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.
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Nasif says:
Well, it is somewhat of a theoretical property…but it is based on experimental observations (of the absorption lines of CO2 and other elements, of their abundances and distribution, of the temperature structure of the atmosphere). You can continue to debate its value if you like, but without any coherent arguments to back up your case, you will find yourself pretty lonely.
See my previous post. I suggest that in the future, you check your own math more carefully before grading mine!
Vincent (13:39:59) :
Leland Palmer:
“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.”
Yes. And there is also the Devonian with 1800-2100 ppm CO2 during which ferns, seed plants, horsetails and the first trees and forests appeared. Further confirming that elevated atmospheric CO2 neither causes thermal runaway or contraction of life forms.
Joel Shore (14:53:18) :
Well, it is somewhat of a theoretical property…but it is based on experimental observations (of the absorption lines of CO2 and other elements, of their abundances and distribution, of the temperature structure of the atmosphere). You can continue to debate its value if you like, but without any coherent arguments to back up your case, you will find yourself pretty lonely.
Joel… sorry, but you’ve got another “F” in mathematics. Heh!
See my previous post. I suggest that in the future, you check your own math more carefully before grading mine!
Mm… Give you the chance of fix the value of α. What that value is?
Joel Shore (14:53:18):
You can continue to debate its value if you like, but without any coherent arguments to back up your case, you will find yourself pretty lonely.
Oooh! I’m alone on this issue. Scientists working on heat transfer, from whom the world has learned good science, are alone. Good… I win, you lose. 🙂
Leif Svalgaard (10:22:42) :
Because you have not answered straightly a single one of my questions in my post Nasif Nahle (14:34:53):, I win, you lose.
Tell that to these people
Global ocean heat content 1955–2008 in light of recently revealed instrumentation problems
S. Levitus, J. I. Antonov, T. P. Boyer, R. A. Locarnini, H. E. Garcia, and A. V. Mishonov1
GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L07608, doi:10.1029/2008GL037155, 2009
You can only meaningfully talk about ‘heat content’ if that which is contained [stored] is heat.
I have nothing to tell them. If they are wrong in their concepts, they are wrong and point:
“In thermodynamics, heat is defined as the amount of energy which flows through the boundaries between a system and the surroundings, as a consequence of a difference of temperature between the system and the surroundings. The same as the work, the heat has some important characteristics:
* Heat is transitory and only appear during a change of state of the system and the surroundings.” (Bolds are mine, i.e. Nasif Nahle’s bolds) (Source: Thomas Engel and Philip Reid. Thermodynamics, Statistical, Thermodynamics & Kinetics. 2006. Pearson Education, Inc. PAGE 16.)
“Heat is energy transferred across the boundary of a system due to a difference in temperature between the system and the surroundings of the system. A system does not contain heat, it contains energy, and heat is energy in transit.” (Bolds are mine, i.e. Nasif Nahle’s bolds) (Source: Potter, Merle C. and Somerton, Craig W. Thermodynamics for Engineers. Mc Graw-Hill. 1993. PAGE 40).
I don’t know where that distinctive Leif Svalgaard’s scientific rigorousness has gone to, but it doesn’t seems to be so good.
Leif Svalgaard (10:10:32) :
No, I and Spencer and Steve and most other people consider heat to be what you have put into a system by heating it. Your confusion comes from the fact that in the English language ‘heat’ is both a noun [an amount of heat] and a verb [to heat].
Please, Leif; don’t come with that childish argument. This is not a case of semantics, but of physical concepts.
This one was not addressed to Leif, but to Joel:
“Because you have not answered straightly a single one of my questions in my post Nasif Nahle (14:34:53):, I win, you lose.”
I apologize, Leif.
Nasif Nahle (17:31:13) :
“In thermodynamics, heat is defined as the amount of energy which flows through the boundaries between a system and the surroundings
And everywhere else it is defined simply as ‘thermal energy’ which is defined as the kinetic energy of the random, disorganized movements of the molecules. This is the useful and generally accepted definition and the one that makes sense in climatology and astrophysics. The definitions you mention are just ‘jargon’ and are not useful of sensible. Remember, a definition is neither right nor wrong. It can be more or less useful or sensible, and there is no doubt which is the useful and hence generally used definition. Rigor has nothing to do with it, except perhaps the rigor mortis of being trapped in useless jargon.
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
From what I understand this theory of orbital shift is what warmists hang their hat on. They say that this proves that human emissions of CO2 are what has prevented us from entering another ice age in our modern era. According to the theory we should’ve entered into another era of glaciation by now, but it’s been prevented by industrialization. Is there evidence that the Earth has re-entered into an orbital pattern that would cause a shift towards glaciation, as this theory suggests?
I do wish that the warmists would just cut to the chase and try as best as they can to ascertain whether greenhouse warming is occurring, first of all–actually measure tropospheric temperature trends. If it is, if they could please ascertain whether it’s being caused specifically by CO2 emitted by industry. I’m tired of this argument of “This has to be it. What else could it be?” That’s speculation, not scientific analysis.
Leif Svalgaard (18:34:49) :
Nasif Nahle (17:31:13) :
“In thermodynamics, heat is defined as the amount of energy which flows through the boundaries between a system and the surroundings
And everywhere else it is defined simply as ‘thermal energy’ which is defined as the kinetic energy of the random, disorganized movements of the molecules. This is the useful and generally accepted definition and the one that makes sense in climatology and astrophysics. The definitions you mention are just ‘jargon’ and are not useful of sensible. Remember, a definition is neither right nor wrong. It can be more or less useful or sensible, and there is no doubt which is the useful and hence generally used definition. Rigor has nothing to do with it, except perhaps the rigor mortis of being trapped in useless jargon.
Come on, Leif; it has nothing to do with jargon. They are scientific concepts. The authors I quoted are clear on defining the concepts. Heat is one thing; thermal energy is another very different thing.
Heat cannot be thermal energy because heat is energy in transit and it doesn’t form part of the internal energy of a system. Thermal energy is the internal energy of a system. The difference is quite clear. Potter and Sommerton say it clear: “A system does not contain heat, it contains energy, and heat is energy in transit.”
Perhaps there are some climatologists and/or astrophysicists who use the term heat thermal energy; they are wrong. I will tell you something what a friend told me: “Science relies on precision in language as well as the precision of measurements.”
Bacteria are not protozoans, a star is not a planet, temperature is not heat, and heat is not thermal energy (or kinetic energy), for example. It’s quite simple.
Nasif Nahle (20:30:36) :
heat is not thermal energy (or kinetic energy), for example. It’s quite simple.
I’m reading a book [The Black Hole War] by L. Susskind [one of the most prominent physisicts of our time]. On page 141 he says that thermal energy = heat. I, of course, agree with him. Heat can be stored and bodies [e.g. the ocean] can contain heat. So it is indeed simple.
Nasif Nahle (20:30:36) :
I will tell you something what a friend told me: “Science relies on precision in language as well as the precision of measurements.”
The precision in language is achieved by making a distinction between ‘heating’ [which is transfer of heat] and ‘heat’ [which is thermal energy]. In other languages [e.g. German as somebody pointed out, and Dutch and Danish that I know well] this problem does not occur. How is it in Spanish?
Mark Miller (19:40:06) :
“Is there evidence that the Earth has re-entered into an orbital pattern that would cause a shift towards glaciation, as this theory suggests?”
According to Milankovich theory past ice ages will not recur for 500,000 years.
http://amper.ped.muni.cz/gw/articles/html.format/orb_forc.html
Leif Svalgaard (21:15:34) :
I’m reading a book [The Black Hole War] by L. Susskind [one of the most prominent physisicts of our time]. On page 141 he says that thermal energy = heat. I, of course, agree with him. Heat can be stored and bodies [e.g. the ocean] can contain heat. So it is indeed simple.
Once the heat is absorbed by the system it stops being heat. If your “star” physicist says on page 141 from his book “The Black Hole War” that heat is thermal energy, he’s wrong; no matter if he’s the King of France. If you agree with him, then you also are wrong because you both are creating a new kind of idealized thermodynamics.
Heat is associated with internal energy, but it is not the internal energy because after it is absorbed, it is no more heat, but potential or kinetic energy. Really, it is so simple.
Leif Svalgaard (21:39:40) :
The precision in language is achieved by making a distinction between ‘heating’ [which is transfer of heat] and ‘heat’ [which is thermal energy]. In other languages [e.g. German as somebody pointed out, and Dutch and Danish that I know well] this problem does not occur. How is it in Spanish?
We are not talking about Merriam Webster’s definitions, but on scientific concepts. What’s heat in Svalgaardish? Perhaps a substance or something with mass?
Here a plain comprehensible text on thermal energy and heat:
http://www.thermalenergy.org/
It’s a short article. Enjoy it!
Nasif Nahle (22:07:49) :
heat is associated with internal energy, but it is not the internal energy because after it is absorbed, it is no more heat, but potential or kinetic energy. Really, it is so simple.
That kinetic energy is what we call heat, so it is indeed simple. What does ‘associated with’ mean? page 140: “Heat is the energy of random chaotic motion”. How true. “Energy” takes many forms, and one of those forms, heat, is joined at the hip with entropy”. You may say that we are all wrong, but that makes you very lonely.
Nasif Nahle (22:11:24) :
What’s heat in Svalgaardish?
The amount of thermal energy in a body. This is a sensible and useful definition. Heat capacity is concerned with how much heat a body can hold, not how much can be transferred to another body [that amount depends on the temperature of the other body in relation to the first]. I’m at a loss why you are hung up on this trivial point.
Leif Svalgaard (12:39:34) :
maksimovich (12:16:03) :
“Explain how there can be any effect from the harmonics of precession… [i.e. with half, third, fourth, etc, the period].”
29th February
Nonsense.
Not at all solstices and equinox were”fixed” in most paleo studies eg imbrie et al 1993
Berger realized this an corrected it around 1997.
Nasif Nahle (22:11:24) :
What’s heat in Svalgaardish?
If we really want to be technical. heat energy is that energy that potentially can be transferred to another body without applying any external forces, but not the transfer itself. There is still heat energy even if no transfer takes place.
Leif Svalgaard (22:28:48) :
That kinetic energy is what we call heat, so it is indeed simple. What does ‘associated with’ mean? page 140: “Heat is the energy of random chaotic motion”. How true. “Energy” takes many forms, and one of those forms, heat, is joined at the hip with entropy”. You may say that we are all wrong, but that makes you very lonely.
No, that kinetic energy is what you call heat.
What about all the authors who say that heat is not internal energy or thermal energy? Show me a single scientific article or book where the author says the heat is the same as kinetic energy; a single one.
maksimovich (23:05:08) :
Not at all, solstices and equinox were”fixed” in most paleo studies eg imbrie et al 1993
Berger realized this an corrected it around 1997.
1st: that has nothing to do with Feb 29th
2nd: correcting an error in the analysis does not create 11ka or 5.5ka real variations in climate, where there are none.
Nasif Nahle (23:31:48) :
Show me a single scientific article or book where the author says the heat is the same as kinetic energy; a single one.
I already showed you an article that said that heat could be stored, and that heat did not disappear upon being stored: ‘the heat content of the oceans’.
Nasif Nahle (23:31:48) :
Show me a single scientific article or book where the author says the heat is the same as kinetic energy; a single one.
To make it easy on you, here is an online book:
http://www.lightandmatter.com/books.html
Chapter six is about thermodynamics:
http://www.lightandmatter.com/html_books/2cl/ch06/ch06.html
Here is a section from the book: http://www.vias.org/physics/bk2_03_02.html
The title of the section is: ‘Heat is Kinetic Energy’
But perhaps that book is not ‘scientific enough’?
I also quoted Spencer’s book. Perhaps that one isn’t science either.
Even wikipedia weighs in:
http://en.wikipedia.org/wiki/Conduction_(heat)
“In heat transfer, conduction (or heat conduction) is the transfer of thermal energy between neighboring molecules in a substance due to a temperature gradient. It always takes place from a region of higher temperature to a region of lower temperature, and acts to equalize temperature differences. Conduction takes place in all forms of matter, viz. solids, liquids, gases and plasmas, but does not require any bulk motion of matter. In solids, it is due to the combination of vibrations of the molecules in a lattice and the energy transport by free electrons. In gases and liquids, conduction is due to the collisions and diffusion of the molecules during their random motion.
Heat can also be transferred by radiation and/or convection, and often more than one of these processes occur in a given situation.”
So heat is something [thermal energy] that can be transferred. Not just the transfer.
Leif Svalgaard (23:00:59) :
The amount of thermal energy in a body. This is a sensible and useful definition. Heat capacity is concerned with how much heat a body can hold, not how much can be transferred to another body [that amount depends on the temperature of the other body in relation to the first]. I’m at a loss why you are hung up on this trivial point.
That’s a confusion, not a sensible+useful definition. You’re confounding the basics, kinetic energy and heat.
Heat capacity is the capability of a substance to store internal energy during a change of temperature (changes of kinetic energy or 1/2mV^2) without undergoing a phase change. 🙂
Is it me who is hung up on this important point? I understand perfectly the difference between kinetic energy and heat. You don’t.