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.
==============================================================
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.
PDF files
- Supplementary Information (291K) This file contains Supplementary Text, Supplementary References and Supplementary Figure 1.
Excel files
- Supplementary Data (688K) This file contains Supplementary Data used in Figure 1.
“tty says:
June 7, 2012 at 12:21 am
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”
Yes.
ONLY Human CO2 emissions are a Climate Forcing and bad. CO2 emissions from Natural sources don’t count. Sounds Like a page out of Animal Farm. 🙂
Neo says: @ur momisugly June 7, 2012 at 8:38 am
…..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 ?
___________________________________
Very simple. It is a real easy “Follow the Money”
So an ADM contribution of over “..$3 million in unregulated “soft money” to Republican and Democratic national party committees during the past 10 years..” netted “..earnings of $1.9 billion for the year ended June 30, 2010, up $246 million over the year ended June 2009…”
Senator Richard J. Durbin, along with Congresswoman Rosa DeLauro have been dedicated to shoving a “Food Safety? Modernization” bill through Congress for the last ten or so years too. The law, passed in 2010 is designed to wipe out small family farms through massive red tape and fines.
Bill Illis says:
June 7, 2012 at 1:05 pm
Gail Combs says:
June 7, 2012 at 12:23 pm
————————-
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….
________________________________
I have no doubt the CO2 levels were low but not as low as the Ice Core data would put them. C3 plants include wheat, rice, daisies, petunias, roses, fruit trees, and conifers.
In the green house examples I linked to above, humidity, moisture and temperature would not be a problem for the plants and yet photosynthesis ceases at ~ 200 ppm, or if not cease it slows growth down to the point fruiting is not going to occur. During the glaciations it was also dryer than it is now. So yes I will agree CO2 probably dipped towards 200 ppm and this made the C4 and CAM mutations viable however below 200 ppm? I do not think so because photosynthesis is dependent on the partial pressure of CO2, O2, temperature and solar energy.
Also if CO2 was below 200 ppm then we would see a an abundance of C4 and CAM plants and we do not.
Last, herbivores do not like to eat C4 plants. They prefer C3. SEE: http://www.jstor.org/discover/10.2307/4215348?uid=2129&uid=3739776&uid=2&uid=70&uid=4&uid=3739256&sid=56242551443
Great spin.
A finding that decouples CO2 from temperature 12 million years ago is presented as evidence of stronger coupling today.
I hope they are paying their PR guys and girls well, they deserve it.
It also has to make you wonder about earlier periods such as Hansen’s favorite Cenozoic period 50 million years ago. Was climate sensitivity then the same as now, as 12 million years ago or something completely different. I believe the just so story makes a nice just so story when it comes to the multiple lines of evidence regarding CS, I’m skeptical that it relates in any way to reality.
Gail,
Help me out here. I think you have a really important point, but I thought that C4 plants evolved in the Tertiary in response to declining CO2 levels and their technological advance was to contain Rubisco to prevent its tendency to go oxidative. Bill Illis’s scenario for the Miocene (and the late Eocene for that matter) agrees with my own. A tremendous expansoin of C4 grasslands at the expense of C3 (dare I say K selected?) forests. Why is that not evidence of C4?
When I was a child, beginning my education in science, I was taught that in order to be considered a proper scientist one had to follow the scientific method – develop a hypothesis, determine the logical consequences of the hypothesis, test the hypothesis through experimentation and observation, and then demonstrate whether the experiment and observations support your hypothesis.
What I have seen from these people who consider themselves scientists is the development of a hypothesis, testing the hypothesis through observations of evidence from the past ( a valid assumption considering historical records), reporting that the evidence does not support their hypothesis and then inventing a reason why the evidence does not support their hypothesis. From my understanding, this is not Science.
A true Scientist would have observed that the evidence from the past does not support his hypothesis and amended or discarded his hypothesis. With the historical record showing that there are periods of time in Earth’s past where the concentration of CO2 does not correspond to Global warming, and in certain cases where it lags GW, it is obvious from a scientific point of view that the hypothesis that increased CO2 levels result in GW are completely wrong. Since there are periods where CO2 concentrations actually follow a period of GW, but there is still a strong correlation between rising CO2 levels and GW, the most logical amendment to the hypothesis would be that the increase in CO2 levels is a result of GW, not the cause of it.
I just wonder at the validity of the results published in this paper.
Both nanno- and microfossils suffer from significant changes during the post core cutting process. It has been shown that up to 80% of nannofossils can “disappear” from core material – including DSDP and OPD cores – within 2 weeks of being brought to surface and stored. This is mainly due to the breakdown of pyrite in the sediment which forms sulfuric acid, in turn generating gypsum from the carbonate of the nannofossil placoliths.
This effect has been documented in a peer reviewed paper by Self-Trail and Seefelt (2005), Core storage even for the DSDP (forerunner of the ODP) was a nightmare with molds and bacteria generating biofilms a wide range of organic acids.
Up to the present day there is no effective way to acheive accurate analysis of drilled sedimentary material, especially quantitative analysis, other than by the use of slides that have been prepared immediately following the sample’s arrival at surface, at wellsite.
As the samples in this study were collected and stored over a period of 12 years from 1990-2002, and they were probably sourced from the ODP core stores after laying there for some years, my opinion is that the derived inferences from the results are virtually invalid.
Of course, the results cannot factor in the natural selective loss of nannofossils in their post-mortem descent from the photic zone to the sea bed, which is probably in the form of concentrations in invertebrate faeces after having passed through their guts!
J.M. Self-Trail, E.L. Seefelt, 2005 Rapid dissolution of calcareous nannofossils: a case study from freshly cored sediments of the south-eastern Atlantic Coastal Plain. Journal of Nannofossil Research 27, 2, 149-158.
Michael Tremblay says:
When I was a child, beginning my education in science, I was taught that in order to be considered a proper scientist one had to follow the scientific method – develop a hypothesis, determine the logical consequences of the hypothesis, test the hypothesis through experimentation and observation, and then demonstrate whether the experiment and observations support your hypothesis.
I recall being taught something similar. Including that a conclusion that the hypothesis is wrong is perfectly valid.
What I have seen from these people who consider themselves scientists is the development of a hypothesis, testing the hypothesis through observations of evidence from the past ( a valid assumption considering historical records), reporting that the evidence does not support their hypothesis and then inventing a reason why the evidence does not support their hypothesis. From my understanding, this is not Science.
In other situations people who cling to theories which are inconsistent with the known facts tend to be called “nutters”.
A true Scientist would have observed that the evidence from the past does not support his hypothesis and amended or discarded his hypothesis.
Discarding is a radical form of “amendment” 🙂
With the historical record showing that there are periods of time in Earth’s past where the concentration of CO2 does not correspond to Global warming, and in certain cases where it lags GW, it is obvious from a scientific point of view that the hypothesis that increased CO2 levels result in GW are completely wrong. Since there are periods where CO2 concentrations actually follow a period of GW, but there is still a strong correlation between rising CO2 levels and GW, the most logical amendment to the hypothesis would be that the increase in CO2 levels is a result of GW, not the cause of it.
But an obviously incomplete theory. Since it dosn’t account for where no link can be found between temperature and CO2 level. Which appears to have been the case for most of Earth’s existence. With CO2 level changes following temperature changes only happening recently.
****
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.
****
I tend to agree w/what I’ve studied. A comprehensive paper I read yrs ago showed that the climate really didn’t cool much until ~1 million yrs after the Isthmus closed. That’s alot of ocean deep-water cycles (hundreds) for a major effect to show up. Even before that, the isthmus area was already quite shallow & deep water transfer had been cut off — only shallow surface water was moving thru. Not saying that it didn’t have an effect, just that I’m skeptical that it was the major factor. OTOH, the opening of the S American — Antarctic connection most certainly had a huge effect on Antarctica’s climate.
beng,
Interestingly Drakes Passage seems to have remained open since the Paleocene. There remains a strange tongue of ocean floor between them as testimony.
Gymnosperm:
It is very easy to conclude that since C4 plants are more efficient at photosynthesis than C3’s, falling CO2 levels was the adaptive force at work.
I don’t go along with that view. Instead, I see aridity as being the main driver.
C4 plants concentrate CO2 in their tissues (C3 plants can’t do this) and then process it .
This allows them to close their stomata after absorbing sufficient CO2 and thus reduce the amount of water needed to a minimum.
In addition, work in 2010 indicates that C4 plants were around some 14 million years earlier than previously thought which places them before the Miocene and into the Oligocene.(http://www.sciencedaily.com/releases/2010/11/101115142007.htm)
This however is still within the time frame that CO2 levels began falling from around 500ppm.
(Note also that some diatoms use C4 synthesis, indicating that this process may be very much older than we had thought.)
Given that adaptation to the environment is a prime driver of evolution, one would expect to see plants from sub-tropical margins adapt in some way to lower water availability in order to expand into drier areas. And even within sub-tropics it is possible to have very dry microclimates, so again, one would expect to see plants adapting to those conditions. The C4 pathway allows for better use of scarcer water resources.
The genus Flaveria ( family Asteraceae/Compositae – Sunflower family) ) has C3, C4 and intermediates within it, and is often used to show the development from C3 to C4 synthesis. Recently, fossillised remains of what is believed to be the progenitor of the Sunflowers have been found in Argentina, dated to around 45 million years ago, but as yet there is no evidence of C4 synthesis that long ago. Asteraceae are the largest family of plants we know of, and are distributed all over the globe, in a very wide range of habitat.
The Drake Passage opened 34.6 Mya, then closed again 27 Mya and reopened again about 13 Mya. There are a number of small plate cratons in the Passage that have been jostled around and alternatively opened, then closed the Passage to mid-depth ocean circulation (it needs to be at least 300 metres deep to get a good current going). These timelines coincide with the glacial advances and retreats in Antarctica.
http://img25.imageshack.us/img25/8785/drakepassagerestricted.jpg
Paper on the ocean current configuration prior to Australia fully separating from Antarctica and the Drake Passage opening. The Ocean Gyres kept Antarctica warm enough in the summers so that most of the snow melted. But once the Antarctic Circumpolar Current started up at 34.6 Mya, within 50,000 years, Antarctica fully glaciated over including ice shelves into the oceans. (Note that it takes some time for a rift valley separation to spread out and deepen enough for mid-depth ocean circulation to start up – as much as 10 million years).
http://www.es.ucsc.edu/~jzachos/pubs/Bijl_etal_09.pdf
Just found another paper ( paywalled) from Germany that proposes the disconnect is due to a combination of tectonic plate movement and greater vegetation cover……
“Energy balance estimates suggest that a reduction in the planetary albedo and a positive water vapor feedback in a warmer atmosphere are the dominating mechanisms to explain the temperature increase. Each of these factors contributes about one half to the global temperature rise of ∼3 K. Our results suggest that a much warmer climate during the Late Miocene can be reconciled with CO2 concentrations similar to preindustrial values”
http://www.agu.org/pubs/crossref/2011/2011GL048873.shtml
Pay your money and take your pick.
“””””……
Comments
Claim: Today’s climate is more sensitive than that of the past
Posted on June 7, 2012by Anthony Watts …..”””””
Well of course it is; nowadays, a 0.09 deg Temperature change is an earth shattering event; but millions of years ago almost nobody noticed such an insignificantr change.
The stupid! It burns!
Reblogged this on gottadobetterthanthis and commented:
As a Nature article, I assume it is paywalled, and I’ll not pay. As Willis says, “There has to be a better way to do science.” But how do they account for their assertions on the basins being different and the circulations being so significantly different? According to Dr. Scotese, this is the way the earth looked 14 Mya: http://www.scotese.com/miocene.htm . The only difference I can see is substantially higher sea level. I notice the caption for the global map indicates it would have been about the same as today starting about 20 Mya. I notice he stipulates “Antarctica was covered by ice and the northern continents were cooling rapidly.” I assume rapid means a half-dozen degrees C over about 15 million years.
How can LaRiviere et al justify claims of such magnitude over such minute differences? It seems silly at best. Primary global circulation has always been considered key to an ice-free earth. Obviously that is impossible, even with the straights (where we now have canals) somewhat open. Of course, my understanding of premodern continental configuration and circumglobal ocean circulation can be flawed and outdated, and the base theory may be wrong, but they are asserting that the ocean was different with no apparent means whereby it might have been. Dr. Scotese suggests sea level and relative land area (and especially ice) are important factors in long-term climate change. I suppose, but the effect cannot be dominant, or we would have never gotten this cold in the first place. http://www.scotese.com/moreinfo15.htm (I suppose I should allow that something may have changed to start the cooling and increasing land and ice keep causing cooling, but then why did we stop? Why have we only gotten this cold? Our current ice age is already over 2 million years running. Why have we stalled at 285 K? Why didn’t we go down to 283 K as we did many millions of years ago? Why didn’t we go even colder? Whatever it is, it sure seems a stretch to attribute significance to CO2!
Read this article for more details:
“Today’s Climate More Sensitive to Carbon Dioxide Than in Past 12 Million Years”
http://www.sciencedaily.com/releases/2012/06/120606164930.htm
especially the last eleven paragraphs.
Here is a picture of the current seafloor isochrons @ur momisugly Drakes Passage. It shows the transform faults where South America and Antarctica slid past a tongue of ocean floor. The 30 ma isochron disapears in all directions (indicating closure?).
This is one of the wierdest pieces of ocean floor on the planet. Even with magnetostratiographic (Apparent Polar Wander) help, it seems speculative to assert that we really know what went on here.
http://geosciencebigpicture.files.wordpress.com/2012/06/drakes-passage.png