From an Oregon State University Media Release (h/t to Leif Svalgaard)
Long debate ended over cause, demise of ice ages – may also help predict future
)
The above image shows how much the Earth’s orbit can vary in shape.
This process in a slow one, taking roughly 100,000 to cycle.
(Credit: Texas A&M University note: illustration is not to scale)
CORVALLIS, Ore. – A team of researchers says it has largely put to rest a long debate on the underlying mechanism that has caused periodic ice ages on Earth for the past 2.5 million years – they are ultimately linked to slight shifts in solar radiation caused by predictable changes in Earth’s rotation and axis.
In a publication to be released Friday in the journal Science, researchers from Oregon State University and other institutions conclude that the known wobbles in Earth’s rotation caused global ice levels to reach their peak about 26,000 years ago, stabilize for 7,000 years and then begin melting 19,000 years ago, eventually bringing to an end the last ice age.
The melting was first caused by more solar radiation, not changes in carbon dioxide levels or ocean temperatures, as some scientists have suggested in recent years.
“Solar radiation was the trigger that started the ice melting, that’s now pretty certain,” said Peter Clark, a professor of geosciences at OSU. “There were also changes in atmospheric carbon dioxide levels and ocean circulation, but those happened later and amplified a process that had already begun.”
The findings are important, the scientists said, because they will give researchers a more precise understanding of how ice sheets melt in response to radiative forcing mechanisms. And even though the changes that occurred 19,000 years ago were due to increased solar radiation, that amount of heating can be translated into what is expected from current increases in greenhouse gas levels, and help scientists more accurately project how Earth’s existing ice sheets will react in the future.
“We now know with much more certainty how ancient ice sheets responded to solar radiation, and that will be very useful in better understanding what the future holds,” Clark said. “It’s good to get this pinned down.”
The researchers used an analysis of 6,000 dates and locations of ice sheets to define, with a high level of accuracy, when they started to melt. In doing this, they confirmed a theory that was first developed more than 50 years ago that pointed to small but definable changes in Earth’s rotation as the trigger for ice ages.
“We can calculate changes in the Earth’s axis and rotation that go back 50 million years,” Clark said. “These are caused primarily by the gravitational influences of the larger planets, such as Jupiter and Saturn, which pull and tug on the Earth in slightly different ways over periods of thousands of years.”
That, in turn, can change the Earth’s axis – the way it tilts towards the sun – about two degrees over long periods of time, which changes the way sunlight strikes the planet. And those small shifts in solar radiation were all it took to cause multiple ice ages during about the past 2.5 million years on Earth, which reach their extremes every 100,000 years or so.
Sometime around now, scientists say, the Earth should be changing from a long interglacial period that has lasted the past 10,000 years and shifting back towards conditions that will ultimately lead to another ice age – unless some other forces stop or slow it. But these are processes that literally move with glacial slowness, and due to greenhouse gas emissions the Earth has already warmed as much in about the past 200 years as it ordinarily might in several thousand years, Clark said.
“One of the biggest concerns right now is how the Greenland and Antarctic ice sheets will respond to global warming and contribute to sea level rise,” Clark said. “This study will help us better understand that process, and improve the validity of our models.”
The research was done in collaboration with scientists from the Geological Survey of Canada, University of Wisconsin, Stockholm University, Harvard University, the U.S. Geological Survey and University of Ulster. It was supported by the National Science Foundation and other agencies.
UPDATE: Science now has the paper online, which is behind a paywall. The abstract is open though and can be read below:
| Science 7 August 2009:
Vol. 325. no. 5941, pp. 710 – 714 DOI: 10.1126/science.1172873 |
Research Articles
The Last Glacial Maximum
Peter U. Clark,1,* Arthur S. Dyke,2 Jeremy D. Shakun,1 Anders E. Carlson,3 Jorie Clark,1 Barbara Wohlfarth,4 Jerry X. Mitrovica,5 Steven W. Hostetler,6 A. Marshall McCabe7
1 Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
2 Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada.
3 Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA.
4 Department of Geology and Geochemistry, Stockholm University, SE-10691, Stockholm, Sweden.
5 Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.
6 U.S. Geological Survey, Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
7 School of Environmental Science, University of Ulster, Coleraine, County Londonderry, BT52 1SA, UK.
O/T
BBC repeated Sackur’s interview with the Greenpeace director on Hard Talk last night. I don’t remember them repeating these interviews, certainly not within 48 hours!
Sackur’s getting there slowly but he’s obviously not prepared to go the whole hog yet. “Let’s see your proof” would have been a nice line at some stage. The mindset is still: it’s happening; it’s our fault; but you’re OTT in your approach. Time to get one of the real fanatics on this prog and really roast them. Sackur’s probably the one to do it if anyone can.
I have one word, Copenhagen. Regardless of what the Obamsiha, KRudd747 and Brown (That seems too exciting even for him), some sort of “cap and trade agreement” will pass, although Penny W(r)ong is not doing any more than “highlighting” their “paper” on climate change for Pacific nations experiencing “sea level” rises (Which isn’t happening). Think Pacific and techtonics.
There is only one way to fight this, but are we willing to go that far? Too cold outside? Too hot? Footy, Corro, Dead Enders, Bold & Beautiful, or some other shyte TV proggy on? Yeah….
I think, unlike the US, we in Aus, NZ, and the UK, (I am a “resident” of all three countries in one form of another) we all pay our taxes, sorry, we have taxes removed from our pay *at sourse*, so we cannot not pay income tax.
There is only one way to stop this.
OT: This article in the Telegraph is getting a lot of reactions -mostly negative !!!!!
‘Cloud ship’ scheme to deflect the sun’s rays is favorite to cut global warming :
http://www.telegraph.co.uk/earth/environment/globalwarming/5987229/Cloud-ship-scheme-to-deflect-the-suns-rays-is-favourite-to-cut-global-warming.html?state=target#postaco
For this theory to work, there has to be a reason the glaciation ice ages started around 5 million years ago and continue to this day. I wonder, did our solar system suffer an unknown event? or did the earth?
I can’t access all the papers, do the researchers say what phase of the cycle the earth is currently in?
ralph ellis (02:44:11) :
>>Anthony, July and August were originally named Quintilis and Sextilis
>>as the 5th and 6th months of the roman calendar.
I always thought that July and August were the additional months, introduced by Julius Caesar and Augustus Caesar respectively, which is why the later months are all displaced by two.
Month (Latin)
Sept-ember = 7 (septem)
Oct-ober = 8 (octo)
Nov-ember = 9 (novem)
Dec-ember = 10 (decem)
So which are the two extra months?
The original roman calendar was 355 days (12 months) with a rather random system of an intercalary month added on the end, what Julius Caesar did was to increase the length of each month to their present lengths and included a leap day every 4 years in February and do away with the intercalary month.
Nasif Nahle (22:42:30) :
If heat was retained, it would be as potential or kinetic energy and it would stop being heat
Heat is the kinetic energy of the molecules bouncing around or vibrating.
Geoff Sherrington (23:31:10) :
“I think the consensus is that we can do this accurately [enough for this purpose] for some millions of years.”
What makes us think that we can model the earth orbit well enough so we can predict temperature changes caused by geometry changes?
Predicting the orbit and predicting the temperature are different things. The orbit calculations are accurate to millions of years. The VSOP82 theory is thought to be good to one million years, and the improved VSOP87 to much longer. The latter is good to 1 arc second for many thousands of years [future and past], and for millions with lesser accuracy, so good enough to compute the solar insolation.
anna v (21:16:14) :
I would say a small and lagged portion of the warming effect.
Consider:
Water vapor rises immediately according to the heat of the air over the oceans, not according to the temperature of the oceans.
No water vapor will rise according to the temperature of the water.
The sun heats the air immediately,
Only in the stratosphere, the troposphere is predominantly heated by IR from below.
the oceans slowly. CO2 has a 800 to 2000 year lag in response, while the oceans warm and the permafrost melts.
In addition CO2 is less than 10% in contribution to the green house effect of the contribution of H2O.
Wrong again!
I am always amazed how people postulating runaway effects from GH gasses can ignore these simple physical characteristics of H2O and can still look at ice age records and talk of CO2 feed backs at the time. It invalidates for me any worth in their paper.
Likewise concerning your misunderstanding about the way the atmosphere works.
Hi all-
This seems to be the simple truth. We are changing CO2 and other greenhouse gases much, much more rapidly than the climate system has ever dealt with before.
Such long term cycles in solar radiation are largely irrelevant to the debate over AGW, because they happen so slowly compared to our geologically instantaneous increases in CO2.
What matters are increases in CO2 and methane concentrations of one percent per year or more, caused by the burning of fossil fuels.
Some folks insist that CO2 enhances global warming caused by natural catalysts. But every time we place global warming caused by CO2 into a model we get nothin like what we observe. However, if we put ENSO parameters into a model we get what we observe. This means than global warming cannot be started or enhanced by CO2, based on both modeled and empirical data. The only thing that can continue global warming are El Nino’s. And just to be sure, one can look in the past to see if increased CO2 causes increased frequency of El Nino’s. It does not. Nor does increased warming caused by an El Nino cause more El Nino’s. The mechanisms for frequency of El Nino’s is not in the temperature trend. But the mechanism for the temperature trend is in the ENSO.
http://www.dse.ufpb.br/Tarcisio/Artigos/Global%20Temperature%20and%20El%20Nino.pdf
Allan MR MacCrae quotes someone:
I suspect that Leif will have something to say about that.
Not a scientist. Isn’t it possible if I may talk politics, that the left believes it will be cooling soon and that what is driving their push to quickly pass Cap and Trade laws? Their laws force Co2 levels down (if they actually worked), then the Earth cools. See how smart we were? You better not believe those right-wing extremist deniers. We saved your lives and the earth…
Just saying…
Gosh, whats up with that isotope 12 and 13 marker that identifies that the bulk of the CO2 increase is fuel burning and not from natural sources?
A gedanken experiment. You have a sealed big vat of carbonated water and you very slowly heat it. It evolves CO2. These are red CO2 molecules. You now introduce a bunch of blue CO2 molecules. Due to the equilibrium shift the blues predominate in the gas area while the rate of evolution changes some too due to the equilibrium shift.
The equilibrium water to gas is 50 to 1. The fact that the blue CO2 predominates in the gas area is not proof of a significant shift in dynamics of the system. It is at least a proof that the evolution of CO2 is somewhat suppressed due to an equilibrium shift. As you would expect.
Vincent (05:41:23) : wrote,
“Eric,
With regard to Nassif’s question on the temperature sensitivity of carbon dioxide you wrote 3 C with a range of +- 1.5 c.
On its own this is a meaningles answer. Do you mean 3 C for a doubling of Carbon dioxide? If so I can only assume you have included the IPCC assumed feedbacks into this. Have you? If so, what is the sensitivity without feedbacks?”
Assuming everything else remains the same, the answer is around 1C.
Ed (22:48:55),
I had always wondered about the spikes in the temp record during glacials. It will be interesting to see if what you posit works out.
Thanks for the effort!
Nasif Nahle (22:42:30) :
Wrote:
“I don’t question the role of the carbon dioxide on rising a little (almost nothing) the temperature of the atmosphere.
I do question the magnitude of the increase caused by the carbon dioxide and do reject absolutely the argument of taking the carbon dioxide as a black radiator with an emissivity of 50% just because it is not real.
The flux of heat from the surface (land and oceans) to the atmosphere is continuous, day and night, thus, if carbon dioxide had a radiative power of 50% for emissivity and 50% for absorptivity we had been toasted long ago.”
This is a straw man argument. CO2 only absorbs certain bands of radiation. No one claims that the CO2 in the atmosphere has an emissivity of 50% of a black body. It is clear that you don’t understand the theory you are criticizing.
“There is no heat retained by the atmosphere. If heat was retained, it would be as potential or kinetic energy and it would stop being heat, that is, energy in transit or energy in the moment of being transferred from one system to another.
Water and mud have the capacity of store energy many times more than the carbon dioxide. For example, during a change of temperature of 0.8 K, the dry air absorbs 956.16 J; liquid water absorbs 3.352 x 10^6 J; and dry clay soil absorbs 1.424 x 10^6 J.
What is the system or systems that maintain the entropy of the air in a quasi-stable state? From the results in the previous paragraph, the systems that maintain the temperature of the air are water and dry clay soil.”
You misunderstand the Greenhouse theory of global warming if you argue that the heat capacity of the air is to small for the theory to be correct. The heat capacity of the air doesn’t determine the greenhouse effect.
“Insolation in the first place, the surface in the second place (Peixoto & Oort. 1992. Page 233). The air (carbon dioxide included) is a distributor of heat and a drainer of heat from the surface to the outer space. Water vapor retains heat, so it is the main cause of the “greenhouse” effect. The time the heat spends in crossing the medium, i.e. the time that the energy spends transiting from one molecule to another molecule, is what is called “greenhouse” effect. Remember, the Earth is not an isolated system in the cold, 3D, unbounded and infinite space.”
The greenhouse gases actually reduce the flow of radiation from the warmer earth’s surface by absorbing it and reemitting half it back towards the ground. The topmost layer of the atmosphere, which emits 50% of the radiation it has absorbed, directly upwardunimpeded, toward outer space, where it is lost to the earth, is cooler than the surface of the earth. The fact the top layer is cooler, reduces the emission rate in the radiation frequency band absorbed by greenhouse gases below the rate of emission at the ground level. This is the reason that GHG’s in the atmosphere reduce the rate of energy loss from the earth, and raise its temperature 33C.
For water absorptivity:
Chaplin, Marin. Water Absorption Spectrum. http://www.lsbu.ac.uk/water/vibrat.html (Last reading on 25 April 2009).
For values of heat capacity of water, air, carbon dioxide and clay:
Boyer, Rodney F. Conceptos de Bioquímica. 2000. International Thompson Editores, S. A. de C. V. México, D. F.
Lubos Motl (09:24:11) : The evidence is essentially based on one number,
I also have a problem with them saying, ‘Long debate ended over cause’, since it is does not take in a big enough picture. It should rather say something like ‘More evidence on a hypothesis about climate’.
Geoff Sherrington (23:31:10) :
“A poor analogy is that satellites need fuel for in-flight corrections to their paths because the paths cannot be modelled accurately enough at launch. What makes us think that we can model the earth orbit well enough so we can predict remperature changes caused by geometry changes? How about some error estimates?”
Goeff,
As you say it’s a poor analogy. Satellite orbits are subject to decay from atmospheric drag. The decay is subject to variation caused by variation in atmospheric density. Even if the decay could be exactly predicted, analytical corrections for the effect of the decay on temperature calculations introduces additional uncertainty, which can be avoided be using propulsion to maintain the satellites position. By contrast, the Earth’s orbital elements and orientation are more predictable by orders of magnitude, including the gravitational effects of the moon and planets, the Earth’s oblateness, solar radiation, and even relativistic effects. I think many here underestimate the accuracy with which the Earth’s position and orientation are known through time.
Having said that, I would second your call for a quantitative statement from a reputable source as to the accuracy of predictions over periods of millions of years, contrasted to a few tens of thousands of years.
Chicago is glacial termination point, even at the weakest point of the Milankovitch cycle.
Actually it is a little farther south (about 100 mi), but Chicago is a good major landmark – for now.
Syl (03:03:30) :
“Why so excited? You are assuming that once the Milankovitch ‘cycle’ triggered a warming, CO2 took over rather than merely contributed to ongoing warming that was due to the ‘cycle’.
Think about it. From bottom to top there was a change of about 100 PPM and a temp change of about 10C. Hansen calculates sensitivity based on CO2 being responsible for most of that temp change!
So where’s the other 9+ C of warming from the latest increase in CO2 of about 100PPM? Under Hansen’s bed? ”
There is an assertion that CO2’s influence follows a diminishing returns curve such that a change from 100ppm to 200ppm is going to create a large change in temps while going from 200ppm to 300 ppm is going to create a much diminished change, etc. which is one reason why going back a few ten million years when concentrations were 1500ppm and higher the climate was not more than a few degrees warmer. CO’s influence is capped out at Earth’s current atmospheric density when you exceed 300-400 ppm. You need to significantly change the barometic pressure of the atmosphere to get CO2 to have more influence above these concentrations.. This is a major problem for warmists and why they depend on the water vapor-as-positive-feedback mechanism to create their chicken little disasturbationism. We now know that its not the oversensitive positive feedback theyre claiming (note some of the alarmist geoengineers are now proposing “cloudships” that generate clouds over oceans with windpower to cool the earth).
Bob Ramar (18:21:43) :
There is a real threat however and that is methane. Methane is the fourth most potent greenhouse gas in the atmosphere (after water vapor, argon, krypton, then methane). And a lot of methane is locked up on the seafloor in the form of methane hydrates. However, methane makes a lovely fuel … .
Indeed, compared to other fuels, burning methane produces less carbon dioxide for each unit of heat released.
“We are approaching the end of our current warming period, and our governments are trying to cool the planet, on the unproven assumption reducing CO2 will do the job.”
It will be interesting to watch then try to “save” the Great Barrier Reef when it is a few hundred feet above sea level.
ERIC: Assuming CO2 is close to an ideal gas
V=RT/PM, where M is the mass of a mole of CO2 or approximately 44gms.
R is the ideal gas constant and T is the absolute temperature.
ALEXEJ BUERGIN: Since the standard values (in SI units) are R=8.31, T=273, P=101000 and M=0.044, the Volume would be 0.510 cubic meters ?
ALEXEJ BUERGIN: I will answer myself:
The correct formula for the ideal gas is pV=nRT, n number of moles. The mass of a particle or of the gas (M) plays no role.
That changes when one calculates the density M/V; then one can see e.g. why moist air is LIGHTER than dry air.
The Volume of the ideal gas at 0°C and 1013hPa is about 23 Liters.
Richard Sharpe (08:51:19) :
Their main conclusions are that anthropogenic global warming has been masked in recent years by reduced solar activity and …
I suspect that Leif will have something to say about that.
I think I have said what should [could?] be said already. There are three things wrong with the conclusion:
1) it is not a given that the warming was AGW
2) it has not been demonstrated that reduced solar activity has enough effect
3) it is not certain that we are cooling. What was the recent July anomaly?
The compounded effect of many wrongs or unknowns does not make a right.
(note some of the alarmist geoengineers are now proposing “cloudships” that generate clouds over oceans with windpower to cool the earth).
Confirmation that pancients are running the asylum.
eric (10:11:54):
This is a straw man argument. CO2 only absorbs certain bands of radiation. No one claims that the CO2 in the atmosphere has an emissivity of 50% of a black body. It is clear that you don’t understand the theory you are criticizing.
Heh! Tell me, what the absorptivity-emissivity of carbon dioxide is? Please answer this question straightly.
You misunderstand the Greenhouse theory of global warming if you argue that the heat capacity of the air is to small for the theory to be correct. The heat capacity of the air doesn’t determine the greenhouse effect.
Mm… Am I arguing that? Could you define the term “heat capacity”, and what is the heat capacity of the air? You also must to explain why you say that heat capacity is not important in heat transfer.
The greenhouse gases actually reduce the flow of radiation from the warmer earth’s surface by absorbing it and reemitting half it back towards the ground.
There is no back radiation warming up the surface because induced emission avoids it.
Now tell me, from your suppossition, what’s the percentage of heat radiated back to the surface from the absorbed heat by a parcel of air?
The topmost layer of the atmosphere, which emits 50% of the radiation it has absorbed, directly upwardunimpeded, toward outer space, where it is lost to the earth, is cooler than the surface of the earth.
If you have not noticed it, you are agreeing with me when I said that warmists say the air have an emissivity of 50% or of a black radiator. 50% downwards and 50% upwards? Heh!
The fact the top layer is cooler, reduces the emission rate in the radiation frequency band absorbed by greenhouse gases below the rate of emission at the ground level. This is the reason that GHG’s in the atmosphere reduce the rate of energy loss from the earth, and raise its temperature 33C.
Water vapor in the first place, carbon dioxide “greenhouse” effect is negligible.
I will let you to learn something before you say something nonsensical:
“Substances with high thermal diffusivity rapidly adjust their temperature to that of their surroundings, because they conduct heat quickly in comparison to their volumetric heat capacity.” (Wikipedia)
The thermal diffusivity of air is 0.0000217 m^2/s
The thermal diffusivity of water vapor is 0.000302 m^2/s
Water vapor thermal diffusivity is 14 times higher than that of the air.
Now let’s see volumetric heat capacity:
pC of air = 1200 J/m^3 K
pC of water vapor = 58.3 J/m^3 K
Wow! The dry air has a volumetric heat capacity 86 times higher than that of the water vapor… So the dry air (carbon dioxide included) takes more time to reach thermal equilibrium than water vapor… Well, who doesn’t understand the “greenhouse” effect?
I have debunked this kind of nonsensical arguments on volumetric heat capacity, specific heat capacity, thermal equilibrium, etc., in another forum, although it was not Eric, but someone nicknamed “questioner”. He also said that heat capacity, specific heat capacity, etc., were non important for the absorption of heat by any system. Heh!