Recent research indicates a significant acceleration in the melting of the Juneau Icefield glaciers in Alaska, with glacier loss rates doubling since 2010 and potentially leading to irreversible declines earlier than predicted. This accelerated melting and increased fragmentation could necessitate revising future projections of glacier retreat and sea level rise.
New research indicates that glaciers in a significant Alaskan icefield are melting faster than anticipated and may reach a point of irreversible decline sooner than previously estimated.
The research, led by scientists at Newcastle University, UK, found that glacier loss on Juneau Icefield, which straddles the boundary between Alaska and British Columbia, Canada, has increased dramatically since 2010.
The team, which also included universities in the UK, USA, and Europe, looked at records going back to 1770 and identified three distinct periods in how icefield volume changed. They saw that glacier volume loss remained fairly consistent from 1770 – 1979 at between 0.65- 1.01 km3 per year, increasing to 3.08-3.72 km3 per year between 1979-2010. Between 2010 and 2020 there was a sharp acceleration when the rate of ice loss doubled, reaching 5.91 km3 per year.
In particular, the research, published in Nature Communications, found that icefield-wide, rates of glacier area shrinkage were five times faster from 2015-2019 relative to 1948-1979.
Escalation in Glacier Shrinkage and Fragmentation
Overall, the total ice loss across the Juneau icefield between 1770-2020 (315.3 ± 237.5 km3) equated to just under a quarter of the original ice volume.
The increased rate of glacier thinning has also been accompanied by increased glacier fragmentation. The team mapped a dramatic increase in disconnections, where the lower parts of a glacier become separated from the upper parts.
Additionally, 100% of glaciers mapped in 2019 have receded relative to their position in 1770, and 108 glaciers have disappeared completely.
Study lead, Dr. Bethan Davies, Senior Lecturer, Newcastle University, said: “It’s incredibly worrying that our research found a rapid acceleration since the early 21st century in the rate of glacier loss across the Juneau icefield. Alaskan icefields — which are predominantly flat, plateau icefields — are particularly vulnerable to accelerated melt as the climate warms since ice loss happens across the whole surface, meaning a much greater area is affected. Additionally, flatter ice caps and icefields cannot retreat to higher elevations and find a new equilibrium. As glacier thinning on the Juneau plateau continues and ice retreats to lower levels and warmer air, the feedback processes this sets in motion is likely to prevent future glacier regrowth, potentially pushing glaciers beyond a tipping point into irreversible recession.”
Alaska contains some of the world’s largest plateau icefields and their melting is a major contributor to current sea level rise. The researchers think the processes they observed at Juneau are likely to affect other, similar icefields elsewhere across Alaska and Canada, as well as Greenland, Norway, and other high-Arctic locations.
Implications for Global Sea Levels
They also say current published projections for the Juneau icefield that suggest ice volume loss will be linear until 2040, accelerating only after 2070, may need to be updated to reflect the processes detailed in this latest study.
Dr. Davies said: “This work has shown that different processes can accelerate melt, which means that current glacier projections may be too small and underestimate glacier melt in the future.”
The team used a combination of historical glacier inventory records, 20th-century archival aerial photographs, and satellite imagery as well as geomorphological mapping conducted during fieldwork in 2022 to piece together a comprehensive picture of changes over the past 250 years.
Dr. Robert McNabb, Lecturer in Remote Sensing, Ulster University, said: “What was really exciting about this research was piecing together thousands of archived aerial photographs to extract elevation, which gave us a really detailed insight into the long-term behavior of the icefield. Putting together this archive of photographs, collected 70 and 50 years ago, was a little like doing the world’s hardest jigsaw puzzle but the quality of the imagery meant we were able to reconstruct the icefield elevation in the pre-satellite era for the first time. Longer term archives like this one are an incredibly valuable resource, as they give us a much better understanding of the thresholds for accelerating change, as we’ve seen on the Juneau Icefield.”
Reference: “Accelerating glacier volume loss on Juneau Icefield driven by hypsometry and melt-accelerating feedbacks” by Bethan Davies, Robert McNabb, Jacob Bendle, Jonathan Carrivick, Jeremy Ely, Tom Holt, Bradley Markle, Christopher McNeil, Lindsey Nicholson and Mauri Pelto, 2 July 2024, Nature Communications.
DOI: 10.1038/s41467-024-49269-y
16 Comments
Nothing is irreversible. If it froze once, it can freeze back again when the time comes. We are NOT gonna become Venus 2.0.
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Straw Man. No one sane is saying global warming will turn Earth into a Venus. But there will be changes on very wide scales.
Nothing except our sun becoming a supernova is an “Irreversible Tipping Point.” We have no control over that. “Irreversible Tipping Point” is a meaningless term. Even extinct species are frequently replaced by functionally and morphologically similar species through what is called convergent evolution.
Continental glaciation has come and gone several times during the Pleistocene, and there have been Ice House and Hot House phases in the past, over which we also have no control.
Using terms such as “Irreversible Tipping Point” is irresponsible fear mongering, not science. If it were science, it would be stated with a probability estimate, its associated uncertainty, and timeline with error bars. At the very least, the probability range for the author’s definition of “likely” should be provided. It is not. Instead, someone who fancies himself to be a scientist resorts to using the vocabulary of a lawyer. I object!
“Nothing except our sun becoming a supernova is an “Irreversible Tipping Point.””
Tell that to the dinosaurs.
BTW, our sun can never go supernova, because only stars at least eight times the mass of our sun have enough mass to go supernova. But our sun will eventually do us in, assuming we stick around long enough. The sun’s energy output increases by 1% every 100 million years. By about 700 million years from now, Earth’s oceans will have boiled away and all life will be extinct. That’s pretty irreversible.
“Even extinct species are frequently replaced by functionally and morphologically similar species through what is called convergent evolution.”
Well, sometimes, but not often. Where are the species that are functionally and morphologically similar to dinosaurs? There are thousands, if not millions, more examples.
“Continental glaciation has come and gone several times during the Pleistocene, and there have been Ice House and Hot House phases in the past, over which we also have no control.”
Very true. But there was no extensive human civilization present during those times. Human civilization is only about 10,000 years old, which corresponds to a period of unusually stable climate. We mess with that at our peril.
As for the term “Irreversible Tipping Point,” in scientific works, it is used in a scientific way. Usually, this term is associated with probability estimate, its associated uncertainty, and a timeline with error bars, at least in the scientific journals. But when journal articles are adapted for general audience magazines or websites, this additional information is often omitted, as most lay people aren’t interested in it. In climate science, at least, all irreversible tipping points are probabilistic, and are acknowledged as such by the scientists involved.
But to return to your initial sentence, there certainly are many irreversible tipping points related to climate, by any reasonable definition of the term. They may or may not ultimately happen, and the time that they do happen is uncertain, but they do exist. For example, if the AMOC collapses, it will have a huge effect on the climate, and there’s no way to reverse that in the foreseeable future. If the Antarctic and Greenland ice sheets melt completely, total sea level rise would be about 65 meters (213 feet), or possibly more. Goodbye, Florida! Worldwide, the homes of hundreds of millions of people would be underwater. Yes, in geological time, the sea levels will eventually drop, but try telling that to the displaced people, who would never live to see it.
When temperatures eventually drop to about where they were in the last century, reconstitution of the glaciers and ice sheets will have begun. Such reconstitution is necessary if sea levels are to drop. For small glaciers, this can take centuries. For the large ice sheets of Greenland and Antarctica, depending on how much they have melted, this process could take hundreds of thousands of years. Considering that human civilization is only about 10,000 years old, from the point of present and near-future humanity, irreversible changes will occur. What will happen 100,000 years from now is impossible to predict, but I think it’s safe to say that the world will be in a very different situation depending on whether or not we get climate change under control.
So if “Irreversible Tipping Point” is defined as “a point at which a change or series of changes occur that cannot be reversed for at least many, many lifetimes” (which is how this phrase appears to be used), then I think it corresponds very well to our reality.
“Usually, this term is associated with probability estimate, its associated uncertainty, and a timeline with error bars, at least in the scientific journals.”
The actual article (DOI: 10.1038/s41467-024-49269-y) in Nature Communications uses the term “tipping point” 5 times. None of the uses has any associated numeric information. I realize it is a sample of 1, but it is a critical sample because it is the object of my criticism, which is a result of personal observations of the use of the term, leading me to have a different opinion than you expressed.
“Tell that to the dinosaurs.”
Many, if not most, biologists consider birds to be dinosaurs. It is obvious that if one is talking about a unique individual, its inevitable death by whatever means is a ‘tipping point’ from which recovery is impossible. That is a trivial use that is so obvious that its use is not warranted — it adds no information about the event. A ‘tipping point’ is a valid term when used with respect to a tree or building falling over. However, my objection is to the broad brush use to events that are cyclical, as climate change and glaciation obviously are.
Using ‘IRREVERSIBLE tipping point’ is first off redundant. Secondly, using the term as a metaphor for events that obviously CAN be reversed, given enough time, is an oxymoron. When a big tree falls over, and smashes to pieces, it is not something that can be undone. There is no caveat about it being reversible in “many, many lifetimes.” It is simply a poor metaphor for reality. Its only value in communication is to scare people into thinking that it is truly a point of no return. You are trying to rationalize a distortion of reality whose purpose is propaganda.
“…, our sun can never go supernova, because …”
You are being a stickler for using a word exactly as defined and commonly used, and objecting to my use of the Supernova ‘metaphor’ for what most likely will be destruction by a Red Giant. Yet, you defend the use of the term “tipping point.” You are logically inconsistent. Beyond that, the argument is a Red Herring. Either you support using precise scientific definitions, or you accept poetic license to describe things. I erred referring to the end of our sun as a “supernova.” Can you bring yourself to admit as much?
“For example, if the AMOC collapses, …”
What is the probability, uncertainty and timeline of the speculation? You have provided an example of the state of climatology where speculation on possible events is preferred over predictions. One of the motivations for science is not just to explain how things happen qualitatively, but to be able to predict quantitatively when and to what effect something will happen. Your speculations are not unlike saying “If an atomic were were to be dropped …,” without specifying the yield of the bomb and when and where it would be detonated. It is not science. It is little more than arm waving.
It is not my place to repeat whole research papers in this comment section. I said “if” because it is not 100% certain that the AMOC will collapse. But a year ago, the probability of its collapse in this century was estimated at 10%; one of the best and most recent estimates now puts that number at 50%. The latest research suggests a shutdown could occur between 2037 and 2064, and that the probability of collapse by 2050 is 59% plus or minus 17%. More statistics are available in the original paper.
For more specific predictions, please see the article “Atlantic Ocean currents could collapse as early as the 2030s, new research suggests.” There you will find statements such as, “In the decades after a collapse, Arctic ice would start creeping south, and after 100 years, would extend all the way down to the southern coast of England.” But also note, “The emphasis in ocean research on the timing of the collapse is a relatively new development.” You can find much more in the original paper, “Probability Estimates of a 21st Century AMOC Collapse.”
So all of these are probabilities, not certainties, but they definitely are not speculation or arm waving. They are backed up by the best science we currently have. If we wait until the science is perfect, it will be too late, and millions will die unnecessarily.
So before calling this all speculation, please do a little research. These papers are easy to find; they are referenced by the many climate stories that appear in all sorts of standard news sources. (We’re not talking social media here.) The information is out there and easily accessible to those who are willing to put in even a little bit of work.
“…, one of the BEST and most recent estimates now puts that number at 50%.”
On what do you base your assessment that it is one of the “best?” It is one of many, none of which have historical evidence to use to validate the estimate.
In other words, “one of the best” estimates of probability (lacking an uncertainty range) is equivalent to the probability of a coin flip coming up tails (or heads). It has no utility in predicting what the next flip will produce, or when it might come up differently if experiencing a ‘run’ of one side.
Anybody can write down numbers. The issue is what those numbers are based on. Climate models are notoriously unreliable, usually running warm. That is a strong suggestion that the models have a defect, commonly an unstated assumption that is wrong.
I would suggest that you are the one who needs to do more than just “a little research.” At issue is whether the “best science we currently have” is adequate for making policy decisions that could have economically devastating consequences. It appears that you have made an assumption that you haven’t really examined.
Earth had quadrillion tons of fossil feul buried, but now is none. Overpopulation has multiplied the emission and pollution process. Climate change & global warming is man made. Our modern emission is popular use of wirelss microwave polluting atmosphere & planet upper surface rapidly. There are numerous other crises in the emergence. Number of human should have been equal to the number of animals today. Humans have devastated the planet already and it’s too late. We can only wait & see.
“Climate change & global warming is man made.”
An assertion for which the support is not in evidence. It is precisely the reason there is controversy. Humans are probably contributing to warming, but the amount and sources are in question. After 40 years there is still not universal agreement on the climate sensitivity to a doubling of CO2.
The support for the anthropogenic cause of climate change is very much in evidence, and in scientific circles is not in doubt. For example, see the paper entitled “Greater than 99% consensus on human caused climate change in the peer-reviewed scientific literature” which appears in the journal Environmental Research Letters. This figure is backed up elsewhere as well. So when you say, “Humans are probably contributing to warming,” you are disagreeing with over 99% of climate scientists, who have spent their careers studying this and who have concluded that essentially all of climate change since the Industrial Revolution has been caused by humans. Do you really think you are smarter than all of these scientists? Please read the paper.
As for the climate sensitivity to a doubling of CO2, yes, there is no universal agreement on a figure, just as there is no universal agreement in many aspects of climate science (or any science, for that matter.) Research continues to be done; there are simply a huge number of variables that need to be taken into account. But the anthropogenic nature of climate change is no longer in doubt.
One of the most impressive aspect of the climate change models is how accurate they have been, even going back to the 1990s and earlier. In 1964, the famed scientist Arthur C. Clarke, who in the 1940s had, to much derision, predicted the development of communication satellite networks, predicted that atmospheric CO2 would reach 400 ppm by 2010, and the effects of climate change would start to be felt by 2013. For a prediction 50 years in the future, he was very close. We reached the 400 ppm level in 2013. Clarke clearly saw climate change as anthropogenic; he said something to the effect that if his prediction came true, we would deserve it. A warning that was not heeded, unfortunately.
“Greater than 99% consensus on human caused climate change in the peer-reviewed scientific literature”
Something that you don’t seem to understand is that science is not determined by voting. Einstein’s theory of relativity was not well received, initially. It triggered a response from 100 physicists lambasting it. Einstein’s appropriate response was, “Why 100 when all it would take would be evidence provided by one to prove me wrong?” Consensus helps to maintain paradigms. However, paradigm shifts in science happen frequently. Those 100 scientists who were defending the paradigm of the day are now considered to have been wrong.
Because you have been dismissive of anyone who is not a degreed climatologist, I will consider Arthur C. Clarke’s remarks to be, at best, anecdotal evidence. I would like to point out that someone who generally has more credibility in climatology than Clark, is Michael Mann. He does not have a degree in climatology; his degrees are in mathematics and geophysics. His background is not all that different from my own.
“Do you really think you are smarter than all of these scientists?”
Not that it is important, but I may be. I qualify for Intertel, which puts me in at least the top 1%. However, even bright people can make mistakes or be misled by their beliefs or other internal conflicts of interest. Therefore, the judgment of a hypothesis should be based on the available facts and their quality, not on the intelligence of the person presenting it or the degrees they have. One of the most serious problems with the hypothesis that anthropogenic CO2 is driving global warming is the lack of short-term correlation and lack of evidence that the long-term correlation isn’t spurious. Anthropogenic CO2, which is fairly constant throughout the year, is only about 4% of the total seasonal CO2 flux and is probably smaller than the Carbon Cycle uncertainty in things like the ocean flux and even the Boreal Winter respiration flux.
You seem to be unduly impressed by credentials rather than facts. That is formally called “Appeal to authority.” There is a famous event in science where the reputation of Lord Kelvin delayed the correct assessment of the age of Earth because no one would openly challenge his calculations. You have much to learn grasshopper.
With regards to the paper “Greater than 99% consensus on human caused climate change in the peer-reviewed scientific literature,” you said:
“Something that you don’t seem to understand is that science is not determined by voting.”
Of course it isn’t; I never claimed it was. As for your example:
“Einstein’s theory of relativity was not well received, initially. It triggered a response from 100 physicists lambasting it.”
This is typical of new theories, especially revolutionary ones. Max Planck famously described this process, which is usually summarized as, “Science progresses one funeral at a time”.
It’s what happens over time that’s important. The solar eclipse of 1919, just four years after Einstein’s publication of General Relativity and fourteen years after the publication of Special Relativity, established widespread scientific support for General Relativity. Even though later analysis of the results from the 1919 solar eclipse showed that they didn’t support GR as was originally thought, all subsequent experiments have verified the predictions of GR, right up through this century’s verification of gravitational waves and the recent verification of the behavior of matter at the event horizon of a black hole. Few scientific theories are backed by as much evidence as SR and GR; the whole GPS system works because it takes into account the effects described in both SR and GR.
For these reasons, SR and GR have the support of more than 99% of physicists, as does quantum mechanics, for the same reasons. The levels of support still fall short of 100%, though, which means that they are essentially equivalent to those of anthropogenic climate change.
It’s the support over time and how that varies that’s important, and not just a single snapshot of the support at a convenient point in time. Climate change first became a subject for serious research around the 1950s, and by the 1970s, Shell Oil and Exxon were able to make rather accurate predictions of climate change that have since come true. (See, for example, the article “Revealed: Exxon made ‘breathtakingly’ accurate climate predictions in 1970s and 80s,” published in The Guardian.) By the 1990s, climate change was beginning to be taken seriously by the broader scientific community. It reached a 97% level of acceptance around 2013, and stands at over 99% today. What scientific theory has followed this level path to acceptance in modern times, only to be proven substantially wrong later? Even Newton’s theories, which were superseded by Einstein’s, are still considered to be substantially correct, and are still used in most common situations.
“Those 100 scientists who were defending the paradigm of the day are now considered to have been wrong.”
Very true. But climate change is not “the paradigm of the day”; it represents a new paradigm, one for which much original research is ongoing, unlike the case of classical mechanics to which you refer.
I asked, “Do you really think you are smarter than all of these scientists?,” and you replied:
“Not that it is important, but I may be. I qualify for Intertel, which puts me in at least the top 1%.”
Well, I had never heard of Intertel, so I checked it out, and sure enough, I too qualify for membership on a number of bases. I am sure that out of the thousands of practicing climate scientists, there are many who qualify as well; it does not seem credible that you and I are smarter than essentially all climate scientists. There are also many types of intelligence, and nothing you have said indicates to me that you know more about climate science than the professionals (or even me).
“Therefore, the judgment of a hypothesis should be based on the available facts and their quality, not on the intelligence of the person presenting it or the degrees they have.”
Of course. I draw my conclusions about climate change mostly from the original research I read, taking into account the quality of the research. The other source of my conclusions is simply watching the evolution of weather patterns, which does not seem possible to explain without acknowledging anthropogenic climate change.
Just a few years ago, articles about climate change appeared in the general media only sporadically. Now I see such stories all over, every day. For example, just today, on CNN’s front page, is the story, “Savannah warns residents of “once-in-a-thousand-year potential rainfall event””.
There have been a lot of “once-in-a-thousand-year” events recently, and their frequency has been increasing. Climate scientists have mathematically and physically sound explanations for this. What fact-based alternative do you have?
“One of the most serious problems with the hypothesis that anthropogenic CO2 is driving global warming is the lack of short-term correlation and lack of evidence that the long-term correlation isn’t spurious.”
I see short-term correlations all the time, and as I have been following the science for decades, I have seen that these correlations are very strong. There is also a huge amount of evidence that the long-term correlation isn’t spurious; without such evidence, there wouldn’t be the near-universal agreement among climate scientists about the validity of anthropogenic climate change.
“Anthropogenic CO2, which is fairly constant throughout the year, is only about 4% of the total seasonal CO2 flux…”
I’m not sure about the 4% figure here; you may very well be correct. But the basic variation you refer to is no secret. You can see it on any reasonably detailed graph of atmospheric concentration of CO2 that covers a multi-year period. But what’s your point? It’s the year-over-year change that’s important. Using average yearly results, atmospheric CO2 has increased from 317 ppm in 1960 to 420 ppm today, an increase of over 32% in 64 years. That’s just 0.44% per year, but the rise is continuing to increase, and the results are disastrous. There is no evidence of any time in history when CO2 levels have risen anywhere near this quickly.
“You seem to be unduly impressed by credentials rather than facts.”
Nothing could be further from the truth. I read the research daily and I judge it on its merits, not by its authors.
“You have much to learn grasshopper.”
And that sounds just plain arrogant. Where is your proof of your assertions? If you’re going to claim that over 99% of climate scientists are wrong and you are right, you’d better have ironclad proof. I don’t see any.