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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- Supplementary Data (688K) This file contains Supplementary Data used in Figure 1.
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?
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
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…
Hmmm… how many coauthors? Asking just to use Willis’ formula to calculate the ammount of bullshit in this… study?
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.
“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?
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.
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.
“It’s a surprising finding, given our misunderstanding that climate and carbon dioxide are strongly coupled to each other.”
There. That’s better.
P.S. Note that “strongly coupled” leaves causality open. Because of the time travel thing, you see.
“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
“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 !
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.
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?
“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’.
Christopher Hanley says:
June 7, 2012 at 1:07 am
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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.
only thing thing they got right was the importance of ocean circulation
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