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.
Heh, ask Muller.
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Hi Willis, Thanks for another interesting essay. D isotopes from ice cores can indeed be a proxy for paleotemperature, but, as you are aware, it is uncertain over how wide a geographical extent the isotope measurements from a single ice core, or from Antarctic ice cores generally, are applicable. This is why the comings and goings of ice ages are commonly defined not by proxy-derived paleotemperatures but by proxy-derived global ice volumes. 18O/16O isotope ratios in the calcium carbonate shells of oceanic foraminifera (forams) vary with, and so can be used as a proxy for, the total amount of snow and ice on the earth’s surface. Several readers have mentioned the paper by Roe (2006) (http://earthweb.ess.washington.edu/roe/GerardWeb/Publications_files/Roe_Milankovitch_GRL06.pdf) where the author argues using graphical data that variations in insolation in the middle latitudes of the NH during the last half million years or so are tracked not by the absolute value of the 18O/16O ratio in foram shells (i.e. by the actual volume of ice) but by the rate of change in the O isotope ratio (i.e. by the rate of change of ice volume). Roe’s approach makes sense when you consider that you can have high values of insolation coinciding with large ice volumes and so on.
Perhaps also worth mentioning in passing that Roe was not the first to come up with the rate of change theory. Journalist Nigel Calder had published a short and quickly forgotten paper in Nature in 1974 making much the same point as Roe. See Nature, Vol. 252, No. 5480, pp. 216-218, Nov. 15, 1974.
We’re getting Calder and Calder, for how long even kim doesn’t know.
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Willis, at one of the meetings for the CLIMAP and SPECMAP projects I recall that John Imbrie who was co-author on the 1976 paper that confirmed the Milankovitch hypothesis, Variations in the Earth’s Orbit: Pacemaker of the Ice Ages, speculating that continental ice might some effect on the temperature signal that made it different from pure insolation. My 35-year-old memory of a passing remark in another life is dim, but I think he was thinking about what you’re questioning. At that time the research effort was focused on orbital parameters over long timescales. It seemed plausible that ice could produce both damping and lagging effects through changes in albedo, ocean currents, etc. that modified the orbital forcing. I also recall comments about harmonic reinforcement of cycles complicating the picture. Imbrie was a geophysicist and FWIW an early recipient of the MacArthur award.
If 100w in solar input only give 12 degrees difference from iceage to present day temperatures the 1.2 w forcing from co2 cant give more than 0,12 degrees Celcius warming. So a doubling of co2 would give a wopping 0,24 C !
Thought this might interest you Willis — a quote from Dr Lindzen during a climate seminar (AMERICAN PHYSICAL SOCIETY) about this subject:
Well, that all about Roe’s hypothesis sounds great, and I hate to contradict Dick Lindzen … but the problem is, when Science of Doom looked at the actual data … well, I’ll let SoD tell it:
As is far too common, we see good agreement for a while and then it goes totally out of phase. SoD’s two posts on the subject are here and here, take a look for yourself …
w.
“I did a Pearson correlation…”
A useless calculation based on an inappropriate technique for the data. Should have done a cross correlation over frequency.
This puts all the emphasis upon the incoming solar variable where as it may only be the triggering event. When a relatively speaking very minor event such as the little ice age can cause it to snow in July in the temperate zone one must consider the changing of albedo. And then there are the oceans, and the thousands of years of less solar effect involved in the M cycles. Like all climate effects the single variable approach will never give the answer and our planet is 70 percent water covered and we still do not understand its effect upon climate.
Still have not figured out how to get percent and parenthetical on this android!!
Thanks Willis. Very interesting article, as always.
All I can say is I’m glad we are out of the ice box now. What’s not to like?
Meanwhile, we ponder the reasons and try to forecast the future.
We should think and act locally, there’s plenty to do to repair local problems.
Willis,
Thanks, once again for a brief essay that starts interesting discussion. With regard to insolation, we can calculate the orbital parameters accurately, but we cannot translate to absorption, which is the relevant quantity, with anywhere near the same accuracy. Thus, your Figure 1 should come with a large error band, but there is no means of estimating one. As Bill Illis (Jan. 23, 4:03 am) has pointed out there is albedo variation, and albedo feedback involved. It is extremely difficult to place a credible value on albedo, I will bet; in fact, I am not sure when people quote albedo values if they are quoting point measurement at specific pairs of angles or hemispherically averaged values–by hemisphere here I mean over the entire hemisphere above the plane of ground surface.
Also, many people have noted that insolation averaged over the entire earth surface varies by less than your Figure 3, because one hemisphere (of the earth) receives more when the other receives less. However, the two hemispheres are not equivalent with respect to ocean/land distribution. There is almost no land mass at 65 south, but a lot of land mass at 65 N. Once again the relevant quantity has to be net absorption.
I think what people don’t take into account is the CHANGE in those cycles that happens during an ice age. The buildup of ice, I believe, changes the location of the rotational pole moving it a bit toward Ellesmere Island. People look at how the wobble of the axis looks today and try to basically pretend that it stays the same but I don’t believe it does during glacial periods. Remove 100 meters of ocean and deposit most of that on the land mass of what is now Canada and things change. The wobble changes and the location of the rotational pole changes. The Southern Hemisphere doesn’t change as much because there isn’t a lot of land mass to accumulate ice relative to the Northern Hemisphere.
Bottom line: Don’t assume the wobble stays the same during glacial periods as it is today.
Thanks to Willis and also to rgbatduke for his fanciful ruminations.
The current hypothesis is that we should see a swing of ~3°C for each additional 3.7W/m2. So according to the current thinking, a swing of 100 W/m2 which is maintained for a thousand years should result in a temperature swing of about 80°C (146°F) …
No.
Steven Mosher January 23, 2015 at 8:43 am
Steven, I get so tired of your drive-by blanket assertions. Please either provide more detail or don’t bother. Look, I know that you’re a smart guy (although to be fair, you were stupid enough to block my comments on your fanciful Facebook claims just because you couldn’t answer my objections), but here you can’t block me.
So how about explaining your point? You may be right, but at present there’s no way to know.
My point was that there is a seasonal see-saw between the NH and the SH, where for half a year you get more sunshine on one half, and in the other half a year vice versa.
Now, at 40 degrees N the size of this seesaw is about 100 W/m2 LARGER at some times than at others. Presumably, this should lead to a much bigger swing, summer to winter. How much bigger?
Now, you’re right that I should have used the transient climate sensitivity (TCS) rather than the equilibrium climate sensitivity (ECS) … if that’s what you meant. According to the models, TCS is about 70% of ECS. So to give us some cushion, let’s use half of ECS as instantaneous climate sensitivity.
That would give us an increase in the annual swings of about 40°C (73°F) … and we don’t see that swing in the records either. And if that was your meaning, fine, I’ve changed the head post to reflect that.
But who knows what you mean? I have great respect for your mental abilities, Mosh, but your drive-by posting habits suck bigtime.
w.
My guess would be that he is raising the issue that although radiation on specific parts of the globe vary by up to 100W/m2 the total radiation on the planet as a whole is much lower?
Mosher is right. Total insolation hasn’t changed by 100W, only the NH view of it. Meanwhile the reduction seen in the NH is increased in the SH and so globally there is no change.
Maybe this discussion explains why the IPCC doesn’t include Milankovitch in their computer models.
Of course, there is always the problem in ignoring Milankovitch changes of omitting a major swing in insolation levels. But then, what’s a 100 watt per square meter swing in insolation here or there?
Time-scale you say? But isn’t this about the accuracy of science and the future of our grandchildren?
Models that try to explain the ice ages do include Milankovitch. The big problem with trying to use Milankovitch to model ice ages is not that the Milankovitch changes are so big but that they are so small. The Milankovitch cycles iproduce almost no change in global average insolation.
Willis, WRT stargazing, Orion’s prominent to the south now after sunset & more interesting than many think. Actually further away from the galactic center than we are, but alot of prominent supergiants. Betelgeuse and Rigel are 20 solar-mass supergiants, but the most massive is the center star in the belt, Alnilam, at a whopping 40 solar-masses. Another 40-masser is the biggest star in the Trapezium, but it’s very young & dimmed by dust. Those stars are truly dangerous to life in the long-run but fortunately far enough away from us.
When you say “far enough away” do you mean far enough away that when they go super nova we won’t be swept away?
Kevin — right. Even bigger stars like Eta Carina (maybe 100 solar-masses) may even produce gamma-ray bursts from a hypernova explosion, but it’s prb’ly far enough away (6000 light yrs) to not be a concern.
The galaxy is a dangerous place and in active areas with huge stars a radiation hell-hole.
Thank Willis. I did voice my own doubts about this process a wile back. Glad to see you have looked at it. However….
Is the southern insolation graph the exact reverse of the one you have for the northern hemisphere? Would that southern graph of insolation provide a better fit, with the Antarctic ice-temperature record??
Also, I don’t see how violent swings in insolation can produce a coherent rise or fall in temperature over many tens of thousands of years. How can the temperature maintain steady trend, up or down, when the insolation has just swung back the other way?
Also, I still have problems with the ice sheets ending just north of London. The UK might be a cold place, but the summers can still be baking hot. How does an ice-sheet remain, under such conditions. I have no doubt they existed where we are told they existed, as I have seen the evidence for ice-ponds in Cheshire and drumlins in Northern Ireland. However, I always have in my mind very cloudy and cool summers, to allow these ice sheets to remain during the UKs warm summers without melting away.
Ralph
So then: a) it wasn’t hot at all in the area where London now stands; b) it did get hot (like at the terminus of Fox or Franz Josef glaciers in NZ), but the snowfall feeding the glacier at its source area and outward radiating path to its terminus exceeded the melt rate; or c) there was a combination of factors minimizing melt (such as persistent cloud cover over the body of ice) along the way. Note that there are plenty of photos online of people standing at the base of the NZ glaciers in shorts and t-shirts. Yes, I know NZ has alpine glaciers, but again, where did the Laurentide ‘start’? Trace its retreat to mountain-covered Baffin Island, where a remnant of that ice mass can be found in the Barnes Ice Cap.
Regarding the loss of ‘green’ area during the Pleistocene–has anyone calculated the trade-off between land lost to the ice and land gained by dropping sea levels 300 feet? A lot of that ‘new land’ from exposed continental shelf is in equatorial or subtropical areas that, even if cooler than today, could have been incredibly productive.
Lastly, I agree that we do need to question everything, including ice core data and all the assumptions guiding our interpretation of it.
Since Earth’s big heat sink is the oceans, that is where we need to be looking. But there is less than a decade of Argo data, and that is not high resolution, nor covering abyssal depths.
It is pretty clear that the onset of the Younger Dryas was caused by a Laurentide meltwater pulse into the North Atlantic that interupted the Atlantic thermohaline circulation for millennia, with global consequences. Who knows how many other mechanisms might be at work varying both the deep and shallow currents, both ‘hot’ like Gulf Stream and ‘cold’ like Humbolt that redistribute heat from the tropics polewards. Simple polar ice formation drives thermohaline circularion. Given crucial shallows like the Bering Strait (avg 60 meters deep now) that were basically dry land at the peak of glaciation (sea level 120 meters lower) (completely changing Arctic ocean circulation by closing it off from the north Pacific), it seems plausible that cyclic changes in ocean currents might be the main drivers of climate change on various timescales like OD events or the 100k yr ice age beat. How and why, dunno.
Great post, Willis. Elicited many thoughtful comments. So much for settled science.
No Rud, no meltwater impulse, that’s unsupported arm waving and you should know better.
The Pleistocene is full of temperature spikes like the dangaard (?) or whatever and the ice core data reveal the stepdown which inevitably followed such spikes.
Nothing new or unusual.
Study the reconstructed temp record of the Pleistocene, please, and you will see that there is a good reason to watch out for the arm-wavers.
Not armwaving. Is the most accepted explanation for the YD onset. See Broecker et.al. Nature 330: 318-321 (1989). Or http://www.ncdc.noaa.gov/paleo/abrupt/ which uses it as a tipping point example. Water from Lake Aggasiz entered via what is now St. lawrence seaway when the glacial icedam went.
Rud
Agassiz drained through the Traverse Gap into the upper Mississippi, which see. Gary Pearse is very well informed and can tell about L. Agassiz. Believe me, the YD was not due to a catastrophic glacial flood. It’s all bs and arm waving.
Consider: annually the rivers of Siberia pour meltwater into the Arctic Ocean which volume totals over 30 cubic km/day at the max flood. The Ob, the Indigirka, the Lena, other big rivers draining a vast continent (the Lena=19 c.km/day). Here is your freshwater flood bigger than any glacial outburst flood, but where is your temperature plunge? Arm Waving by idiots, Rud.
@Mpainter, you forgot the melt water that goes there from Canada as well, McKenzie river etc.
Asybot,
Yes, add another 2.5 cubic km/ day at max flood. Scientists get these ideas and then become enamoured of their pets and never test them against reality.
Cycles associated with solar activity, the shape of Earth’s orbit and position of the axis of the earth relative to the sun may overlap. One thing is certain CO2 has nothing to make things.
This is a more accurate picture except that it should be far whiter where the ice-sheets are (70% Albedo), whiter where the sea ice is (45% to 65% Albedo), whiter where the land is especially in the winter where there was snow on the ground (45% Albedo) and it should be browner in the summer since most of the planet was tundra, desert and grassland (25% Albedo) (as in the Amazon rainforest was only one-third the size of today and forests grew in the US southeast but nowhere else in the US etc.
Solar Insolation * (1-Albedo) = Net Solar Insolation. The Milankovitch Cycles are not going to do anything to the white areas except melt them slowly from the edges. If a Milankovitch upturn does net melt enough ice from the edges before another downturn hits, the ice age doesn’t end.
Albedo is the big driver of the climate history on the planet. The component that changes the Earth’s Albedo the most, is when there is “white” ice and snow. Rearrange the continents so that none of them are near the poles and we have very little white frozen water. Put all the continents over the South Pole and we have Snowbal Earth. Move Greenland just that last 80 kms further north and we have periodic ice ages depending on how much solar insolation varies at 75N combined with the resulting Albedo that develops.
http://i.ytimg.com/vi/AHHTIFMUXA4/maxresdefault.jpg
http://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/gif_files/gfs_t70_nh_f00.gif
As I noted there are more than a dozen paradoxes and anomalies that disprove the theory that orbital changes to insolation at 65N causes the glacial/interglacial cycle. (See my above comment for three in your face paradoxes). There is unequivocal observational evidence in the paleoclimatic record of cyclic abrupt climate change. The finding of cyclic abrupt climate change (both poles) was not expected. What is causing the cyclic abrupt change both poles is what causes the glacial/interglacial cycle.
Look at the paper I provided a link to above and below that shows there were 342 cyclic warming and cooling events in the Southern hemisphere with the same periodicity of the cyclic warming and cooling in the Northern hemisphere. What the heck is causing cyclic significant warming and cooling of the planet, both poles? Insolation changes at 65N cannot cause cyclic warming and cooling and most certainly cannot cause simultaneous warming and cooling of both poles. Insolation is 180 degrees out of phase comparing the Northern hemisphere to the Southern hemisphere, come on man, the insolation theory at 65N is obviously an urban legend.
http://wattsupwiththat.files.wordpress.com/2012/09/davis-and-taylor-wuwt-submission.pdf
http://wattsupwiththat.com/2012/09/05/is-the-current-global-warming-a-natural-cycle/
The field of ‘Paleoclimatology’ is riddled with urban legend theories and old disproved mechanisms. There is no formal structural process in ‘pure’ science to remove incorrect theories by summarizing the paradox/anomaly observations that create irreconcilable problems for the theory/mechanism (the theories/mechanisms in question are dead, deceased, not viable, urban legends), to summarize all the data in a holistic manner, to force the field into crisis. A pernicious error in a field of science is to have multiple fundamental errors and incorrect theories, rather than no theory and the specialists are forced to try to solve the problem. It is impossible to solve a problem if the correct theory/mechanism is not considered. I will include a comment on the urban legend that changes to the Northern Atlantic drift current is the cause of the Younger Dryas abrupt cooling event or is somehow the cause of the Dansgaard-Oeschger cycle or is any way connected to the Dansgaard-Oeschger cycle.
The correct forcing mechanism (there are more than 50 logical pillars to support that assertion, i.e I did not guess, I went from field to field found the paradoxes/anomalies and solved the dang problems (multiple fields, urban legends/paradoxes all over the place) which makes all of the anomalies/paradoxes go away, the sun is different than believed, that is a big thing in terms of the scientific impact on cosmology and practically due to what is currently happening to the sun) that is causing abrupt cyclic climate changes on the earth is immense, cyclic changes to the geomagnetic field strength (factor of two to three less intensity in the glacial period and more in the interglacial period) and orientation that is caused by a cyclic immense change to the sun, that occurs after the solar magnetic cycle has been interrupted (there is astronomical observational evidence and piles and piles of astronomical paradoxes/anomalies to support the sun is different assertion). The immense cycle change to the sun causes the cyclic abrupt climate change (the geomagnetic field and the solar heliosphere block/deflect high speed cosmic particles that strike the earth causing ions which in turn changes the amount of cloud cover on the planet and cloud properties that changes cloud albedo and cloud lifetime) are modulated by the orbital parameters and are directly affected by the surface area and the location that is covered with ice sheets which explains why roughly a million years ago the glacial/interglacial cycle changed from a 41,000 year cycle to a 100,000 year cycle.
There is direct proxy evidence that cyclic abrupt changes to the geomagnetic field strength and orientation has occurred in the past (there needs to a mechanism explanation as to why the abrupt, too fast, too large, cyclic abrupt geomagnetic field changes occurred in the past). Interestingly or surreally the geomagnetic field intensity is currently/suddenly dropping at 5% per decade (it was previously dropping at 5% per century, the increase the rate of the drop in the geomagnetic field intensity to 5%/decade is a paradox, not possible if the primary cause of the geomagnetic field is changes in the liquid core, there are three more paradoxes associated with the core mechanism) which is 10 times faster drop than the last 200 years and is 10 times faster than possible if the primary cause of the change is liquid core changes, i.e. Something significant and unexplained is currently happening to the geomagnetic field, abrupt climate change cooling is not a theoretical problem).
Svensmark’s mechanism and the time delay for the liquid core to integrate rapid surface forcing to the geomagnetic field provides an explanation as to how an immense cyclic change to the geomagnetic field intensity and orientation would cause abrupt climate change on the earth, such as the Younger Dryas event (Last major Heinrich event at 12,800 yr BP, the 8200 yr BP event has a minor Heinrich like event) when the earth went from interglacial warm back to glacial cold in less than a decade for 600 years and then abruptly went back to interglacial warm.
Comment: The ‘Quaternary’ is the geological name for the period, the last 2.7 million years, in which ice sheets started to form in the northern hemisphere and the start of the global north and south glacial/interglacial cycle.
http://www.esd.ornl.gov/projects/qen/transit.html
This one chart proves that none of your objections is worth a hill of beans: http://en.wikipedia.org/wiki/Milankovitch_cycles#mediaviewer/File:Vostok_420ky_4curves_insolation.jpg
–AGF
First off the obliquity factor has to be factored into all of this when it comes to Milankovitch Cycles which show the tilt varies and this item has to be evaluated along with eccentricity of the orbit of the earth and precession, but Milankovitch Cycles are but one part of the Ice Age puzzle.
In addition the initial state of the earth’s climate( land arrangements ,elevation, magnetic field ,ice dynamic, random terrestrial events) , internal variation within the sun itself have to be taken into the account, along with the random, chaotic ,non linearity aspects of the climatic system of the earth and the randomness of outer space (say within 20 light years of earth) which is why x+x does not equal an x outcome when a given item changes in a given way that has an effect on the climatic system of the earth.
The one item cause giving an X climate result is not going to work.
In addition the climatic system of the earth is always trying to seek a balance which is why it is very hard to change the global temperature as a whole but not necessarily as hard to change it on a regional basis. In addition a paradox for lack of a better word is present which is in the grand scheme of things the climatic system of the earth is quite stable but it only takes a very small deviation from this stability to cause a drastic climate change to some regions of the globe.
Remember during Ice Ages the temperatures for many parts of the globe were not effected only certain regions and those being mostly the N.H. down to around 40 N latitude.
Then as to consider other abrupt climatic changes which can not be connected to Milankovitch Cycles per say because they occur and end much to rapidly to be correlated in a direct fashion to this cycle.
Panama isthmus closing changed salinity in the Atlantic. Atlantic is now the saltiest major ocean. http://polar.ncep.noaa.gov/global/nc/?-global-salinity-000-small-rundate=latest
Changed salinity will probably change global thermohaline circulation. Changes in the thermohaline circulation will have significant impacts on the Earth’s energy budget and climate.
The average temperature of the world ocean is only 3.9 °C. A well mixed ocean will be very cold for centuries or until it stratifies again.
Only the ocean have the heat capacity needed for fast climate change and the water moves around.
The very fast changed condition from glacial to interglacial periods may be to changes in the global thermohaline circulation. Wich also explain the fast paleo changes in atmospheric CO2 levels.
My bet is on the Benguela current impact on northbound currents in the Atlantic.
Northbound current is also a northbound flux of energy towards the arctic region.
http://polar.ncep.noaa.gov/global/nc/?-eqatl-temperature-100-small-rundate=latest
Consensus and settled science:
Sorry that was meant for tips and notes. Mods, remove please if you like.
I think Milankovich Cycles, the Initial State of the Climate or Mean State of the Climate , State of Earth’s Magnetic Field set the background for long run climate change but can not explain all the short term abrupt climatic changes which I think are tied in large part to the Initial State of the Climate which you see I am using as a factor for both long term/short term climatic changes.
The initial state of the climate (how close the climate is to the inter-glacial/glacial threshold) goes a long way in determining how effective a given force may be on the climate and how much of a change in that given force on the climate is needed to give a particular climatic outcome.
In addition the initial state of the climate takes into account random and the given state of terrestrial /extra- terrestrial events at a given time ,land/ocean arrangements all of which can cause the non linear climatic system of the earth to undergo radical changes at times of seemingly little forcing being applied to the climate system, or under go little change with that same amount of forcing or even a greater amount.
It’s clearly a clock circuit. So, in order to predict the circuit’s behavior, we’d need to understand what are the actual components in the circuit. I think we don’t really have a clue what they all are. One thing I would challenge the insolators with is, how do we know that temperature is more important than accumulation and the areal distribution of the accumulation? Here is food for thought. Some of the most amazing snow pack I’ve ever seen here in CA was when we had a strong positive ENSO. In reality, during a strong ENSO temperature is elevated above normal and the snow level tends to be 1 to 2K feet higher during the typical snow event. But the volume …
Everyone ought to read the paper which Mr. Handler references. It is 49 pages long, I warn, but it is quite readable and immensely interesting. Duncan Steel, author of this paper, offers two important things. First, that climate modelers have mis-understood how to apply solar insolation values from tabulated sources, and the correctly calculated values provide a forcing that is of the correct sign and larger magnitude than is needed to explain warming of recent centuries and also explain observations of climate change differences between the earth’s two hemispheres.
Second, he provides a useful discussion of albedo, and uses data from Aqua to calculate earth averaged values.
Assuming reasonable albedo values he then runs an experiment in absorbed energy between 1750 and present day. Here is the take-away point.
Moreover, here is my nomination for a climate quote of the decade…
Climate modelers are using enormous resources, and very powerful computers, to calculate the effects of climate forcing to a supposed level of uncertainty that one cannot justify on the basis of the uncertainty of foundational concepts. This is the very thing we tell engineering student not to do in engineering 101 through senior capstone design.
Kevin Kilty quotes Duncan Steele as saying: “Recall that the new IPCC (2013) estimate for the effect of AGW since the Industrial Revolution is 0.17 per cent of the solar flux at our distance from the Sun.”
Well that does not do much for Steele’s credibility. IPCC puts total anthropogenic forcing at 2.3 W/m^2, which is just under 1% of the total insolation of 240 W/m^2.
Haven’t actuall looked at Steele’s paper since I had trouble downloading it.
Ask yourself if there is a difference between flux and insulation.
Insolation
Willis,
As aligned in your graph (figure 3 above), there doesn’t appear to be much correlation between Insolation and Temperature. However, if you realign them with the Temperature of -10c being equal to the insolation of 575 Wm2 then there is a correlation, even between the major temperature peak during the low insolation peak of 400K years ago and the similar high temperature peak during the similar current low insolation peak
Havn’t had time to read all the comments, but…
There is a nice little book on this that gives the history of Milankovitch and along the way also explains the theory rather well. It isn’t just “how strong the sun shine is”…
http://books.google.com/books/about/Ice_ages.html?id=GIxRp9fRDGwC
Ice Ages: Solving the Mystery. By Imbrie and Imbrie.
The key bit most folks miss is that it is NOT how strong the sunshine is. It is how long the sunshine is strong…
When summer happens at apogee, there are more summer days than when it is at perigee. Thus more melting days.
So interglacials tend to happen when summers are furthest from the sun, and with slightly less sunshine due to that distance (but a whole lot more hours of it, and shorter winters too).
The book is a good read in any case, and still points out some of the loose ends, like the 41 ky vs 100 ky cycles change. IMHO that is just due to it being warmer in the past and some more minor ‘warm times’ were good enough to melt the polar ice at the N. Pole. Then things got colder and the weaker ones were no longer enough warmth. (That is in keeping with the general cooling trend observed, too).
Now we only get warm enough to melt N. Pole ice on the bigger 100 ky rises.
Eventually even that may not be enough and it is Snowball Earth again…
Oh, and there were also land form changes (Panama) and ocean current shifts that likely helped.
Panama is out. Recent study (Jamarillo et al GSA bull.2014) shows that the isthmus is a strip of continental terrain since before the Paleocene, according to dating. No seaway, no proto Gulf Stream, none of that .
Care to give a better reference to that?
What problems do you have with the reference?
I beg your pardon, I misspelled; should be Carlos Jaramillo et al GSA Bulletin 2014. NOT Jamarillo.
This was a big study funded by the Smithsonian Tropical Research Institute of Panama. It identified at the neck of the isthmus granites of the Paleocene intruded into a basement complex and uplifted and eroded by mid Eocene times. The Isthmus is apparently a strip of continental crust like Cuba or the Florida Peninsula, an accident of continental drift.
So the isthmus has always been there and the hypothesized closure of the Panama seaway and redirection of the proto Gulf Stream falls to the ground.