Claim: Today's climate is more sensitive than that of the past

Press Release 12-107

Today’s Climate More Sensitive to Carbon Dioxide Than in Past 12 Million Years

Geologic record shows evolution in Earth’s climate system

Image of the phytoplankton Emiliania huxleyi.

The phytoplankton Emiliania huxleyi offers clues about climate past, present and future.

Credit and Larger Version

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.

==============================================================

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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CO2 here, CO2 there, CO2 everywhere.
“In the late Miocene, there must have been some other way for the world to be warm. ”
Not a word about the times CO2 was 10 times that of today’s.
Again: shoot the arrow, then paint the target around it.

“It’s a surprising finding, given our understanding that climate and carbon dioxide are strongly coupled to each other,” Perhaps the ‘strongly coupled’ part is questionable?

tty

This was only to be expected in the runup to the new IPCC report. The warm climate of the Miocene (and Pliocene) has always been a problem since it shows pretty conclusively that CO2 is not an important climate driver.
This paper (without any real evidence) essentially says “Yes, yes but NOW it depends on CO2, so there”

All this assumes that there is currently such a strong coupling between temperature and CO2 !
While CO2 reportedly exceeds 400 ppm for the first time ever in teh Arctic, temperatures stubornly refuse to follow suit
Game, set and match Mother Earth

DirkH

Complete fantasy, but quite inventive. As the last 15 years have shown climate is exactly not coupled to changes in CO2 levels, so the premise falls flat on its face, and from a scientific point of view it makes no sense to examine their line of argument any further. For aspiring science fiction writers, it might be interesting… but I guess David Brin has depleted the Global Warming science fiction market segment already to a point that he now has to compare climate skeptics to German Landjunkers… probably his next move will be “I’m a celebrity, get me out of here”… so that market seems to be dead as well…

Nylo

Hmmm… how many coauthors? Asking just to use Willis’ formula to calculate the ammount of bullshit in this… study?

Willis Eschenbach

So … the claim of the AGW crowd all this time has been that CO2 is the secret control, the magic temperature dial. They say that when CO2 goes up and down the climate has to, must, is required to follow. There’s no choice, they say, it’s “basic physics”.
Now these scientists are saying that no, the earth can go for millions of years with the temperature paying no attention to the CO2 levels.
Sure wish they’d make up their minds …
w.

mizimi

“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.”
So water vapour isn’t a greenhouse gas?
With higher SST CO2 would be less soluble so I would expect higher atmospheric levels….so where did the CO2 go to?
Could it be warmer is better and both growing season and growth range would increase thereby locking up more CO2 in plant material?

Espen

Good grief, it’s epicycles all over again. Instead of drawing the obvious conclusion that the colder oceans of the ice age we’re in drive co2 and not vice versa, they’re clinging to AGW theory. It’s the oceans capacity for draining the atmosphere of co2 during glaciations that’s the difference to the Miocene! Draining to a level where plants are starving (during the last couple of glaciations co2 was dangerously low). . The 280 ppm level during interglacials is probably an equilibrium level where plants start to starve slightly and thus stop sucking co2 out of the atmosphere.

Rob

This paper is a good thing. Finally it is dawning on some people that CO2 isnt the only driver of climate. Maybe they’ll start to look more closely at todays ocean circulation, e.g. the PDO.

Brian H

“It’s a surprising finding, given our misunderstanding that climate and carbon dioxide are strongly coupled to each other.”
There. That’s better.

Brian H

P.S. Note that “strongly coupled” leaves causality open. Because of the time travel thing, you see.

Christopher Hanley

“Until now, studies of Earth’s climate have documented a strong correlation between global climate [temperature?] and atmospheric carbon dioxide…”
Then this widely available reconstruction must be wrong:
http://www.americanthinker.com/%231%20CO2EarthHistory.gif

3x2

“The results explain the seeming paradox of the warm–but low greenhouse gas–world of the Miocene,”
Paradox – unless the 1.4 billion km3 of liquid water has something to do with the climate.

The real mystery is not why it was warmer in the Miocene, but instead why the Earth cooled during the Pliocene triggering regular glacial cycles. They seem to be proposing that the closing of the Panama isthmus closed down global ocean circulation of heat. In that case, we should challenge current GCM models to reproduce conditions in the Miocene by using the land distribution existing 12 million years ago !

peeke

I would say that natural climate sensitivity would be higher during ice ages than inbetween. Durable changes in avarage temperature would cause changes in ice cover at lower latitude, where any change would have far higher implications for earths albedo.

“In the late Miocene, there must have been some other way for the world to be warm.”
Because physics was just so very *different* in the late Miocene, yanno…

The first paragraph claim that warm periods in the past had high atmospheric concentrations of CO2, the converse being true as well is a lie! The Ordovician had very high atmospheric CO2 concentrations, some research claim 8000ppmv, but the Ordovician had a severe ice age.
After that false claim I left the rest especially since the writers wish us to believe that atmospheric physics changed for no apparent reason.

Perry

Richard (thick as two short planks) Black has been bigging it up at the Bullsh1t Broadcasting Corporation with his report that “team of scientists warns that life on Earth may be on the way to an irreversible “tipping point”. Who are these clowns?
http://www.bbc.co.uk/news/science-environment-18339905
As it will be another 5 billion years before this planet ends up inside the Sun, which is posited to expand to a diameter of 250 million miles; that should be quite long enough for Earth to “recover” to whatever state of pristine verdancy existed before we clever apes stood up and decided to improve our circumstances. In other word, this planet will continue to spin on its axis on its orbit around the Sun, for billions of years after we humans are extinct. Irreversible tipping point? ‘Koff.

Isn’t it strange how Richard Black looks almost the same as Michael Mann who appears also to be very similar to Gavin Schmidt? Are they actually all the same person?

Steve C

“In the late Miocene, there must have been some other way for the world to be warm.”
And why not? There’s “some other way for the world to be warm” now, after all, as anyone who’s tried to correlate CO2 with anything knows.

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’.

richard verney

Christopher Hanley says:
June 7, 2012 at 1:07 am
//////////////////////////////////
Absolutely (although I am always sceptical of proxy recontructions).
The same lack of correlation between CO2 and temperature can be seen in the instrument record from 1850 to date. There is no correlation (sometimes even anti correlation!!) between CO2 and temperature and this is why ‘fudge’ factors such as aerosols need to be added to try and explain why temperatures fell (or plateaued) whilst CO2 levels increased.
When one further considers the ice core records which seem to suggest that CO2 lags temperature and is therefore a response not a driver to temperature change, one would consider that it is time to reconsider the basic premise as to whether as a matter of so called ‘basic’ physics CO2 controls temperature.

gopal panicker

only thing thing they got right was the importance of ocean circulation

Manfred

Sounds to me like stage setting premises covering two key bases: to permit on the one hand, a potential exit from the modeled doctrine of CO2 – temperature coupling, in order to allow a greater latitude of explanation for present day observations, and on the other, to lay ‘supported’ claim to high climate sensitivity in order to provide support for CAGW models.
It would seem, from this current publication under discussion, that ‘multiproxy strategies in paleoceanographic studies’ have come a long way since 2000 (see ref. below). Nevertheless, paleoceanography remains as uncertain a discipline as paleoclimatology. Both disciplines require considerable trust in mulitple proxies of every variable under analysis. Furthermore, the pCO2 conc. error bars (and proxies range) are sufficiently generous to permit a substantial laxity of interpretation, see Fig S1 1. Estimates of atmospheric pCO2 SUPPLEMENTARY INFORMATION Nature 486, 97–100 (07 June 2012). In this graphic representation, I personally struggle with the superimposition of a (gray) straight line across 15Myr (the full range of the x axis) that actually represents a point of ‘known’ value – pre-industrial pCO2 concentration – on a graph about ‘estimation’, and a selected known point in time (no error bars) spanning 15Myr. But then, why get in the way of marketing?
Alkenones and multiproxy strategies in paleoceanographic studies
A. C. Mix et al.
Geochemistry, Geophysics, Geosystems
Review, Volume 1, November 22, 2000 Paper number 2000GC000056, ISSN: 1525-2027
Copyright 2000

beng

****
peeke says:
June 7, 2012 at 1:50 am
I would say that natural climate sensitivity would be higher during ice ages than inbetween. Durable changes in avarage temperature would cause changes in ice cover at lower latitude, where any change would have far higher implications for earths albedo.
****
Of course. As ice/snow extends into lower latitudes, it reflects more sunlight. Ice/snow is rather easily changeable, so now large areas of land (mostly N hemisphere) are subject to these relatively rapid albedo changes where they weren’t before. So the warmers’ whining complaints about sensitivity studies using current conditions not being able to explain ice-age conditions are absurd.

thingadonta

It’s ok for c02 and climate not to be linked in the Miocene when there are no coal power stations around, no tourism in the Maldives to worry about, and no Earth Hour. But what on earth are all these environmental socialists going to do if it isn’t linked in the current time period either?

Robert of Ottawa

This is just more epicycles to cover holes in their theory.

Paul Carter

The complex explanation given by the authors is a candidate for Occam’s Razor. This tells us that the assumed relationship between CO2 and temperature is probably wrong.

CodeTech

“It’s a surprising finding, given our understanding that climate and carbon dioxide are strongly coupled to each other,” LaRiviere says.

I read about this sort of research, and my surprising finding is that people who should know better are so often surprised by findings.
Seriously, his own qualifier, “given our understanding” should probably be the tip-off. Probably a more accurate statement would have been:
“It’s a surprising finding, and one that may indicate that climate and carbon dioxide are not strongly coupled to each other, or at least not in the direction we believed.”
However, I seriously doubt that people who are committed to showing how harmful human achievement is to the planet are capable of recognizing that things aren’t nearly as dire as they believed.

Steve in SC

Absolute BS and they know it.

Richard M

The paper was probably rejected before the wording was changed to praise the appropriate comrades.

So when it was assumed that there was a correlation between paleo climate and CO2, it was proof of CO2 induced global warming, now that CO2 is not correlating with paleoclimate it is proof of CO2 induced global warming, which is proving that global warming is not falsifiable, hence it is not science but dogma.

Neil Jones

“‘Where are the books? The poems? The plays? The goddamn operas?” So asked Bill McKibben, author and environmental campaigner, venting frustration at the cultural failure to address climate change. ” – http://www.telegraph.co.uk/earth/environment/9305638/A-cold-climate-in-the-arts-world.html
Looks like creative writing to me.

So basically, the study found that the climate was insensitive in the past, then the authors jump through hoops to say that this doesn’t contradict the belief that it is very sensitive now.
Excuse me while I suppress laughter and tears.

Chuck Nolan

Willis Eschenbach says:
June 7, 2012 at 12:30 am
So … the claim of the AGW crowd all this time has been that CO2 is the secret control, the magic temperature dial. They say that when CO2 goes up and down the climate has to, must, is required to follow. There’s no choice, they say, it’s “basic physics”.
Now these scientists are saying that no, the earth can go for millions of years with the temperature paying no attention to the CO2 levels.
Sure wish they’d make up their minds …
w.
—————-
Science is hard enough but, climate science is really hard.
It’s not easy hitting a random moving target.

Gail Combs

“It’s a surprising finding, given our understanding that climate and carbon dioxide are strongly coupled to each other,” LaRiviere says.
_______________________________________
Well LaRiviere, the scientific method says when the evidence blows a big hole in your “Understanding” then your “Understanding” is DEAD WRONG and it is time to come up with a different hypothesis. That is how science advances. Clinging to a disproven conjecture is not science.
If you and your buddies do not “Understand” that very critical part of the scientific method, it is time for you to turn in your PhDs and find another job like washing dishes in a diner.

J Crew

As stated many times before and still appropriate: what a waste of time, grants, and research pursuit.
So much time, money and effort spent but so little gain, if any.

Bill Illis

I have a database of CO2 estimates that I continually update as new estimates are made. I think I have all the estimates they used in this paper (added a couple of new ones from the paper).
[There is one series they used that I have excluded, Pagani 2010 which used a new methodology that produces CO2 estimates that are much higher than the ice cores in the period they overlap so we have to assume this methodology is not accurate – I’ve excluded another methodology, paleosols or fossil soils or pedogenic carbonates since this method has been shown to not be reliable since it depends on the time of year or season that the samples were laid down and this varies by large amounts throughout a season so it is not reliable).
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.
http://img338.imageshack.us/img338/5300/co2last25mys.png
CO2 going back 150 million years. If you also have the temperature estimates for the period, one would see even longer “decoupling”.
http://img138.imageshack.us/img138/2633/co2last150mys.png
CO2 going back 750 million years – more decoupling.
http://img213.imageshack.us/img213/7295/co2last750mys.png
The sources for these charts are: Antarctic Epica DomeC ice cores, Pagani 2005, Pagani 2008, Berner GeoCarb III, Royer 2004, Royer 2006, IPCC AR4, Pearson 2000, Pearson 2009, Triparti 2009, Bao 2008, Honisch 2009, Seki 2010, Beerling and Royer 2011, Bartoli 2011.

mfo

The only evidence revealed by this is the use of micro-fossils from deep-sea sediment cores dated to the late Miocene period of Earth’s history, as proxies, to demonstrate that “temperatures across a broad swath of the North Pacific were 9-14 degrees Fahrenheit warmer than today, while atmospheric carbon dioxide concentrations remained low…”
All the rest is “may be”, “must have”, “could have”, “one possibility”. Just speculation which falls down when simply tested with CO2 / temperature comparisons from the last 11,000 years.
http://wattsupwiththat.files.wordpress.com/2012/04/gisp220temperaturesince1070020bp20with20co220from20epica20domec1.gif
http://wattsupwiththat.com/2012/04/11/does-co2-correlate-with-temperature-history-a-look-at-multiple-timescales-in-the-context-of-the-shakun-et-al-paper/

Mark

Espen says:
Good grief, it’s epicycles all over again. Instead of drawing the obvious conclusion that the colder oceans of the ice age we’re in drive co2 and not vice versa, they’re clinging to AGW theory.
When the theory dosn’t account for all of the facts/observations. Then it’s time for a different theory. That is the basis of what we call “science”. Clinging to a theory regardless is more the behaviour of a “nutjob conspiracy theorist”.
It’s the oceans capacity for draining the atmosphere of co2 during glaciations that’s the difference to the Miocene! Draining to a level where plants are starving (during the last couple of glaciations co2 was dangerously low). . The 280 ppm level during interglacials is probably an equilibrium level where plants start to starve slightly and thus stop sucking co2 out of the atmosphere.
So far as many species of plant are concerned (possibly including those which have evolved CAM and C4 metabolic pathways) below 1,000 ppm is deficient. So much so that there are products available specifically to increase the level in commercial greenhouses beyond this. Humans can breath such air indefinitly. Indeed calling carbon dioxide a “greenhouse gas” makes most sense in that it is a good gas to have in a greenhouse.
The obvious conclusion is the ancestors of many living organisms (including us) were alive at a time when Earth had greater than 1,000 ppm co2 in its atmosphere.

Mark

Perry says:
Richard (thick as two short planks) Black has been bigging it up at the Bullsh1t Broadcasting Corporation with his report that “team of scientists warns that life on Earth may be on the way to an irreversible “tipping point”. Who are these clowns?
Wonder if they can explain why such “tipping points” don’t appear to have happened in the past. Thus we are around to consider their possible existance.

P. Solar

The scientists suggest that this deep thermocline resulted in
“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.
This is only a “paradox” is one subscribes to the erroneous idea that CO2 has a major effect on climate.This does not require that the climate has “evolved” or the laws of physics have changed, it simply requires that climate “science” evolves to encompass the critical thinking that we commonly presume is the foundation of all science.
“… a distribution of atmospheric water vapor and clouds that could have maintained the warm global climate.” Yeah, like the climate we know today.
WEIRD.

P. Solar

>>
Indeed calling carbon dioxide a “greenhouse gas” makes most sense in that it is a good gas to have in a greenhouse.
>>
Good line that, I’ll remember that one.

Mark

Willis Eschenbach says:
So … the claim of the AGW crowd all this time has been that CO2 is the secret control, the magic temperature dial. They say that when CO2 goes up and down the climate has to, must, is required to follow. There’s no choice, they say, it’s “basic physics”.
In which case what do physicists have to say about it? Arn’t they more qualified to comment on “basic physics” than climate scientists. (That being the approach the latter often taken when someone outside their group treads on their “turf”.)

Pamela Gray

Logically, based on their contention that oceanic circulation was an overwhelmingly strong driver of temperature trends capable of devouring whatever effects CO2 may have been capable of, they did not answer their own question: What makes ocean circulation such a weak player now? The assumption has been made that today, oceanic circulation is a benchsitter compared to eons ago.
The paper fails to answer how much capacity the previous driver (oceanic circulation) has lost to generate temperature trends. And how did it lose it? And where did it go? In order for such a tiny player (CO2) to overwhelm oceanic circulation as the power house temperature trend driver, the oceans must lose their capacity in LARGE measure. Epic fail.

“The Miocene Problem” is one that has been around for quite a while. Early on, I think there were attempts made to try to disprove the warmth of large intervals of the Miocene. That didn’t work out. The last thing on this (previous to me) was the pore size analysis on some fossil leaves in some attempt to (I think) prove the CO2 was actually higher during the Miocene.
Now, it’s the total disconnect. Great. I suppose the full article has the breakdown of the Miocene, because there’s a pretty good break around the time the Antarctic ice started accumulating. In the Gulf of Mexico depositional history, it’s basically the difference between the Upper Miocene and the Lower Miocene. In other words, even within the Miocene, you had some serious changes going on – I suspect the formation of the Antarctic ice in the middle of the Miocene was much more of an EVENT. A fast chill.
I suspect The Miocene Problem will remain just that.

Steve Keohane

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. …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.
Don’t see the low level of CO2 here: http://i46.tinypic.com/2582sg6.jpg
nor here: http://i55.tinypic.com/11awzg8.jpg
Don’t see climate coupled to CO2 either, ice cores show CO2 coupled to climate, not the other way around.

Doug Proctor

Causation or correlation?
It is causation when it supports one’s beliefs, and correlation, when it does not.

P. Solar

Don’t be so harsh everyone!
What these scientists are doing is trying to publish the proof that CO2 AGW is bullshit but they know that they will loose their jobs if they say so openly. These are soft bellied, scientists who’s idea of a heavy conflict is bravely sending in an unfavourable peer-review to someone’s paper.
They are not mujahideen warriors. They don’t do conflict.
So what they have to do is call it a “paradox” and then present the scientific evidence that shows “other factors” such as water vapour and cloud _may_ also have and impact. They then dress it up with the usual AGW spin in order to get it published and to ensure they get their grants for next year.
Then if 5 or 10 years time when we are all shivering our way through summers of crop failure they can come back and say: “well of course we published proof that CO2 was not the primary driver it was assumed to be as early as 2012 but no one was really ready to listen at that time. You know how slow it is to change the scientific authodoxy…”
One of my favourite examples of this is ER Thomas et al’s “unprecedented warming in Antarctica” claim
GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L20704, doi:10.1029/2009GL040104, 2009
Ice core evidence for significant 100-year regional warming on the Antarctic Peninsula
Abstract
[1] We present a new 150-year, high-resolution, stable isotope record (δ18O) from the Gomez ice core, drilled on the data sparse south western Antarctic Peninsula, revealing a ~2.7°C rise in surface temperatures since the 1950s. The record is highly correlated with satellite-derived temperature reconstructions and instrumental records from Faraday station on the north west coast, thus making it a robust proxy for local and regional temperatures since the 1850s. We conclude that the exceptional 50-year warming, previously only observed in the northern Peninsula, is not just a local phenomena but part of a statistically significant 100-year regional warming trend that began around 1900. A suite of coupled climate models are employed to demonstrate that the 50 and 100 year temperature trends are outside of the expected range of variability from pre-industrial control runs, indicating that the warming is likely the result of external climate forcing.
Received 16 July 2009; revised 4 September 2009; accepted 23 September 2009; published 24 October 2009.
Keywords: ice cores, Antarctic Peninsula, climate change.
Now, buried in the pay-walled article is a graph that shows a circa 120y “principal component” peaking around y2k. It’s not even covered in the text but it’s telling us what most readers here already know. Global warming is over for the foreseeable future.
It’s like the esoteric writings of the middle ages. There is the obvious message for the profane reader and the “hidden knowledge” only visible to the initiated.
Science has become the church that is was intended to replace. It has its monks and high priests and its secret writings. And the surfs must pay their tithes and taxes to pay for the fine robes and pot bellies.