From Purdue University , another “just in time for Durban” press release. When you see phrases like “the mother of all tipping points” and you know this is overhyped control knob science.
Drop in carbon dioxide levels led to polar ice sheet, study finds
WEST LAFAYETTE, Ind. – A drop in carbon dioxide appears to be the driving force that led to the Antarctic ice sheet’s formation, according to a recent study led by scientists at Yale and Purdue universities of molecules from ancient algae found in deep-sea core samples.
The key role of the greenhouse gas in one of the biggest climate events in Earth’s history supports carbon dioxide’s importance in past climate change and implicates it as a significant force in present and future climate.
The team pinpointed a threshold for low levels of carbon dioxide below which an ice sheet forms in the South Pole, but how much the greenhouse gas must increase before the ice sheet melts – which is the relevant question for the future – remains a mystery.
Matthew Huber, a professor of earth and atmospheric sciences at Purdue, said roughly a 40 percent decrease in carbon dioxide occurred prior to and during the rapid formation of a mile-thick ice sheet over the Antarctic approximately 34 million years ago.
A paper detailing the results was published Thursday (Dec. 1) in the journal Science.
“The evidence falls in line with what we would expect if carbon dioxide is the main dial that governs global climate; if we crank it up or down there are dramatic changes,” Huber said. “We went from a warm world without ice to a cooler world with an ice sheet overnight, in geologic terms, because of fluctuations in carbon dioxide levels.”
For 100 million years prior to the cooling, which occurred at the end of the Eocene epoch, Earth was warm and wet. Mammals and even reptiles and amphibians inhabited the North and South poles, which then had subtropical climates. Then, over a span of about 100,000 years, temperatures fell dramatically, many species of animals became extinct, ice covered Antarctica and sea levels fell as the Oligocene epoch began.
Mark Pagani, the Yale geochemist who led the study, said polar ice sheets and sea ice exert a strong control on modern climate, influencing the global circulation of warm and cold air masses, precipitation patterns and wind strengths, and regulating global and regional temperature variability.
“The onset of Antarctic ice is the mother of all climate ‘tipping points,'” he said. “Recognizing the primary role carbon dioxide change played in altering global climate is a fundamentally important observation.”
There has been much scientific discussion about this sudden cooling, but until now there has not been much evidence and solid data to tell what happened, Huber said.
The team found the tipping point in atmospheric carbon dioxide levels for cooling that initiates ice sheet formation is about 600 parts per million. Prior to the levels dropping this low, it was too warm for the ice sheet to form. At the Earth’s current level of around 390 parts per million, the environment is such that an ice sheet remains, but carbon dioxide levels and temperatures are increasing. The world will likely reach levels between 550 and 1,000 parts per million by 2100. Melting an ice sheet is a different process than its initiation, and it is not known what level would cause the ice sheet to melt away completely, Huber said.
“The system is not linear and there may be a different threshold for melting the ice sheet, but if we continue on our current path of warming we will eventually reach that tipping point,” he said. “Of course after we cross that threshold it will still take many thousands of years to melt an ice sheet.”
What drove the rise and fall in carbon dioxide levels during the Eocene and Oligocene is not known.
The team studied geochemical remnants of ancient algae from seabed cores collected by drilling in deep-ocean sediments and crusts as part of the National Science Foundation’s Integrated Ocean Drilling program. The biochemical molecules present in algae vary depending on the temperature, nutrients and amount of dissolved carbon dioxide present in the ocean water. These molecules are well preserved even after many millions of years and can be used to reconstruct the key environmental variables at the time, including carbon dioxide levels in the atmosphere, Pagani said.
Samples from two sites in the tropical Atlantic Ocean were the main focus of this study because this area was stable at that point in Earth’s history and had little upwelling, which brings carbon dioxide from the ocean floor to the surface and could skew measurements of atmospheric carbon dioxide, Huber said.
In re-evaluating previous estimates of atmospheric carbon dioxide levels using deep-sea core samples, the team found that continuous data from a stable area of the ocean is necessary for accurate results. Data generated from a mix of sites throughout the world’s oceans caused inaccuracies due to variations in the nutrients present in different locations. This explained conflicting results from earlier papers based on the deep-sea samples that suggested carbon dioxide increased during the formation of the ice sheet, he said.
Constraints on temperature and nutrient concentrations were achieved through modeling of past circulation, temperature and nutrient distributions performed by Huber and Willem Sijp at the University of New South Wales in Australia. The collaboration built on Huber’s previous work using the National Center for Atmospheric Research Community Climate System Model 3, one of the same models used to predict future climates, and used the UVic Earth System Climate Model developed at the University of Victoria, British Columbia.
“The models got it just about right and provided results that matched the information obtained from the core samples,” he said. “This was an important validation of the models. If they are able to produce results that match the past, then we can have more confidence in their ability to predict future scenarios.”
In addition to Huber, Pagani and Sijp, paper co-authors include Zhonghui Liu of the University of Hong Kong, Steven Bohaty of the University of Southampton in England, Jorijntje Henderiks of Uppsala University in Sweden, Srinath Krishnan of Yale, and Robert DeConto of the University of Massachusetts-Amherst.
The National Science Foundation, Natural Environment Research Council, Royal Swedish Academy and Yale Department of Geology funded this work.
In 2004 the team used evidence from deep-sea core samples to challenge the longstanding theory that the ice sheet developed because of a shift from warm to cool ocean currents millions of years ago. The team found that a cold current, not the warm one that had been theorized, was flowing past the Antarctic coast for millions of years before the ice sheet developed.
Huber next plans to investigate the impact of an ice sheet on climate.
“It seems that the polar ice sheet shaped our modern climate, but we don’t have much hard data on the specifics of how,” he said. “It is important to know by how much it cools the planet and how much warmer the planet would get without an ice sheet.”
Writer: Elizabeth K. Gardner, 765-494-2081, ekgardner@purdue.edu
Sources: Matthew Huber, 765-494-9531, huberm@purdue.edu
Mark Pagani, 203-432-6275, mark.pagani@yale.edu
Related website:
Matthew Huber Climate Dynamics Prediction Laboratory: http://web.ics.purdue.edu/~huberm/Matthew_Hubers_Climate_Dynamics_Prediction_Laboratory/CDPL.html
Related news releases:
Antarctic iced over when greenhouse gases – not ocean currents – shifted, study suggests: http://www.purdue.edu/uns/html4ever/2004/041227.Huber.Antarctica.html
Prehistoric global cooling caused by CO2, research finds: http://www.purdue.edu/uns/x/2009a/090226HuberPete.html
Abstract on the research in this release is available at: http://www.purdue.edu/newsroom/research/2011/111201HuberGlaciation.html
For a mother of all tipping points it’s certainly got a long fuse, not quite as dramaitc as “ice free by 2020” is it
eventually reach that tipping point,” he said. “Of course after we cross that threshold it will still take many thousands of years to melt an ice sheet.”
There is a major problem with this study, it assumes that CO2 is the cause and not the effect even though there is no empirical data to support such a claim. The only data showing good correlation between CO2 and temperature comes from Antarctic ice cores and shows that CO2 lags temperature.
Cart before the horse, anyone? It is becoming boring.
A report based on some rubbish model.
As far as we know the atmospheric CO2 levels have varied over large values for billions of years. We do not know the exact levels 100 years ago let alone thousands/millions of years ago. Claims that recent levels have been 280ppmv can be shown to be wrong by looking at the measured levels in the 1800’s in Europe which go up to 490ppmv near Gore’s tipping point. And it was colder then.
Fossil evidence shows that corals, molluscs etc all thrived with high atmospheric CO2 levels. And not a drop of acid sea water in sight!!!!
Sorry guys I have to do this. I have just read this report and my BS filter just went into overdrive. Words and phrases such as “appears”, “mystery”, “tipping point”, “likely”, ” is not known”, ” modelling”, and the mother of them all ” but we don’t have much hard data”. Jeez. I’m done, have a great day .
Even if the correlation does exist, correlation does not explain cause.
Take the financial markets as an example. People trade within their own mindset, for their own motivations, according to their thruth about the markets, …
Within those trades you can find correlations for sure which are higher than can be explained with the random theory, but this doesn’t mean that those correlating measures are the driving force behind the market moves.
And yes, even the moon seems to give a higher correlation to the financial markets, but would it be rational to mark the moon as a ‘direct’ driving force?
. . . continuous data from a stable area of the ocean is necessary for accurate results . . . Constraints on temperature and nutrient concentrations were achieved through modeling of past circulation . . .
“The models got it just about right and provided results that matched the information obtained from the core samples,”
Redundant tautology is redundant.
It’s fascinating that the mechanism producing the sudden drop in atmospheric CO2 is said to be unknown. I personally suspect it was a significant drop in global temperatures and that, mirabile dictu, we have researchers unwilling to consider they’ve got cause and effect wrong way ’round.
correlation or causation? Can they really see the date so specifically in this proxy to know?
Question 1 – what is the main source of CO2 in the atmosphere it produces ~ 96%?
That’s right nature, plants and animals.
Question 2. What happens to that natural source of CO2 when it is buried under a ‘mile high ice sheet’?
That’s right it plants and animals die and stop producing CO2 and what CO2 is produced is ‘buried under a mile high ice sheet’.
So one would expect a drop in CO2 – claiming that it is the cause displays confirmation bias not logic.
“Mammals and even reptiles and amphibians inhabited the North and South poles, which then had subtropical climates.”
Is that correct? Doesn’t the North Pole have a long night when the sun is barely seen. Was the earth’s axial tilt different then?
What drove the rise and fall in carbon dioxide levels during the Eocene and Oligocene is not known.
I think we need to know the answer to this question before we establish policy that may have a detrimental effect on the human race. Besides that I do not think we will be here in 100,000 years to worry about something that may actually be good to the ecosystem.
They tried a new technique for estimating CO2.
At 5 of the 7 drill core sites, the CO2 numbers came in near previous estimates of 1,500 to 3,000 ppm with no discernable drop at the Antarctic glaciation time period until millions of years later.
2 of the 7 sites, however, showed a reduction around the right timeline from 1,000 to 600 ppm. So just using the two contradictory sites, they make a conclusion. Interesting.
Huber next plans to investigate the impact of an ice sheet on climate.
“It seems that the polar ice sheet shaped our modern climate, but we don’t have much hard data on the specifics of how,” he said. “It is important to know by how much it cools the planet and how much warmer the planet would get without an ice sheet.”
And here I thought the change in climate created/melted ice sheets. The Arctic alarmists say the Arctic will be ice free due to climate change. Will somebody make up their mind?
Surprise! Surprise! I thought that it was reasonably accepted that 65 million years ago CO2 in the atmosphere was about 3000 ppm. Antarctica was a warm wet greenhouse. Despite this CO2 the earth cooled for 20million years when South America had drifted far enough from Antarctica to open Drakes Passage and allow the circumpolar current to freeze the Antarctic and change earth climate to a succession of Ice Ages. In the Vostok cores the CO2 changes lag 6-800 years behind the temperature changes -one of the many reasons to query their role in greenhouse effect. Is all this known only to geologists? There is no “Gulf Stream” equivalent in the southern oceans. Mystified, Geoff Broadbent
Let’s look at just one little quote from Matthew Huber:
What is it with this intense fixation on carbon dioxide being such a powerful climate driver? What if it’s not in the driver’s seat but just a passenger? What if it were the oceans that cooled, which cooled the atmosphere while at the same time becoming a huge sink for atmospheric carbon dioxide? Seen in this light, perhaps one day a climate scientist might just say something like this:
Of course, if you drop carbon dioxide as a major climate driver, you’re left with a messy situation … what’s changing the climate with the resultant changes in carbon dioxide levels?
And one day, the scientists will find that the answer to the climate question is: “All of the above.”
“40 percent decrease in carbon dioxide occurred prior to and during the rapid formation of a mile-thick ice sheet over the Antarctic”
As the oceans cooled, they aborbed more CO2, and the atmospheric CO2 decreased. This is just a rehash of Al Gore’s graph showing CO2 and temperatures go up and down together. Scientists checked and found that the warming occurred 800 years before the CO2 went up.
Sounds to me like they use the same methods as young-earth creationists. They start with many assumptions from authority, limit their data to the two sites they like, and then run models, known to not work, to prove their assumptions are correct, and then assert that the results validate the model.
Okay, perhaps it is a bit more involved than that. I hope it is. But there are many unsupported assertions in the write-up, and perhaps the assertions are supportable, but they all sound like they are based on assumptions about how the world was so long ago. I suspect the confidence in each of the assumptions and findings is rather low, yielding very low overall confidence that CO2 played a significant role in the ice sheet formation. The old hypothesis had to do mostly with the location of the land masses. That hypothesis seems reasonable still. This is a water world. It is reasonable to suppose land masses affect the water circulation. It is not obvious that CO2, as such a small trace gas in the low-heat value atmosphere is actually ever significant. I also note that most geoscientists discount global warming alarmism entirely.
Overall, the conclusions are based on a lot of extraordinary claims, and the rule is, extraordinary claims require extraordinary evidences.
A drop in carbon dioxide appears to be the driving force that led to the Antarctic ice sheet’s formation
roughly a 40 percent decrease in carbon dioxide occurred prior to and during the rapid formation of a mile-thick ice sheet over the Antarctic approximately 34 million years ago.
What drove the rise and fall in carbon dioxide levels during the Eocene and Oligocene is not known.
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A drop in temperature caused it…..the drop in temps caused CO2 levels to drop….ice doesn’t form until after that
Of course weathermen wouldn’t know…….grasses evolved and drove CO2 levels down to where they are limiting today…and have remained limiting ever since
So, am I to take it that all the previous research to the effect that changes in CO2 levels have always lagged changes in global climate by almost 1000 years are all wrong?
This is, therefore, a seminal paper.
Sounds like an argument for increasing CO2, not decreasing it. Better warm than cold.
This is supposed to be funny, right?
“Tipping” takes many thousand years? Even if they were right about the role of CO2 here, that doesn’t sound scary. We’d have time to adapt to the much nicer and warmer climate, then.
I see possible correlation, but certainly not proof of causation or anything remotely close, and, most obviously, well timed speculation possibly intended to induce fear driven political agreement . . . . . When they’ve produced evidence that the rise and decline of ice follows the rise and decline of CO2 and nothing else throughout most of Earth’s history then we’ll have evidence that might be worth looking at, though even then both the ice and CO2 levels may be the product of some other as yet unknown changing factor . . .. . . All of which is surely very obvious, even to climate scientists . . .
Now it only remans to explain why the Oligocene Ice Age 1 (Oi-1) in Antarctica mostly melted in he Late Oligocene with no noticeable increase in the CO2 level. The definitive freeze-up only happened about 14 million years ago, when the CO2 level was much the same as now.