Today’s Climate More Sensitive to Carbon Dioxide Than in Past 12 Million Years
Geologic record shows evolution in Earth’s climate system
The phytoplankton Emiliania huxleyi offers clues about climate past, present and future.
Until now, studies of Earth’s climate have documented a strong correlation between global climate and atmospheric carbon dioxide; that is, during warm periods, high concentrations of CO2 persist, while colder times correspond to relatively low levels.
However, in this week’s issue of the journal Nature, paleoclimate researchers reveal that about 12-5 million years ago climate was decoupled from atmospheric carbon dioxide concentrations. New evidence of this comes from deep-sea sediment cores dated to the late Miocene period of Earth’s history.
During that time, temperatures across a broad swath of the North Pacific were 9-14 degrees Fahrenheit warmer than today, while atmospheric carbon dioxide concentrations remained low–near values prior to the Industrial Revolution.
The research shows that, in the last five million years, changes in ocean circulation allowed Earth’s climate to become more closely coupled to changes in carbon dioxide concentrations in the atmosphere.
The findings also demonstrate that the climate of modern times more readily responds to changing carbon dioxide levels than it has during the past 12 million years.
“This work represents an important advance in understanding how Earth’s past climate may be used to predict future climate trends,” says Jamie Allan, program director in the National Science Foundation’s (NSF) Division of Ocean Sciences, which funded the research.
The research team, led by Jonathan LaRiviere and Christina Ravelo of the University of California at Santa Cruz (UCSC), generated the first continuous reconstructions of open-ocean Pacific temperatures during the late Miocene epoch.
It was a time of nearly ice-free conditions in the Northern Hemisphere and warmer-than-modern conditions across the continents.
The research relies on evidence of ancient climate preserved in microscopic plankton skeletons–called microfossils–that long-ago sank to the sea-floor and ultimately were buried beneath it in sediments.
Samples of those sediments were recently brought to the surface in cores drilled into the ocean bottom. The cores were retrieved by marine scientists working aboard the drillship JOIDES Resolution.
The microfossils, the scientists discovered, contain clues to a time when the Earth’s climate system functioned much differently than it does today.
“It’s a surprising finding, given our understanding that climate and carbon dioxide are strongly coupled to each other,” LaRiviere says.
“In the late Miocene, there must have been some other way for the world to be warm. One possibility is that large-scale patterns in ocean circulation, determined by the very different shape of the ocean basins at the time, allowed warm temperatures to persist despite low levels of carbon dioxide.”
The Pacific Ocean in the late Miocene was very warm, and the thermocline, the boundary that separates warmer surface waters from cooler underlying waters, was much deeper than in the present.
The scientists suggest that this deep thermocline resulted in a distribution of atmospheric water vapor and clouds that could have maintained the warm global climate.
“The results explain the seeming paradox of the warm–but low greenhouse gas–world of the Miocene,” says Candace Major, program director in NSF’s Division of Ocean Sciences.
Several major differences in the world’s waterways could have contributed to the deep thermocline and the warm temperatures of the late Miocene.
For example, the Central American Seaway remained open, the Indonesian Seaway was much wider than it is now, and the Bering Strait was closed.
These differences in the boundaries of the world’s largest ocean, the Pacific, would have resulted in very different circulation patterns than those observed today.
By the onset of the Pliocene epoch, about five million years ago, the waterways and continents of the world had shifted into roughly the positions they occupy now.
That also coincides with a drop in average global temperatures, a shoaling of the thermocline, and the appearance of large ice sheets in the Northern Hemisphere–in short, the climate humans have known throughout recorded history.
“This study highlights the importance of ocean circulation in determining climate conditions,” says Ravelo. “It tells us that the Earth’s climate system has evolved, and that climate sensitivity is possibly at an all-time high.”
Other co-authors of the paper are Allison Crimmins of UCSC and the U.S. Environmental Protection Agency; Petra Dekens of UCSC and San Francisco State University; Heather Ford of UCSC; Mitch Lyle of Texas A&M University; and Michael Wara of UCSC and Stanford University.
-NSF-
Media Contacts
Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov
Matthew Wright, Consortium for Ocean Leadership (202) 448-1254 mwright@oceanleadership.org
Related Websites
Integrated Ocean Drilling Program: http://www.iodp.org
JOIDES Resolution: http://joidesresolution.org/
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2012, its budget is $7.0 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives over 50,000 competitive requests for funding, and makes about 11,000 new funding awards. NSF also awards nearly $420 million in professional and service contracts yearly.
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Late Miocene decoupling of oceanic warmth and atmospheric carbon dioxide forcing
Jonathan P. LaRiviere, A. Christina Ravelo, Allison Crimmins, Petra S. Dekens, Heather L. Ford, Mitch Lyle & Michael W. Wara
Nature 486, 97–100 (07 June 2012) doi:10.1038/nature11200
Received 15 November 2011 Accepted 02 May 2012 Published online 06 June 2012
Deep-time palaeoclimate studies are vitally important for developing a complete understanding of climate responses to changes in the atmospheric carbon dioxide concentration (that is, the atmospheric partial pressure of CO2, pco2)1. Although past studies have explored these responses during portions of the Cenozoic era (the most recent 65.5 million years (Myr) of Earth history), comparatively little is known about the climate of the late Miocene (~12–5 Myr ago), an interval with pco2 values of only 200–350 parts per million by volume but nearly ice-free conditions in the Northern Hemisphere2, 3 and warmer-than-modern temperatures on the continents4. Here we present quantitative geochemical sea surface temperature estimates from the Miocene mid-latitude North Pacific Ocean, and show that oceanic warmth persisted throughout the interval of low pco2 ~12–5 Myr ago. We also present new stable isotope measurements from the western equatorial Pacific that, in conjunction with previously published data5, 6, 7, 8, 9, 10, reveal a long-term trend of thermocline shoaling in the equatorial Pacific since ~13 Myr ago. We propose that a relatively deep global thermocline, reductions in low-latitude gradients in sea surface temperature, and cloud and water vapour feedbacks may help to explain the warmth of the late Miocene. Additional shoaling of the thermocline after 5 Myr ago probably explains the stronger coupling between pco2, sea surface temperatures and climate that is characteristic of the more recent Pliocene and Pleistocene epochs11, 12.
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The findings also demonstrate that the climate of modern times more readily responds to changing carbon dioxide levels than it has during the past 12 million years.
Sorry! The Bible does not allow you to change the laws of physics. Improvement needed.
Jeremiah 33
Easy-to-Read Version (ERV)25 The LORD says, “If my agreement with day and night does not continue, and if I had not made the laws for the sky and earth, maybe I would leave those people.”
When did the laws of physics change? Do I get a vote? Does the scientific method mean anything?
Jeez, this reminds me of a guy I once worked with. He claimed that the great pyramids could have easily been built by humans in ancient times because there was less gravity. Seriously, no kidding.
These people are idiots: the greatest Chemical Engineer on history made empirical ,measurements of the emissivity [=absorptivity] of CO2. It levels off at 200ppmV.
The explanation is that the IPCC’s assumption of direct thermalisation is wrong. In reality, it’s indirect and it seems that like the walls of the container at which that indirect thermalisation occurs [Tyndall’s brass tube, the PET bottle] clouds likewise reduce the CO2-specific band energy on re-emission, perhaps more so because they also getter local CO2.
It’s discussed further here:http://tallbloke.wordpress.com/2012/06/07/mdgnn-limits-on-the-co2-greenhouse-effect/#more-6600
Mike Jonas says:
It’s that simple. Eyal Porat’s idea that they “shoot the arrow, then paint the target around it” just doesn’t stand up under this kind of argument. I think it’s called ‘argument by assertion’.
It’s more like SAYING “The arrow hit the target” without even bothering with an arrow or a target…
Isn’t this paper basically just saying “It’s different this time?”
The report’s conclusions center on a measure of the amount of the earth’s land surface that has been transformed by people, from forests and prairies to uses such as cornfields and parking lots. The percentage of transformed land now stands at 43 percent, with the world’s population at seven billion.
Given this, how can any “green” politician think that “bio-fuels” are a viable solution ?
“Until now, studies of Earth’s climate have documented a strong correlation between global climate [temperature?] and atmospheric carbon dioxide…”
Ahhhh…NO!
I don’t think there has been any study of Earth’s historical climate that shows a strong correlation between global atmospheric temperatures and atmospheric CO2 levels. There have been lots of models that show such a correlation because they are programmed to do so, but the actual atmosphere does not. Granted, some studies have done a curve fit of late 20th Century temperature to the late 20th Century rise of CO2, but beyond that time frame, there are no indications of a correlation.
We do not have to go back 5 million years to find a ‘disconnect’ between temperature and CO2. Anytime other than the late 20th Century will do, including the start of the 21st Century.
If the truth sets us free…What do lies do?
“The findings also demonstrate that the climate of modern times more readily responds to changing carbon dioxide levels than it has during the past 12 million years.” Hum, since the physics and chemistry have not changed why should this be even remotely considered. The oceanic circulation patterns are variable the physics and chemistry are not. This is simply more hypothetical modeling bullshit.
Did it not occur to anyone on the Committee of Seven savants who put their names on this paper that their ‘understanding’ was plain wrong?
That’s usually a serious possibility when your experimental results conflict with established ideas.
Apparently the Biblical adage remains true: “There are none so blind as those who will not see.
/Mr Lynn
Every novel scientific discovery has a ‘wow’ factor, wherein one goes “I never would have predicted that!” And this hypothesis seems equally unlikely.
However I will play the mind game with them. The middle Miocene is noted for a dramatic cooling that caused mass extinctions, huge grass lands instead of forests, bordered by continental deserts. The cooler atmosphere simply could not absorb as much moisture as it previously did. Or so paleontologist say. The Earth is still in this phase. So shouldn’t a bit of warming be a good thing? The Earth can then get back to the good old days, when it was less sensitive to the dreaded CO2 and tropical forests were far more extensive. The central deserts were grass lands and Australia a paradise. In other words, I tend to concur with some here who surmise that these scientists are really skeptics demonstrating that atmospheric CO2 is self correcting.
TomB says:
June 7, 2012 at 8:19 am
Jeez, this reminds me of a guy I once worked with. He claimed that the great pyramids could have easily been built by humans in ancient times because there was less gravity. Seriously, no kidding.
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Sure, but since the average Egyptian worker at the time the great pyramid was built was only three inches tall, the low gravity didn’t help all that much. Once you allow folks to make up facts and adjust data to suit their needs, you end up with fourteen dimensional chess, chaos, economics, nutrition … or “climate science”.
I should think that the first response of any thinking entity confronted with this should be — are we sure that the CO2 and temperature proxies being used are any damn good? Apparently that’s not a reasonable question.
As mentioned above, no causal relationship was established. Since the work supports a vast political machine, from the perspective of government, the grant money spent and the time required for the work were not wasted.
This paper is a prime example why not everyone show receive higher education.
I think the significance of the closing of the Isthmus of Panama is overestimated. You can toggle the continents through time in Google Earth and it is clear that not much water (and certainly no deep water) was getting through there even as far back as the Eocene.
There was a better channel through Indonesia so one would expect no “warm pool” there. The Bearing passage was wider but the continental shelves remained in contact preventing deep water escape and the Aleutian Arc (closer to the strait then) would have been a further restriction.
Let’s have a look at the Miocene Earth, 14 million years ago.
http://www.scotese.com/images/014.jpg
No real ice in the Northern Hemisphere (Greenland was still Green but got very cold in the winter and there was probably some Arctic sea ice in the winter). Over the next 11 million years Greenland moved 220 kms to the northwest, (it has been moving at 2 cm/yr for the past 55 million years since splitting away from Europe). This extra 220 kms was just enough so that it became succeptible to the Milankovitch Cycle downturns and it subsequently glaciated over sometime around 3 million years ago.
The Panama Isthmus is still open, the Meditterrean-Tethys link to the Indian Ocean is still open, there is a much stronger East to West equatorial current which may have been able to completely circulate the planet at this time (rather than being directed into the Gulf Stream and Kuroshio Current as it does today). Sea level higher and much of the continents are flooded.
There is almost no savannna or desert at this time. The planet was almost completely forested. At about 8 million years ago, there appears to be a significant change in the climate where rainfall declined substantially and this marks the emergence of deserts and savannna grasslands. C4 grasses pollen is very, very low in the geologic record until 8 million years ago.
Antarctic ice is about one-half of todays level although in the next few million years, it reglaciates again. But at 14 Mya, it is mainly in the interior.
So, the Miocene planet is very, very different than the current one. It certainly has lower Albedo than the current Earth (about 27% versus 30% today) given there is less ice, more forest and more ocean. More sunlight able to warm the Earth so ti is warmer.
Simple enough explanation in my opinion (which also works for just about any other period in Earth History you want to look at). No CO2 changes are required to explain it, just continental configurations and the resulting Albedo.
*Sigh*. You forgot the “/sarc” tag. People will think you’re serious.
Mike Jonas says:
June 7, 2012 at 3:19 am
“We all know that CO2 is the only significant driver of Earth’s climate. Why is it so difficult to formalaccept that fact, simply because for a brief period “about 12-5 million years ago climate was decoupled from atmospheric carbon dioxide concentrations“? The far more important period from 1976 to 1998 demonstrates beyond all possible doubt how CO2 drives the global temperature. Obviously, in something as complex as climate, there will be brief periods when the temperature fluctuates independently of CO2. This period 12.5 million years ago was obviously one of them. The period from 1940 to 1976 was another, as was the last 14 years. But when the current brief fluctuation ends, then the temperature will continue to be driven higher by the high concentrations of CO2.
It’s that simple. Eyal Porat’s idea that they “shoot the arrow, then paint the target around it” just doesn’t stand up under this kind of argument. I think it’s called ‘argument by assertion’.”
Mike,
That is way tooooo funny! You should do stand up comedy, Sir!
Characterizing a 7 million year long late Miocene Period (from 12 million to 5 million years ago) as a “brief period” where CO2 is decoupled from climate effects is epic understatement! Then attempting a direct comparison to the truly brief 22 year long time period between 1976 and 1998 when a weak correlation existed is comedic mastery!!!! Finally, stating that we should focus on the miniscule 22 year time period as the ‘CO2 vs Climate norm’ and reject the decoupled 7 million year long period as the ‘anomoly’ rises to previously unvisited satirical flight levels! I think it should be called ‘argument by abstruse absurdity’ and your picture (as the poster child!) should be shown in the dictionary, next to the term! Well Done, Sir!
Perhaps you should add a ‘sarc’ tag to your posts though….. I find that, if I don’t, sometimes my sarcasm is misinterpreted.
MtK
gymnosperm says:
June 7, 2012 at 10:37 am
I think the significance of the closing of the Isthmus of Panama is overestimated. You can toggle the continents through time in Google Earth and it is clear that not much water (and certainly no deep water) was getting through there even as far back as the Eocene.
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I’m inclined to agree. The shallow passages would be significant for the evolution of shallow water faunas. Reef dwelling fish and invertebrates on the two sides of the isthmus probably wouldn’t diverge much until the passages closed. But I doubt the impact on climate would be great once massive — and especially deep water — exchange through the passage between North and South America was throttled down
Basically then, CO2 causes temperature rises, except during times when it doesn’t. Does that sound a bit lame to the public at large? Then add a dose of scientific jargon, call it “decoupling” and hey presto! we have waived away all that pesky conflicting evidence.
Unfortunately, we have now created a “Jekyll and Hyde” phenomenon. This schizophrenic gas, is supposed to behave perfectly rationally one day, yet subvert the laws of physics on another.
Somehow I think the one’s exhibiting dangerous signs of delusion, are these scientists, not our wonderful gas. Only in the minds of a committed zealot can such nonsense spew forth.
Bill Illis says:
June 7, 2012 at 6:04 am
….So here is all the reliable CO2 estimates going back 25 million years. The authors could have extended the “decoupling” time period back to 25 million years ago. CO2 fell below 280 ppm, for perhaps the very first time, 24 million years ago and it has been there (give or take an ice age lowering it to 185 ppm and some outlier 450 ppms) ever since.
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No those are not “Reliable” CO2 measurements those are the “Blessed by the Team” CO2 measurements.
To put it bluntly if CO2 went as low as 185 ppm we would not be here nor would most other animals or plants.
The atmosphere could never be below 200 ppm and have CO2 uniformly distributed without wiping out C3 plants at a minimum. The stomata data disagree with the Ice core data. ( WUWT discussion ) Dr. Zbigniew Jaworski exposed the lies surrounding the CO2 measurements and so did Beck and Dr. Tim Ball.
Here is real life data, completely divorced from the climate debate, that shows those measurements are a large crock of fertilizer.
And here is a paper that is a real kicker. It of course has the usual nod to CAGW as a get out of Pal-Review Free Card.
Gail Combs says:
June 7, 2012 at 12:23 pm
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In the ice ages, when (and I guess if) CO2 fell to 185 ppm, the broad-leafed C3 vegetation did not do very well. In fact, they died. The forests during this time are the US southeast, the Amazon at one-qaurter the current size and some of the equatorial regions only. The reason is that these areas had enough rainfall so that the C3 plants could have larger stomata and not be succeptible to drying out from envirotranspiration. The rest of the planet, however, is grassland, desert and tundra.
http://stommel.tamu.edu/~baum/paleoveg/veg-adams-big.gif
The obvious explanation is that the laws of physics have changed since the Miocene. Because obviously the radiative physics of CO2 is essential to the earth’s temperature now, but not then. At least no other explanation is conceivable, given that scientists are simply never wrong.
Okay, let me get this straight. The study discovers that CO2 and temp don’t correlate at all if you look back 5 to 12 million years, but somehow this strengthens the argument for causality (and the causality itself) in more recent times.
Could any line of “reasoning” be more completely doofus?
This study proves one thing beyond any shadow of a doubt.
It really is impossible to polish a turd.