperature for the earth. Earth, the planet, will do fine with higher or lower temperatures. So will life. It’s just that we might not be part of the thriving species.
There’s a saying – fools go where angels fear to tread. The scientists are fearful because they see many warning signs.
In response to AG3 on June 5, 2025 9:39 am:
“…, then the right approach is to leave things alone.”
I’m not advocating that we engage in climate modification solely for the purpose of achieving an optimal climate, how ever it is defined. However, some alarmists ARE suggesting that we do so to prevent changes they think are dangerous; I thought that you were in that group. The claim is that the warming climate is the result of unintended consequences from using fossil fuels to run our energy-intensive technology. Isn’t a proposal to replace fossil fuels with other energy sources a form of attempted climate modification when you say that you think that the right approach is “leave things alone?” What guarantee do we have that shifting to so-called renewable energy won’t have its own set of unique unintended consequences? I have presented an argument that warming is not such a bad outcome. Unless you can make a compelling case that warming is actually an existential threat, then I think we should follow your advice and let things play out.
“Confused, because you say it is easy to add clothes (true), but then it would be better to err on the side of cooler earth and just add clothes.”
There are at least two problems with your response. Animals cannot put on clothes and two lines of evidence suggest that biodiversity is decreased by cold. Only technologically advanced cultures can resort to more or better clothes, which require energy to manufacture. There is a lower limit on cooling when glaciation starts to reduce the available arable land and the bigger question becomes how to feed people rather than keep them warm.
” And, given that the rise in the last few decades has been steep, the temperature will likely continue to rise rapidly.”
How steep the rise has been, which we could quibble about, really says nothing about the likelihood of it continuing. NASA has documented a ‘Greening’ of the Earth, which is pulling an increasing amount of CO2 out of the atmosphere. Assuming that anthropogenic CO2 is actually responsible for the recent warming (There is no agreement on the ‘climate sensitivity, which ranges from ~1 to 6 deg C per doubling of CO2), ‘Greening’ will reduce the amount of CO2 and therefore the rate of increase in temperature, if anthro’ CO2 is reduced.
“We know that melting snow in the polar regions will disrupt this current because of the changing salinity of the melting polar waters.”
We do NOT “know” that. Many are concerned because models of questionable reliability have predicted it. However, there is no empirical evidence to support the claim that it is happening.
Speaking of being “simplistic,” your understanding of evolution and extinctions is quite simplistic. Extinctions have always happened at various rates throughout the past. There are very few complex life forms that have survived for hundreds of millions of years. Sometimes evolution provides competition that is better adapted, sometimes there are bolide impacts or Large Igneous Province vulcanism that rapidly changes the environment. However, probably the most important is plate tectonics. During orogenies (mountain building), as the mountains grow in elevation, new environmental conditions are created by the addition of land, decreasing temperatures resulting from the lapse rate, and increased precipitation from orographic uplift. This will correspond to rapid evolution opportunities to fill the newly-created ecological niches. Once the mountain building episode stops, erosion takes over as the dominant change, leading to a reversal of the conditions that encouraged evolution. Humans, as we know them, WILL change and probably become extinct. There is no point in worrying about IF. Rather it is WHEN.
“That said, that human activities are changing the climate climate is now an established fact. There’s zero doubt about the core ideas.”
While I don’t endorse voting to establish facts, I suspect that you have been influenced by the claims that an overwhelming number of climatologists support the paradigm of anthropogenic warming.
Therefore, I would recommend reading the following:
https://wattsupwiththat.com/2025/05/29/𝐓𝐡𝐞-𝟗𝟕-𝐂𝐨𝐧𝐬𝐞𝐧𝐬𝐮𝐬-𝐌𝐲/
“Even if humanity manages to reverse climate change and cool the Earth back down to the 1.5°C target, glaciers around the world are already on a path to centuries of continued melting.”
So what? Nothing about the surface of the Earth is permanent. I’m sure that the villagers in the Alps that were threatened by advancing glaciers during the Maunder Minimum are very happy that the advances stopped. Episodic advances and retreats are what glaciers do, as evidenced by the late-Pleistocene terminal moraines.
“So what? Nothing about the surface of the Earth is permanent.”
By this same logic, we should not try to treat diseases because all of us will age and eventually die anyway.
Your line of reasoning is an attempt to justify irresponsibility. After all, everything in earth changes, and earth will eventually die – so keep pollution going, because eventually it won’t matter.
Speaking of twisting words! We value our lives and that of our loved ones. We don’t want to die prematurely. Those are not rational decisions, but emotional. Humans have the capability to cure many of our diseases, so why shouldn’t we? “The proper study of mankind is Man.” — Pope
Some people may object to glaciers melting for the same reason I object to wind turbines — esthetics. I have a lot more influence over wind turbines than I do glaciers. I have faith that glaciers will come and go whatever anyone does, and continue to do so long after homo sapiens are gone. When one looks into the depths of the Grand Canyon, revealing a mile of rocks — not counting the Great Unconformity with a billion years of rocks missing — it is evident that humans play a small role in the grand scheme of things. However, some think that their alter-ego was Prometheus. Trying to play the role of a god may result in a similar punishment because of the rule of unintended consequences.
You say: “We value our lives and that of our loved ones. We don’t want to die prematurely. Those are not rational decisions, but emotional.”
How do you define ’emotional’ vs. rational? Preserving one’s life seems to be the most rational choice in the world of the living, given that almost all living beings are making that choice. You may not care if a Person X lives or dies, but it is intensely important to Person X. If X = you, then it is very likely rational to you.
If you are crying while you euthanize your pet, that is an indication it is a rational decision overriding your emotions. If you can’t bring yourself to do it despite knowing the pet is in pain, then you are ruled by your emotions. If it is done without emotional involvement, as one might with an invasion of ants in the house, then it is a rational decision.
In the bigger scheme of things, people have short lifespans, and individually, few of us ever do anything that has long-lasting effects on the general population.
To understand a rational decision, see the movie “Hero” starring Jet Li.
1) “Currently, far more humans die from from cold exposure than heat.” A very general statement covering a great many variables involved. I had thought that you didn’t like sweeping statements, especially when they may include non-causative coincidences.
2) Episodic retreats and advances of glaciers don’t really matter as long as the retreats don’t diminish the water supplies of about 3 billion people governed by bloody-minded politicians and religious nutters with heavily armed militaries, additionally with nuclear weapons to drop on each other.
‘
I believe my objection was to using the words “all” or “always.” I don’t have the time or resources to personally determine the global mortality rate resulting from weather. However, a quick search of the internet yields different sources that come to that conclusion, with assigned numbers. Yes, there can be contributing factors other than temperature, but if the coroner determines that someone died as a result of being out in a Winter storm, or that their opinion is that someone died of hyperthermia, the fact still remains that had the temperature not been so extreme, they would not have died. Alarmists have predicted that in the not so far future children won’t know what snow is, and it is generally agreed that the diurnal lows are increasing faster than the high temperatures. I think that should convince one that the future also probably holds fewer deaths from cold weather.
It isn’t just advancing or retreating that is of concern to people who depend on glacial meltwater. The rate has to be considered, and what impacts the rate(s). However, an increase in melting will supply more water — until all the ice is gone. The other side of that coin is that cooling will result in decreased melting and a decrease in the amount of water the population has become accustomed to receiving. That is, ANY significant change, episodic or uniform long-term, has potential consequences. Short-term, cooling has more risk of destabilizing political regimes than warming, up until the time that the last of the ice disappears. Your broad, generalization, “Episodic retreats and advances of glaciers don’t really matter as long as the retreats don’t diminish the water supplies,” is the kind of sweeping statements that I find objectionable. Such events usually happen over several human generations and any reduction in water, for whatever reason, will stress the population if there is little or no surplus water. It only requires one annual crop failure to cause widespread famine.
That big, perpetually exploding ball of hydrogen that wakes us up every morning affects our climate a lot more than anything we do here on Earth. Meet every Green goal, turn the technology clock back 200 years, and one major solar event will make all of it irrelevant.
Earth was much warmer when the Dinos ruled; it happened before, it’ll happen again. Hopefully, without four-foot mosquitos.
Humans didn’t exist when dinosaurs ruled. The earth can easily go back to that regime – but without us.
????
Never mentioned humans and Dinos coexisting.
You brought in Dinos in an article about the current state of the world. Why?
All too frequently their human counterparts get elected or bribe or fight their way to high office
I was comparing then to now, now to yet-to-come. The Dinos simply describe the time difference.
Here’s a thought experiment: imagine what googly eyed creatures will roam this planet 600my from now, after we’re all extinct. That’s what my mosquito comment referenced.
I get the comparing across time. What I don’t get is the relevance of such comparison with respect to this article.
You are right that earth was much warmer earlier, but is that what we (= humans) want? We care about global warming because we think it will kill a lot of us. A warmer earth with no humans isn’t necessarily a good state for us to go towards. Meanwhile, the planet earth won’t care a bit about any of that.
“A warmer earth with no humans isn’t necessarily a good state for us to go towards.”
You are assuming that a warmer Earth WILL result in extinction of humans. Where is the evidence to support that assumption? Humans are adaptable, having occupied even the most extreme climates of the Arctic and Sahara before technology. Look at what the Saudis have accomplished with technology and energy.
Once more Bristol is running about screaming the sky is falling when clearly it isn’t. They are working from models (nothing new there) and assumptions when these in fact have yet to match or predict real world observations. And, once more, we are in an interglacial and loss of glaciers is expected. Are we heating as they claim. NO! Their alleged temperature increases fall within the instrument error of most of the measuring devices. Is this an unusually rapid increase in temperatures? Again, the answer is a profound NO! Apparently Bristol chooses to ignore geologic history and records!