Ancient global warming: but which came first, the temperature or the CO2?
From the National Oceanography Centre, Southampton (UK)
Variations in atmosphere carbon dioxide around 40 million years ago were tightly coupled to changes in global temperature, according to new findings published in the journal Science. The study was led by scientists at Utrecht University, working with colleagues at the NIOZ Royal Netherlands Institute for Sea Research and the University of Southampton.
“Understanding the relationship between the Earth’s climate and atmospheric carbon dioxide in the geological past can provide insight into the extent of future global warming expected to result from carbon dioxide emission caused by the activities of humans,” said Dr Steven Bohaty of the University of Southampton’s School of Ocean and Earth Science (SOES) based at the National Oceanography Centre in Southampton.
It has been known for some time that the long-term warmth of the Eocene (~56 to 34 million years ago) was associated with relatively high atmospheric carbon dioxide levels. However, scientists were previously unable to demonstrate tight-coupling between variations in atmospheric carbon dioxide and shorter-term changes in global climate.
To fill this gap in knowledge, the authors of the new study focused on one of the hottest episodes of Earth’s climate history – the Middle Eocene Climatic Optimum (MECO), which occurred around 40 million years ago.
Algae use photosynthesis to harvest the energy of the sun, converting carbon dioxide and water into the organic molecules required for growth. Different isotopes of carbon are incorporated into these molecules depending on the environmental conditions under which algae grow. Ancient climate can therefore be reconstructed by analysing the carbon isotope ratios of molecules preserved in fossilised algae.
The researchers took this approach to reconstruct variations in carbon dioxide levels across the MECO warming event, using fossilised algae preserved in sediment cores extracted from the seafloor near Tasmania, Australia, by the Ocean Drilling Program. They refined their estimates of carbon dioxide levels using information on the past marine ecosystem derived from studying changes in the abundance of different groups of fossil plankton.
Their analyses indicate that MECO carbon dioxide levels must have at least doubled over a period of around 400,000 years. In conjunction with these findings, analyses using two independent molecular proxies for sea surface temperature show that the climate warmed by between 4 and 6 degrees Celsius over the same period.
“We found a close correspondence between carbon dioxide levels and sea surface temperature over the whole period, suggesting that increased amounts of carbon dioxide in the atmosphere played a major role in global warming during the MECO,” said Bohaty.
The researchers consider it likely that elevated atmospheric carbon dioxide levels during the MECO resulted in increased global temperatures, rather than vice versa, arguing that the increase in carbon dioxide played the lead role.
“The change in carbon dioxide 40 million years ago was too large to have been the result of temperature change and associated feedbacks,” said co-lead author Peter Bijl of Utrecht University. “Such a large change in carbon dioxide certainly provides a plausible explanation for the changes in Earth’s temperature.”
The researchers point out that the large increase in atmospheric carbon dioxide indicated by their analysis would have required a natural carbon source capable of injecting vast amounts of carbon into the atmosphere.
The rapid increase in atmospheric carbon dioxide levels around 40 million years ago approximately coincides with the rise of the Himalayas and may be related to the disappearance of an ocean between India and Asia as a result of plate tectonics – the large scale movements of the Earth’s rocky shell (lithosphere). But, as explained by Professor Paul Pearson of Cardiff University in a perspective article accompanying the Science paper, the hunt is now on to discover the exact cause.
The researchers are Peter Bijl, Alexander Houben, Appy Sluijs, Henk Brinkhuis, Gert-Jan Reichart (Utrecht University), Jaap Sinninghe Damsté and Stefan Schouten (NIOZ Royal Netherlands Institute of Sea Research) and Steven Bohaty (SOES). The research was funded by the Netherlands Organization for Scientific Research Utrecht University and Statoil, and used samples and data provided by the Ocean Drilling Program (ODP).
Publication: Bijl, P. K., Houben, A. J. P., Schouten, S., Bohaty, S. M., Sluijs, A., Reichart, G-J., Sinninghe Damsté, J. S. & Brinkhuis, H. Transient middle Eocene atmospheric CO2 and temperature variations. Science 330, 819 – 8215 (2010).
DOI: 10.1126/science.1193654
http://www.sciencemag.org/cgi/content/full/330/6005/819
Science Perspective:
Pearson, P. N. Increased atmospheric CO2 during the middle Eocene. Science 330, 763-764 (2010). DOI: 10.1126/science.1197894
http://www.sciencemag.org/cgi/content/short/330/6005/763
h/t Dr. Leif Svalgaard
Sort of interesting but!
Why wasn’t it vice versa?
Too large? What about the volcanism associated with tectonics? Forgive me but is it not plausible that the vast amounts of CO2 postulated could have derived from the magma?
This all sounds very much like opportunistic speculation to me. In accordance with accepted scientific method these people should be asked to provide hard evidence for their suggestions, their likelys, and their plausibles. Until then please don’t expect to have this sort of alarmist speculation treated as serious scientific research. Bolding mine.
Will (comment 10):
If two substances with different specific heats are subjected to the same energy input, the one with a lower specific heat will increase temperature more.
CO2 has a specifc heat of 0.844 kJ/kgK. 0.844 kJ of added energy will increase the temperature of 1 kg of CO2 by 1K.
N2 has a specific heat of 1.04 kJ/kgK. 0.844 kJ of added energy will increase the temperature of 1kg of N2 by 0.88K.
Temperatures were even higher during the Cretaceous period and atmospheric CO2 levels were 3000ppmv, probably due to volcanic activity. But the high temperatures have been put down to an acceleration of the plate tectonic system, cause unknown, which resulted in shallower oceans.
Ice core research has shown a lead in temperature over CO2 of 600 to 1000 years for the past 60,000 years. Resolution in measurements 40million years back is very poor and a time of 600 to 1000 years virtually impossible to see.
Did AGW just jump the shark? My bs alarm went of the meter.
Somehow related to my debate with a warmer who defended IPCC’s rejection of other natural factors for the planet’s past climate cycles,
http://funwithgovernment.blogspot.com/2010/11/climate-stupidity-part-4.html
I agree with Uk Sceptic:-
“Understanding the relationship between the Earth’s climate and atmospheric carbon dioxide in the geological past can provide insight into the extent of future global warming expected to result from carbon dioxide emission caused by the activities of humans,” If that ain’t a preloaded statement I don’t know what is! Surely there would have been so called mass extinction events, but according to dinosaur theory that was 65 million years ago, but then again according to others the asteroid only polished them off as their climate & landscape were a changin anyway, I know it for a fact, I saw that documentary about it all lasting an hour & a half, now what was it called again, oh yes I remember, “The Flintstones”! Who really knows, they’re all theories & most are possible, but not necessarily likley, except CO2 theory & especially the manmade stuff! Also why can’t these guys just do the simple thing & say a 5°C rise +- 1°C. Did they use a “model” to test their pest theory? I do hope not. I do have a real problem when someone models something & get the answer they expected, time to look for the glaring errors I think.
Any cooling under that ash cloud yet?
http://www.wunderground.com/hurricane/2010/merapi_vaac.png
http://www.bom.gov.au/jsp/awap/temp/index.jsp?colour=colour&time=latest&step=0&map=maxanom&period=daily&area=nat
http://weather.unisys.com/surface/sst_anom.html
So where did the CO2 go? Back into coal. Wasn’t this an explosion of life at this time, I mean we are here today are we not so was the rise that bad?
40 million years ago, India collides with Asia, rerouting of major sea-currents, still no landbridge between North and South America. Large parts of Europe, Asia, Africa and South America where still covered by shallow seas, i gues there you have it.
RE: The Gray Monk says:
“Either that, or we have to accept that volcanic action plays a larger part in CO2 emmissions than the AGW folk want to admit.”
Volcanoes have played a very large role in changing CO2 concentrations in the past. Read a climate science textbook that looks at past climate to see; you’re looking for the carbonate-silicate cycle.
Doubling CO2 over 400,000 years is something that volcanoes could, in principle, do. Causing a 40% increase in 150 years isn’t something they aren’t doing today. We know that, because we know that the amount of CO2 in the atmosphere is going up more slowly than humans are putting it in. We’re pumping out about 30 billion tons/year, and the amount in the atmosphere is going up ~15 billion tons/year.
CO2 from volcanoes is around 0.15 billion tons/year (USGS).
So to believe CO2 is coming from volcanoes, you have to do some severe intellectual acrobatics and assume modern day science is horrendously wrong when it considers things like conservation of energy…
So why is there a relationship between earthquakes on the East Pacific Rise and El Nino if volcanoes don’t control the climate?
Will: as well as the mistake that Red has pointed out, you must also consider that CO2 is in a mixture where it interacts pretty regularly with the other particles in the air (i.e. many times a second).
This means that if its temperature rises above the ambient, then it will transfer heat to the other molecules quickly to try and re-establish equilibrium.
The actual, weighted change in specific heat capacity of the atmosphere is miniscule. From 0.00028% to 0.00038% CO2 would be a miniscule change in heat capacity anyway.
However, even that is not too relevant! What is important is the _flux_ of heat in and out. The Earth will tend towards equilibrium and the only significant way it can exchange energy with space is radiation. Given a certain heat input, the only way it can reach a new equilibrium is to radiate, and the total radiation is a function of temperature but not heat capacity.
A lower heat capacity simply means you will obtain equilibrium more quickly. If your theory was correct, then the upper ocean would always be much cooler than the atmosphere, because it has a higher heat capacity. This isn’t true.
The website you posted is pseudoscientific rubbish. It completely misunderstands the greenhouse effect, invents a broken ‘logic’ for how it thinks the greenhouse effect works and then confuses itself in trying to take apart this imaginary hypothesis. The author should read something beyond an introductory planetary physics textbook to see where they’ve gone wrong – for example, consider the crazy idea that absorption probability can take values OTHER than 0 or 1. Wild, I know!
They’ve given the answer but ignored it:
“We found a close correspondence between carbon dioxide levels and sea surface temperature over the whole period”
Sea surface temperatures rise due to solar variability, orbital changes, cloud quantity and albedo variations, volcanic activity, internal ocean cycles or whatever.
Warm sea surfaces absorb less CO2 than cold sea surfaces whilst the biosphere carries on its merry way so CO2 accumulates in the air.
So sea surface temperature changes must even then have preceded the change in CO2 quantities just as throughout the entire subsequent ice core record.
This is just a cynical attempt to deal with that inconvenient ice core record. If they can suggest that it was different with CO2 acting as a forcing agent at any time in the past they think that will help them to say that the current human contribution to CO2 can operate as an unnatural forcing agent notwithstanding that the natural way of things is temperature first and CO2 later.
It’s the same strategy they used to try and explain away the cooling of the stratosphere right through the late 20th century warming spell. The stratosphere is ‘supposed’ to warm up when the sun is more active but it simply did not so the cooling stratosphere was assumed to be a consequence of human CO2 and CFCs upsetting the natural order.
I think they are soon going to find out that the stratosphere cools naturally when the sun is more active and warms naturally when the sun is less active despite the well known uv effects on stratospheric ozone.
Do they know what the initial concentrations or CO2 were or just a relative comparison of before and after?
As I understand it the introduction of CO2 to the atmosphere could have a big effect on the temperature, but only if there was very little to start with.
Further increases in the amount of CO2 have rapidly diminishing effects ….
Page 8 here..
http://jonova.s3.amazonaws.com/sh1/the_skeptics_handbook_2-3_lq.pdf
Nial.
Funny how when you start a study to prove something, such as CO2 heating the earth, you can fit the flimsy data to the answer you where looking for. The main problem I have with this study though is they are assuming the only reason that temps went up was because of CO2 only, The path of science has been long and hard but it has now arrived at the point of finding questions to the answers you want.
Einstien would be ashamed.
I’m also amazed that these scientists can tell us what clouds and storms where doing 65 million years ago but ask ’em about next week and they’ll not be able to give you an answer.
Ulric Lyons says:
November 11, 2010 at 3:09 am
Any cooling under that ash cloud yet?
People may recall the recent catastrophic failure of one of the four Rolls Royce Trent engines on a Qantas Airbus a380 flying out of Singapore bound for Sydney. Had this occurred whilst the Mt Merapi ash clouds were located where indicated in your http://www.underground link no doubt this event would now have whole extra layer of speculation as to the cause.
Sorry I have added 25 million years to there study.
One wonders if the actual physical impact of continents smashing into each other with enough force to create mountain ranges might have a bit of a heating effect. I mean the heat caused by all that friction around this particulary active period had to go somewhere, did it not? In this case it did not produce much volcanic activity as no subduction occurred in the Himalayas. Interestingly some folk believe the formation of the Himalayas caused the last ice age and had a role in decreasing CO2 levels.
I believe that CO2 concentration is just one of a number of factors that affect the climate. I do not think we can reliably draw inferences on the past if we have yet to develop accepted theories that explain why our atmosphere is structured the way it is, how it radiates convected heat to outer space and why the well-known prehistoric climate changes have occurred. That may not be possible as long as the CO2 concentration is widely assumed, as a matter of faith, to be the primary climate driver.
As presented here, this project has the appearance of a ‘fishing expedition’ for evidence to associate high concentrations of CO2 in the atmosphere with high temperatures in the past.
And during the Ordovician Ice Age, when CO2 levels were twelve times what they are today…
As has been said the crucial evidence in this paper is the rise in sea surface temperatures. There has been other research that shows that there is a clear link between sea surface temperature and solar activity. As we know the oceans are a key source of CO2 atmospheric emissions.
It is entirely plausible that an increase in solar activity 40 million years ago would result in warmer seas resulting in an increase in CO2. The Vostok data supports that hypothesis.
If they are correct then why did we not get the expected runaway greenhouse warming? Why did the Earth not become like Venus? The Arctic was warm with palm trees and crocs so what about the feedback that kept warming those regions without end? Was it the Azolla event that saved us? A comet impact? Did they consider to look at methane?
http://www.ncbi.nlm.nih.gov/pubmed/11536496
http://linkinghub.elsevier.com/retrieve/pii/s0012821x03001882
http://dx.doi.org/10.1007%2Fs00374-002-0452-x
http://www.springerlink.com/index/04QV1MVMLBVCFRFP.pdf
http://geology.rutgers.edu:16080/kgmpdf/01-Katz.Pocean.pdf
http://www.ucmp.berkeley.edu/tertiary/eoc.html
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V61-48JK2R6-4&_user=10&_coverDate=06%2F15%2F2003&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1536745587&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=0c9d1584bebb90866205344d845278d3&searchtype=a
@ur momisugly Nial , November 11, 2010 at 3:36 am:
You took the words out of my mouth – why did they not give the amount of CO2 at the start of their doubling, and why did they not give the amount at the end of that process of 400,000 years?
It looks like another piece of quite nice science (carbon isotope ratios in fossil algae) being abused for political activism.
Cancun, anybody???
Skeptical Science did a big write up on this. The comments were so smug….
However, I had recently done an article up about CO2 levels and the solubility of water.
Clearly changing temperatures are more than enough to cause significant changes in atmospheric CO2 levels. When that is taken into account with the simple fact that CO2 levels lag at the END of an interglacial and it is clear that CO2 does not cause anything.
CO2 was a reasonable proxy for temperature, but I will agree that it is no longer a valid proxy.
John Kehr
The Inconvenient Skeptic
“Shevva says:
November 11, 2010 at 3:56 am
Sorry I have added 25 million years to their study.”
It’s OK. In climate science, this sort of “slip” (Meaning bad data, errors in processing data and even losing original data) is par for the course. There will be an inquiry , where you supply the data you will be tested by, and they will exonerate you for any wrong-doing.