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
So they don’t know what the rise in co2 was caused by, but they know enough about its cause to say it wasn’t caused by the initial increase in temperature?
I’ll grant it to these scientists, they can indulge in some pretty neat doublethink when they need to.
C02 does not in of itself create Energy (heat or otherwise).
The only energy we get from burning fossil fuels is the solar energy stored in them.
Gravity causes the sun to undergo thermonuclear reaction and generate the energy.
Once it is used, it escapes, as Earth wants to shed the excess back into space in order to be in equilibrium.
Earth does not have the mass to hold it’s breath (received solar energy) as long as the massive Sun does, though life itself has conspired to store it chemically…. for our benefit.
Some folks just can’t resist kicking a gift horse in the mouth. Ingrates.
Isn’t it obvious? The dinosaurs must have had an advanced civilisation (Post their 65 million year ago supposed demise) that was pumping CO2 into the atmosphere!
Either that, or we have to accept that volcanic action plays a larger part in CO2 emmissions than the AGW folk want to admit.
Pardon my ignorance, but is it possible that the increased incidence of CO2 was the result of the inferred temperature change?
And so, personal opinion is elevated to scientific fact.
I don’t see how this can work. Eocene Earth is Ice free. This means it is hotter because the Earth’s albedo is much lower.
There is no way it is possible to prove that extra CO2 in an already hot earth causes 4-6C of warming.
OK this is my take:
From my press release: Scientists find a close correspondence between the temperature and frequency of people wearing short sleeved cloth, suggesting that wearing short sleeves plays a major role in seasonal warming during the spring-summer period,” said expert. The researchers consider it likely that the occurrence of people wearing t-shirts during the late spring resulted in increased seasonal temperatures, rather than vice versa, arguing that the increase in t-shirt sales played the lead role.
So they are looking for evidence to support their preconceived theory of global warming? Whatever happened to impartial science?
Blast paywall.
“We found a close correspondence between carbon dioxide levels and sea surface temperature over the whole period”
but which came first?
The specific heat capacity of CO2 is lower than O2 and N2.
http://www.engineeringtoolbox.com/spesific-heat-capacity-gases-d_159.html
Therefore increasing CO2 in the atmosphere must actually have a cooling effect.
http://www.spinonthat.com/CO2_files/The_Diurnal_Bulge_and_the_Fallacies_of_the_Greenhouse_Effect.html
Meaningless and does not bear the interpretation put on it. It is no surprise that CO2 levels and temperature were closely coupled but with inadequate temporal resolution who is to say which is cause and which is effect. And at a time of great geological upheavals too.
Kindest Regards.
If we take the simple explanation that ratios of certain isotopes used in climate reconstruction are fractionated through physical mechanisms such as evaporation from sea; if then we see studies reaching back 40 million years; can we not ask why the repetition of processes has not homogenised isotopes to such an extent that it is invalid to assume uniformitarianism?
There are some doubts about the thermometer readings from this year. There is reason to believe that historical thermometer readings are being subtly adjusted all the time. Proxy records for the last thousand or so years are highly confusing and some are quite dodgy. But we know what the temperature in relation to CO2 was 40 million years ago. We know that there wasn’t some other explanation for an apparent correlation other than CO2 theory. Who could have a problem with that?
In a system with liquid water and gases like CO2 there will always be a strong coupling of temperature and gas-concentration above the watersurface. That’s basic physical chemistry with the causation temperature first then CO2-concentration. On the other hand huge amounts of CO2 could have been produced during the colliding phase of India and Asia by enhanced volcanic activity. This would create an amount of additional CO2 temporarily outside equilibrium with water and the rocks it has come from. Equilibrium with water is a quick process, rocks need a lot of time until they are washed to sea producing buffers for CO2. So keep on drilling guys and be careful with time and causation.
In terms of the ‘ancient climate’ (presumably meaning in geological time), what we have now is Extreme Global Cooling (EGC):
http://www.americanthinker.com/%231%20CO2EarthHistory.gif
It´s disapointing… They so sure to point out CO2, watching their graph, im not so too see a cause-effect relationship in that way… But it’s curious the earth had over 4000 ppm of CO 2 and we are still alive…
They used algae and plankton. Sea life. Did they account for the change in PH balance of the oceans from the extra CO2 in the air? And I thought that these lifeforms were in mortal peril from current CO2 levels?
……….
“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.” So CO2 levels “at least doubled over 400,000 years and temperatures rose between 4 and 6 C. CO2 has gone up from 280 to 390ppm over the last 100 years leading to a 0.7C or so increase in global temperatures so the AGW argument goes. It would seem that 4-6C is a bit of an exaggeration using the same logic. 400,000 years to double CO2 is not what I would call rapid and could easily be the result of a sequence of natural events. They appear to be starting from the premise that CO2 is the culprit and ending with confirming that as the likely cause.
Here we go again… Another paper based on speculation, assumptions about proxies and a world that 40 billion years ago was a completely different to what we find today.
“Their analyses indicate that… ”
“…using two independent molecular proxies for sea surface temperature…”
“The researchers consider it <b<likely …”
“Such a large change in carbon dioxide certainly provides a plausible explanation for the changes in Earth’s temperature.”
“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…”
Lots of weasel words but few facts. It is also interesting that on the worst case guess of a rise of even 6C over 400,000 years, this equates to a rise of 0.00015C per decade… How alarming is that! This paper is a FAIL.
The sea floor is lifted over a very large area and turned into mountains. Yet nothing could account for the rise of CO2. OK, how about 2 simple possibles:
1) All that crustal movement lets volcanoes dump a load.
2) If that sea floor had methane clathrate (as we find all over the world now) there would be one heck of a load of outgassing when it was lifted and dried… then oxidized.
I think they need to learn to never say never…
4-6 degrees celsius from a doubling or tripling over 400,000 years.
What were the levels of CO2 at that time period?
OMG here we go again. The co2 must have caused the increase in temperature because an increase in temperature would not have resulted in the increase in co2 that we observe.Could the co2 and temperature have increased at the same time for different reasons?The argument that we keep hearing here is that temperature has a small effect on co2 over time but this also true about the effect of increased co2 on temperature despite what we are told by the IPCC today.
I’m fascinated. “The change in carbon dioxide 40 million years ago was too large to have been the result of temperature change and associated feedbacks,” How do they know? We don’t even know now the causative connection between atmospheric temperatures and CO2 levels, let alone the magnitude and sign of feedbacks, and I’d bet good money there were different feedbacks operating then.
Until I see better than this I’ll stick with my hypothesis that rising temperatures release more CO2 from oceans and biomass.
re post by John A says: November 11, 2010 at 12:51 am
personal opinion arrived at from a whoppin’ dose of circular logic…. or gee, which came first? Perhaps instead of circular logic resulting in that personal opinion, it was personal bias resulting in the rationalization of circular logic. Either way, its clear CO2 did it, because nothing else could explain the magnitude of the result. /sarc
While I am no scientist, I can read and understand English and as I see it, Jurai V sums up their ‘science’ very neatly (and with some humour). My interpretation of this paper is; we don’t understand causality but PLEASE keep that grant income rolling in