Princeton University-led researchers have extracted 2 million-year-old ice cores from Antarctica that provide the first direct observations of Earth’s climate at a time when the furred early ancestors of modern humans still roamed.
Gas bubbles trapped in the cores — which are the oldest yet recovered — contain pristine samples of carbon dioxide, methane and other gases that serve as “snapshots” of prehistoric atmospheric conditions and temperatures, the researchers recently reported in the journal Nature. The cores were collected in the remote Allan Hills of Antarctica.
First author Yuzhen Yan, who received his Ph.D. in geosciences from Princeton in 2019, explained that because ice flows and compresses over time, continual ice cores only extend back to 800,000 years ago. The cores he and his co-authors retrieved are like scenes collected from a very long movie that do not show the whole film, but convey the overall plot.
“You don’t get a sense of how things changed continually, but you get an idea of big changes over time,” said Yan, whose graduate research on ice cores supported by a 2016 Walbridge Fund Graduate Award for Environmental Research from the Princeton Environmental Institute (PEI) was a basis for the current work.
Gas bubbles trapped in the cores contain pristine samples of carbon dioxide, methane and other gases that serve as “snapshots” of the ancient climate. Because ice flows and compresses over time, the cores the researchers retrieved are like scenes collected from a very long movie that do not show the whole film, but convey the overall plot.
The ice cores reported in Nature are the latest to come out of the research group of senior author John Higgins, a Princeton associate professor of geosciences, PEI associated faculty and Yan’s doctoral co-adviser. A previous team led by Higgins recovered a 1 million-year-old ice core from the Allan Hills, which was the oldest ice core ever recorded by scientists when it was reported in the journal Proceedings of the National Academy of Sciences in 2015. The cores were dated by measuring isotopes of the gas argon trapped in bubbles in the ice, a technique developed by co-author Michael Bender, Princeton professor of geosciences, emeritus, and PEI associated faculty.“The ability to measure atmospheric composition directly is one of the biggest advantages of ice cores,” Yan said. “That’s why people spend years and years in the most isolated places getting them.”
In the latest publication, the researchers use data from the ice cores to answer long-held questions about how our current glacial cycle emerged. Up until roughly 1.2 million years ago, Earth’s ice ages consisted of thinner, smaller glaciers that came and went every 40,000 years on average.
Then, after what is known as the Mid-Pleistocene Transition, there emerged our current world characterized by colder and longer glacial cycles of 100,000 years. The two periods are known as the 40k and 100k world, respectively.
The researchers collected the 2 million-year-old ice cores in the remote Allan Hills, where high winds help create the environmental conditions that draw ancient ice toward the surface. They found that although a long-term decline in atmospheric carbon dioxide did not directly lead to today’s colder glacial cycle, temperature and global ice volume nonetheless tracked carbon dioxide closely.
Photos by Sean Mackay, Boston University
Some existing theories have stated that the 100k world — which includes the last ice age that ended 11,700 years ago — came about because of a long-term decline in atmospheric carbon dioxide, Yan said. But the researchers found that this was not the case — average carbon dioxide was relatively steady through the 40k and 100k worlds. While the lowest temperatures and carbon dioxide levels of the 40k world were greater than the low points of the 100k world, the highest levels of both ages were similar.“It could be the case that after the Mid-Pleistocene Transition, something occurred that lowered global glacial temperatures and atmospheric carbon dioxide values,” Yan said. “This is the first time we have direct access to these greenhouse gas measurements. The ice core also opens up an array of new measurement possibilities that can give us insights into the 40k world when glacial cycles were very different from what we have today.”
Although a long-term decline in average atmospheric carbon dioxide may not have directly led to the 100k world, the researchers nonetheless observed a correlation between carbon dioxide and global temperature, Bender said.
“To say that carbon dioxide is not a factor would be completely wrong,” Bender said. “During the 40,000- and 100,0000-year glacial-interglacial cycles, temperature and global ice volume tracks carbon dioxide rather closely. Carbon dioxide changes are required to get from the cooler glacial temperatures to the warmer interglacial temperatures.”
The newly reported cores are the latest to come out of the research group of senior author John Higgins, Princeton associate professor of geosciences. A previous team led by Higgins recovered a 1 million-year-old ice core from the Allan Hills, which was the oldest ever recorded when it was reported in 2015.
Photos by Sean Mackay, Boston University
The amount of carbon dioxide now in the atmosphere tops 400 parts-per-million (ppm), which is nearly 100 ppm higher than the highest levels of the 40k world, Yan said.“We’re seeing carbon dioxide levels not seen in 2 million years,” Yan said. “While our data suggest that long-term carbon dioxide decline was not the decisive factor in the Mid-Pleistocene Transition, it does not mean that carbon dioxide does not have the capability to bring about global-scale changes.
“We’re in a different situation now — carbon dioxide is the major player in our current world,” he said. “If we want to look into the geologic past for an analogy of what’s going on in our world today, we need to go beyond 2 million years to find it.”
The paper, “Two-million-year-old snapshots of atmospheric gases from Antarctic ice,” was published Oct. 30 in the journal Nature.
Contacts and sources:
Morgan Kelly Princeton University
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The article has careful wording including: “During the 40,000- and 100,0000-year glacial-interglacial cycles, temperature and global ice volume tracks carbon dioxide rather closely. Carbon dioxide changes are required to get from the cooler glacial temperatures to the warmer interglacial temperatures.” Cause is usually followed by effect. The implication here is that temperature follows carbon dioxide and not the other way round. In the unlikely event that this is true we need to ask when the transition occurs. Every other ice core analysed shows that temperature moves first and carbon dioxide level changes follow with often a considerable delay.
The other important factor here is the assumption of a closed system in which the atmospheric gases trapped remain in the same proportions as they were in the ancient times shown by the time proxy. Zbigniew Jaworouski has shown that there are about 20 mechanisms that ensure that this is not so. It is therefore wise to regard ice core measurements as qualitative rather than quantitative.
I agree with both Peter and Jerry, the untampered-with evidence says the temperature moves first, and CO2 follows it 800 years later. While the article is interesting, I cannot agree with the author’s conclusion.
The 100K and 40K Milankovitch cycles are not acknowledged as contributors or possible drivers to glaciation cycles in this article let alone a multitude of other potential contributing phenomena.
Since when did scientists devolve into having only one eye with an apparent scale blurring that one eyed vision?
I read a recent comment referencing multiple hypothesis. Acknowledging the probable “sum of the parts” is a first step towards competence, credibility, and knowledge. Dealing with something in isolation is, ummm, arh, well, isolated to the point of potential irrelevance.
Degenerating into not standing on the shoulders of giants but belligerent denial of that which is strongly supported by commonly accepted observation, research, and correlation is the realm of headless chickens and chasing that allusive goose.
“the researchers use data from the ice cores to answer long-held questions about how our current glacial cycle emerged.” That is a patently untrue statement.
Maybe the article writer missed something! Princeton University? Geez!
Congratulations on researching where to find and acquiring an old chunk of ice. Well done.
I read this item with considerable interest. All the right information, carefully presented, then it took a decidedly wrong track (sic). After stating that the CO2 tracked the ice volume and temperature suddenly CO2 was the leader and Ice the thing tracking.
And I wanted to ask if the core showed any evidence of Large Ice sheets in the Southern Hemisphere.
‘One swallow does not a summer make’.
It is always interesting to read comments by any and all (including myself) excepting specialists in the science under discussion – who might offer at least a dismissive or supportive if not explanatory word. Missing here, for example, is something by “Javier,” the very learned author of a 240+ recent paper on Dr. Curry’s Climate Etc., titled “Nature Unbound: Earth’s Cyclical Climate.”
One theme developed in Javier’s work, as I remember, very convincingly refuted the argument for 40,000 year and 100,000 year cycles. I do not precisely recall his reasoning nor do I feel qualified to join in by passing it along secondhand. I will, however, second the criticism of other contributors here who question the validity of studies so enriched with confirmation bias. We used to call it “Presbyterian research,” pre-ordained in heaven.
“Carbon Dioxide is the major player in our current world.”
Complete BS.
This manages to ignore all previous honest science.
CO2 is a minor trace gas with zero to negligible climate/warming effect, but absolutely huge ecological importance: it’s plant food, the basis of Earth’s food chain.
I highly recommend geology Prof. Ian Plimer’s great book: Heaven And Earth Global Warming: The Missing Science. 500+ pages, 2,000+ ref’s to peer-reviewed papers etc., & well indexed.
This is a major work of scholarship, with chapters on History, The Sun, Earth, Ice, Water, Air & more.
Plimer is completely dismissive of both CO2 as a climate driver & of the UN IPCC as a scientific body. And he is correct. Any attempt to demonise CO2 must be seen now for what it is: an attack on this planet’s food chain & industry, as CO2 is a byproduct of industry. It’s an attack on mankind’s survival, & should be debunked & derided as such.
JD.
incorporated for charitable purposes. Head Office: 27 Old Gloucester Street, London WC1N 3AX.
Peter F Gill
| #
The article has careful wording including: “During the 40,000- and 100,0000-year glacial-interglacial cycles, temperature and global ice volume tracks carbon dioxide rather closely. Carbon dioxide changes are required to get from the cooler glacial temperatures to the warmer interglacial temperatures.” Cause is usually followed by effect. The implication here is that temperature follows carbon dioxide and not the other way round. In the unlikely event that this is true we need to ask when the transition occurs. Every other ice core analysed shows that temperature moves first and carbon dioxide level changes follow with often a considerable delay.
The other important factor here is the assumption of a closed system in which the atmospheric gases trapped remain in the same proportions as they were in the ancient times shown by the time proxy. Zbigniew Jaworouski has shown that there are about 20 mechanisms that ensure that this is not so. It is therefore wise to regard ice core measurements as qualitative rather than quantitative.
Reply
Jerry
| #
“We’re in a different situation now — carbon dioxide is the major player in our current world,”
There is no experimental evidence that quantifies co2 atmospheric sensitivity to support that claim.
https://notrickszone.com/50-papers-low-sensitivity/
Reply
Andy Rowlands
| #
I agree with both Peter and Jerry, the untampered-with evidence says the temperature moves first, and CO2 follows it 800 years later. While the article is interesting, I cannot agree with the author’s conclusion.
Reply
Matt Holl
| #
The 100K and 40K Milankovitch cycles are not acknowledged as contributors or possible drivers to glaciation cycles in this article let alone a multitude of other potential contributing phenomena.
Since when did scientists devolve into having only one eye with an apparent scale blurring that one eyed vision?
I read a recent comment referencing multiple hypothesis. Acknowledging the probable “sum of the parts” is a first step towards competence, credibility, and knowledge. Dealing with something in isolation is, ummm, arh, well, isolated to the point of potential irrelevance.
Degenerating into not standing on the shoulders of giants but belligerent denial of that which is strongly supported by commonly accepted observation, research, and correlation is the realm of headless chickens and chasing that allusive goose.
“the researchers use data from the ice cores to answer long-held questions about how our current glacial cycle emerged.” That is a patently untrue statement.
Maybe the article writer missed something! Princeton University? Geez!
Congratulations on researching where to find and acquiring an old chunk of ice. Well done.
Reply
Michael Clarke
| #
I read this item with considerable interest. All the right information, carefully presented, then it took a decidedly wrong track (sic). After stating that the CO2 tracked the ice volume and temperature suddenly CO2 was the leader and Ice the thing tracking.
And I wanted to ask if the core showed any evidence of Large Ice sheets in the Southern Hemisphere.
‘One swallow does not a summer make’.
Reply
Tom Anderson
| #
It is always interesting to read comments by any and all (including myself) excepting specialists in the science under discussion – who might offer at least a dismissive or supportive if not explanatory word. Missing here, for example, is something by “Javier,” the very learned author of a 240+ recent paper on Dr. Curry’s Climate Etc., titled “Nature Unbound: Earth’s Cyclical Climate.”
One theme developed in Javier’s work, as I remember, very convincingly refuted the argument for 40,000 year and 100,000 year cycles. I do not precisely recall his reasoning nor do I feel qualified to join in by passing it along secondhand. I will, however, second the criticism of other contributors here who question the validity of studies so enriched with confirmation bias. We used to call it “Presbyterian research,” pre-ordained in heaven.
Reply
John Doran
| #
“Carbon Dioxide is the major player in our current world.”
Complete BS.
This manages to ignore all previous honest science.
CO2 is a minor trace gas with zero to negligible climate/warming effect, but absolutely huge ecological importance: it’s plant food, the basis of Earth’s food chain.
I highly recommend geology Prof. Ian Plimer’s great book: Heaven And Earth Global Warming: The Missing Science. 500+ pages, 2,000+ ref’s to peer-reviewed papers etc., & well indexed.
This is a major work of scholarship, with chapters on History, The Sun, Earth, Ice, Water, Air & more.
Plimer is completely dismissive of both CO2 as a climate driver & of the UN IPCC as a scientific body. And he is correct. Any attempt to demonise CO2 must be seen now for what it is: an attack on this planet’s food chain & industry, as CO2 is a byproduct of industry. It’s an attack on mankind’s survival, & should be debunked & derided as such.
JD.
Reply