Guest Post by Willis Eschenbach
Inspired by a random comment by Steve McIntyre over at his marvelous blog Climate Audit, I got to thinking about the ice ages. I’ve long heard that the ice ages are caused by the changes in summer insolation in the northern hemisphere. As the story goes, the Milankovitch cycles of variations in the earths orbit make it so that there is a variation in how strong the summer sun is in the northern hemisphere. When the summer sun is weaker, the ice sheets advance, and eventually the buildup of ice reflects enough solar energy to spiral us into the icebox. Then about every hundred thousand years, the sun gets stronger again, and melts away the ice, and within a few thousand years the great ice sheets melt away and we’re out of the icebox.
So of course, once I’ve had that thought, I was doomed, and so I had to take a look. I got the data, and here is the variation in average northern hemisphere insolation for the months of June, July, and August.
Figure 1. Average insolation during the summer months (J-J-A) at 40° north latitude. DATA SOURCE: NOAA
Now, I found that surprising. I hadn’t realized the size of the swings. The cycles are about 21,000 years long and the swings are quite large, up to 100 W/m2 from trough to peak. So IF the temperature is following the forcing as the current hypothesis claims, a swing of 100 W/m2 is certainly large enough to cause a very large swing in temperatures. The current hypothesis is that at equilibrium we should see a swing of ~3°C for each additional 3.7W/m2 of forcing. However, we’re talking annual swings. Transient climate sensitivity is about 70% of equilibrium sensitivity, so I’ll use 50% to give some cushion. So according to the current thinking, a swing of an additional 100 W/m2 which is maintained for a thousand years should result in an increased annual temperature swing of about 40°C (73°F) … and we don’t see anything in the geological records even half that size.
I also didn’t realize that there is an underlying ~400,000 year cycle, which leads to the larger peaks at about 200,000 and 600,000 years before present (BP), and also leads to the very, very small peak at about 400,000 years BP.
But obviously we don’t see such a swing in geological temperatures. In fact, we don’t see anything even near that. So, scratching my head, I went and got the longest temperature record we have. This is the record from the ice cores at the EPICA dome in Antarctica. Figure 2 shows that record:
Figure 2. Antarctic temperature variations estimated from deuterium data. DATA SOURCE: NOAA
Here, we can see the ~ 100,000 year cyclical nature of the emergence from the ice ages. The swing is generally on the order of about 12°C, and the usual estimate is that because the poles swing more than the tropics, the global swing is half the Antarctic swing, or about 6°C. We can also see that the current interglacial period, the “Holocene”, has lasted quite a while compared to the other interglacials.
Note also the very large and roughly symmetrical peak at about 400,000 years.
So … how does this relate to the Milankovitch cycles? Figure 3 shows the temperature overlaid over the Milankovitch cycles.
Figure 3. Antarctic temperature variations estimated from deuterium data, overlaid on the Milankovitch insolation cycles.
I gotta say I’m just not seeing it. The biggest oddity is that around 400,000 years, the very small insolation peak is correlated with a very large temperature peak. In addition, in general there seems to be very little correlation between the swings in insolation and the swings in temperature. Finally, the most interesting thing is the total lack of any 21,000 year cycle in the temperature.
Now, some authorities say that the crucial factor is not the insolation at 40°N, but the insolation at 60°N. So I checked that … but the difference in the pattern is only trivial. It mainly just affects the size of the swings, which are somewhat smaller at 60°N, but the pattern of large and small swings is essentially unchanged.
Now as might be imagined, I’m not the first one to be puzzled by this. It’s widespread enough that there’s a Wikipedia page entitled “The 100,000-year problem”, which points out that:
The 100,000 year problem is a discrepancy between past temperatures and the amount of incoming solar radiation, or insolation. The latter rises and falls according to the strength of radiation given off by the sun, the distance from the earth to the sun, and the tilt of the Earth’s axis of rotation. However, the recent change between glacial and inter-glacial states that occurs on a circa 100,000 year (100 ka) timescale, does not correlate well with these factors.
Due to variations in the Earth’s orbit, the amount of insolation varies with periods of around 21,000, 40,000, 100,000, and 400,000 years. Variations in the amount of incident solar energy drive changes in the climate of the Earth, and are recognised as a key factor in the timing of initiation and termination of glaciations. Isotope analysis shows the dominant periodicity of the climate response to be around 100,000 years, but the orbital forcing at this period is small.
However, my perplexity seems to be for a different reason than the other folks discussing this, which is that the really large insolation swings occur on a 21,000 year cycle, and there’s no trace of that in the EPICA data. I’m not so much interested in the existence of the 100,000-year cycles in the temperatures, as I am by the lack of any temperature response to the ~100 W/m2 swing in the insolation. Yes, I know that overall for the globe as a whole the swing is small because the hemispheric changes oppose each other, but for each hemisphere the changes are very large. Why do we see no trace of those very large swings?
Anyhow, all comments welcome.
Best wishes to all. It’s one AM, there was a new moon earlier tonight, I’m going outside for some stargazing, and I wish the same level of joy and awe to all of you.
w.
As is my custom, I ask that if you disagree with someone, please QUOTE THE EXACT WORDS YOU DISAGREE WITH so that we can all understand the exact nature of your objection.
This is another for the climate file called, “It’s settled but not really” cross indexed with another climate file called, “It’s settled we’ll figure out why and how later”.
It does remind me of the countless conditions and mechanisms from the macro to micro level are in place and working together to make this earth very fertile for life. I’d call it a miracle, not in a supernatural sense, but in the sense it is astounding.
The Milankovitch cycles affect the distribution of insolation, not the insolation as a whole over the whole globe. So i dont think you can apply global temperature anomaly expected variation as a function of the insolation at any given latitude. Eg you cant say I expect global temperatures to go down because there is a 100W/m2 drop at 60 degrees north.
The general pattern is a rapid climb out of an ice age followed by an interglacial then a relatively slow decline back to lower temperatures. I believe the rapid climb out is due to an increase in northern latitudes insolation which melts the great ice sheets with reduced albedo feedback causing more warming etc etc …. But I agree with you it cant just be the insolation as the correlation is weak.
Whatever happened to low climate sensitivity? The negative feedback from clouds?
OK, I’ll bite. The clouds hate you! 😉
“ice ages typically develop slowly, whereas they end more abruptly.”
That is exactly how the ice-laying and ice-break happens in nordic lakes, each year.
The ice-break in spring, even in large lakes, happens within hours – but ice-laying can take weeks.
This is well-known for us in northern Sweden, but maybe not elsewhere?
The question is what summer solar insolation is required to melt out all the snow from the winter. Once, a location falls below about 420 W/m2 in the summer peak, that seems to be the level where there isn’t enough energy to melt the snow and ice in the summer and the only location where there happens is 75N to 90N.
The variation you show at 40N is always high enough to melt out the snow in the summer. And the other issue is the 40N insolation is really 1000 W/m2 in the daytime solar peak and 0 W/m2 at night. It is really the daytime solar peak one should be concerned about. And even at 65N, the summer daytime solar peak is always energetic enough to melt the snow.
The other issue is that winter, the solar energy has the opposite cycle to that of the summer. When the summer is down, the winter is up, so the annual change is not nearly so much different in the Milankovtch as the chart makes it seems. 40N is getting enough energy (at low Albedo levels) that it is warm enough to keep the snow away in summer and even in the winter at a low Milankovitch cycle.
75N is where the action is.
Then it is just a meter of how the ice-Albedo feedback kicks in and reflects the sunlight so that even an upturn in the Milankovitch Cycle does not do enough to melt the ice because, most of the extra summer sun just gets reflected away.
Bill Illis January 23, 2015 at 4:03 am
Thanks, Bill. There are several problems with your hypothesis. First, moving the measurements north doesn’t change the shape of the insolation curve, just the intensity.
Second, at 75°N, it’s daytime all the time in JJA.
Third, at 75N the peaks of the average insolation do not exceed 200 W/m2.
Fourth, there is still the pesky interglacial at 400 Kyears, and the peak insolation at 75°N at that time is only about 188 W/m2.
Fifth, the swing in insolation is much smaller at 75°N, only about 40 W/m2 max peak-to-trough.
But in any case, we’re nothing if not a full-service website, so here’s the 75°N data, you can check it for yourself.
w.
Eureka Nunuvut Canada at 80N solar radiation tower data from 2009.
By May, solar radiation down gets up to 400 W/m2, but the snow reflects back 70% of that and net solar is only about 50 W/m2.
By early June, however, the snow has melted and the net solar radiation rises into the 450 W/m2 range. The snow comes back in early September and the net solar falls toward just a few W/m2
http://www.esrl.noaa.gov/psd/arctic/observatories/eureka/img/eurekaData.png
The Ice Ages start right where this radiation tower is located. The SW data in this chart (left side) is the indicator of the ice ages.
When the summer daytime peak solar radiation falls to 410 W/m2 in a Milankovitch Cycle, the snow stops melting completely out over a summer period at Eureka and it builds up and turns into ice eventually. Then Milankovitch can vary by large amounts but 70% of it is just getting reflected back to space. Ice age lasts for 100,000 years until the ice has melted back starting at Chicago (18,000 years ago) and ending at Eureka (8,000 years ago).
The 400,000 year ago period was similar to that today in that the summer net solar radiation at Eureka always stayed above 420 W/m2 and the snow always melted out the summer. It lasted for only about 25,000 years however.
In the next 52,000 years, Eureka peak daytime solar radiation is going to stay above 440 W/m2 and there will be no Ice Age.
Assuming that TSI stays constant.
Bill, thanks for that lovely Canadian data, and I’d greatly appreciate a link to it … but how does that explain the interglacial 400 Kya ago when there was only a small increase in insolation up north?
Best regards,
w.
Eureka Radiation Tower data here.
http://www.esrl.noaa.gov/psd/arctic/observatories/eureka/eureka_tower.html
Other info on the station here which is a world-class climate monitoring station.
http://www.esrl.noaa.gov/psd/arctic/observatories/eureka/
http://www.esrl.noaa.gov/psd/iasoa/stations/eureka
And somehow, this guide for the station got hosted on WUWT?
https://wattsupwiththat.files.wordpress.com/2010/04/visitor_guide_to_eureka_apr_2010.pdf
If you smoothed the insolation data, and then took the derivative of it, there would be a close correspondence.
qwaezee, do you have a citation for that claim? Or perhaps a graph? I find lots of people are very sure of things that turn out not to be true once they go looking for actual data to support their hypothesis … including myself, sadly, as this post clearly demonstrates.
In any case, you say “smooth the insolation data” … I’m always extremely reluctant to use smoothed data in an analysis, because smoothing is known to introduce spurious correlations. See my 2008 post here for some practical examples of the problem, or google “yule slutsky”.
Best regards,
w.
I do not have a citation or a graph. But note that when the peak-to-peak value decrease, it gets colder. The opposite is true when they increase. There is a very strong correlation.
Now I know you’re just waving your hands, qwaezee. Look at the period around 400 Kyears ago … very small peak-to-peak values, very high temperatures.
w.
Willis, check Gerard Roe’s 2006 paper. There are several graphs in that paper, highlighting what qwaezee noted above. He was a former student of Lindzen’s.
Lubos Motl does a write up here
http://motls.blogspot.com.au/2010/07/in-defense-of-milankovitch-by-gerard.html
And the correlation between rate of change of ice volume and the Milankovich cycles is indeed close. But of course rate of change of ice volume vs actual ice volume begs the question as to how much impact albedo really has. Afterall we would expect faster rates of melt when there is more insolation…its a bit of a no brainer. But the analysis still doesn’t prove the point about albedo changes being the cause of ice ages.
The graph looks impressive:
http://lh4.ggpht.com/_4ruQ7t4zrFA/TDL7RSCEgZI/AAAAAAAAEGE/0HeA3XYGVmM/milankovitch-roe-fig2.JPG
Concerning albedo
How do you assess this factor when it happens that glaciation reversed when the albedo reached maximum? This hardly points to an important feedback mechanism.
Glaciers can have Albedos up to 75%. In the summer, Greenland’s Albedo is 75% on the majority of the glacier (the edges are lower). The changes in the Milankovitch do nothing to the central glacial mass since 75% of the changes are reflected back to space.
At the edges, now Milankovitch can have an impact and the melt has to start at the edge and move inwards. It takes a long time to melt out a 2km high glacier starting from the edges inward.
You are considering only N summer insolation but there is a reverse effect for winter and for S hemisphere so that things are largely cancelled out. Seems that the proper causes need to be considered and integrated over the year.
Ray, I’m just investigating the generally accepted explanation, which is that it is the insolation variations in the northern reaches of the northern hemisphere that make the difference. Globally, as I pointed out in the head post, the hemispheres largely cancel each other out.
w.
What warms the world is the ocean. So it would be insolation variation which caused most direct sunlight on most ocean water which causes global warming
If you heat land the most, one simply causing more energy to escape into space- the net result would be global cooling.
So we live in icebox climate because the ocean is not being warmed enough.
It also “seems” that when we begin get the ocean warmer we then dive into a glacial period.
So it appears the icebox climate has mechanism which stops ocean from warming up very much and thus prevents our world from being warm.
So our question is not what causes warming, but rather what causes cooling.
And rather look that things +10,000 years ago, we could start by looking at the Little Ice Age.
What caused the cooling which gave us the Little Ice Age.
Determining what caused the Little Ice Age is far more important to the humans currently living
on Earth, because a minor “little ice age” will kill million if not billions of people.
Or drop of .5 C is more important to the billion people living in poverty as compared to rise of twice as much [1 C].
Plus what causes cooling is more important in terms of scientific interest.
Anyways it’s thought volcanos and sun spot have something to do with the Little Ice Age, but to me this doesn’t fully explain it.
Though if it was merely sunspots and volcanic activity- that’s not good news, as it looks like we entering a low solar activity period- and we don’t control volcanoes.
gbaikie writes “If you heat land the most, one simply causing more energy to escape into space- the net result would be global cooling.”
This feels intuitively right to me. IMO there are far more things going on than simply changing insolation causing ice based albedo changes.
Ray, your point is related to the point I wanted to make. The Milankovitch cycles are obviously the superposition of a number of periodic effects. I don’t know the origin of all the periods, but perhaps a phase difference for the southern hemisphere cancels the 21k cycle and leaves something at 100k. That would help to explain why a 100k cycle is observed but a 21k cycle is not.
Is that possible?
If you want to try and match the northern hemisphere summer cycles you may wish to use Greenland ice cores not Antarctic ones. As others have mention when the insolation is low in the northern summer it is higher at other times and places, it all balances out pretty well over the year for the total earth. The theory is based on a lot of feedback from less summer snow melt. Like all model based climate theories I would be very skeptical.
Use the changes in global average insolation because the atmosphere and oceans transport heat quite efficiently around the world. Notice local insolation changes from 1,000 W/m^2 to zero in just 12 hours everyday but it doesn’t freeze in the tropics every night.
Yes, but local insolation changes to zero and back in the polar regions, and they definitely freeze alternately. If your theory that “the atmosphere and oceans transport heat quite efficiently around the world” actually worked, we wouldn’t have winter in one hemisphere and at the same time summer in the other hemisphere, would we? …
w.
Winter and summer are seasonal and geographic variations. Your Figure 1 is seasonal and geographic. Figure 2 is not seasonal and different geographic location. Don’t expect to find correlation much less causation between the two graphs. 3.7 W/m^2 is global and all-year round. If you’re looking for global changes in temperature, look at the whole picture – global changes in insolation.
Look at the seasonal variation of solar insolation at 40 degrees north latitude. It’s about 300 W/m^2 every year but it doesn’t cause big changes in global temperature. It’s offset by insolation variation in southern hemisphere. It’s important to look at the whole picture.
Just how do you measure insolation during the summer months 800 thousand years ago ?
Good question, WitchFinder. It’s calculated from the well-understood cyclical variations in the earth’s orbit around the sun …
w.
Why don’t we question the record from the ice cores at the EPICA dome in Antarctica?
Are we sure they are showing what we think they are showing?
And are we sure they are representative of anything, except the area of the EPICA dome in Antarctica?
Why should any sceptic want to question any ice-core record?
They show that climate on this planet change naturally, That it has varied in a cyclical pattern for hundreds of thousands of years, long before any possible suggestion of human causation. They show that previous inter-glacial periods were warmer than this one. They clearly show the Minoan, Roman and Medieval warm periods, contradicting Michael Mann’s hockey stick.
http://jonova.s3.amazonaws.com/graphs/lappi/gisp-last-10000-new.png
They provide what Science of Doom calls ‘An Inconvenient Temperature Graph’; well worth reading
http://scienceofdoom.com/2009/11/22/temperature-history/
Why question that?
Sometimes sceptics get so used to rejecting any scientific measurement that they end up rejecting evidence that supports their case (that’s what being a sceptic means I suppose).
I question the ice core record as it doesn’t seem to fit with the theory of how ice ages start,.
Just because evidence supports my case doesn’t mean I should support the evidence. My case might be wrong. Evidence supports my position – my position should have no impact on how I interpret the evidence.
And I still can’t see why a local thing like an glacier is expected to reflect the whole planet.
How do ice ages start? What doesn’t fit?
We have ice core records from both ends of the world, from Greenland where the GISP2 record comes from and from Antarctica where the Vostok ice-core comes from. All the ice-cores show broad agreement with the glaciation periods. What I forgot to mention is that the Vostok ice-core shows that CO2 levels follow temperature changes, not the other way around
http://upload.wikimedia.org/wikipedia/commons/c/c2/Vostok-ice-core-petit.png
The ice-cores provide the most important evicence for the sceptic position that climate varies naturally.
Is that an instrumental on a proxy, and does correlation of the rise at the end with the rise of CO2 mean there is causality?
Note the rises into the optima. CO2? Likely not. So where are you?
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We should question it because we should question everything. Skeptics often rightly accuse AGW proponents of being spoon fed, or blindly following the MSM. Don’t blindly accept anything only because it currently supports your ideas.
MikeB wrote: “Why should any sceptic want to question any ice-core record?”
Because we are skeptics.
There are too many people on both sides of this debate who will blindly accept any evidence, no matter how specious, that supports their side and reject any evidence, even when quite solid, that supports the other side. A pox on such people.
The plot shown by MikeB shows significant increases of dust levels as each period of cooling progresses. When the dust gets to a sufficiently high level the temperatures rise rapidly, at which time the dust levels drop back to close to zero. Any explanations?
Could dust be driving climate?
(Dust in Norwegian is ‘fool’, so this must be a very foolish climate theory!)
Tim Crome,
More likely it is climate driving dust.
The cooler, the drier; the warmer, the wetter. At the beginning of the Holocene, precipitation doubled very quickly, as evidenced in the Greenland ice cores. Arid regions became well-watered, as the Sahara, the Gobi, the American west, other places.
Odd graph label, given that not one bit of it actually shows the Younger Dryas. This is the graph of the Holocene. The YD is about 2000 years left of the earliest date BP.
Makes one worry about how well the creators are connected to reality.
rgb
Willis, you have stumbled upon something which just about who has studied earth sciences comes across at some point, that Milankovitch cycles don’t correlate all that well with ice age records.
However, there are at least several suspected reasons I have heard why the fit isn’t too good.
First is that ice itself drives its’ own climate (mostly through albedo, but also changes in ocean currents and vegetation), and it takes long periods of time for this ice to build up and therefore there are also long delays for the full effects of large amounts of built-up continental ice to kick in. We are talking tens of thousands of years of delay.
Also, the rate of ice melt, once underway, is quicker than getting it built up in the first place. There is a tipping point when ice fails to melt in summer, and another major tipping point when the first land begins to appear beneath the ice in summer. In both cases, the relationship with insolation is not linear. On a continental scale, with a mile of ice over North America and Canada and Eurasia, this makes a difference. What you get is periods where temperatures are moving much more rapidly in one direction, particularly during the melt phase. There is no linear relationship here with incoming insolation, continental-scale ice likes to operate on its’ own timescales.
Another potential factor concerns how the build up of continental ice itself affects ocean currents. When the sea is 180m lower, the pattern of ocean currents and heat distribution changes. There is land between Australia and Papua New Guinea, as well as North America and Asia, as well as the UK and Europe, as well as other places (including possibly the ?Mediterranean, if I remember).
Also, because the world is cooler during ice ages, there is less vegetation and rainforest cover, which may affect temperatures.
Orbital variations include the actual time of year when the earth is closest and most distant from the sun (ice ages are strongest when the earth is furthest away during the northern hemisphere summer), as well as how far away in total it is, as well as variations in tilt. These combine in complex ways with ice build up and ocean currents. Most mathematicians are not glaciologists.
Hope this helps.
Excellent points. Additionally the Sun experiences fluctuation of solar output; sometimes more sometimes less which can be observed in ratios of various isotopes formed in the atmosphere by solar energy (and particle) interactions. Also given the long time cycles observed, it has been proposed that solar radiance may also be affected by “dusty” portions of space as our solar system cycles through our galaxy.Hence the resolution problem which likely has no single answer.
The correllation is fantastic if you consider the derivative of ice volume versus insulation at 60 N. See Roe 2006.
–First is that ice itself drives its’ own climate (mostly through albedo, but also changes in ocean currents and vegetation), and it takes long periods of time for this ice to build up and therefore there are also long delays for the full effects of large amounts of built-up continental ice to kick in. We are talking tens of thousands of years of delay.–
It may take time to do this. But suppose it were to occur in a instant.
So get a lot of snow and built the ice caps which were a mile high on north America continent-
this elevation of the ice, would cause the ice to be cold.
Or if average surface was 5 C per year- a mile up has below 0 C average temperature.
In in conditions of hottest year ever, such man made snow doesn’t melt.
And one could have more snow is added per year. And living near enormous ice mountain make the lower elevation around this ice, cooler- so that region’s snow doesn’t melt as much.
But other than regionally cold temperature, does this actually cause the world to cool?
I don’t think vast lava pit or vast ice mountain affects global temperature- it doesn’t warm or cool the world- it is hot or it is cold, but it’s not warming or cooling the world. It could do things like alter the jet stream and affect the world. It could involve a mechanism of sucking in moisture or could bringing moisture somewhere. Or it could change weather patterns, and because it alters weather patterns it could have some kind of a global effect- but vast lava pit might cool and ice mountain might warm.
Though of course it’s possible the lava pit could warm and ice mountain could cool the world.
Lands do not warm or cool oceans, oceans do warm land.
And it is the temperature of Earth vast ocean which is the Earth’s average temperature of 15 C.
Continental-scale ice cover affects albedo.
In geological history, there is a correlation with how much land is near the poles and ice ages, combined with how much the continents are all stitched together. This is because if there is more land nearer the poles, it allows more ice build up which re-inforces itself and leads to runaway icehouse. More land together also enhances this effect, as oceans provide a buffering effect to more ice cover. The actual shape of the continents also effect ice build up-more land polewards is generally better for ice build-up (such as North America, but not South America). There is also evidence that more land about both poles enhances the ice age effect, as is currently the situation.
We are currently heading into permanent icehouse, as Africa is joining Eurasia and gradually closing the Mediterranean, which is a remnant of the Tethys sea. What you will then have is land from northern Russia to Africa, which might be the final nail in the coffin where there are no more interglacials, which are able to melt away all the ice which advances from the north, but which is currently inhibited by the Mediterranean. Once the Mediterranean closes in a few million years, ice will be able to move down more easily into Africa from Europe. One wild card is the current break up of East Africa, which would allow warmer waters to eventually flood into Africa inhibiting ice build-up.
North America and South America have also now joined. In North America, ice advances from the north, but this will always be stopped by the shape of the Gulf of Mexico. If South America were flipped, ice ages would be worse, as currently there is little land south of Brazil, which doesn’t allow much ice build-up, but the shape of North America enhances ice build up, since most of the land is in the north.
So continental configuration and shape definitely affects ice ages and earth temperatures. We are currently getting colder and colder, larger due to Africa joining Eurasia, India has also joined Asia.
The 100,000 year cycle is dominant at present because even thought the 21,000 year cycle is stronger, it is too short to allow much ice build up. What happens is that the 100,000 year cycle combines with the 21,000/40,000 year cycles during a longer term cooling trend to tip the balance to widespread glaciation; the process needs multiple cycles which combine to enhance each other, in conjunction with longer term ice build up, to produce the greatest cooling effect.
Mathematicians don’t integrate the effect of long term ice build-up, so they miss it.
And by the way, the 400,000 year warming peak in the record probably occurs because of the lack of any cooling at that time over a longer period; it is this long period of relative stasis, which allows more continental ice to melt, to give a very low overall earth ice albedo, and a warmer, broader peak to occur.
Willis, have you done any of your frequency analysis on the ice core data? Are there any 21k yr / 400k yr signals to be found that way?
The Milankovitch Cycles are not as simple as this article assumes.
There are multiple components which do not vary in unison and so there is considerable variation in the way the componentrs interact such that there is an infinite number of different ways that the variations can impact on global temperature.
http://www.indiana.edu/~geol105/images/gaia_chapter_4/milankovitch.htm
Furthermore:
“It is of primary importance to explain that climate change, and subsequent periods of glaciation, resulting from the following three variables is not due to the total amount of solar energy reaching Earth. The three Milankovitch Cycles impact the seasonality and location of solar energy around the Earth, thus impacting contrasts between the seasons.”
Does the sun do something we’ve never see?
Pretty likely. We haven’t ‘seen’ it for long.
Better, since we have new ways of observing and theorizing, it’s doing something new every day.
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Correction, ‘new to us every day’.
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What happens to sun if a rock size of Vesta hits it [there are thousands maybe millions of Vesta rocks in our solar system. And Sun is the most hit object in our solar system [because it’s the biggest [and also gravity- but not just because of it’s dominating gravity].
Jupiter impacts we seen:
http://www.spacetelescope.org/images/?search=shoemaker+levy
And seen comets diving into the sun:
http://www.space.com/11661-comet-dives-sun-solar-eruption.html
So small rocks diving into the sun [and one time saw small rocks hit Jupiter] are
commonplace- but yet to see something big hit the sun.
Would it make massive sun juggle a bit?
I imagine if looking at a lots of stars we will see it [from safe distance].
Evidence that this will continue to be an extended interglacial period is put forward by the paper Evidence for a Global Warming at the Termination I Boundary and Its Possible Cosmic Dust Causeby Paul A. LaViolette.
The Cryogenian period may have ended ~635 million years ago due to volcanism under the ice sheets, or due to a reduction of albedo over time as lower precipitation rates persisted and the ice sheets became more translucent.
For some reason, it’s less controversial to point to a period in our distant past!
One thing I have read is there definitely seems to be faster plate tectonics (from palaeomagnetic reconstructions etc) around ~600Ma-500Ma, also meaning more volcanism. Not sure about exact timing with de-glaciation though.
Yes, the merger of the Rodinia super continent is supposed to have the freeze by interference with ocean temperature transport.
There is observational evidence from early astronomers from places like babylon and egypt that the current calculations for the earth’s obliquity cycle may not be correct. while this is routinely dismissed as incorrect due to their primitive instruments, one should keep in mind that these people were just as smart us, and perhaps had even a greater incentive to try and get the right answer in their quest, like us, to predict the future.
Nice point. It would seem they used more methods to predict the future, but I’d have to think about that.
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Lost a detailed comment due to wonky connection in a beach cabin in South America. May try again when closer to civilization.
But here’s the 1976 paper that convinced most climatologists that Milankovitch was right after his being ridiculed for so many decades:
http://www.ncbi.nlm.nih.gov/m/pubmed/17790893/
Willis…
…
Check out the diagram on page 3
http://www.math.wsu.edu/faculty/genz/315/lessons/l407.pdf
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Looks like the Milankovitch cycles are forcing the glaciers as a harmonic system
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Willis, I suggest you take a look at Gerard Roe’s 2006 paper In defense of Milankovitch, published in GRL. Roe maintains that one should not attempt to correlate temperature with insolation, but, rather, the time derivative of temperature.
See also comments by Luboš Motl: http://motls.blogspot.com/2010/07/in-defense-of-milankovitch-by-gerard.html#more
Henry, M-cycles fail on all counts:
1. correlation with climate is no more than by chance
2. slow evolving cycle cannot explain the precipitous temperature increases seen at the onset of interglacials or interstadials as evidenced in ice core records.
3. Ice age cooling was worldwide and included the tropics, yet tropical insolation would increase when high latitude insolation decreased per cycle.
From all considerations, M-cycles fail to account for ice ages.
Rather than take the time derivative of the temperature, which is always an iffy busines with data, take the integral of the Milankovitch cycle (minus the dc component) and then do the comparison to check out Roe.
I’ve done that, and the integral shows no correlation at all with the ice ages.
w.
One big problem with the proxie ice core data is estimating time. The estimates of oldest times can be off by thousands of years. Years ago I did a cycles analysis of all the ice core data I could download. Please read the section on ice cores in http://www.kidswincom.net/climate.pdf and give me your thoughts.
fhhaynie–
Nice work. Your data appears to end in 2009. I wonder now that 5 years have passed, whether another run of your least-squares fits to the several cycles would return similar estimates. You had predicted then a decline in SST in a few years, which does not seem to have developed.
As it turned out, it appears that a rise in a longer cycle tended to cancel some of the decline in the 20 year cycle so we ended up with a “hiatus” which was already in progress. There is a lot of error in my results. I haven’t looked at any ice core data younger than 1984.
Your observations are right on the money, and agree with my own when I first read about Milankovitch, looked at the data, and uttered a discrete “bullshit” cough before returning to my muttons. However, do not bring this up with a climate scientist, as (aside from veiled references to the 100,000 year problem) they will tell you that Milankovitch plus feedbacks is the Answer to it all. And truth be told, there is some evidence that Milankovitch is a (set of) factor(s) in glaciation, only not over the last 600,000 years. If you take the temperature data of the Pliestocene in general, 3 million years ago at onset the glaciation had a very clear roughly signal that more or less fits the short period orbital cycles e.g. obliquity at 41,000, precession of the axial tilt at 26,000. I’d say that the evidence is strong for this up to around 1 mya. The ~40 ky cycle then shifted to a ~100 ky cycle and nobody knows why!
This is up there with the argument that the Pliestocene started in the first place because of the closing of the Panama isthmus. Why? Because correlation, obviously, is causality! Except when it isn’t.
The scary thing about the Pliestocene record:
http://upload.wikimedia.org/wikipedia/commons/6/60/Five_Myr_Climate_Change.png
is that the glacial cycle is obvious deepening over the entire period of 5 million years. Look at the amplitude — the deepest parts of the Wisconsin were 9 C colder than the present. That’s centigrade! On a finer scale, the Eemian interglacial was 1-2 C warmer than the present in a significant pulse that lasted some thousand years.
I personally think that claims of knowledge of cause and/or ability to make pronouncements predictive, projective, prophetic, or just qualitative are highly exaggerated by all who participate in this discussion. There are far too many things about the evolution of the Earth’s climate that make little overt sense. No, it doesn’t correlate well with the solar cycle over the short run record. The annual ~91 W/m^2 variation anticorrelates with the annual temperature variation — the Earth is coolest, on average, when it is closest to the sun and receiving on a daily basis some absolutely stupendous number of joules of TOA insolation more than it does in NH summer when it is farthest away and global temperatures are highest. The relaxation times associated with Stefan-Boltzmann type radiation cooling are hours (or at least, order of days) — and I while I’m happy enough to imagine the ocean introduces a lag in forced response as it buffers all changes, it is difficult to understand the lack of immediate response in land based temperatures to the reduction in forcing. The glacial episodes do not correlate well with Milankovitch, and while sure, one can make up a story about glacial albedo feedback, this is highly implausible because if it were that simple, we’d be one enormous snowball as glacial ice would basically never melt.
I think that we are missing one or more major factors in the evolution of climate. One of them could simply be spatiotemporal chaos on stupendously long time scales with complex multivariate feedbacks and drivers. However, I’m open minded about many other possible explanations, including new physics. My favorite science fiction example is dark matter. If we postulate dark matter (defined as the non-EM-coupled mass that apparently screws up simple gravity so that galactic scale orbits don’t correspond to visible mass), then there should be an enormous amount of the stuff around. Since it doesn’t interact electromagnetically, it is not driven away from stars by things like solar wind (light pressure). At the same time, the vast clouds of the stuff are constantly being stirred by star systems as they orbit the galactic center, but it cannot clump together via short range forces the same way normal matter does, so it probably forms things like rings around star systems, with a fair chunk of the Sun’s mass at the core actually being dark matter that has fallen into it and the rest in a diffuse orbit, being dragged along and cleared out by the planets (which also probably have dark matter cores).
As the solar system orbits, however, it very likely moves in and out of new bands of the stuff. Dark matter macroscopically would be very wierd — over time one could easily enough build weakly (gravitationally) bound “whorls” of DM which wouldn’t form actual chunks like asteroids but would be more like a gas with a long range attraction force that cools the clumps to coalescence via evaporation to where they are semi-stable. These local clumps could have substantial mass — easily asteroid scale mass since DM is supposedly quite massive and prevalent.
What would happen as the sun and planets moved through this inhomogeneous background? A clump of DM falling into the sun (or a locally thicker patch of DM falling into the sun, or the earth) would have extremely odd effects. For one thing, there would be no spectacular explosion, because DM doesn’t interact with atoms more than enormously weakly. The hot Sun would remain hot, the DM would remain cool because the two forms of matter barely interact. BUT the clumps WOULD exert an IMPULSE on the solar interior, acting like a “pucker point” where solar mass gravitationally compresses out of place. This compression would heat up the solar matter locally in the pucker, which would affect solar dynamics global and local. I could easily see solar output being substantially modulated in a sustained way by passage through DM clouds and/or could see events like CMEs being associated with the orbits of invisible cold clumps of DM through the actual solar body and tracing the moral equivalent of compression wave along a line through the photosphere and nucleating a magnetic response. A second interesting question is what might happen if blob of comparatively dense DM condensate — say, one the size of Mt. Everest — intersected the Earth. Again, not what you’d expect, not necessarily mass extinction or the like, because it would be like a big blast of neutrinos — you’d never even notice it from direct interaction as the Earth is 99.99…% transparent to neutrinos. But it could cause a local puckering of gravity a gravitational anomaly that yanks the crust, the mantle, the ocean, the atmosphere, into a transient state of higher density and compression heating. And what the effects of these sorts of things might be it is hard to say. It could be the actual cause of many things we attribute to chaos or random chance — the emergence of a volcano, Tunguska-like episodes, lights in the sky at night caused by compression heating of chunks of atmosphere, ball lightning. Very difficult to detect as one cannot see the cause, only the effect, and the effects one sees often or even generally do not have specifically attributable causes.
Well, enough SF for the morning, back to work. But as I said, since the climate depends on physics, and since physics is incomplete, it is astoundingly difficult to exclude the possibility of exotic explanations that are simply omitted from consideration in any climate model or hypothesis because we don’t have a good enough grasp of or evidence for the physics itself to know how or whether to include it.
rgb
Might the planets, through their orbits, somehow moderate dark matter entry to the sun?
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My objection to the whole concept of dark matter is that it ought to be always there already.
It ought to be formed into rings around our Sun (like the asteroid belt. It ought to show up in the motion of the planets. It ought to be bashing our world all the time – with the volcanoes and new cracks in the tectonic plates.
But it doesn’t.
It just shows up between the stars.
It seems to me like it’s a math error or a failure of the physics model. Yes, I doubt that there is any physical thing to be found that is dark matter.
And don’t get me started on dark energy.
Heh, M C, turbulence?
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http://wp.production.patheos.com/blogs/exploringourmatrix/files/2014/02/Doesnt-Matter.jpg
OTOH, the cosmological observations that support it are both old, repeatedly confirmed, and almost certainly neither a math error or observational error. It is a simple point of fact that the orbits of stars in galaxies and the variation of the expansion of the universe at long distances have anomalies that at the very least cannot easily be explained by Newtonian or Einsteinian gravitation.
But as I tried to point out above, DM is going to be highly counterintuitive because it lacks EM coupling. Normal matter cooled to where it coalesced by radiating away EM energy (now visible as the 3 K background). If DM is truly only coupled to other matter by gravitation, it has no fast cooling channel and is likely still carrying a lot of the kinetic energy it had immediately post Big Bang. Gravity wave cooling is likely enormously slow for DM interacting with DM, somewhat faster where DM interacts with large massive normal matter objects, so that it WOULD weakly condense into blobs around galaxies, but those blobs are very, very “hot” and have no EM stickiness and hence no tendency to form DM “objects” that can bash things at all. I’m not at all certain my assertion of POSSIBLE blobs (likely nucleated on dense chunks of ordinary matter) holds up — it depends in some detail on what you postulate as coupling mechanisms with ordinary matter.
Neutrinos are a perfect example of something we can actually measure (because they do couple to ordinary matter, however weakly, and carry essential energy and momentum in decay events) and that even have a tiny mass (probably) but they interact SO weakly that if you didn’t do just the right experiments and go looking for the missing mass-energy, you’d never find them. A neutrino is happy going straight through the middle of the Earth as if it weren’t there, and certainly doesn’t get itself into thermal equilibrium with the Earth.
So your worries about “whacking around” and it being “obvious” are well taken — certain less invisible forms of DM with some sort of coupling would indeed whack around, thermalize with ordinary matter, and might well be observable if we looked in the right places. But if DM REALLY only couples gravitationally, it isn’t clear that there would be any small scale stable condensate, merely a weakly bound “gas” at a temperature far higher than escape temperature from anything but black holes and ultra dense objects.
No whacking, and maybe only TINY modulations of things like solar density as it moves through slightly denser clouds of the stuff swirling through the galaxy. But tiny modulations can produce big effects for things like solar fusion efficiency and gravitational compression, and the dense heart of stars is the kind of place one MIGHT have sufficient local coupling to gravity to speed up thermalization, even if thermalization is comparatively hot.
rgb
Ok, probably not a math error then (although I doubt anyone could get published easily if it was). But I thought it far more probable that it was a failure of our model of gravity.
If you need to invent something that can’t be seen to make the physics work then you aren’t breaking Ockham’ s razor – but it’s being blunted.
OK, so there may be some form of dark matter that only interacts by gravity, more elusive than neutrinos, and yet somehow not evenly distributed. There might be.
But it still looks like a fudge factor to me. Perhaps I lack the poetry to stare at the stars and say “I feel I understand”.
How does this matter behave with respect to inertia? Does it resist acceleration or does that not even apply when it is only affected by gravity. Is it at least a normal form of mass and not merely an additional constant in only one type of calculation?
Not the gravitational interaction of the sun with the planets, rather the interaction of the planets with the dark matter, derivatively dark matter with the sun.
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rgbatduke: “No, it doesn’t correlate well with the solar cycle over the short run record. The annual ~91 W/m^2 variation anticorrelates with the annual temperature variation — the Earth is coolest, on average, when it is closest to the sun and receiving on a daily basis some absolutely stupendous number of joules of TOA insolation more than it does in NH summer when it is farthest away and global temperatures are highest. The relaxation times associated with Stefan-Boltzmann type radiation cooling are hours (or at least, order of days) — and I while I’m happy enough to imagine the ocean introduces a lag in forced response as it buffers all changes, it is difficult to understand the lack of immediate response in land based temperatures to the reduction in forcing.”
I didn’t understand that. Doesn’t the lower heat capacity of all that Northern Hemisphere land, where the insolation concentrates during our summer, make up for the lower overall insolation at that time? I.e., less heat but also less heat capacity so higher temperature?
(By the way, I did enjoy the “science fiction.”)
“Tunguska-like episodes, lights in the sky at night caused by compression heating of chunks of atmosphere, ball lightning.”
From personal observation I am convinced that some ball lightning is produced with an ionized metal core. Some years ago I was stopped in traffic on a city street because of a medium voltage power line that was torn lose from high wind and swinging into the adjacent power line, every time contact was made the arc ball was so bright that I had to look away. After several cycles of this, the one line finally snapped and a very bright ball of ionized gas from 1 to 2 feet in diameter was ejected from the broken line at a ~45 degree angle and flew some 500 feet disappearing into a residential area. The object seemed to actually have weight as it traveled in an arc like that of a tossed ball.
This is up there with the argument that the Pliestocene started in the first place because of the closing of the Panama isthmus. Why? Because correlation, obviously, is causality! Except when it isn’t.
I’d be interested in your argument regarding the closure of the isthmus of Panama formation.
There’s strong evidence of a divergence in the salinity of the Atlantic and Pacific Oceans following the shoaling of the Central American Seaway starting about 4.2 million years ago.
Nice segue, Phil.
Phil.,
Panama closure theory has been debunked. The isthmus has been there since the Paleocene. See Jamarillo et al, GSA Bull. 2014.
I don’t have one. I’m just not completely convinced by the observation of supposed coincidence in time. It also doesn’t explain the subsequent deepening of the glaciation. These are geological times. The Earth is as close to being in a local equilibrium as it is possible for it to be in movements at this scale, they are ALREADY coarse grain averaged/smoothed at the data level over hundreds or thousands of years when you plot climate on a million year basis.
It is too easy to wave one’s hands. I can believe glaciation can be triggered at ANY time by a purely chaotic fluctuation in the Gulf Stream, as we do not understand and cannot predict or compute the thermohaline circulation NOW. So we can understand exactly how it worked in imperfectly mapped oceans 3.5 million years ago? So sure, I can believe it. I also doubt it. How, then, can you increase my degree of belief, if mere coincidence isn’t enough?
rgb
You should check out this paper Willis, apparently climate scientists do not properly understand astronomers, or how to use their data. Insolation in the polar regions is normally done incorrectly and can have large consequences. http://www.duncansteel.com/archives/996
The basic point is that climate modellers do not understand the time system used by astronomers and get the insolation wrong because of that. Duncan Steel did a sabbatical at my department last year and was a solid scientist.
That is an interesting contribution. Thanks for the link. About twenty years ago I read a paper in Science (I think) by David Thompson which discussed the need for better de-seasonalizing of long term temperature records, and I had the idea at the time that he had confused precession of perihelion with precession of the vernal equinox. Duncan Steel has shown my concern was not misplaced.
Thanks, William. I’m sorry, but I don’t think that his arguments hold water. For example, he talks of changes in the timing of the perihelion, saying:
And he’s correct about the phenomenon and the size, a quarter of a percent is about 0.8W/m2 … but the problem is, it’s not a change in total forcing. It’s just a change in the TIMING of the forcing. He seems to think that such a timing change is important. He points out, for example, that because of the change in the timing of earth’s closest approach to the sun, the northern hemisphere is getting more energy earlier in the year, which is true. As a result, he says:
But that totally ignores the fact that if that were the cause we would see earlier freezing, but we would also see earlier melting … and that is definitely NOT “just what is observed”.
As you point out, his claim is that climate scientists don’t properly understand astronomers … my point is that at least one astronomer doesn’t properly understand climate science. Shifting the timing of the energy makes little difference. For example, suppose that for some reason, all over the world the sun rose ten minutes earlier, and set ten minutes earlier … would that change how hot the day got?
The paper is interesting, but I don’t think his claims stand up.
w.
Let us suppose for a moment that Duncan Steel does not propose any change in total insolation, but rather only a change in the timing of its variations through the year. Then this would still be significant in the following way: additional insolation during the Spring leads to earlier Spring, which in turn leads to lowered albedo, which leads to increased absorption. In this sense albedo is a positive feedback.
However, the passage that I quoted from Steel in my comment below should dispel any idea that he does not also propose a change in total insolation. The sequence of causation is this: Differences in precession of perihelion and equinox lead to the earth presenting a larger cross sectional area to the solar flux when it is closest the sun. This increases the total insolation value.
You describe him as a solid scientist–i agree. He certainly raises an interesting point.
This is a great thread, thanks to Willis and all who participated! I’m off to read Scienceofdoom.