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.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Nasif Nahle (13:45:35) :
You are referring to thermal energy, not to heat; however don’t worry, it is a common confusion.
In the [new thread] Steve F uses the sensible phrase:
“1. Slow heat accumulation in the world’s oceans delays the appearance of the full effect of greenhouse forcing by many (eg. >20) years.”
Here again ‘heat’ refers to retained heat, not to the transfer of energy. It would be silly to say ‘1. Slow transfer of energy accumulation …’. So ‘heat’ has a wider and more useful meaning than the strict thermodynamic one.
Leif Svalgaard (22:41:37) :
Nasif Nahle (13:45:35) :
You are referring to thermal energy, not to heat; however don’t worry, it is a common confusion.
Rather than nit-pick about the meaning of heat in strict thermodynamic sense, it is more useful to adopt the more practical point of view as expressed here: http://www.powermasters.com/heat_energy.html
For example, the following makes sense and is the way this is usually expressed:
“More heat energy is required to increase the temperature of a substance with high specific heat capacity than one with low specific heat capacity”. In the last two uses of ‘heat’ the reference is to heat retained.
That’s the correct way of explaining it and it’s not in contradiction with the distinction between thermal energy and heat. When heat is retained by a molecule it could be as potential energy or as kinetic energy, which is thermal energy. The energy that is being transferred from a warm system to another system, i.e. the energy in transit, not stored or retained, is heat.
I was looking for an article a bit simpler than the article that you provided for you could see clearly the difference, but my search in the network was not successful.
in my
anna v (22:12:24) :
in reply to
Phil. (08:35:27) :
I should amend 2) to:
2) Water vapor depends on the saturation of the air above plus the surface temperature, and this will be happening more during the sunlight hours : the heated by direct sunlight few millimeters and the evaporation into the drier from heat air. Convection of course plays a large role in the evaporation process and in heating the atmosphere too, bringing in unsaturated air sweeping over the waters and heated land. Commonly known as winds
“Phil: The original question was ‘was is the Specific Volume of CO2′ so Eric is right
0.510m^3/kgm.”
Except that he wrote V= … , and one should not use the same symbol V for “Volume” and “specific Volume”. Correct would be v=V/m (and that in Italics, but that goes too far here). (And your last m is part of kilogram (kg) and not an abbreviation for mol ?)
“”
Joel Shore (19:01:10) :
Nasif Nahle says:
4 W/m^2 (a guess) of radiative forcing means that doubling the CO2 in the atmosphere would cause a change of temperature (some people say it’s an anomaly) of 0.7 K.
The 4 W/m^2 is not a guess. It is a value (to within ~10%) that even Roy Spencer and Richard Lindzen seem to accept. And, the evidence from what we understand to be the difference in forcings between the Last Glacial Maximum and now is that the change in temperature that this would cause would be more like 3 C, although no serious scientist claims to know this value exactly. You must be the most brilliant climate scientist alive to KNOW that this will cause a change of temperature of 0.7 C.
“”
You’re right about the increased absorption of a co2 doubling now not really being a guess to 10%. To go finer than that however is as the effects of line broadening beyond the basic (Voight) curve, dymers, etc. are not that well understood and being that the atmosphere actually varies in gas content in time and position, that information is also not well known. ALSO, it would seem that number is the difference in power output for CLEAR SKY conditions at a particular altitude- such as 70km or 22km or the at the Tropopause. Clear skies is a condition known to be wrong by over 50% at time as cloud cover is around 62%. That number is also closer to 3.5 to 3.7w/m^2 as the number 4 is presumably a rounding up to indicate 1 significant figure of accuracy – but most importantly – to push the number higher by 10%.
For those willing to look, the sensitivity – or value of Kelvins per W/m^2 forcing variation is not that hard to glean an idea about. For one thing, the Earth actually is warmer than a simple radiative balance blackbody would show by around 33 Kelvins. That means that the average rise in Kelvins per W/m^2 of forcing increase is going to be 33 K divided by the total amount of forcings dues to ghgs. By using the same sort of calculations one must do to ascertain the effect of a CO2 doubling, one finds that there is a total GHG associated forcing of around 150 W/m^2 under clear skies and the results being less than 1/4K per W/m^2. Cloudy skies dramatically reduce the effects of co2.
Note that while this doesn’t include the amount of increased h2o vapor which is split out already, you need to compare this to a simple straight radiative only solution to see that it is somewhat less than the result expected. That means there is a negative net feedback present reducing the effects of the increased forcing. One still has to deal separately with the h2o effect but this shows there’s no net positive feedback present as the net feedback can’t be both positive and negative.
more later….
cba (04:31:51):
You’re right about the increased absorption of a co2 doubling now not really being a guess to 10%.
Then explain the experimental and/or direct observational process by which the value was obtained.
Otherwise it’s a guess.
Leif Svalgaard (22:53:09) :
In the [new thread] Steve F uses the sensible phrase:
“1. Slow heat accumulation in the world’s oceans delays the appearance of the full effect of greenhouse forcing by many (eg. >20) years.”
Here again ‘heat’ refers to retained heat, not to the transfer of energy. It would be silly to say ‘1. Slow transfer of energy accumulation …’. So ‘heat’ has a wider and more useful meaning than the strict thermodynamic one.
Which is quite incorrect because heat is energy that crosses the boundaries of the system out towards another cooler system. Heat is energy in transit and stops being heat in the moment it is absorbed. Kinetic energy is not heat, but internal energy (thermal energy). Other way of classifying potential and kinetic energies is like mechanical energy.
Nasif Nahle (08:09:38) :
Which is quite incorrect because heat is energy that crosses the boundaries of the system out towards another cooler system. Heat is energy in transit and stops being heat in the moment it is absorbed.
What I’m pointing out is that the ordinary [and sensible] use of ‘heat’ conflicts with the ‘correct’ term. The ordinary use is preferable as language is communication and communication is hindered by the jargon of specialists. So ‘heat accumulation” as used by Steve F in his article is sensible communication.
Nasif Nahle (08:09:38) :
Which is quite incorrect because heat is energy that crosses the boundaries of the system out towards another cooler system. Heat is energy in transit and stops being heat in the moment it is absorbed.
Our esteemed Roy Spencer uses this phrase [“Climate Confusion” page 58] “All the heat […] accumulating in the lowest layers of the atmosphere…” and [page 60] “a portion of the heat that builds up at the Earth’s surface”, and on and on. This is a very reasonable use of the word.
What you advocate is better expressed by the word ‘heating’, which is indeed the process that makes heat cross the boundary from one system to another.
Confusing ‘heat’ and ‘heating’ makes for poor communication.
“”
Nasif Nahle (07:53:33) :
cba (04:31:51):
You’re right about the increased absorption of a co2 doubling now not really being a guess to 10%.
Then explain the experimental and/or direct observational process by which the value was obtained.
Otherwise it’s a guess.
“”
Getting much better than 10% is a guess. Great effort was put into the study of IR absorption emission lines in the atmosphere. I’m familiar with the Hitran database which has line by line information and it is a combination of lab experiments and theory. Combine the 10s of thousands of lines with reasonable line width forms and atmospheric concentrations and you have the ability to generate a rather complex and fairly accurate rendition of the atmospheric spectral absorption. It is used among other things for the development of military IR hardware. To even try to apply a single lab, a single test, a single researcher or even a single decade when it was done is to grossly underestimate the effort put into this system. It’s not perfect but it should provide an excellent bit of information for the vast majority of molecular emission/absorption modes for co2 and practically every molecule of possible importance to Earth’s atmosphere. It’s also well beyond what could be implemented in any sort of a climate GCM that would be capable of running even real time with modern super computing power.
Now there again, one can calculate this absorption for a column of atmosphere with particular concentrations, temperatures, and pressures and have a fairly good clear sky value. As stated, toss a cloud in and all bets are off for the ultimate effects and most of the sky in daylight is cloudy.
About the only way to measure the sensitivity of the atmosphere is to look at a change and determine the change in temperatures. The fun part of this is that the albedo is variable by much larger forcing amounts than by any other factor one might try to measure and that value is poorly measured for thirty years and not measured prior to that. Consequently, there’s practically no capability to measure forcing accurately, without accounting for an unknown that is bigger than the variation being measured. Paleo gets even more fun because who’s to say exactly what the cloud cover was at any point in time prior to our ability to measure it.
Leif Svalgaard (09:02:59) :
What I’m pointing out is that the ordinary [and sensible] use of ‘heat’ conflicts with the ‘correct’ term. The ordinary use is preferable as language is communication and communication is hindered by the jargon of specialists. So ‘heat accumulation” as used by Steve F in his article is sensible communication.
And confusing communication because heat could be wrongly taken as kinetic energy or, what is more confusing, as temperature. Don’t you agree?
@Leif…
Regarding Steve Fitzpatrick’s phrase, “1. Slow heat accumulation in the world’s oceans delays the appearance of the full effect of greenhouse forcing by many (eg. >20) years”, the heat is being introduced into the system “world’s oceans”, but it is not accumulated like heat because it is into the boundaries of the system like internal energy, i.e. kinetic energy. It stops being heat as soon it is accumulated. If a portion of that internal energy accumulated is transferred into another system, as soon as the energy had crossed the boundaries of the system “world’s oceans” in a trajectory towards another colder system, it would be heat.
Heat can be stored, of course; however, once stored, it stops being heat. Thus, kinetic energy is not heat.
Nasif Nahle (09:23:39) :
And confusing communication because heat could be wrongly taken as kinetic energy or, what is more confusing, as temperature. Don’t you agree?
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].
Nasif Nahle (09:40:16) :
Heat can be stored, of course; however, once stored, it stops being heat.
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.
Nasif Nahle (09:40:16) :
Heat can be stored, of course; however, once stored, it stops being heat. Thus, kinetic energy is not heat.
Hi Nasif, sorry to butt in, please could you explain how the storage of the energy as kinetic energy accounts for the thermal expansion seenby satellite altimetry. Is it in the increased vibration of the water molecules or their constituent atoms for example?
Thanks
Berger (2006( raises some interesting points in the double equatorial insolation maximum/minimum.
eg .
Many new paleoclimate information indicate that these regions are indeed more important than previously thought. They seem to play an important role in 5 the glacial-interglacial cycles and even in the warming of the last 50 years (see Kerr, 2001, 2003, for a few references).
In this paper, we show an additional reason to believe that the tropics can play an
important role in the response of the climate system to the astronomical forcing. This
reason is the presence of significant 100-kyr, 11-kyr and 5.5-kyr cycles in the amplitude of the seasonal cycle of the energy that the intertropical regions receive from the Sun, cycles directly related to eccentricity and harmonics of precession.
maksimovich (10:55:19) :
the energy that the intertropical regions receive from the Sun, cycles directly related to eccentricity and harmonics of precession.
Explain how there can be any effect from the harmonics of precession… [i.e. with half, third, fourth, etc, the period].
Nasif Nahle says:
Yes, it is not dogmatic, but it does progress and indeed progress has been made since Arrhenius’s time. The fact that even skeptics like Lindzen and Spencer don’t dispute this does show how broad the agreement is. After all, Spencer even has done some mild disputing of facts as broadly accepted as the fact that the rise ***in CO2 levels*** is due to humans.
Well, it is a nice formula but you have to use it correctly. Your value of 0.7 C is not what comes out of this formula if you use the accepted value of α and the value of T that is relevant for the effective radiating level in the atmosphere, which is ~255 K. You then get a value of ~1.0-1.1 C. Furthermore, this is the amount of warming the absence of feedbacks, which is a useful starting point, but is not the final answer in regards to the amount of warming that one expects.
Whereas in German “Wärme” is clearly defined as the disordered movement of the molecules, there seems to be an ambiguity about “heat” in English (like “weight” is mass for some people and gravitational force for others). The SI defines only the unit of “amount of heat” (joule, like work or energy). Therefore it is probably better to avoid using the word, or say heat-energy, heat-capacity, heat-flux etc.
Leif Svalgaard (11:39:44) :
maksimovich (10:55:19) :
the energy that the intertropical regions receive from the Sun, cycles directly related to eccentricity and harmonics of precession.
Explain how there can be any effect from the harmonics of precession… [i.e. with half, third, fourth, etc, the period].
29th February
Joel Shore (11:44:58) :
Yes, it is not dogmatic, but it does progress and indeed progress has been made since Arrhenius’s time. The fact that even skeptics like Lindzen and Spencer don’t dispute this does show how broad the agreement is. After all, Spencer even has done some mild disputing of facts as broadly accepted as the fact that the rise ***in CO2 levels*** is due to humans.
Arrhenius said the value for α was 5.35 W/m^2. He was wrong. The science has been progressing since Arrhenius, of course, but not thanks to Arrhenius, whose ideas has not made another thing but paving the road to the greatest hoax in the history of science. In the last 19 years, science has been distorted by solipsists.
You say science is not dogmatic; you are resorting once and once again to dogmatism, however:
“…fact that even skeptics like Lindzen and Spencer don’t dispute this…”
If it is wrong, it is wrong; no matter if skeptics or believers think it is right. Nature is right, so show me any experiment or direct observation from which the value for α could have been deduced. If you don’t demonstrate it, then it is simply and purely guess.
ΔT = [α] ln [(CO2) ∞ / (CO2) s] / 4 (σ) T^3.
Well, it is a nice formula but you have to use it correctly. Your value of 0.7 C is not what comes out of this formula if you use the accepted value of α and the value of T that is relevant for the effective radiating level in the atmosphere, which is ~255 K. You then get a value of ~1.0-1.1 C. Furthermore, this is the amount of warming the absence of feedbacks, which is a useful starting point, but is not the final answer in regards to the amount of warming that one expects.
Joel… sorry, but you’ve got another “F” in mathematics. Heh!
Come back in few minutes…
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.
Jeremy:
“You are right it was and remains BAD. Real BAD. The most difficult Engineering program and University to enter in the country.”
So, did you study atmospheric physics, as you originally claimed, or engineering? Strange that you don’t name this university.
“What you and many others do not seem to realize is this:
The atmosphere is a highly complex system with many other processes (like convection). The modern prevailing view that CO2 is a major force behind global temperatures is WAY “oversimplified” and shows ignorance.”
This simply doesn’t make sense. You seem to be just saying phrases without really considering what they mean. If you think that the constituents of the atmosphere do not determine its energy balance, then you are woefully ignorant.
@ur momisugly Joel et al…
ΔT = [α] ln [(CO2) ∞ / (CO2) s] / 4 (σ) T^3.
ΔT = [4 W/m^2 (as you’ve said)] ln [2] / 4 (5.6697 x 10^-8 W/m^2 K^2) (255.15 K)^3 = 0.736 K
🙂 🙂 🙂
Nasif (14:17:44):
I did not say that α has a value of 4 W/m^2. I said that doubling of CO2 produces a forcing of 4 W/m^2. Since ln(2) is not equal 1, these two statements are not equivalent. If you write the formula in term of ln, then 4 W/m^2 for a doubling of CO2 would imply α = 5.8 W/m^2. [Alternately, if you used log-base-2 instead of ln (which is log-base-e), then in such an equation, α would have a value of ~4 W/m^2.]