Another paper for the Copenhagen train. This is an estimate according to the abstract. Here’s the abstract and the supplemental information, of course the publicly funded paper is behind the AAAS paywall.
From UCLA News: Last time carbon dioxide levels were this high: 15 million years ago, scientists report
By Stuart Wolpert October 08, 2009 Category: Research
You would have to go back at least 15 million years to find carbon dioxide levels on Earth as high as they are today, a UCLA scientist and colleagues report Oct. 8 in the online edition of the journal Science.
“The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland,” said the paper’s lead author, Aradhna Tripati, a UCLA assistant professor in the department of Earth and space sciences and the department of atmospheric and oceanic sciences.
“Carbon dioxide is a potent greenhouse gas, and geological observations that we now have for the last 20 million years lend strong support to the idea that carbon dioxide is an important agent for driving climate change throughout Earth’s history,” she said.
By analyzing the chemistry of bubbles of ancient air trapped in Antarctic ice, scientists have been able to determine the composition of Earth’s atmosphere going back as far as 800,000 years, and they have developed a good understanding of how carbon dioxide levels have varied in the atmosphere since that time. But there has been little agreement before this study on how to reconstruct carbon dioxide levels prior to 800,000 years ago.
Tripati, before joining UCLA’s faculty, was part of a research team at England’s University of Cambridge that developed a new technique to assess carbon dioxide levels in the much more distant past — by studying the ratio of the chemical element boron to calcium in the shells of ancient single-celled marine algae. Tripati has now used this method to determine the amount of carbon dioxide in Earth’s atmosphere as far back as 20 million years ago.
Aradhna Tripati
“We are able, for the first time, to accurately reproduce the ice-core record for the last 800,000 years — the record of atmospheric C02 based on measurements of carbon dioxide in gas bubbles in ice,” Tripati said. “This suggests that the technique we are using is valid.
“We then applied this technique to study the history of carbon dioxide from 800,000 years ago to 20 million years ago,” she said. “We report evidence for a very close coupling between carbon dioxide levels and climate. When there is evidence for the growth of a large ice sheet on Antarctica or on Greenland or the growth of sea ice in the Arctic Ocean, we see evidence for a dramatic change in carbon dioxide levels over the last 20 million years.
“A slightly shocking finding,” Tripati said, “is that the only time in the last 20 million years that we find evidence for carbon dioxide levels similar to the modern level of 387 parts per million was 15 to 20 million years ago, when the planet was dramatically different.”
Levels of carbon dioxide have varied only between 180 and 300 parts per million over the last 800,000 years — until recent decades, said Tripati, who is also a member of UCLA’s Institute of Geophysics and Planetary Physics. It has been known that modern-day levels of carbon dioxide are unprecedented over the last 800,000 years, but the finding that modern levels have not been reached in the last 15 million years is new.
Prior to the Industrial Revolution of the late 19th and early 20th centuries, the carbon dioxide level was about 280 parts per million, Tripati said. That figure had changed very little over the previous 1,000 years. But since the Industrial Revolution, the carbon dioxide level has been rising and is likely to soar unless action is taken to reverse the trend, Tripati said.
“During the Middle Miocene (the time period approximately 14 to 20 million years ago), carbon dioxide levels were sustained at about 400 parts per million, which is about where we are today,” Tripati said. “Globally, temperatures were 5 to 10 degrees Fahrenheit warmer, a huge amount.”
Tripati’s new chemical technique has an average uncertainty rate of only 14 parts per million.
“We can now have confidence in making statements about how carbon dioxide has varied throughout history,” Tripati said.
In the last 20 million years, key features of the climate record include the sudden appearance of ice on Antarctica about 14 million years ago and a rise in sea level of approximately 75 to 120 feet.
“We have shown that this dramatic rise in sea level is associated with an increase in carbon dioxide levels of about 100 parts per million, a huge change,” Tripati said. “This record is the first evidence that carbon dioxide may be linked with environmental changes, such as changes in the terrestrial ecosystem, distribution of ice, sea level and monsoon intensity.”
Today, the Arctic Ocean is covered with frozen ice all year long, an ice cap that has been there for about 14 million years.
“Prior to that, there was no permanent sea ice cap in the Arctic,” Tripati said.
Some projections show carbon dioxide levels rising as high as 600 or even 900 parts per million in the next century if no action is taken to reduce carbon dioxide, Tripati said. Such levels may have been reached on Earth 50 million years ago or earlier, said Tripati, who is working to push her data back much farther than 20 million years and to study the last 20 million years in detail.
More than 50 million years ago, there were no ice sheets on Earth, and there were expanded deserts in the subtropics, Tripati noted. The planet was radically different.
Co-authors on the Science paper are Christopher Roberts, a Ph.D. student in the department of Earth sciences at the University of Cambridge, and Robert Eagle, a postdoctoral scholar in the division of geological and planetary sciences at the California Institute of Technology.
The research was funded by UCLA’s Division of Physical Sciences and the United Kingdom’s National Environmental Research Council.
Tripati’s research focuses on the development and application of chemical tools to study climate change throughout history. She studies the evolution of climate and seawater chemistry through time.
“I’m interested in understanding how the carbon cycle and climate have been coupled, and why they have been coupled, over a range of time-scales, from hundreds of years to tens of millions of years,” Tripati said.
In addition to being published on the Science Express website, the paper will be published in the print edition of Science at a later date.
UPDATE: Bill Illis add this graph in comments, which brings up the obvious correlation questions.
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William,
Every person on the planet, every single one, could live inside the state of Texas, at a density of less than 40 people per acre. Do the math yourself if you would like. Is 40 people an acre unreasonable? I do not know but a city about 20 minutes from me wants to pass an ordinance saying all new construction must be designed to handle 40 or more people per acre so someone thinks it is fine.
Regarding CO2 lag.. The Real Climate guys, you know, those hard core AWG deniers, kind of sort of admits that CO2 increases do not cause temp increases. Or at least spins it as best as they can.
============================
“http://www.realclimate.org/index.php/archives/2004/12/co2-in-ice-cores/
This is an issue that is often misunderstood in the public sphere and media, so it is worth spending some time to explain it and clarify it. At least three careful ice core studies have shown that CO2 starts to rise about 800 years (600-1000 years) after Antarctic temperature during glacial terminations. These terminations are pronounced warming periods that mark the ends of the ice ages that happen every 100,000 years or so.
“Does this prove that CO2 doesn’t cause global warming? The answer is no.
“The reason has to do with the fact that the warmings take about 5000 years to be complete. The lag is only 800 years. All that the lag shows is that CO2 did not cause the first 800 years of warming, out of the 5000 year trend. The other 4200 years of warming could in fact have been caused by CO2, as far as we can tell from this ice core data.”
============================
Oh, I get it, we know that temp leads CO2 for the first 800 years but after that.. we can’t tell, it could, or it could not, we do not know. Somehow after 800 years of temp leading CO2, the relationship somehow magically changes and what, temp gets tired of leading? Temp wants to be fair and let CO2 lead? How exactly does that work?
Seriously, is the gist of this extract, a claim by A. Tripati that the increase of 100 ppm of CO2 up to around 400 ppm could raise the sea levels by 75 feet, because she figures those were the facts 14 million years ago?
Hell’s teeth, her parents will have paid good money for her education and she comes up with that. They must be tearing their hair out in despair.
” Kum Dollison (14:46:54) ”
They might have been. We don’t have data from that time to make an apples to apples comparison with data what we have now.
We do know with great certainty that the interglacial previous to this one was warmer than this one has been. Much warmer, in fact. Areas that are now tundra were forested during the last interglacial.
I don’t think it has a lot to do with CO2 levels.
Makes sense to me. Temperatures were 5-10 deg F (very scientific we are) higher I’ll take 7.5, and sea levels were 75-120 feet higher I’ll settle for 100; and there was no ice anywhere.
Now just imagine how much land area was inundated by that 100 ft sealevel rise, so we have a considerable increase in the percentage of earth surface that is ocean, and an even bigger increase in the percentage that is open water (no ice), and the earth is 7 1/2 deg F hotter.
Surely that results in massive outgassing from an even bigger amount of ocean than we have now. I could believe that is enough to get the CO2 level up to 387 ppm.
Wonderful work Professor Tripati. So what does that mean for today; since 15 million years ago the earth was quite different from today, including its climate. Just think of how humid it might have been with even more ocean that was hotter.
Glad humans weren’t around to mess up that lovely place back then.
And the LOL award of the thread goes to…
” Fred from Canuckistan . . . (11:08:45) :
Mann & Briffa are both in the Penalty Box for Illegal Use of the Stick, so the coach has sent in Aradhna Tripati to kill off the penalties.”
Or, I don’t know…maybe you have to be Canadian to get that one.
Aaron W
William is correct to say that c02 does have some heating effect – only it is a marginal one, or else an extraneous factor. When its saturation window closes then adding more doesn’t actually increase the temperature – it only shortens the absorbtion distance. That means that if there were 100ppm in the atmosphere, it would have th esame effect as 500ppm – only 500 ppm would just shorten the distance of absorbtion – it wouldn’t increase the temperature beyond 100ppm
Whee. Another study.
The devil is, as always, in the details.
As has been known for many years, what we call temperature is an averaging method of describing molecular vibration. Now vibrating molecules tend to change over time. So we take a specimen which is alleged to be 20,000,000 years old. There is a prodigious gap here. Can we assume that the molecular composition today is the same as the molecular composition 20,000,000 years ago?
Come on. Even solids show evidence of diffusion, and over historic time periods at that.
Boron is a solid. Carbon dioxide is a gas (well, above -100 C). Dare we conclude that boron and carbon dioxide diffuse at the same rates?
I am unable to conceive of a scientific demonstration which would demonstrate that molecular composition is stable over millions of years. How would you do that?
Measure a sample. Put it on the shelf. Come back later (MUCH later). Measure it again.
It may well be the case that the measured concentrations today are as claimed. But the claim that the measured concentrations now are the same as those extant millions of years ago is simply not demonstrable, therefore not in the realm of science.
Instead this is a publication in the interest of grant funding and propaganda.
Steve (14:49:35) :
So, according to RealClimate, we can produce CO2 for 800 years without any impact. I think there will be no coal left by then. But that’s OK, because we will have fusion going by then.
rephrasing: 500ppm wouldn’t increase the temperature beyond what the 1st 100ppm was able to
william (14:14:19) :
“Even McIntyre and McKitrick do not argue with AGW on first principles. It’s because it’s not arguable.”
McIntrye and McKitrick choose not to argue AGW on first principles because the physics of climate is not their forte and they wisely stick to their area of interest, namely the statistical analysis of observed data.
You go on to state “Increased CO2 = higher temperature” implying that skeptics espouse that atmospheric CO2 concentration has zero effect on atmospheric temperature. This is the classic straw man argument. Even us non climatologists are perfectly aware that the trace gas CO2 absorbs infrared radiation in a few narrow bands and that it plays some role in raising atmospheric temperatures above what they would be in the total absence of CO2. But the climate system is dominated by water with CO2 playing some small role that diminishes with increasing concentration. So there is much latitude to argue the quantitative role of CO2 in the climate system and this could still be considered argument from first principles.
Well, that chart up above shows CO2 as being “flat as a pancake” right through the MWP, and, also, the LIA.
Are we accepting that as correct? If we are, all of the skeptics’ interpretations of the reasons for the present rise in CO2 is out the window, right?
“”” Joel Shore (14:02:33) :
anna v says:
The site this appears in does not seem to be a geology site, it is rather a pot pouri site from biology to ….
I will be very surprised if it is peer reviewed. I spent some time on http://www.sciencemag.org/about/ and could find nothing about peer reviewing. Does anybody have a link to the acceptance policy?
Are you seriously telling me that you haven’t heard of Science? It and Nature are probably the two most prestigious interdisciplinary science journals in the world! Many scientists would probably sacrifice their first-born child to get a paper in there. “””
Well Joel; the paper is actually in Sciencexpress; it hasn’t really been published in SCIENCE.
I’d send you a copy of the paper; but since it is likely copyrighted that wouldn’t be kosher; so you’ll have to get it yourself; well I’m sure your institution has access to it.
During the mid-Pliocene warm period (3.3 to 3 mya), CO2 levels were comparable to today; yet the Earth was ~2.5C warmer that it is now.
During the early to mid Oligocene (30 to 27 mya), CO2 ranged from 400ppm to 700ppm; yet the Earth was no warmer that it was during the mid-Pliocene warm period.
If the ice core CO2 data are quantitatively correct, the Sangamon interglacial (130,000 to 115,000 ya) CO2 levels were 80ppm lower than today; yet it was 1C to 2C warmer in the Sangamon than it is now.
If the ice core data are correct… CO2 does not drive climate change.
If the fossil plant stomata data are correct… 380ppm CO2 has been very common in the Cenozoic Era.
The trouble is, just as whether you believe in treenometers, ice cores can give you any finely resolved assessment of CO2 levels to, say within plus or minus a hundred years or two: and for that matter to any useful range of precision either. Personally I doubt it very much.
Kindest Regards
Lashaffer and Smokey
I’m actually a climate skeptic and view the people who post at RC as those who worship on the altar of AGW. I consider myself a “warmer” and my views are consistent with Dr. Roy Spencer who also believes that increased CO2 causes warming. How much warming and understanding clouds and whether they are a +/- feedback is really the issue at this point.
So “perhaps it’s not a BAD thing for the planet” ?
Or are you one of those who are against ALL and any human activity that “perhaps” might make changes to our natural environment? (Fertilizers, water usage, fishing, farming…)
So the last time CO2 levels were this high temps were 5 – 7 degrees higher. This just begs for the next question: If CO2 levels drives temperature, why isn’t it hotter today? Obviously the direct linkage of CO2 levels and temperature doesn’t work. It would seem to me this research should be used by us “deniers” that in fact CO2 levels are pretty much bit players in driving global temperatures.
Perhaps she should be asked to make a study of Carbon dioxide at the end of the Ordovician some 420 million years ago, when we had perhaps more species disappear than at any other time in the earths history- from extreme cold weather. Carbon dioxide levels were estimated to be 7 to 10 times higher than the current level.
Al Gore’s investment company is based here in London, actually
william (14:38:56) :
“Warmer”. Perhaps that is a good term for the middle of the road climate people. We could have these “degrees” of belief: warm, warmer and warmist! A “warm” believes CO2 has some theoretical warming function but the incremental contribution is immeasurably small and inconsequential. A “warmer” believes that the climatic effect of CO2 is measurable but doesn’t believe that we are all going to die. A “warmist” embraces catastrophic global warming, ice caps melting, sea levels engulfing coastal areas etc.
It’s very easy to understand.
At the Phaerozoic Eon scale, geological processes overwhelm the secular relationship between CO2 and temperature… Then from 1900-1977 and since 1998, local variability has obscured the secular relationship between CO2 and temperature.
😉
william:
Clearly you don’t pay attention to the effects of clouds on the local temperature, or you wouldn’t say that CO2 only has slow effects. When clouds move in in the night, the temperature stops falling immediately. If CO2 is as powerful as you seem to believe, temperatures shouldn’t fall. 100ppm up, temps 10C up – but that hasn’t happened, and won’t.
With all of the data about Earth with 1000ppm CO2 and a max temp avg of 22C, the scare tactics just don’t work. Models aren’t science, they’re models of science. If measurements contradict them, the models must be corrected.
“We estimate the permeation coefficient for CO2 in ice is ∼4 × 10−21 mol m−1 s−1: Pa−1 at -23°C in the top 287 m (corresponding to 2.74 kyr). Smoothing of the CO2 record by diffusion at this depth/age is one or two orders of magnitude smaller than the smoothing in the firn. However, simulations for depths of ∼930-950 m (∼60-70 kyr) indicate that smoothing of the CO2 record by diffusion in deep ice is comparable to smoothing in the firn. Other types of diffusion (e.g. via liquid in ice grain boundaries or veins) may also be important but their influence has not been quantified.”
http://www.ingentaconnect.com/content/igsoc/jog/2008/00000054/00000187/art00012?crawler=true
I see no correlation between estimated CO2 concentrations and estimated temperature in the second graph. There are periods of high temperature and low CO2, so according to this graph CO2 has not been a major driver of temperature in the past.
In Britain girls wear shorter skirts in the winter. As a result of this more children are born the following autumn than at any other time of the year and humans are bad for the planet. The message is clear – mini skirts harm the environment. This UN backed study concludes that women should wear burkas and that a green-Marxist-Islamist ideology can save the planet, which is in line with George Monbiot’s activism and Respect Party.
william (13:47:07) : “It make take decades for increased CO2 levels to build up the inertia (perhaps by warming the oceans) to bump up Global temps by 3-5C. Why do you all expect the earth to respond instantly to that change?”
He may have a point here: perhaps 20th Century global warming was caused by all those 19th Century SUVs. 🙂