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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GK (00:57:33) :
So this DEFINITIVELY proves that CO2 played no part in previous climate cycles.
There are 2 stunning conclusions from this :
1) The increase in CO2 that follows about 800 years after each interglacial starts has no (or very little) impact on earth`s climate.
2) It those massive increases in CO2 had no impact in earth`s climate back then, then CO2 can not possibily have an inpact now.
This finding proves there is no man made AGW.
No it proves that you haven’t read the paper, like most of those who’ve commented so far.
OT, but there was a nice mention yesterday in the Washington Examiner of Anthony, and the Surface Stations project. Unfortunately, although they mentioned Anthony by name, they did not mention surfacestations.org web site. I mentioned the web site in the comment section however. Here is the link: http://www.washingtonexaminer.com/opinion/blogs/beltway-confidential/Weather-stations-give-flawed-temperature-data-meteorologist-claims–52563192.html
“”Dave vs Hal (08:29:53) :
cba (06:16:14)
“THat difference is even more interesting considering that the surface albedo of ocean is about 1/3 to 1/5th that of land surface . What is happening is the ocean water is involved in a water vapor cycle creating clouds that reduce the albedo – something that can’t happen easily when there is little to no additional water available”
If what you say is true, it demonstrates the negative feedback qualities of the oceans.
“”
I think most of my comments above are correct or should be acceptible. Some may be just be hypotheses. It should demonstrate the oceans & water vapor cycle provide the negative feedback or even a temperature setpoint and control system. It also should demonstrate the importance of the Earth’s surface configuration and heat dissipation system. After all, this 8 W/m^2 +/- average annual variation which results in a Temperature curve that is maximum during NH summer where the insolation is at a minimum and a maximum during SH summer where the insolation is at a minimum means that the surface configuration related factors over ride this average difference in insolation with room to spare.
This also adds in the precession of the equinoxes – where the dates for the aphelion and perihelion (furtherest and closest approach to the Sun) shift relative to the tilt direction of the Earth (seasons). When they have shifted by 6 months, then the perihelion will occur in June/July and the aphelion will occur around January so that summer in the NH should be even hotter and winter should be colder (all else being unchanged) – with the exception that if somehow there is persistant snow cover started that reduces albedo then all bets are off on how warm things can get with that extra albedo if it exists. Otherwise, it would seem that perhaps we’d be in more of a hothouse condition as there might be less cloud cover formation and hence lower albdeo. Consequently, I’m not even sure if one could simply predict what portion of these cycles would actually permit the formation of glaciation or would actually cause the opposite or if simply some internal random variation – like ENSO – might be enough to randomly kick us into the other mode (glaciation / nonglaciation).
Nasif –
by some altitude, a doubling in co2 will increase clear sky absorption by around 3 1/2 W/m^2. This will also cause an increase in absoption and in emission for any parcel of air at a give temperature. Due to the geometry (cold space outward, warm surface inward) the power is basically absorbed only coming outward but this parcel must radiate inward at the same rate it radiates outward. Increasing the emissivity demands that more power will be radiated if the T remains unchanged – which means that the T will have to drop a bit unless there is more power coming from above as well. Of course, 62% or so of the atmosphere has cloud cover that is already doing substantial blocking as well.
Considering the whole system has a rough rise of 33 K for all GHGs and that it has around 150 W/m^2 of ‘blocking’, one can simply take 33/150 to see the actual average ‘sensitivity’. This is just under 0.25 Kelvins per W/m^2. One can also determine that a straight radiative solution to an increase in absorption results in the need for the surface to rise in T by around 0.3 K to pass an additional 1W/m^2 all the way out. That suggests that the Earth system has net negative feedback going on. It also suggests that a CO2 doubling results in about 0.75 Kelvins after all feedbacks have been accounted for in the real world.
That brings us back to the feedback/setpoint mechanism of cloud/atmospheric albedo increasing with increased water vapor – which is the realm where Lindzen’s IRIS effect ideas come from. It also provides us with a rather random sort of a mechanism that can be influenced by cosmic rays, the solar magnetic field, and solar cycle phenomenon affecting Earth’s atmosphere in a far greater fashion than a mere 0.1% solar cycle TSI variation would suggest. It also opens us up to more volcanic influence and potentially pollution factors.
My own suspicion places this current sensitivity to around half of the simple average or between 0.1 and 0.2 Kelvins per W/m^2.
You have no evidence that the authors put the reference to AGW in because of political pressure. None at all. If you have, I would love to see it.
If you want my opinion as to why they put it in, it’s because they knew their science would be misrepresented by websites like this. And that’s exactly what happened. Climate scientists have known for years about the Milankovich cycles, and studied them. That was how they knew to use the Milankovich cycles as an explanation for the end of the last glaciation. They didn’t just discover them.
Pamela Gray (14:18:08) :
Pamela Gray Wrote:
“Eric, what then causes the temp to correlate so highly, both in overall trend and ups and downs, historically as well as currently, with oceanic oscillations? Is there no place for oceanic circulation patterns (which have changed over the millions of years) and oscillations (which have also changed over the millions of years) in your model? How can that be when we see direct and obvious cause and affect, complete with data and well-known mechanisms? Just how and when do you jump from Earth bound natural variation ending as the driver to CO2 acting as the driver?”
These ocean oscillations, especially El Nino, affect the sea surface temperature over a wide area of ocean. The sea surface temperature by definition is part of global temperature, and will affect the air temperature over land as well. There is nothing mysterious about that. The coupled ocean atmosphere models show El Nino like phenomena but do not exactly predict the occurence of El Nino’s. The recent data shows El Nino are correlated with the oscillations in global temperature, but are not related to the overall long term 30 year trend.
http://skepticalscience.com/Global-warming-and-the-El-Nino-Southern-Oscillation.html
Currently dry conditions in asia resulting from El Nino has lead to buring of huge tracts of forest land releasing large amounts of CO2.
http://www.eleconomista.es/telecomunicaciones-tecnologia/noticias/1385944/07/09/Emerging-El-Nino-set-to-drive-up-carbon-emissions.html
In addition there is more naturally occuring emissions of CO2 from the warmer ocean water resulting from El Ninos.
While the ocean absorbs around half of human CO2 emissions, empirical observations reveal the oceans are losing their ability to absorb CO2.
http://www.skepticalscience.com/human-co2-smaller-than-natural-emissions.htm
“Quéré 2007 found that the Southern Ocean has reached its saturation point, diminishing its ability to absorb more CO2.
Schuster 2007 found that CO2 absorption by the North Atlantic has dropped even more dramatically, halving over the past decade.
Park 2008 found a sudden, considerable reduction in the recent uptake of CO2 in the East/Japan Sea.
If this trend continues, it potentially leads to a positive feedback where the oceans take up less CO2 leading to CO2 rising faster in the atmosphere leading to increased global warming.”
We can even see the correlation between emissions of CO2 from portions of the ocean, and El Nino conditions, where the surface temperature of the oceans is warmed.
“”” cba (17:08:00) :
“”Dave vs Hal (08:29:53) :
cba (06:16:14)
“THat difference is even more interesting considering that the surface albedo of ocean is about 1/3 to 1/5th that of land surface . What is happening is the ocean water is involved in a water vapor cycle creating clouds that reduce the albedo – something that can’t happen easily when there is little to no additional water available” “””
I wouldn’t be hollering about the “surface albedo” of the oceans. Given that the Fresnel reflection for water at normal incidence is about 2% for a refractive index of 1.33, and that reflection coefficient remains reasonably constant out to the Brewster angle which is about 53 degrees incidence angle, the net surface reflection is perhaps 3% for the complete hemisphere sans clouds; which would give the greatest albedo effect from the oceans; that makes the deep oceans a reasonably black body absorber with an emissivity of about 0.97 for the solar spectrum range of wavelengths (albedo applies only to solar spectrum reflections).
So Nyet for the oceans being a significant albedo contributor.
And since I just got back from a week of fishing in the Sea of Cortez, which can be as deep as 10,000 feet, I can assure you that that deep water looks visually black when you look down into it, and if you put on your polarized glasses to eliminate surface reflections then it is quite black. Yes of course when whipped up by winds; you do get higher reflections from the white water.
George
The finding proves that nothing stops the ice age from coming on or retreating. It offers nothing concrete as to how CO2 (AGW) is going to accelerate or prevent an ice age. As for the paper being behind a paywall, that is against the spirit of the Freedom of Information Act.
So, unless you are on the govt. payola grant, or can afford to throw money around, you get the leftovers (abstract). Science is for sale. I will definately take this up with my Congressman, whose party is not pleased with the lack of transparency.
4 years ago when I dug into studies of galaxies, it was rare to see papers for sale. Now it’s turned into a big business. Even older studies paid for by taxpayers are behind this paywall.
And on a further note; the albedo component due to clouds exceeds that of any earth surface terrain. so nyet on clouds reducing earth’s albedo by covering up ocean.
The polar regions ice cover is not much of an albedo component, even though it is most often cited. There’s a reason all that ice and snow is there at the poles; there’s very little solar radiation there to Albedize, in the first place.
George
Nasif Nahle wrote:
“The carbon dioxide more than being an amplifier of warming effects (which definitively it is not) it’s a distributor of heat and a drainer of heat into the outer space. A very different subject is water in anyone of its three phases. I have no doubt; Arrhenius inflicted a great damage to climate science with his assumptions.”
It is pretty clear that you don’t understand the influence of GHG’s on the climate of the globe. Without the GHG’s 100% of the upward radiation from the earth’s surface would escape to outer space. The GHG’s send about half of the radiation they absorb back toward the surface of the earth. That mechanism has been understood by physicists for 150 years since Tyndall pointed this out. This is not an assumpton. It is proven physics and is the basis for the atmospheric greenhouse effect. It has been refined by computer calculations which include the lapse rate of the atmosphere to make more accurate calculations of the greenhouse effect than Arrhenius was able to make in 1896.
By the way, I haven’t read the paper yet; so I haven’t commented on it. I get the dead tree issue of SCIENCE to keep in perpetuity; so I haven’t seen that issue yet.
But if the headline is meaningful and not hype; then maybe I will get more information out of it than the many times I read that “it is just Milankovitch cycles.”
All well and good by what exactly are the variable ranges of “Milankovitch cycles” ? I’m too long in the tooth to wade through all that orbital mechanics myself; and just how much do we know about the possible occasional encounter with other truly massive galactic objects that may have come through non-destructively but created one time perturbations of the whole solar sytem orbits.
Maybe astronomers are smart enough to actually untangle such events from the geologic records; they seem bloody clever at getting answers that would seem to be unavailable given the remoteness of their laboratory knobs.
George
I actually thought that solar forcing causing the ice age periodicity was accepted science. What else could cause the accuracy of the periodicity? Earthly oceanic or chemical cycles would make them all over the place.
The periodicity of the ice ages starts 3 million years ago. The only possible cause is continental drift. The forcing, being orbital, was there before. This implies the Earths climate is now in a state where it is highly sensitive to solar variation. This sensitivity, being oceanic, takes hundreds of years to manifest.
So the question is, why is the Earths climate not equally sensitive to CO2 forcing? It probably is, but only over centuries. Therefore, although CO2 emissions are a problem, there are centuries of time to find a solution.
George E. Smith (17:30:18) :
So, in this solarly minimumed environment, are clouds or moisture more effective at albedo?
Would they cause the sun to appear dimmer due to wavelength strength changes?
I would assume that clouds cause albedo and vapor causes greenhouse effect. Same as in any environment.
Well, well, so Dr. Milankovitch has been shown to be correct after all!
“CO2 forcing”… Carbon Dioxide levels are a following trend, not a leading trend. One thing that really gets me pissed in all the debate about human caused global warming is that carbon dioxide is the least of our worries. It can be and is removed from the atmosphere by biological processes and sequestered in rock in the form of calcium carbonate. 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 … .
eric (17:44:20),
Why is it that alarmists always leave out Arrhenius’ 1906 correction to his 1896 paper? Maybe because it pulls the teeth from his earlier paper?
Arrhenius’ 1906 climate sensitivity number was still too high. But those pushing the CO2=AGW conjecture can’t accept a lower number, because it would mean that CO2’s effect is insignificant and can be completely disregarded for all practical purposes.
But that’s exactly what the planet is telling us: CO2 has much less of an effect than warmists want to believe. In fact, it has no measurable effect at all.
Carbon dioxide, in the minor trace amounts both current and projected, is entirely beneficial. Why is that so hard to accept? It’s what the real world is telling us.
It is not difficult to imagine the Sun melting the glaciers.
Anyone ever been in Chicago in July? In Yellowknife in July? How is a glacier going to survive when the snow has melted by March 1st in Chicago and by April 25th in Yellowknife.
If the Sun is 2 degrees lower on the horizon and the Earth is 1 million kms farther away, I can see some glacier melting in the summer in Yellowknife but by late August, the snow is falling again.
Chicago? Well the glacier front is going to be melting from March till late September even when the Sun is 2 degrees lower on the horizon and 1 million kms farther away. The glacier front is not going to make it much farther south. Summer temps at the glacial front in Chicago still get to +15C and the ice and snow has completed melted well before the end of the summer – Chicago is glacial termination point, even at the weakest point of the Milankovitch cycle.
But in Yellowknife, the glacial front is going to be pushed past you south because it is only melting for a few months of the year and snowing for the rest. The 2 km high glaciers north of you are going to push right past you (gravity alone) when the Sun is only melting those glaciers for 1 month of the year and it is snowing for the other 11 months.
The CO2 changes produce a degree or so of warming, enough to melt the ice in Yellowknife on July 1st instead instead of July 15th. By that time the glaciers in Chicago are long gone because the Sun is now at its present angle in the sky and it is 1 million kms closer in the summer, the ice and snow has been melting since February. It is all gone in Chicago about March 15th so the little 1.0C of CO2 warming has had Zero impact on the glacial retreat.
Yellowknife just needs to wait the 1,000 years for the glacial front to melt back completely. Another 1,000 years and the glaciers are only left in the Arctic.
Take Yellowknife and move it 200 kms north (the relative difference in solar energy provided by Milankovitch cycles). The snow and ice will still melt completely in the summer and there will be no glaciers. But put a 2 km high glacier in the Arctic archipeligo in the same conditions and its coming south to Yellowknife.
It is not CO2 but snow accumulation versus snow melt at the height of the summer in the Arctic archipelgo.
eric (17:44:20) :
Nasif Nahle wrote:
“The carbon dioxide more than being an amplifier of warming effects (which definitively it is not) it’s a distributor of heat and a drainer of heat into the outer space. A very different subject is water in anyone of its three phases. I have no doubt; Arrhenius inflicted a great damage to climate science with his assumptions.”
It is pretty clear that you don’t understand the influence of GHG’s on the climate of the globe. Without the GHG’s 100% of the upward radiation from the earth’s surface would escape to outer space. The GHG’s send about half of the radiation they absorb back toward the surface of the earth. That mechanism has been understood by physicists for 150 years since Tyndall pointed this out. This is not an assumpton. It is proven physics and is the basis for the atmospheric greenhouse effect. It has been refined by computer calculations which include the lapse rate of the atmosphere to make more accurate calculations of the greenhouse effect than Arrhenius was able to make in 1896.
It is pretty clear that I don’t believe [snip]. Answer each one of the questions from my post at Nasif Nahle (14:34:53), and then we’ll talk.
Reply: Could use a rephrasing please. ~ ctm
If Milankovich cycles are solely responsible for glaciation, would not the Earth experience a continuous cycle of glacial advance and retreat?
How do we explain the geological record that suggests glaciation is confined to periods of several million years separated by about 200 million years?
The Solar System completes its orbit around the centre of the Milky Way Galaxy once each 226 million years – can periods of continental glaciation have an extra-Solar System cause? One that may be modified in some way by Milankovich’s Cycles – but not caused primarily by those relatively short (geologically speaking) variations in planetary orientation and orbit?
One of the most irritating things I see in papers like this is the need of the authors to grovel to the prevailing panic so as not to lose face (or funding) or be a marked man (or woman) by the alarmists.
“Ken S (07:44:03) :
Has anyone seen the papers by Australian engineer Dr. Peter Harris
He authored a paper entitled “Probability of Sudden Global Cooling.”
and “An Urgent Signal For The Coming Iceage”
Link at Iceagenow
http://www.iceagenow.com/Probability_94%25_for_imminent_global_cooling%20.htm
His papers have a nice graph that he uses to show what he thinks is the relationship of Preccssion, Obliquity, Eccentricity, and Solar Forcing to each of the
Stages of recent Glaciation.”
Would at least one knowledgable person please look at the paper at the second link Titled – “An Urgent Signal For The Coming Iceage”.
Here is a different, but direct link to the pdf file.
http://westinstenv.org/wp-content/ANURGENTSIGNALFORTHECOMINGICEAGE.pdf
I was wondering what others thought of Dr. Peter Harris’s ideas?
Thanks,
Ken S
The recent data shows El Nino are correlated with the oscillations in global temperature, but are not related to the overall long term 30 year trend.
But, surely, that was never the correlation at all, was it?
The correlation is with the Pacific Decadal Oscillation (et al). And the PDO affects Ninos and Ninas, minimizing the one and enhancing the other, depending on its phase.
From 1976 to 2001 half a dozen or more major oceanic-atmospheric multidecadal cycles turned from cold to warm. Then, the taps all being on hot, temperatures stabilized–at a high level. Recently, the PDO went cold, and temperatures have dropped. Is that so very hard to assimilate?
There is your correlation. Your 30-year trend. Not conclusively proven, but standing to reason. Over the last century the cycles correlate better with known climate than does CO2.
Ninos and Ninas continue, but they are merely short-term drivers which are affected by the bigger picture. Both will occur no matter what the overall phase of the Southern Oscillation and PDO.
Nasif Nahle (19:34:06) :
eric (17:44:20) :
It is pretty clear that you don’t understand the influence of GHG’s on the climate of the globe. Without the GHG’s 100% of the upward radiation from the earth’s surface would escape to outer space. The GHG’s send about half of the radiation they absorb back toward the surface of the earth. That mechanism has been understood by physicists for 150 years since Tyndall pointed this out. This is not an assumpton. It is proven physics and is the basis for the atmospheric greenhouse effect. It has been refined by computer calculations which include the lapse rate of the atmosphere to make more accurate calculations of the greenhouse effect than Arrhenius was able to make in 1896.
It is pretty clear that I don’t believe [snip]. Answer each one of the questions from my post at Nasif Nahle (14:34:53), and then we’ll talk.
Reply: Could use a rephrasing please. ~ ctm
Oops! Sorry… Rephrasing my comment:
It is pretty clear that I don’t believe in arguments made a priori, but in experimentation and good, clear physics. Answer each one of the questions from my post at Nasif Nahle (14:34:53) and then, we’ll talk.
Patrick K (20:44:40) :
How do you illustrate an undetectable change without exaggeration?
Show two identical (to the naked eye) illustrations & the influence is apparently non existent.
Which part of “not to scale” did you not understand?
DaveE.
” Bill Illis (19:13:19) : ”
Another subtle point people miss. If Chicago is under a mile of ice, then the surface of that ice is at 5000 feet altitude. Temperatures at 5000 feet above Chicago might be somewhat different than at the surface today.
In fact, the Northern Rockies might practically disappear under the ice. You might be able to walk Westward from Chicago, gaining altitude as you do, and see some hilltops sticking out of the ice, if that.
Archonix (13:49:05) :
Julius gave us July but you neglected to inform us that Augustus gave us August – maybe it was just too obvious. Maybe the ice ages occurred because there were two months of summer missing.