Just a quick question – how can hypotheses be “tested” through numerical model experiments? I thought that models threw out results which in turn are “tested” by coincidence with reality/observations? A further question is that if this paper sheds new light on a possible factor in climate change which “would require higher resolution sea-ice and ocean models than used in todays global climate models”, does this not suggest that todays global climate models are insufficiently able to project climate change?
That’s a nice graph you have here, but unfortunately there are no units on the Y-axis. Can the upper 4 (coloured) lines all be converted to (say) equivalent temperature or radiative forcing (to see the relative importance), and then added (or otherwise combined) to produce a line that correlates with the black line?
I’m thinking that the earth can become imbalanced, but that could be imposible, maybe not. If a wheel is off balance it would be taken into a tire shop, set onto a machine and spun, that will let the person know where the wheel is off balance, then he will ad a weight that is required to balance the wheel. What if the weight was removed. The earth is completely round in all directions from space. The earth tilts, then we have change of weather. What if a massive amount was removed from one side of the earth to the other could that cause the earth to wabble? the removal of steel, metal,iron or maybe even “OIL” with the combination of all of these burnt into smoke. Is the smoke from all of these that i mentioned part of the cause for the ozone layer to be thinning?
Nice idea Dick, but isnt that the problem the authors have too? I imagine that they certainly dont know with any degree of certainty the exact contribution from each of their forcings. So it is probably impossible/indeterminate/pointless to combine the curves except on a trial-and-error basis. It looks to me like there is sufficient randomness in the cycles they are offering (and I imagine that there are a lot of other potential candidates that they are not offering, including dear old CO2) to allow almost any solution to be found that may *corelate* plausibly with the ice record.
But such an accidental coincidence would hardly rate as truth, eh? Its a lottery, not science.
Would not the accelerated dinural movement of the magnetic poles be at least considered in the mix of solar forcings? Up until approx. 1992, the average trek of the poles have been ~10km annually. With this relatively slow movement, the megnetic flux lines were of a more congruent, harmonious pattern offering the best protection against the solar radiation. As noted on several sites describing the magnetic pole acceleration, a consensus reporting of a reduced “shield” against solar radiation have been as high as 10%, but average 6-7%. This means the effectiveness of the magnetic shield has been reduced as a result of the bending and subsequent distortion of the flux lines from the increased speed of up to 40km annually.If this movement is the beginning of the long 5k to 8k year cycle of pole reversal, than it could be expected that during any of these cycles, solar forcing would have a greater effect with increased energy passing through into the atmosphere.
I understand how the build-up of ice sheets would isolate the Arctic Ocean. But I thought sea ice would reach an equilibrium with temperature, not continue to increase. And any increase would be small relative to the volume of the ocean, so the increase in salinity would be minimal. As well, I am not familiar with the vertical structure of Arctic water, I would have assumed that water temperature decreased with depth, and anything else would be unstable and correct itself relatively quickly.
I don’t have access to the original paper, so it would help if its hypothesis was clarified.
This “new” model is a slight variation on an old idea about sea ice cycles and heat buildup in the ocean beneath the ice. They have added a fresh water input element. What isn’t clear to me is how their model copes with the Younger Dryas event and similar events that occurred in earlier cycles. Why didn’t the Younger Dryas event stop the warming for once and for all? Massive amounts of meltwater, not only from North America, but also from Scandinavia, would seem to put a cap on the heat input from the Arctic Ocean.
To answer your question, the graph shows the three astronomical cycles which affect paleoclimate, the most commonly proposed forcing calculation, and a paleoclimate record for the last million years.
1. Precession: difference between the longitude (along our orbit) toward which the axis is tilted, and the longitude of perihelion, multiplied by earth’s eccentricity. Range is from about -0.05 to +0.05.
2. Obliquity: tilt of the earth’s axis. Range from about 22 deg. to 24.5 deg.
3. Eccentricity: non-circularity of earth’s orbit. Range from about 0 to 0.05
4. 65N summer: this is the insolation (incoming solar energy) on midsummer day at latitude 65 deg.N. This is often suggested to be the main factor influencing the decay of ice sheets in the northern hemisphere. Range about 510 to 590 watts per square meter.
5. Paleoclimate: I don’t know for sure, but this record is too long (1 million years) to be an ice core, so I’m guessing it’s a stacked sediment core, showing delta-O18 from ocean foraminifera. Is this the “LR04″ stack?
I don’t understand the energy reference. The paper refers to a few W/m2 for greenhouse gases and >40 for Milankovich. I was under the impression that greenhouse gases swamp Milankovich annual contribution to the energy budget, but that the Milankovich inputs are “slow and steady”, i.e. not so much each year, but continuous.
The few W/m^2 for greenhouse gases apply to the entire planet. The 40 (or more) W/m^2 due to Milankovitch cycles apply only to one specific latitude (usually 65 deg.N), but an increase at one latitude is compensated by a decrease at other latitudes. The global forcing from Milankovitch cycles is generally not more than 0.3 W/m^2.
re #10, is that correct RC concerning Milankovitch cycles only causing increasing anountsof sunshine to fall on certain parts of the planet rather than all of it for GHG concentrations ?
[Response: Yes it is. Tamino's comments are almost invariably accurate, and this one is no exception. As Tamino notes, Milankovic cycles do lead to a slight modulation of the annual average, but it is very small, especially for the 100KYr cycle. The big numbers are in what Milankovic does to the seasonal cycle amplitude. In some sense, the search for a theory of glacial-interglacial cycles amounts to a search for the "rectifier" which turns the modulation of the amplitude of the seasonal forcing into a rectified signal in global ice volume. --raypierre]
In the context of this post, the question “What triggers ice ages?” only applies to the late Pleistocene (since about 800,000 years ago). From the onset of northern-hemisphere glaciation (about 3 million years ago) to the “mid-Pleistocene transition” (about 800,000 years ago), glacial advance and retreat follows a strong 41,000-year cycle, which has led to its being called “the 41 ky world” (Raymo & Nisancioglu 2003, Paleoceanography, 18, 1011). This is surely due to the changes of earth’s obliquity, since changes in the amplitude of the climate signal correspond to changes in the amplitude of the obliquity cycle (Lisiecki & Raymo 2007, Quaternary Science Reviews, 26, 56).
But since the mid-Pleistocene transition (not precisely since, this happens intermittently before that time) glacial changes are dominated by a 100,000-year cycle. The behavior during the “late Pleistocene” was originally attributed to changes in earth’s eccentricity, but that idea has now fallen out of favor. Huybers & Wunsch (2005, Nature, 434, 491) and Huybers (Quaternary Science Reviews, 26, 37) have convincingly shown that even during the late Pleistocene, the timing of deglaciations is strongly correlated to the obliquity cycle. They find no such relationship for the precession cycle or the eccentricity cycle.
Huybers (Quaternary Science Reviews, 26, 37) has proposed a simple model in which deglaciation is triggered when the obliquity cycle is high, and when ice mass is sufficiently high. The match of his model to actual paleoclimate is impressive, but that doesn’t necessarily mean it’s right — especially since Huybers made no suggestion about what the physical mechanism is which brings this about. The fresh-water theory fits this idea neatly; it provides a physical mechanism whereby deglaciation can be triggered only when total ice extent is sufficiently large.
Personally, I disagree both with Huybers’ model and the fresh-water theory. I have my own theory, of course! With any luck, you can read about it in an upcoming issue of GRL.
Rasmus : “Previous modeling studies find that GHG make up roughly 50% of the total LGM to present temperature response…”
Martinson and Pitman III discuss of the “abrupt terminations” of glacial period. The CO2 rise is a slower process (with an initial lag of several centuries) and it counts for 50% in a 15.000 yrs equilibrium comparison (from LGM to mid-Holocene, for example). I’ve not access to Martison / Pitman III paper, but it seems you don’t exactly speak of the same phenomenon (that is, the CO2 objection may be not pertinent for the question of abrupt transition).
Re 1: In a sense, a hypothesis is already a model, but because it’s verbal it’s poorly specified and hard to simulate accurately and thus hard to reject. Translating the hypothesis to a numerical model forces you to confront the ambiguities; along the way there are many points where you might reject the hypothesis because of a discovery from first principles (violation of conservation laws, dimensional inconsistency, qualitative failure to replicate the hypothesized behavior mode, absurd behavior in extremes, etc.). If the hypothesis implemented in a model passes those tests, then you need data to calibrate and verify, but data by itself is often a weak test. Presumably in this case you’d start with a model that’s already been tested against a lot of data and thus serves as a compact proxy for that information.
The magnetic field of the earth only shields against charged particles coming from the sun (the so-called “solar wind”) and charged particles coming from outer space (some varieties of cosmic rays). The total energy in these particles is insignificant compared to the energy in the form of light from the sun, so the variation of the magnetic field will not have a direct effect on Earth climate.
A weakening magnetic field might lead to more cloud formation because more air molecules would be ionized by incoming high-energy radiation, and ionized air molecules are nucleation sites for cloud droplets. More clouds means higher albedo, which in turn might mean a cooler climate.
[Response: Note also that more low clouds would unambiguously mean a cooling effect, but more high clouds could lead to either a warming effect or a cooling effect, depending on the altitude of the clouds and the typical particle size in the GCR-induced clouds (if any). --raypierre]
The FFT is a poor choice, because is requires the data to be evenly spaced in time (which often it is not), and requires the number of data points to be a power of 2 (which it almost never is).
I applied the DCDFT (date-compensated discrete Fourier transform) to generate Fourier power spectra of all five signals shown in the original plot (assuming that the last graph is the LR04 stack). I’ve posted them on my blog.
When giving the range of 65N insolation, I mistakenly looked at the data for insolation at the pole (90N). The correct range for 65N insolation is aobut 390 to 490 watts per square meter.
[[What if a massive amount was removed from one side of the earth to the other could that cause the earth to wabble? ...the removal of steel, metal,iron or maybe even "OIL" with the combination of all of these burnt into smoke. ]]
Wobble. Yes, it does. But the effect is far too tiny to detect. Compare the mass of iron ore mined since the beginning of the industrial revolution to the mass of the Earth. There’s no comparison. Don’t worry about it.
[[Is the smoke from all of these that i mentioned part of the cause for the ozone layer to be thinning? ]]
Probably not. That seems to be from human use of chloroflurocarbons for spray cans and refrigerants. The Montreal Protocol of 1979 banned use of these, and industry now uses substitutes.
On the subject, Robert Ehrlich has a recent paper on solar forcing of ice ages. He claims to have solved all but one of the major “problems” of Milankovitch forcing:
Solar Resonant Diffusion Waves as a Driver of Terrestrial Climate Change
A theory is described based on resonant thermal diffusion waves in the sun that explains many details of the
paleotemperature record for the last 5.3 million years. These include the observed periodicities, the relative strengths
of each observed cycle, and the sudden emergence in time for the 100 thousand year cycle. Other prior work
suggesting a link between terrestrial paleoclimate and solar luminosity variations has not provided any specific
mechanism. The particular mechanism described here has been demonstrated empirically, although not previously
invoked in the solar context. The theory, while not without its own unresolved issues, also lacks most of the problems
associated with Milankovitch cycle theory.
He argues that stochastic variation is responsible, although wimps out of actually coming up with an explanation. His alternative hypothesis regarding abrupt climate change was rubbish too, but thats another story.
The long-term stability of the massive ice sheets of Antarctica, which have the potential to raise sea levels by hundreds of meters, has been called into question with the discovery of fast-moving rivers of water sliding beneath their base.
Scientists analyzing satellite data were astonished to discover the size of the vast lakes and river systems flowing beneath the Antarctic ice sheets, which may lubricate the movement of these glaciers as they flow into the surrounding sea.
The discovery raises fresh questions about the speed at which sea levels might rise in a warmer world due to the rate at which parts of the ice sheets slide from the land into the ocean, scientists said at the American Association for the Advancement of Science in San Francisco.
“We’ve found that there are substantial subglacial lakes under ice that’s moving a couple of meters per day. It’s really ripping along. It’s the fast-moving ice that determines how the ice sheet responds to climate change on a short timescale,” said Robert Bindschadler, a NASA scientist at the Goddard Space Flight Centre in Maryland, one of the study’s co-authors.
While the water under the Antarctic ice is not itself related to global warming, the suprisingly large amount of water, the surprising speed with which it moves, and its effect of “lubricating” the movement of the Antarctic ice, may affect how the ice sheets respond to warming. This new discovery is of course not accounted for in the IPCC AR4 and suggests we may be in for some unpleasant surprises from Antarctica.
[[1,000 kyear --- no significant continental drift in that time span, right? Just checking. ]]
Actually, I think there might well be significant continental drift over that period. I assume by 1,000 kyear you mean 106 years? It wouldn’t be as obvious as over 100 million years, but it would be enough to distort maps noticeably.
There’s not a lot of tectonic movement in a “mere” million years, but it may not take a lot to have a climate impact. For example, closure of the Isthmus of Panama, and restriction of the Indonesian seaway, have been suggested as reasons for the onset of northern-hemisphere glaciation 3 million years ago (but that’s 3 million, not 1 million).
Re #21: SteveF, thanks for the link to the new paper. Regarding Wunsch, both he and Huybers (who was Wunsch’s grad student) have done follow-up papers, one of which was linked by Tamino in #19.
Re #23: SA (and what a great handle that is, BTW), the moment I saw this I wondered if it could explain the other recent results showing a sudden slowdown in two of the Greenland outlet glaciers. Despite being trumpeted in certain circles as meaning that there’s really nothing to worry about regarding the Greenland ice sheet, the authors made a point of noting (although not in this press release) that an additional source of mass loss needs to be identified in order to reconcile their results with the GRACE data (which do not show a reduction in mass loss for the same period). Similar subglacial water activity in Greenland would seem to fill the bill nicely, in particular because it would also explain the sharp changes in outlet glacier speed.
Re #25, #26, #27: The Indio-Australian plate moves generally north at a very high rate for a tectonic plate. So in a mere one million years the Himalayan Mountains and in general the Tibetian Plateau would have been modified. To the east, the boundary between the Indian Ocean and the South China Sea would have been altered.
Comment by David B. Benson — 16 Feb 2007 @ 4:34 PM
Can anyone add something about how the biology is changing in that time span?
That would, I’d guess, be interesting as a very fast feedback effect if, say, plankton’s changing year by year as one or more of those other signals change.
Might be some proxy for total primary productivity, or biomass, or respiration, or photosynthesis, or chemistry of diatom shells or lack thereof in each slice of the sediment core.
Not sure how to tease that out, just wondering if Gaia’s in there swinging behind some of that variation.
Re #30: Hank Roberts — Not directly the answer to your latest question, but at each major sea low stand, East Asia expands to the east and Southeast Asia grows into Sundaland. Both locations will continue to contribute to biological productivity in contrast to the expanded deserts in many other locations.
Comment by David B. Benson — 16 Feb 2007 @ 5:16 PM
I’ve always been impressed by the rapidity with which glacial periods end, despite the expected high feedback of all that ice cover. I don’t follow climate science in detail, with all the ins and outs of competing models, but as an interested non-specialist I hope to live long enough to see a consensus explanation emerge!
The principal glacier of the world’s biggest tropical ice-cap could disappear within five years as a result of global warming, one of the world’s leading glaciologists predicted yesterday.
The imminent demise of the Qori Kalis glacier, the main component of the Quelccaya ice cap in the Peruvian Andes, offers the starkest evidence yet of the effects of climate change, according to Lonnie Thompson, of Ohio State University.
Although scientists have known for decades that Qori Kalis and the other Quelccaya glaciers are melting, new observations indicate that the rate of retreat is increasing, Professor Thompson said. When he visits this summer, he expects to find that the glacier has halved in size since last year, and he believes that Qori Kalis will be gone within five years.
“This widespread retreat of mountain glaciers may be our clearest evidence of global warming as they integrate many climate variables,” Professor Thompson told the American Association for the Advancement of Science conference in San Francisco. “Most importantly, they have no political agenda.”
The Quelccaya ice-cap, covering 17 square miles (44 sq km) in the Cordillera Oriental region of the Peruvian Andes, is the world’s largest tropical ice mass. Qori Kalis, its biggest glacier, has receded by at least 0.6 miles (1.1km) since 1963, when the first formal measurements were made from aerial photographs. The rate of retreat has increased: between 1963 and 1978, it shrank by 6.5 yards (6m) a year, a rate that has now risen tenfold to 65 yards annually.
Professor Thompson predicted six years ago that the celebrated snows of Kilimanjaro would be gone from Africa’s highest mountain by 2015, and he now thinks that that estimate may have been too conservative. He said: “Tropical glaciers are the canaries in the coalmine for our global climate system, as they integrate and respond to most of the key climatological variables – temperature, precipitation, cloudiness, humidity and radiation.”
A critical piece of evidence from almost fifty scientific expeditions to seven shrinking tropical ice-caps points to global warming as the reason for their decline. In all but one case, snowfall has increased as ice volume has fallen. More snow should mean advancing glaciers, unless rising temperatures are melting the extra precipitation and the ice tongues themselves.
Is it reasonable to think this is the other side of this question ‘What ends hot ages’, especially artificial ones, WITH INSUFFICIENT ARTIFICIAL HELP? I keep hearing about how much hotter it’s going to be in 2100, but nothing about after that, as though one way or another it’s going to end there. With all the forms of positive feedback we already see, what’s going to create negative feedback while life is still possible on Earth, like before the oceans have finished evaporating and adding to greenhouse gasses? It also seems many changes are occurring faster than scientists previously expected. Does someone have some hope for our grandchildren and beyond? Is it possible that even climate scientists believe only what their minds can tolerate and ignore the rest?
What is alarming other than the word alarm in the title? You say there is a surpisingly large amount of water, what amount of water would you expect? And the water is moving at a surprising speed, what speed would not surprise you?
I find this new information interesting and important but not alarming.
“A new report on climate over the world’s southernmost continent shows that
temperatures during the late 20th century did not climb as had been predicted by
many global climate models.”…
…”Bromwich said that the increase in the ozone hole above the central Antarctic
continent may also be affecting temperatures on the mainland. “If you have less
ozone, there’s less absorption of the ultraviolet light and the stratosphere
doesn’t warm as much.”
That would mean that winter-like conditions would
remain later in the spring than normal, lowering temperatures.
sense, we might have competing effects going on in Antarctica where there is
low-level CO2 warming but that may be swamped by the effects of ozone
depletion,” he said. “The year 2006 was the all-time maximum for ozone depletion
over the Antarctic.”
Bromwich said the disagreement between climate model
predictions and the snowfall and temperature records doesn’t necessarily mean
that the models are wrong.
“It isn’t surprising that these models are not
doing as well in these remote parts of the world. These are global models and
shouldn’t be expected to be equally exact for all locations,” he said.”….
…”Meltwater from glacial Lake Agassiz (southwest of Hudson Bay) draining catastrophically into the North Atlantic via Lake Superior and the St. Laurence seaway was once thought to have initiated ocean circulation changes leading to the Younger Dryas cold period. Regional removal of ice sheets, however, occurred nearly 1000 years later, and hence draining of Lake Agassiz could not likely have caused the Younger Dryas cold reversal. This cold spell may have instead been triggered by increased outflow into the Arctic Ocean, the Fram Strait east of Greenland, and ultimately the eastern North Atlantic, between 12,900 and 12,800 years before present, as suggested by the glacial model of Tarasov and Peltier. On the other hand, Leventer et al. indicate that the timing of deglaciation in eastern Antarctica roughly coincides with the onset of meltwater pulse 1B. “….
Comment by BarbieDoll Moment — 17 Feb 2007 @ 4:15 AM
Another hypothesis for why the glacial periods terminate and restart is GCR modulation by changes in the intensity of the earth’s magnetic field. GCR changes of course as we all know, it is hypothesized affect global cloud cover. I am not sure why the response to the hypothesis that changes in the intensity of the geomagnetic field, triggers/controls the timing of the ice ages in this forum was “rubbish”. The rubbish comment noted that geomagnetic field intensity changes do not correlate with the ice age cycles. Perhaps we are looking at different data.
The following is data from the review paper “Time Variations in Geomagnetic Field Intensity”
See Page 4-22, Figure 9: Geomagnetic field intensity level derived from composite volcanic records, not sea floor sediments, for the past 45 kyr.
Obviously, Figure 9 shows that 40 kyrs ago the earth’s magnetic field intensity was 75% less (2×10^22Am^2) than the geomagnetic field’s current intensity (8×10^22Am^2) and that the earth’s magnetic field intensity peaked at around (12×10^22Am^2)and has dropped 30% in the last 1000 years and that the geomagnetic field intensity is now dropping at the rate of 5%/100yrs.
1)The geomagnetic field researchers do not even have a hypothesis as to why there are cyclic changes in the geomagnetic field intensity. Something is fundamental incorrect with the most basic assumptions concerning what creates the geomagnetic field, and what causes it to change. Rather than address the absolute failure of their model, they have thoughtfully decided to ignore the problematic data.
2)The paper I referenced states that the proxy magnetic field intensity derived from sea floor sediment data does not match obital frequencies however other papers state that it does. The real problem is the volcanic data and sea sediment data (proxy data that is used to determine the intensity of the geomagnetic field) indicates that climate changes directly affects the intensity of geomagnetic field. As there is no explanation as to how climate changes could possibly affect the intensity of the earth’s magnetic field, it was decided that it would be easier to believe that proxy sea floor sediment data should be adjusted (“corrected”)for sea water temperature.
3)Other indications of the absolute failure of the geomagnetic field model is the so called heat flux problem or the recent discovery of very,very rapid geomagnetic field intensity and inclinition changes (All researchers agree that the very, very rapid field changes could not possibly be due to changes in the earth’s core. If the problematic data is correct, the earth’s magnetic field is not generated in the core.)
Lake Vostok, for example, has a maximum depth greater than 500 m, is deeper than Lake Tahoe, and has a surface area similar to that of Lake Ontario. It is the largest of at least 68 lakes located 3 to 4 km beneath the East Antarctic Ice Sheet.
As the article cited in #23 indicates, the existence of these lakes is not related to global warming. Rather, “they are maintained in a liquid state by geothermal heating, pressure, and insulation by the overlying ice.”
Science 10 December 1999
Vol. 286. no. 5447, pp. 2094 – 2095
What is new, and newsworthy, is that the extensive system of liquid water under the ice may provide a better understanding of ice sheet dynamics:
An Active Subglacial Water System in West Antarctica Mapped from Space
Helen Amanda Fricker, Ted Scambos, Robert Bindschadler, Laurie Padman
Satellite laser altimeter elevation profiles from 2003-2006 collected over the lower parts of Whillans and Mercer ice streams, West Antarctica, reveal 14 regions of temporally varying elevation which we interpret as the surface expression of subglacial water movement. Vertical motion and spatial extent of 2 of the largest regions are confirmed by satellite image differencing. A major, previously unknown subglacial lake near the grounding line of Whillans Ice Stream is observed to drain 2.0 km3 of water over ~3 years, while elsewhere a similar volume of water is being stored subglacially. These observations reveal a widespread, dynamic subglacial water system which may exert an important control on ice flow and mass balance.
Science (Published Online February 15, 2007) http://tinyurl.com/ys49wu
I don’t think anyone is suggesting that global warming has any impact on the temperature of the earth’s interior – the earth’s core has that well under control.
Wang Dang wrote: “What is alarming other than the word alarm in the title? You say there is a surpisingly large amount of water, what amount of water would you expect? And the water is moving at a surprising speed, what speed would not surprise you?”
Chuck Booth wrote: “The existence of lakes beneath Antarctic ice is nothing new – this has been known for decades … What is new, and newsworthy, is that the extensive system of liquid water under the ice may provide a better understanding of ice sheet dynamics”
What is alarming is that the volume of water and the extent and rapidity of its movement is suprisingly much greater than previously believed, and that a possible, perhaps likely, effect of this on ice sheet dynamics is to make the ice sheets less stable and more likely to respond more quickly to global warming than previously expected.
The cool reception to the suggestion that GCR’s are involved in glacial-interglacial cycles comes because there is overwhelming evidence that Milankovic is the basic pacemaker, which needs to be supplemented with an amplifying feedback (certainly involving CO2) and some kind of rectifier of the seasonal cycle. It would be extremely improbable for GCR’s to just happen to give the same periodicities as Milankovic. It is not out of the question that solar fluctuations, either through luminosity or perhaps GCR, play a role in Pleistocene climate transitions, including abrupt changes like Heinrich events. In systems that have a threshold, or switch, a little bit of noise whether from solar variability or something else, can tip the balance once you get near the transition point. Stefan has proposed some ideas about Heinrich events based on this line of reasoning.
The Pleistocene does offer some possibilities to directly look for evidence of GCR influence. One of the critical periods to look at is the Laschamp Magnetic Excursion. I’ll take the liberty of quoting in full from the abstract of Lloyd Keigwin’s paper ( http://www.agu.org/pubs/crossref/2005/2003JB002943.shtml ):
“We have recovered two new high-resolution paleomagnetic records of the Laschamp Excursion (~41,000 calendar years B.P.) from deep-sea sediments of the western North Atlantic Ocean. The records document that the Laschamp Excursion was characterized locally by (1) declination changes of ±120°, (2) inclination changes of more than 140°, (3) ~1200-year oscillations in both inclination and declination, (4) near 90° out-of-phase relationships between inclinations and declinations that produced two clockwise loops in directions and virtual geomagnetic poles (VGPs) followed by a counterclockwise loop, (5) excursional VGPs during both intervals of clockwise looping, (6) magnetic field intensities less than 10% of normal that persisted for almost 2000 years, (7) marked similarity in excursional directions over ~5000 km spatial scale length, and (8) secular variation rates comparable to historic field behavior but persisting in sign for hundreds of years. All of these features, with the exception of anomalously large directional amplitude, are consistent with normal magnetic field secular variation. Comparison of our Laschamp Excursion paleomagnetic records with other late Quaternary excursion records suggests that there is a group of excursions, which we term class I, which have strikingly similar patterns of field behavior and likely share a common cause as part of the overall core dynamo process. Three general models of secular variation are described that can qualitatively produce class I excursions. On the basis of these observations we conclude that class I excursions, epitomized by the Laschamp Excursion, are more closely related to normal secular variation and are not necessarily a prelude to magnetic field reversal.”
With these monumental changes in the shielding effect of the Earth’s magnetic field, you’d expect to see fairly massive climate consequences if the GCR crowd are right. After all, the implied changes in GCR flux are huge compared to what is expected from the gentle modulation of the Earth’s magnetic field arising from recent solar activity changes (not that there’s any trend in those that would explain recent warming). Readers can look for themselves at the Greenland ice core record and decide whether there’s anything of consequence going on around 41K before present that looks any different from other glacial-interglacial cycles.You can look at the GISP data yourself by downloading
Maybe I am confusing surprised and alarmed. As I understand it, this is a first observation of its kind and it tells us we don’t know as much as we thought we did. I am not surprised, because I had no preconcieved notion of how much water is under the ice and how it moves. To spin this into alarm is a little premature.
BTW I am not surprised that you are alarmed, but I might be alarmed if you were only surprised.
I wonder if you comment on the fact that the historical climate records of GISS, the National Climate Data Centre and the Hadley Centre have been adjusted started in 2000.
It looks like the older temperature records from the 1930s for example have been adjusted downwards by 0.2C and the newest temperature records have been adjusted upwards by 0.3C.
These adjustments would account for all of the recorded 0.6C increase in temperatures in the 20th century.
I imagine readers would like to know this has occurred and why.
[Response: The adjustments are only for US stations and come from time of day adjustments, station location adjustments etc. and were clearly documented in Hansen et al, 2001 and references therein. -gavin]
[Response: ...and the citation of 0.6C as the net observed warming is considerably out of date and a significant underestimate. More recent assessments (e.g. IPCC '07 SPM) place the number close to 0.8C, and even that number is fairly conservative. -mike]
Re #48: The regulars over at Climate Audit would like to know, anyway. The complexity of climate science is such that folks who come to it already convinced that it’s all a vast conspiracy can engage in endless discussion that they think proves their points, but in fact proves nothing.
There is an important role to be played by climate scientists in educating the piblic and policymakers about the science, a role that is exemplified by this blog. It’s rather less constructive for climate scientists to spend their time engaging in endless rounds of nit-picking with denialists who are in the end unconvincable. We had quite enough of that with the hockey stick.
*Why* is it important to pay close attention to making the historical record in the U.S. as accurate as possible? It’s not so some huge deal can be made of, e.g., 1934 now being thought to have been slightly cooler than 1999, because in and of itself that’s pretty meaningless, but rather because data accuracy in turn affects the accuracy of climate model projections and in particular (in the case of this data) regional projections for the U.S.
Of course the Climate Audit regulars think the models are hopelessly defective as well, but that’s another discussion.
A tidbit about what cycles:
” … coccoliths evolved fairly recently. The earliest appeared just 200 million years ago. Their effect was only to expand the world’s calcium carbonate sinks from the shallow continental shelves to some of the deeper ocean (Westbroek 1991).”
>There is an important role to be played by climate scientists in educating the piblic and policymakers about the science, a role that is exemplified by this blog. It’s rather less constructive for climate scientists to spend their time engaging in endless rounds of nit-picking with denialists who are in the end unconvincable.
For those of us with an open mind about the issues, answering the ‘nit-picking’ questions at least once is important as well.
In looking at the data (for the US), there seems to be a very systematic pattern to the adjustments. Temperatures are reduced from 1920 to 1960, and increased from 1980 to 2000. Why do the adjustments look so systematic? The only adjustment that would obviously have a long term dependence on time (urban) should go in the other direction (and does in Hansen et al, 2001, but is very small).
In reply to “With these monumental changes in the shielding effect of the Earth’s magnetic field, you’d expect to see fairly massive climate consequences if the GCR crowd are right. After all, the implied changes in GCR flux are huge compared to what is expected from the gentle modulation of the Earth’s magnetic field arising from recent solar activity changes (not that there’s any trend in those that would explain recent warming).”
The hypothesized physical reason why there were not wide swings in climate (the planet was close to the glacial maximum, at the time of the Laschamp excursion of course. i.e. very, very cold) during the Laschamp excursion is: Although GCR does increase as the geomagnetic field decreases, there is a saturation point where additional ions created by GCR does not increase cloud cover. The concept of asymptotic approach to a level of GCR where further increases has less and less affect on cloud cover, is the same as with CO2 increases. The question for both forcing functions, CO2 and the set of cloud modulation forcing mechanisms is: What is the correct parameterization?
As noted, one of the unanswered questions is: What caused the observed 1993 to 2001 reduction in planetary cloud cover? The hypothesized mechanism is electroscavenging which is due to changes to the global electric circuit. Changes to the global electric current can and do occur, initiated by solar changes, independent to changes to GCR.
It has been stated in this forum that the increase in global temperature in the last decade of the 20th century does not correlate to GCR changes, which is correct. There is, however, no mention that the increase in global temperature does correlate with the observed reduction in planetary cloud cover, 1993 to 2001. In addition, the cloud cover decrease, 1993 to 2001 is restricted to regional areas, which matches the mechanism that Tinsley and Yu predicted, as Palle noted in his paper. For example, there is a reduction in clouds over the Atlantic Ocean at latitudes where the global circuit change is greatest. The atmosphere above the ocean is ion poor as compared to the atmosphere over the continents, as there is natural radiation from the continental crust. There is not natural radiation from the ocean.
I believe there was been no discussion of electroscavenging in this forum. The retort is always the same, “The 20th century temperature increase, does not correlate with GCR changes”. The electroscavenging hypothesis does explain the reduction in cloud cover. Electroscavenging removes the ions that GCR produces, which makes it appear that changes in cloud cover no longer correlates with the solar cycle modulation of GCR.
Science is not defending a position, but rather solving puzzles. This is a rare time where there are multiple crises in interrelated scientific areas: the geomagnetic field, the solar cycle, GCR/Global Electric Circuit atmospheric science, and the climatic cycles. The issues are with first order changes: What causes the termination and initiation of the glacial cycles; What causes changes in clouds, what causes the abrupt temperature changes; What is causing changes in the geomagnetic field; and What is the relative warming affect of enhanced CO2?
[Response: This is just science fiction. You can spin all the word tales you want, but until you come up with a set of equations saying why the cloud cover changes should have been less in glacial times, or why the climate should have been less sensitive to cloud cover at the time, you might as well be talking about space aliens blocking the sunlight. You talk a good tale, Mr. Astley, but science is a high stakes game, and you've got to pony up some real equations if you want to play. --raypierre]
Comment by William Astley — 17 Feb 2007 @ 10:08 PM
Reading the published work, they thought they had a correlation picking a few areas of the planet; when they got in enough data to study it globally, they didn’t find an effect:
” … the geographical variation of the correlation between low cloud and predicted ionization level from cosmic rays at an altitude of 2 km. When analysed globally, we find that the correlations do not correspond to the latitude variation of cosmic ray flux and they are not field significant. ….
Then they went back to the areas where they said they’d found a correlation, and did a what-if:
Re: 45. A credit where credit is due thing. Although I’m sure Lloyd Keigwin did enough to deserve to be put on the paper, it is much more apt to call the Laschamp Excursion study “Steve Lund’s paper”. He did the bulk of the work and is responsible for characterizing the magnetic field behavior. Picky, I know, but had to be said.
[Response: Not at all picky. I should have called it Lund's paper, and it was just sloppy of me to call it Keigwin's. I have a habit of remembering papers by the author I know best, not by the first author. A lot of people seem to do the same, the most famous case of which is the original Nuclear Winter paper, which a lot of people think of as "et al and Sagan." --raypierre]
Also, why is the GCR thing still in play? Anyone who still believes this to be an important hypothesis need only to graph the Climax neutron incidence data for the past 50 years against global temperature. There’s simply no long term trend in the GCR to correlate with the increase in temperature. Furthermore, the higher frequency trends in the GCR (i.e., sunspot related oscillations), which have MUCH higher amplitude than any remotely imagined long-term trends, don’t seem to have an effect that rises above the background noise in the temperature record. Again, why is anyone taking this seriously?
I was browsing the NASA interactive satellite temperature data for the troposphere which stretches from 1979 to 2003. It has a global map that’s colored in shades of red for heating and blue for cooling. Flipping through the time sequence it’s obvious that almost all the heating anomalies are in the snow covered far north. South of Canada down to Antarctica isn’t really heating at all. Moreover, there’s a graph of the average temperature anomalies of all areas (below the world map) and that shows that the net of heating and cooling is just about zero. I was wondering what could account for this pattern of heating and cooling and it occured to me that if the albedo of the snow cover in the far north was declining that would do it. So I looked around and dug up a study of snow albedo that appeared in the Journal of Atmospheric Sciences, Volume 37, August 1980 which confirmed that carbon soot from manmade sources (including forest fires) migrates thousands of miles and accumulates on permanent snow cover causing melting and temperature increases. The antarctic is relatively free of soot buildup but the arctic has been well contaminated.
This explains the heating (and lack of heating) patterns quite well. How does CO2 greenhouse heating explain these patterns and why is the global average temperature not really increasing?
[Response: Congratulations, you've just discovered "polar amplification." This pattern is common to most means of heating up the planet, including CO2, and is not prima facie evidence for soot controlling everything. A superficial look at the patterns can make it look like all the warming is in the Arctic, since that is indeed where the effect is strongest so far. However, as the recent National Academy report pointed out at great length, a careful study of the most careful satellite retrievals indicates consistency between the satellites and the surface network regarding the warming -- and that means that there is indeed warming in the midlatitudes and tropics, not just in the Arctic. I'll leave it to Gavin to comment on the status of the soot-albedo issue. Hansen made some pioneering attempts to estimate the magnitude of these effects, but like most pioneering attempts they're not the last word on the subject.
By the way, for further illumination readers should click on the DaveScot's name below the comment, to follow the link to where he has posted his take on the satellite trends (a classic case of jumping to the desired conclusion based on a superficial analysis). The link takes you to Dembski's Intelligent Design web site. The common cause being made between global warming skeptics and Intelligent Designers, both of which dress up their arguments with the exterior trappinggs of science, is -- as Mr. Spock would say -- "fascinating." --raypierre]
So, when would we have been due for another ice age, assuming there had been not AGW? I can’t tell by the graph very well, but it looks like it would have been soon in geological terms (which might be hundreds, if not thousands of years from now).
Is it possible that our current AGW, if it goes on without drastic mitigation, could push us out of this glacial-interglacial cycle into something a lot hotter that stays that way a lot longer than most past times (except the 55 & 251 mya events)?
Comment by Lynn Vincentnathan — 18 Feb 2007 @ 9:58 AM
Re #55: Lynn Vindentnathan — My understanding is that without AGW the climate should have been very slightly cooling and doing so for the next 50,000 years. At that time it might be cool enough for an ice age to start. The next opportunity is in another 50,000 years or so.
Comment by David B. Benson — 18 Feb 2007 @ 1:37 PM
Re #56: I have seen estimates from ten thousand to fifty thousand years before the next ice age begins. So the idea that global warming saved us from the ice age does not hold water (or ice).
Your second question is more interesting. Three degrees of warming takes us back about three million years, to an era known as the Pliocene. This was a much more stable climate that lasted a long time. The Earth seemed quite “happy” with this climate, although happiness included sea levels 25 to 35 meters higher than today.
The real question is what caused the increasingly severe ice ages in the first place? I have not seen a clear answer to that. I suspect that after the greenhouse pulse stopped, the climate would return to near normal (ie. Holocene interglacial) in a few hundred years. But not quite normal because carbon dioxide levels take a long time to decay to nothing. So global warming might actually delay the next ice age, but only ten thousand years from now.
[Response: We've just come out of one of the big every-100KYr glaciations, and the normal course of events is to build up to another biggy through a series of small, short glaciations over the next 100KYr. In the normal course of events, the first try at an ice age would be due sometime in the next 20,000 years but I myself wouldn't try to pin it down more than that. One of the most interesting attempts so far to say what global warming might do to the glacial cycle is in the paper (pdf) by Archer and Ganopolski that appeared in the AGU journal GGG. I'll leave it to David to say whether that has been followed up by more detailed GCM work. --raypierre]
Real Climate regulars will be glad to learn that in a few short minutes, DaveScot has overturned decades of climate research:
Pretty incredible. I take one look at the real satellite temperature data instead of the pencil whipped crap thatâ��s foisted upon the public and in a few hours figure out the real cause of global warming and then find the studies that confirm my suspicions. Gawd Iâ��m good. Weâ��ve been lied to. C02 greenhouse effect is a lame duck. All politics and no science.
He did this after lunch. Before lunch, he was busy overturning 150 years of evolutionary biology.
I was at a talk by Jim Hansen awhile back, where he argued that anthropogenic warming has brought us to a point where future ice ages are effectively impossible, provided that atmospheric levels of GHGs remain at or above their current levels. His point, as far as I recall it, was that the radiative forcing of anthropogenic GHGs is already greater than that of the Milankovich cycles that are thought to trigger ice ages. I’m curious about your take on this.
[Response: In the annual average, Milankovich only gives you a around 5 W/m^2. Whereas athrogopogenic CO2 and other human-enhanced GHGs are now about 2.5 W/m^2 above their preindustrial values. We will certaintly push over 5 before the start coming down again. So Hansen is right, basically. On the other hand, it is the seasonal forcing in summer that really determines whether glaciers can survive the summer, and GHGs are not going to approach the magnitude of seasonal Milankovich forcing. So I would not cavalierly state that future glaciations are impossible. --eric]
Comment by Zeke Hausfather — 18 Feb 2007 @ 3:27 PM
Raypierre — Thank you for your comments at #58 by Blair Dowden. Unfortunately, the link to the paper by Archer & Ganopolski fails to function correctly for me…
Comment by David B. Benson — 18 Feb 2007 @ 4:13 PM
On Gaia, evolutionary biology overturns _you_.
Can’t hardly do climate change research without considering the ‘cold case’ from geological time — I guess climate change research isn’t possible without “Darwinism” eh?
And if we didn’t look at the geological history, if all we could look at is the current few centuries of more reliable records — who could know anything useful from just that much?
Has anyone illustrated what’s known about climate forcings for various points in geologic time, the same way the IPCC does forcings nowadays.
snips and cites:
“Biostratigraphy is the differentiation of rock units based upon the fossils which they contain. Paleoenvironmental analysis is the interpretation of the depositional environment ….
200,000 years ago
” …. Calcareous nannofossils are … made of calcium carbonate. Nannofossils first appeared during the Mesozoic Era and have persisted and evolved through time. … One extant group that produces “nannofossils” is the Coccolithophorans, planktonic golden-brown algae that are very abundant in the world’s oceans. The calcareous plates accumulate on the ocean floor, become buried beneath later layers, and are preserved as nannofossils. Some chalks, such as those comprising the White Cliffs of Dover, are composed almost entirely of nannofossils. …. … planktonic mode of life and the tremendous abundance of calcareous nannofossils makes them very useful tools for biostratigraphy.”
Nice drawings there, cited to unpublished training manuals, worth a look.
and a hat tip to British Petroleum for data; anyone know if this kind of imagery is online?
“paleoshorelines through the 240 million years of the Mesozoic and Cenozoic are presented within this atlas. Thirty-one maps, generally corresponding to stratigraphic stages, provide a snapshot of the continents and their shorelines at approximately 8 million year intervals.”
Re #34 OT: “Great Andean Glacier Will Melt to Nothing by 2012″
Thompson’s suggestion is that the main Quelccaya outlet glacier, Qori Kalis, will disappear by 2012, not that the whole ice cap will. That has a way to go yet. See http://en.wikipedia.org/wiki/Quelccaya_Ice_Cap – Qori Kalis is the little valley glacier left of centre in the sat pic. I should find a more recent image to add to the animation.
From Acton’s paper that discusses the Africian Afar anomaly: “One lava flow has recorded both of the antipodal transitional components, with the two components residing in magnetic minerals with unblocking temperature above and below approx. 500C,… Hence the configuration of the geomagnetic field, appears to have jumped nearly instantaneous from a north-hemisphere transitional state to a south-hemisphere one during this normal-to-reverse polarity transition.”
From Coe et al’s 2002 paper that discusses the Oregon anomaly: “Paleomagnetic results from lava flow recording a geomagnetic polarity reversal at Steens Mountain, Oregon suggest the occurrence of brief episodes of astonishing rapid field changes of six degrees per day. The evidence is large, systematic variations… in a single flow… most simply explained by the hypothesis that the field has changed direction as the flow cooled.”
How about this one?
“… (All researchers agree that the very, very rapid field changes could not possibly be due to changes in the earth’s core. If the problematic data is correct, the earth’s magnetic field is not generated in the core.)”
Looking at the stages of glaciation line at the bottom, I’m thinking that the cooling downswing is gradual & hitting plateaus, while the warming upswing is rather sharp & strickly increasing.
It seems that the positive warming feedbacks are somewhat stronger than the positive cooling feedbacks — struggling against them, if you will. It may be that both cooling & warming may trigger methane clathrate release from the oceans (which eventually breaks down into CO2). These are at various sea levels, apparently some closer to sea level than previously thought, according to a recent study.
I’m imagining this scenario (which may be wrong): As it cools the sea level goes down with ice going into glaciers, and this exposes the clathrates at various levels, which melt during warm summer days, and go into the atmosphere, cause warming, or counterbalance or slow the cooling. Other geological cataclysms, such as landslides, are also releasing these.
Then during the warming, even though the sea is rising, it is also warming, releasing these clathrates, reinforcing the other warming mechanisms. But it never quite warms deep enough to melt all of it, though underwater landslides, earthquakes, or volcanoes could release these deeper/colder deposits now and then.
Which brings us to now. Here we are lickity split (in geological time) releasing carbon into the atmosphere, causing warming to perhaps go above the usual thermal maximums, and even though the sea is rising, it is also warming rapidly, so we could expect more methane to be released as we heat up.
Does the atmospheric carbon chart follow this slow nonstrictly cooling and quicker strictly warming patterns, as least for some of the events (of course, other mechanisms would be at play, since they’re not staying constant)?
Comment by Lynn Vincentnathan — 19 Feb 2007 @ 8:55 AM
My thinking about GCR & magnetic fields is this: we can’t really do much about them. So, if they do have an effect on warming, then we need to focus even more strongly on what is under our control, and that is our own GHG emissions. What if all these warming factors were to converge – solar, GCR, magnetic fields, volcanos, AND our high GHG emissions — we’d really be in hot water. So we must do all we can to reduce our GHG as quickly as possible. We human might just be the straw that triggers the greatest mass extinction ever.
Comment by Lynn Vincentnathan — 19 Feb 2007 @ 9:07 AM
I don’t think it’s the greater rapidity of warming feedbacks over cooling feedbacks that causes the skewness of glacial patterns. It’s more likely due to the fact that building an ice sheet is a slow process of steady accumulation, a thermodynamic process, while wasting an ice sheet can happen rapidly, as a mechanical process. Think of an iceberg calving off a glacier into the sea; in a few seconds, the glacier loses tons of ice. But the creation of that ice happens one snowflake at a time.
Could this fresh water inflow and change in salinity also be the force behind the 3500 years cycle shown here: http://virakkraft.com/greenland_curves.html
and how much of the ongoing warming at high latitudes could be caused by this natural cycle?
My take on the GCR forcing mechanism is that it is an interesting hypothesis that should be investigated further. However, given that we already have even larger variations on an 11 year timescale, and that the CR fluxes in the space era have not changed, it’s hard to credit the hypothesis.
The speculations about the geomagnetic field are in my opinion rather wild. If you look at the way a field flip occurs, initially you start seeing more of the energy going into the higher multipoles. These configurations are not stable and oscillate rapidly. Perhaps these flows took place during the few thousand years of a flip, and the anomalies are due to rapid local variations. To hypothesize the the geomagnetic field might originate somewhere other than the core is well beyond speculative.
I think what we see here is the tendency of humans to try to explain the unexplained in terms of the unexplained (or at least the not-well-understood). Humans seem to like even better to explain things in terms of SEP (somebody-else’s-problem) or best of all NP (Nobody’s problem i.e. nobody can do anything so lets all sit in the deckchairs on the Titanic and pop a cold one rather than rearranging them).
[[Response: This is just science fiction. You can spin all the word tales you want, but until you come up with a set of equations saying why the cloud cover changes should have been less in glacial times, or why the climate should have been less sensitive to cloud cover at the time, you might as well be talking about space aliens blocking the sunlight. You talk a good tale, Mr. Astley, but science is a high stakes game, and you've got to pony up some real equations if you want to play. --raypierre]]
It’s fair enough to ask for equations to back up speculative arguments and to suggest that without them one might as well be suggesting space aliens are involved.
I clicked the link to http://icebubbles.ucsd.edu/CaillonTermIII.pdf to find the equations, but that link is dead. I found this, icebubbles.ucsd.edu/Publications/CaillonTermIII.pdf which contains no equations showing how this positive feedback mechanism works in practice. So, is there a paper showing a model for the evolution of both Temperature and CO2 with time based on any known physical processes? Does solution of these equations suggest an 800 year lag in CO2? Does the solution explain cycles in temperature etc.?
I’ve been wondering because as it stands, the RC article is interesting, but it would be nice to see it firmed up and quantified so the speculative idea could be tested.
Re #62: That joke is great, Hank. It’s the funniest thing Yakov Smirnov never said. :)
Re #75: But why risk sullying the purity of your denialist views?
Seriously, Margo, if you think there’s anything to William Astley’s stuff, I believe you have a blog you can devote to exploring it in detail. You might start with taking the obvious step of backing up to the main pub page at the link you noted and looking at all those other papers. The try Google Scholar and make use of your fine university library. If you have any remaining questions, try emailing Jeff Severinghaus. Good luck with that.
In the meantime, if the RC authors think an idea amounts to flat-earthism, IMHO spending any time on it beyond a brief summary refutation is contrary ro the purposes of this blog.
How is that any sort of answer to my question? Why are you suggesting I am thinking of anything to do with William Astley?
I asked whether or not there is a complete theory describing the speculative feedback mechanism advanced here at Real Climate. Presumably, since the whole team at RC wrote the post proposing the existance of a positive feedback between T and CO2, and raypierre is holding a high standard against mere speculation about physical mechanisms, someone here at Real Climate has seen such a mathematical model. If they have should be able to point me to they paper.
As it happens, if such a theory exists, it would touch on the topic or what triggers the ice ages– so I suspect others might like to see it.
(It also happens that if the whole team doesn’t know of such a paper describing such a model, then that might suggest that raypierre doesn’t really think these mathematical models really need to exist to before one can speculate about phenomenology. It won’t make the previous commenters speculation correct–but it would suggest that little space alien comment was a bit harsh. )
For the record Steve, it may come as a surprise to you, but I am not a denialist. I think we’ve increased the amount of CO2 in the atmosphere and I think it’s likely resulted in some increase in global temperature.
Also, for what it’s worth, I’m under the impression that the authors of RC actually like to provide references and explanations for their theories when they have them. However, if you are correct and they don’t like to do so, I’m sure they can tell me that themselves.
So, in the hope of getting what I most want, let me close by saying:
If the team or raypierre, or their guest author is familiar with a paper that contains an actual full mathematical model describing the effect of a positive feedback mechanism between CO2 and T discussed in their previous article, I’d like to read it. Honestly.
“… 26 May  in Geophysical Research Letters, Marten Scheffer of Wageningen University in the Netherlands and colleagues at the Potsdam Institute for Climate Impact Research in Germany and the Centre for Ecology and Hydrology in the United Kingdom use newly acquired ancient climate data to quantify the two-way phenomenon by which greenhouse gases not only contribute to higher temperatures, but are themselves increased by the higher temperatures. This higher concentration leads to still higher temperatures, in what scientists call a positive feedback loop.”
(I don’t know if the commenters here have mentioned it; not finding it with the search tool)
Hank Roberts[[Er. You're asking for a "complete theory" and "an actual full mathematical model" -- can you say what papers you would say don't meet your standards, of the major ones?]]
I wasn’t saying I knew of papers that don’t meet standards. I was saying that the paper cited in your real climate article What does the lag of CO2 behind temperature in ice cores tell us about global warming? speculated about the existence of a positive feedback but cited zero articles containing anything that could remotely be called a mathematical model to describe any sort of positive feedback loop. -That’s why I was asking for a citation. (Like Raypierrs, I happen to like these models– which is why I said it’s reasonable to ask for them. That’s why I wished the earlier RC post had cited a model — it would make the idea more concrete and testable. )
So far, no one had suggested a paper containing a model. The only person who responded was Steve Bloom, who seemed to think I should not be asking for any such paper. (Or something.)
The link you gave was for the press release– but I think I found the pre-press version here:
Re #77: Regarding the Astley reference, it sounded on first reading as if you were defending him. On a more careful reading I see that what you were really doing was snarkily equating Ray with him. Whatever.
Regarding your particular brand of denialism, it appears clear enough from your blog and posting record that you’re only interested in learning enough about climate science to go on the attack against it. Of course you’re free to refer to yourself using any term you like.
On the substance, I was curious enough about this issue to be willing to do some of your research for you. I couldn’t find public-access copies of any of the papers, but the short answer seems to be that the equations are built into specialized models (not GCMs) that are used to look at ice age behavior. This student paper from 2005 has a nice narrative of the history of these modeling efforts and then discusses in some detail the plans for improving the McGill one, although I’m sure plenty has happened in the intervening two years. It names many if not most of the models involved, so it should be easy to go find current information on them and extract the relevant algorithms. As you’ve recently been spending time trying to pick apart the GISS GCM, that shouldn’t be too tall of an order for you.
BTW, you use the phrase “speculative feedback,” but the existence of the feedback itself is not a matter of speculation at all. The exact mechanism for the feedback is not settled (call that speculative if you want), although many of its parameters have been determined.
Re #78/9: The paper Hank linked is on the strength of the amplification effect of anthropogenic GHG emissions at the present time, which is rather different issue from the past lagged relationship between glaciations and CO2.
Re 81 Steve Bloom. The paper Hank suggested does not contain a positive feed back model of the sort that would explain why the 800 years lag in CO2 in ice cores. As it happens, the student paper you cite contains no such model. In fact, it doesn’t even contain a single equation — which would be a rather minimal requirement for a paper describing a mathematical model.
But since you ask me what I am looking, I shouldn’t be surprised the paper you suggested doesn’t provide a mathematical model. Here’s what I am looking for:
A specific model that would support thespecific argument in What does the lag of CO2 behind temperature in ice cores tell us about global warming? written by the RC team. The argument they advanced in their article includes the claim that the 800 year lag in CO2 can be explained by a positive feedback mechanism. That’s a rather precise claim–not only is there a positive feedback, but it’s consistent with the 800 year lag in CO2, and the whole ball of wax explains the magnitude of the changes in temperature associated with ice ages and interglacials.
A reference containing such a model should be rather easy for the team to supply if– as raypierre’s response to Astley suggests– the RC team members really don’t accept speculation until after they have read and accepted some sort of mathematical model to explain the speculation.
Of course if there is no such paper, or even if it exists, but the RC authors are unaware of the paper, then with regard to this specific theory explaining the meaning of the ice cores, maybe that would suggest the RC authors, including raypierre don’t actually believe these sorts of models are always required before one can accept a speculative argument.
[Response: I don't really know what you are looking for since I don't know that anyone has ever claimed to have a pure mathematical basis for the changes in oceanography and biology that control the CO2 level. However, there are lots of reasonable heuristic models that demonstrate the reasonableness of the idea - Didier Pallaird for instance (Paillard, 1998; 2001, and references therein.). It should be clearly stated that a full understanding of ice age carbon dioxide cycles is still elusive, but conceptually, there is absolutely nothing difficult about a lags in the system on the order of the ocean overturning timescale -on the contrary it is to be expected. -gavin]
Tamino said: “The FFT is a poor choice, because is requires the data to be evenly spaced in time (which often it is not), and requires the number of data points to be a power of 2 (which it almost never is).”
The number of data points does not have to be a power of 2. Modern FFT algorithms automatically break up the time series into a subset of primes. It goes faster as a power of two, though, and this can be effected simply by padding the series with zeros up to the power of two. Zero padding can also be used to increase the resolution of the PSD. See the classic text by Oppenheim and Schafer (the latter one of my old profs).
Unfortunately, though, the FFT does require the data to be evenly spaced in order to take advantage of the symmetries of the Fourier series.
Reid, thats true that you don’t neccessarily need a factor of 2. Padding the series with zeres is essentially the same as interpolating the time series, and if you’re going to interpolate it anyway you might as well make it a power of 2 AND give it even spacing. Tamino’s use of the DCFT was appropriate though, and makes the issue moot. DCFT takes a lot more compute power but in this era of Core 2 Duo laptops and matlab licenses, who cares? :) (I’ve got an old pre-Yonah “Dothan” Pentium M thinkpad which gets the job done just fine).
I still think that the frequency graphs are more intriguing than the original time series (I work in MRI physics, so I have a bias towards the frequency domain). If you’re trying to establish a case for the complexity of inputs to the warming cycles, then overlaying the various peaks on each other on a single colored graph would be immensely useful for a layman.
I’m a reader, not a contributor here. Don’t mistake me for a climate scientist. I read, try to learn, try to ask questions to clarify. Having looked at Margo’s website, I’m done replying to your questions here, it seems you’re trying to be another “auditor” — anonymous, at that. If you think you’re doing science, send it to a refereed journal for help. The “auditors” might as well set up card tables and pull out e-meters, it’s not science.
1) I do think it’s important to comment when inline replies are nothing but snark and double standards.
Contrary to raypierre’s snark about “space aliens”, the standard for a a more or less respectable idea is not that one must “come up with a set of equations saying why….” to support your idea. Heuristic explanations are widely used, and perfectly respectable. Based on your final reply, RC is, in fact, relying on non-mathematical heuristic explanations when discussing the ice core data. (That’s what I thought you were doing when I first read the article.)
2) If someone had actually come up with a set of equations to explain why the ice core data looks the way it does, I would have loved to have see that. Evidently, no one has come up with one and only heuristic explanations exist. That’s fine with me from a science point of view. ( However, the fact that this bang on explanatory mathematical model does not exist does illustrate that Raypierre was erecting a double standard in his snarky reply.)
So, thanks for the links to the papers. I’m reading them, and I find them interesting.
For what it’s worth: I’m entirely unfamiliar with what Astley is talking about. It was the snarky reply that caught my eye. But if Astley’s heuristic argument has some deficiency other than not being described by “a set of equations saying why….” , could someone explain the deficiency? If your position that the idea is just not even fleshed out enough to engage that’s fine. But if an inline reply is warranted, surely it should provide a legitimate criticism.
[Response: I get your point, but on the specifics of GCR-climate links, Ray is correct. There has not been even one credible estimate of what the radiative forcing for a change in GCR would mean for climate. This is something that clearly is amenable to 'equations' and the like, and is the standard by which all potential forcings (CO2, CH4, volcanoes, solar, aerosols etc.) are measured. Until that happens, claims that GCR forcings are the dominant force in climate will continue to be dismissed as they are not based on anything quantitative. We know to a pretty high accuracy what the man-made greenhouse gases have done, there is no comparable estimate for GCR effects. That has nothing to do with heuristic arguments about the glacial-interglacial cycle. -gavin]
Re #82: Margo, you need to read what I wrote. The student paper was useful because it a) contained a good (AFAICT) narrative of how the science had developed up through a little less than two years ago and b) named at least some of the relevant models. IMHO people who aren’t in the field tend to have a hard time really understanding the state of the science without something like that as a guide, so I was very happy to have found it. In any event, I didn’t say the paper included the models or their underlying math, but rather that it named them such that an interested party (you, e.g.) could go look at them to find out about the math.
Just to restate a little what Gavin said, I think your question betrayed a basic misunderstanding (which is why I thought the student paper would be so useful for you). The behavior of the CO2 around the glaciations can’t be a forcing as such because that would conflict with our understanding of its physical behavior; i.e., it can’t start an increase or decrease by itself. Something else is making it behave that way, which means that it is a feedback to a forcing (or forcings). The way these terms are defined leaves no other option. So, to even refer to a “speculative feedback” betrays a fundamental misunderstanding. Exactly how the behavior of that feedback is modeled is a very interesting question in climate science, and as Gavin says not fully resolved as yet, although it seems clear that the general answer is Milankovitch forcing leading to a combination of feedbacks (e.g. ocean and vegetative) that in turn result in the CO2 change. The test of the models is how well they replicate ice sheet behavior (in terms of timing, size and location), and based on that paper it doesn’t seem like they’re terribly far away from that.
[Response: In addition, the main point of Severinghaus' post, referenced at the beginning of this thread, was not to explain the possible mechanisms for the glacial-interglacial CO2 fluctuations, but only to explain that the lead-lag relation cannot be used to infer that CO2 is "caused by" temperature rather than vice-versa. He was shooting down a fallacy in reasoning. As such, it's a point that is mathematical, and independent of the specific mechanisms causing the CO2 feedback on temperature. Jeff explained this in words, to be more accessible, but it's quite easy to cook up a pair of differential equations with an external periodic forcing (think Milankovic) which illustrates the point in quantitative terms. By the way, many scientists have proposed specific testable mechanisms for the CO2 glacial-interglacial cycle. They have all been falsified, but that's just science. The credit goes to the people who have formulated things (like ice cover /gas exchange feedback) that can be quantified to the point of being tested. This is very different from much of the commentary you see from the GCR crowd,notably Mr. Astley's waving a magic wand and inventing a lower glacial-climate cloud sensitivity to make the problem with the Laschamp Magnetic Anomaly go away. --raypierre]
RE: #48 – The Dust Bowl years are extremely politically incorrect. They make the 90s look too good.
[Response: Not at all. Take a look at the midwest regional climate report from Union of Concerned Scientists. We already have hit as many or more days per year of extreme heat (>97F) than there were here in the Dustbowl. Then take a look at where we're heading in a hundred years. In fact, the Dustbowl makes the future look really, really scary. --raypierre]
Actually, Aziz, zero padding the time series can be considered equivalent to interpolating in the frequency domain. In reality, it results in sampling the actual fourier transform of the finite time series on a finer grid so, it’s a little more subtle than just saying it’s an interpolation. I wasn’t criticizing tamino’s methods, just setting the record straight. Also, the number of calculations involved in performing a straight fourier transform rises so fast that, even with modern computers, it can become untenable for a large set of data. And, since there is no sampling theory for unevenly spaced data, the results are often disappointing. I would recommend a least squares type of algorithm based on an ARMA model in that case.
Why ice ages happen is a good question. Milancovich cycles have always happened but only in the last 3 million years have they caused ice ages. previous ice house cycles have happened at roughly 250 million year intervals.
One theory I have read is that the incidence of ice age cycles matches the rotation of the sun around the rim of the Milky Way galaxy. At a certain point in the Sun’s orbit something happens to cause it to dim slightly. This means that at certain stages in the orbital cycle the Sun is not strong enough to melt the ice formed the previous winter, thus causing ice ages. Anybody heard this theory?
[Response: Sounds like you're referring to the "Muller and Macdonald" theory. Its all but dismissed now by serious researchers in the field. A nice, concise explanation of why is provided in this Science article by Clark et al (1999): Muller and MacDonald [ R. A. Muller and G. J. MacDonald, Science 277, 215 (1997)] argued that the origin of the 100-ky cycle involves non-Milankovitch changes in the Earth’s orbital inclination, which caused the Earth to periodically pass through a cloud of interplanetary dust. Sedimentary records and calculations of dust flux, however, do not show large changes in extraterrestrial dust accretion [F. Marcantonio, et al., Nature 383, 705 (1996); F. Marcantonio, et al., Earth Planet. Sci. Lett. 170, 157 (1999); S. J. Kortenkamp and S. F. Dermott, Science 280, 874 (1998)], whereas spectral analyses of the marine 18O record of global ice volume suggest that this mechanism is unnecessary [J. A. Rial, Science 285, 564 (1999); A. J. Ridgwell, A. J. Watson, M. E. Raymo, Paleoceanography 14, 437 (1999)]. Hardly a ringing endorsement. Muller’s “death star” hypothesis for explaining the major geological extinctions events including the K/T extinction, hasn’t fared much better. –mike]
Back on the original topic, Martinson and Pitman’s idea doesn’t seem all that far afield from the old Ewing and Donn hypothesis (discussed in the Discovery of Global Warming about halfway down this page).
IN reading here seeking causefffects patterns & cycles i find rare or no reference to or using natural ‘rebalancing’ weather & climate cycles at all.
In Gaia Ecology self-regulation is always toward balancing energy for life systems in bioregions & whole biosphere. So omitting ‘balancing’ is fatal flaw in climate modeling & predicting coming patterns causes & effects. That maybe largely why huge climate computer models rarely predict any cycles accurately. ANYONE TRACKING NATURAL CLIMATE BALANCING CYCLES?? thet’re yin/ynag flips happening every day, season, years & longer cycles. Also the patterns of electromagnetic frequency waves we call ‘ionic charges’ in air & water effect weather called pressure fronts, but is also ionic charge zones & MOVEMENTS of weather systems we need to learn how their energy works in simple natural words, not scientease. The only book i know on this is ‘The Ion Effect’ 1980 by Fred Soyka, but weathermen don’t like air ionic charges or lighteing at home,
its very exciting on TV tho. Our sky does have energy, it ain’t empty vaccum.
Here is my favorite Gaia Ecology self-regulation process:
After many years of reviewing solutions to anthropogenic global warming (AGW) I believe this technology
can manage Carbon for the greatest collective benefit at the lowest economic price, on vast scales.
Below is my review of these efforts in the Academic and private sectors, please forward this to all the experts you know, if you think it merits their time and support.
Terra Preta Soils Technology To Master the Carbon Cycle
Erich J. Knight
E-mail: shengar at aol.com
Comment by Erich J. Knight — 21 Feb 2007 @ 12:29 AM
re Carbon capture and Storage technologies.
There is no real technological problem with separating out C02 from the airstream of a coal-burning power station. It does make generating electrical power a whole lot more expensive though.
Sequestration is the big problem and quite honestly, the proposals that are made for it look very suspect. More or less, to dump it and leave it for future generations to deal with, based on some vague and untested ideas.
Deep ocean storage seems positively dangerous. Even the IPCC report on Carbon Capture and storage admits that it will leak out within a few hundred years.
Given that it’s the oceans that play the most important role in the Carbon cycle and ocean acidification is potentially disastrous, this is a proposal which should be opposed at all costs.
“Injection up to a few GtCO2 would produce a measurable change in ocean chemistry in the region of injection, whereas injection of hundreds of GtCO2 would eventually produce measurable change over the entire ocean volume.”
Geological storage is largely an unproven technology. The only real case studies are based on oil industry practices used in exploiting marginal reserves.
It might also be used by coal companies to extract methane deposits from economically marginal coal seams.
I think it’s inescapable that the US and China (which produce 54% of the world’s coal) have to reduce their production levels and move towards renewable energy on a massive scale.
It’s also inescapable that mass transport systems need to move away from using oil
[[IN reading here seeking causefffects patterns & cycles i find rare or no reference to or using natural 'rebalancing' weather & climate cycles at all.]]
Could you perhaps explain what “natural rebalancing cycles” are? Models do take account of many known cycles, depending on which sort of model we’re discussing. Do you mean the daily cycle, the seasonal cycle, the ENSO cycle, the carbonate-silicate cycle?
RE #75, 82, 88, I agree that this whole notion of “feedback” is difficult for people, and I don’t think I would have caught onto it so fast, if I had not read articles about positive v. negative feedbacks in the social sciences. I’ll give you a simple example, when we look at the correlation between education and income, that makes a lot of sense to us. That’s why we sweat bullets at the university, so we can get good jobs and incomes (and why we can snicker at the poor, who were lazy & didn’t go for the higher education). So, education is the independent (causal) variable, and income, the dependent (effect) variable.
But what about a person’s parents’ income? Doesn’t that help them to study during high school (rather than work part-time, or drop out), get better learning aids (encyclopedia sets, etc), then go to better colleges with high tuition fees? So then income becomes the independent (causal variable) and education the dependent (effect) varible, and putting these two cause-effect aspects together, the rich get richer.
Similarly, GHGs can be an independent or causal variable (a forcing) of warming, and (this is the really scary, super-alarmist part) they can also be a dependent or effect variable, as when warming causes nature to emit GHGs from methane clathrates, permafrost, decay of plants dying from the heat or heat-caused fires (the CO2 lagging the warming in the ice core, extremely confirms this — turns this hypothesis into an evidence-supported theory, contrary to denialists claiming it disproves that CO2 can’t cause GW — since we know some variables can be both effect AND causal variables). And both aspects together in a single system can form a positive feedback loop, in which (in our present case) the initial extra GHGs emitted by humans is causing extra warming, which will cause extra GHG emissions from nature (not to mention reduced albedo, which then causes further warming), which will cause extra extra warming, and so on. Aparently nature has an abundance of these GHGs stored up for just such a mass extinction from severe global warming scenario.
By looking at that chart above, I’m thinking it’s really really unfelicitous that we just happen to be at a high point in the natural warming (inter-glacial) already, posed after many thousands of years at a warm plateau-peak to start cooling back down. But instead we’re using this high point as a lauching pad to even greater warming.
I can use this chart as an exhibit for my Eco-House of Horrors next Halloween, with a broken line shooting upward (say, into a ball of fire) from the current high point.
I’ve been perhaps one of the most extreme alarmists on this site, but now I realize I’ve underdone it; I’ve been sleeping on the job; I’ve severely underestimate the deep doo-doo we’re in. Now don’t come back with platitudes not to worry, because I can see it plainly on the chart — we’re at a high natural peak in the warming-cooling cycle. And it’s being used as a launching pad for still greater heating. This is serious.
Comment by Lynn Vincentnathan — 21 Feb 2007 @ 9:42 AM
Barton, I looked. Don’t go there, it’s newage stuff.
Lynn, i agree that you are at one end of a continuum of opinion, that exists on this website, with our climate science friends being somewhat closer to the centre. I think it is very useful to have a range of legitimate opinions.
I have had a look at Mark Lynas’s website, i would say that he is lining up along side Fred Pearce and James Lovelock. Perhaps the key point in the ‘super-alarmed’ arsenal, as i see it, is the extent to which the 1.5 to 2 DegC of warming we are commited to, begats further feedbacks.
There must be a curve which describes the amount of feedback that is created by each 1 degC of extra warming. Is there any plotted historical data on this one?
Is ‘super-alarmed’ a legitimate, scientifically valid veiwpoint? I feel that AAAS president (Prof Holdren) is setting the right tone, in saying that we are driving towards a cliff in a car with bad brakes, in the fog. So how well are the scientists among us sleeping? Holdren says we are now fighting to save our planet, not from dagerous CC (which is here), but fromcatastrophic CC.
Our moderators have been doing a tough job (ie fighting the deniers propoganda machine), for a long time. I think this site is a demonstration of their commitment to getting the ‘message’ out. Maximum respect for that. :-)
So now the battle against the deniers is nearly won, will our climate scientists be ‘coming out’, as having more in common with the ‘super-alarmed’ than previously stated? Should we all cut the flannel, because 2007 is gonna be even hotter, and therefore accept that Greenland and the WAIS are as good as gone?
I think that the battle-lines, on this blog, and in the world in general, may be redrawn, as the pressure on the scientists, in the future, comes from the ‘super-alarmed’, not the deniers.
I am keen to hear that people tell us we are hysterical, Lynn, and to metaphorically slap us around the face. This may be necessary on an increasingly frequent basis!
You might be interested to know, especially if you live in the US, that I am applying to study for a degree, starting in September, in Flood Risk Management, as part of an initiative by the Environment Agency!Fortunately, my socialist (and probably KGB inspired) government is prepared to pay my course fees, for my accomodation whilst on placement, and it is also offering Â£12k a year, which would cover living costs. Is that very generous, or merely telling? Here in Europe, the wallets are being opened! Any way, i might not get in, so fingers crossed…
My apologies for filling your blog with unscientific, off topic ‘noise’, but RC is the only quality forum I have. It has undoubtably inspired and informed me, in thinking about my future.
This is a good one I’ve read about before — there’s solid science done on past use of charcoal as a soil amendment, and also good work done on extracting hydrogen from carbohydrates, leaving charcoal behind that can be added to soil.
Following that link led me to a cite Erich posted there, that I think merits posting here:
 Day, D., Evans, B., Lee, J., Reicosky, D.
“Economical CO2, SOx ,and NOx capture from fossil-fuel utilization with combined renewable hydrogen production and large-scale carbon sequestration”
in press for Energy: The International Journal; (pre-press copy) http://www.eprida.com/hydro/ecoss/background/Energy_article.pdf
Did someone mention the effect of the ice mass on the Arctic water passage. I understand that the ice can push down the land masses substantially. The ice builds up, the arctic passage opens as land mass is squished, the ice warms up as warm water inflows.
I can’t access the Science article, but the theory concerned the cause of ice house periods generally, not the 100,000 year periods within the cycle, where the dust theory does seem a bit dubious.
Some mechanism that dims the sun at certain intervals enough for orbital cycles to plunge the Earth in to ice ages seems necessary. Any good theories about?
Reid, you’re absolutely right. I misspoke, what I should have said was “padding the frequency domain with zeroes is essentially the same as interpolatig the time series” (in MRI, we acquire data in frequency domain, so I always think “backwards”.) And you are also right that you will essentially get some error, I assume from truncation or ringing of some sort.
I knew you werent critiquing tamino- i just found the discussion a fun tangent :)
For the purposes of these graphs, a crude analysis would be simply interpolate the time series onto a power of 2 and evenly-sampled axis, and then slam an FFT on it. I doubt a more rigorous approach would give substantially different results. The idea really is just to see where the frequency spikes overlap, if at all.
The simple harmonic oscillator provides an ultra-simple model of ice ages. I tuned the oscillator to have a natural period of about 125 ky and then added orbital forcing to vary the tuning. The resulting system is a more complex form of the Mathieu equation in that the orbital forcing occurs at several different periods, not just one. Nontheless, the results are similar. I ran the program for a simulated 2.688 My.
The response has 48% of the power in the 85.3–128 ky band, 40% of the power in the 64–85.3 ky band and only 8% of the power in the forcing bands. Interestingly, about about 4.6% of the power is in bands longer than 128 ky. (Numbers do not add to 100% due to rounding.)
The response is ordinarily rather slow. The fastest rates of change are about 5% per ky, so the fast recovery from LGM is not well modeled.
Nonetheless, this little exercise shows that even frequency modulation of a harmonic oscillator suffices to demonstrate some aspects of ice age climate.
Comment by David B. Benson — 21 Feb 2007 @ 7:51 PM
Re: playing with models of glaciation
The simplest model of ice volume which gives anything like a realistic picture is the “Imbrie model” (Imbrie & Imbrie 1980, Science, 207, 943). Ice volume V is actual expressed as its deviation from a rather high value, so the modelled parameter V is usually negative. The model is
dV/dt = – (1 +/- b) (I(t) + V) / T
The function I(t) is the driving function, often taken as the midsummer solar insolation at latitude 65deg. (June 21st for the northern hemisphere, December 21st for the southern). T is a time constant, giving the timescale of the response to forcing (10 ky is not an unreasonable value). The constant b gets added during deglaciation, and subtracted during glaciation, to simulate the observed fact that deglaciation tends to happen faster than glaciation; b=0.3 is not an atypical value. If you enjoy playing with models, try a variety of values for the parameters, and try different parameters for the different hemispheres.
One of the problems is that the forcing function (midsummer insolation) responds to the precession cycle more strongly than to the obliquity cycle, while observed global ice volume shows greater response to obliquity than precession. But Raymo et al. (2006, Science, 313, 492) have made a strong case that the reason is that obliquity affects both hemispheres the same while the effect of precession is 180 degrees out of phase between the hemispheres. When precession causes ice to grow in one hemisphere, it shrinks in the other, so for the impact on global ice volume the opposite hemispheres mostly cancel out the precession effect. For obliquity, growth and decay are in phase between hemispheres.
Of course there are still unanswered questions. Glacial changes are much stronger during the last 800 ky or so, than in the preceding 2 million or so; this may be due to slow but steady decrease in the “zero point” of CO2 concentration. Also in the last 800 ky or so, there is a strong 100 ky cycle, originally attributed to eccentricity (rather than obliquity or precession), but that idea is now out of favor (but not dead). The best idea I’ve heard is that recent glaciations (global ice valume) are driven by obliquity, but for some reason deglaciation is only triggered every 2 or 3 obliquity cycles (Huybers 2007, Quaternary Science Reviews, 26, 37). The reason is unclear (but I’ve just submitted a theory on that to GRL).
Regarding the driving force between changes in the Earth’s orbit around the sun and glacial cycles, I have seen no comment on the recent paper by Gerard Roe (available draft version | final GRL article)
in which he clearly shows that 65N solar radiation is linked to the time rate of change in ice volume (dV/dt) rather than the ice volume, V, that is commonly used.
I am no expert but his arguments seemed convincing to me. Add in ice albedo feedback, CO2 feedback (e.g. colder water can dissolve more CO2) and water vapour feedback and dust then the large swings in global mean temperature would appear reasonably consistent with theory.
[Response: I get yo..... We know to a pretty high accuracy what the man-made greenhouse gases have done, there is no comparable estimate for GCR effects. That has nothing to do with heuristic arguments about the glacial-interglacial cycle. -gavin]
Thanks for the more detailed answer on the GCR effects; this is much more satisfying than the “space alien” bit.
As to this bit: “We know to a pretty high accuracy what the man-made greenhouse gases have done..”
Steve Bloom will be stunned to learn that I agree with that to a large extent particularly since you don’t need a GCM to predict that there should be some effect, and many of the uncertainties have nothing to do with what’s involved with coding GCM’s. ( Example: clouds. )
(BTW. I think given Steve’s comments, I think it’s worth nothing that the just because I think some of the narratives I read about GCMs seem to oversell, that doesn’t mean I think they are useless. My reading of the papers suggests many things are done with degrees of approximation just somewhat beyond the level done back when Launder and Spaulding were working on models. In many ways I’m even ok with that but certain types of overstatement set my teeth on edge. )
Re 88: [Response: ..... eff explained this in words, to be more accessible, but it's quite easy to cook up a pair of differential equations with an external periodic forcing (think Milankovic) which illustrates the point in quantitative terms. By the way, many scientists have proposed specific testable mechanisms for the CO2 glacial-interglacial cycle. They have all been falsified, but that's just science. .... .... --raypierre]
Raypierre: I recognize that what Severinghaus considered to be his main point. For what it’s worth, I realize the fact that CO2 lags doesn’t necessarily mean T “causes” CO2 to rise. I am familiar with positive feedback (like the kind that caused this bridge to fail.)
I also know it should be easy to cook up a pair of differential equations that reflect the narrative in that article. Or at least it should be easy if we understand the effect of temperature on CO2 uptake or release and if we also understand the effect of CO2 on factors that affect the energy balance.
One thing I was trying to find out was has anyone done it? Have the solutions of these DE’s differential equations been compared to the data and found to work? (Or not?) Do we have mathematical models for the effect of temperature on the CO2 uptake and release?
You seem to be saying maybe some mathematical models involving the CO2 Temperature linkage have been proposed but found failure? I agree failure is part science. :) And, as it happens I’d be interested in reading papers describing the failed models. (And not, because I’m trying to find holes– I’m curious about what someone tried to come up with in equation form rather than just words. Do you have references? Names? Titles? I can find them, but it’s a bit hard to google with random words.)
Re 88: Steve: I did read what you said. I asked for something specific. You decided to suggest a reference that did not discuss that specific thing. Thanks anyway.
Re #110: Margo, it seemed to me that a list of various modeling efforts would be helpful in that you could go check them out. Of course each of those modeling efforts would need to involve some sort of algorithm along the lines of what you say you want to see, but I guess what you really wanted was a direct pointer to one or more of them. Sorry, I’m interested in this subject but not interested enough to devote time to such a search.
By coincidence, though, I did just happen across this new paper (not through peer review yet). It uses an AR4 GCM (recalling that as of two years ago GCMs weren’t being used for this sort of thing, but these authors have access to loads of time on an advanced supercomputer) and seems to get pretty good results. I haven’t read through it carefully yet, but it does include an equation or two.
Re 111: Steve Bloom. I don’t know why it seems to you that student paper will help me find what I want. I’ve downloaded many of the papers discussed in section 2.4 in the paper you linked, and let me assure you, they don’t describe the sort of thing I am looking for. The paper you found today is even further from the mark.
Raypierre can very close to giving a qualitative description of what I want when he said:
[[.....eff explained this in words, to be more accessible, but it's quite easy to cook up a pair of differential equations with an external periodic forcing (think Milankovic) which illustrates the point in quantitative terms. By the way, many scientists have proposed specific testable mechanisms for the CO2 glacial-interglacial cycle. They have all been falsified, but that's just science.]]
I agree that — if the physical processes are sufficiently well understood — then it would be quite easy to cook up these equations. If I’m understanding Raypierre correctly, he is suggesting he is aware of some people who have attempted the “quite easy” task of cooking up equations of this sort, but their models didn’t pan out — that is to say, they were falsified.
If Raypierre knows the names of authors who documented their efforts to develop these models and compare them to data , I’d like to know those so I can search for the papers. (Falsified models are not generally widely cited. So, if Raypierre doesn’t mention some names to give me a place to start, I really don’t think I’m going to find them.)
… a close temporal coupling between events in the tropical and high latitude North Atlantic during the last deglaciation . We recently extended this record to approximately 120,000 years BP in order to track vegetation change over a full glacial cycle at millennial to orbital timescales. High frequency oscillations in the Î´13C composition of long chain fatty acids during MIS 3 appear to coincide with Dansgaard/Oeschger variability in high latitude ice cores, with positive (negative) excursions occurring during stadial (interstadial) periods. The largest enrichments (up to 8 per mil) are associated with Heinrich Events in the North Atlantic. After a relatively stable MIS 2 period, Termination 1 is marked by a rapid 13C depletion over the Glacial-Bolling transition followed by a return to somewhat heavier values during the Younger Dryas, similar to earlier observations . These high frequency fluctuations are superimposed upon a long-term trend that tracks the variation in overhead insolation…..
There’s always something interesting — setting aside the fact that these astronomical variations are minuscule compared to the rate of the current human contribution to climate change, there’s plenty of interesting science.
Someone can now add this variable to all the others:
“One pole of the sun is cooler than the other. … data from the ESA-NASA Ulysses spacecraft.”
I don’t know if that temperature difference detectable from the unique orbital perspective over the Sun’s poles is also detectable in the plane of Earth’s orbit now that we know to look for it (that is, I don’t know if the whole Solar System is warmer on one side of the Sun’s magnetic field — it’s a funny asymmetry, eh?).
And on the cosmic ray stuff:
And New Scientist last week had a good article on the upcoming chance to slingshot another deep space probe — there’s a configuration coming soon that would allow a spacecraft to pass Jupiter and be slung very fast out along the line the Sun will be traveling, which could get among other things advance info on any change in dust levels; one’s certain to happen when we leave the local ‘bubble’; there may be streams or clouds of dust. And yes, Svensmark is mentioned — changes in dust will have local consequences, changing cosmic ray rates, though no one’s quite sure yet how. No online text that I am aware of; library/sub required.
Aziz – not to beat a dead horse, but just be aware that interpolation is like low pass filtering and it will smudge and attenuate the higher frequencies. Unless it’s a high order interpolation, which might amplify portions of the spectrum.
Re #102, thanks, Mark. And I, too, would like to know about:
“There must be a curve which describes the amount of feedback that is created by each 1 degC of extra warming. Is there any plotted historical data on this one?”
I know Mark Lynas’s book SIX DEGREES is coming out March 19th, and I’m hoping he’s addressed this very question.
GW is a big, complex issue, & we need some people to bring it all together in lay terms.
I just read that the Texas Water Dept Board projected that 85% of Texans will not have adequate water by 2060 during drought conditions….and they didn’t even take GW into consideration, which would imply a still worse scenario.
So glad you are going into a field that could use a GW perspective.
Comment by Lynn Vincentnathan — 23 Feb 2007 @ 5:32 PM
Re #102 & #117: Mark Schneeweiss & Lynn Vincentnathan — The paper “Positive feedback between global warming and atmospheric CO2 concentration”, by Marten Scheffer, Victor Brovkin and Peter Cox, describes an important part of what you wish to know.
You can either web trawl for the preprint version of the paper or else find the comment here on RealClimate where the link was posted on the 19th or 20th of this month.
Comment by David B. Benson — 23 Feb 2007 @ 6:07 PM
Re #112: I imagine it’s the case that not every piece of a model appears in a paper, Margo; if anything I would expect just the opposite until such time as one of the teams thinks they have it all nailed own, at which time I would expect all of the details to be carefully described in papers. Your next obvious step is to email the modelers, since the one thing we can be confident about is that each of those models must contain a version of what you’re after. Also, not to put words in Ray’s mouth, but when he said “falsified” I don’t think that was the same thing as saying that there aren’t valid algorithms that describe the relationships between the things we have paleo records of (e.g. CO2 levels, ice sheet mass and location, and vegetative response per the paper Hank just linked) or can calculate with exactness (Milankovitch forcing). The Japanese team does appear to be quite close (with e.g. far better results than the McGill model was getting a couple of years ago).
What’s still missing, and the reason why their model too continues to be falsified, is that there are literally dozens of important feedbacks and physical parameters that must be gotten right in order for the model not to be falsified. They named a few that they know they need to continue to work on, and I have to say it seemed like a pretty short list. Comparing their overall results to what the McGill team was getting a couple of years ago, it seems likely that they have the guts of it right. (That said, I’d love to know what other modelers think about this.) Anyway, we’ll see what happens over the next couple of years as they plug in those changes.
Just to add to the above a little: I’m obviously no expert, but it seems to me that it would be a comparatively trivial exercise to develop a set of equations that describe, e.g., the relationship between CO2 levels, insolation and ice sheet mass. Could you use that set of equations in any direct way to describe the timing and location of the ice sheets? I suspect not. As I think about it, it’s not entirely clear to me that the modelers would need to go through a formal step of developing such a set of equations unless those steps were amenable to plugging into the model in a fairly direct way. I did notice that the Japanese team had a fair number of equations they used to describe various relationships within their model, but those may not be taken from the model in a strict sense. IOW, did they write those equations after they wrote the code simply as a convenient way to describe what they did?
Putting this whole thing another way, would it be possible as to state an entire GCM as a set of formal equations (as opposed to code)? Whether it is or not, it seems clear that it would be pointless.
Academic Press, 2002
is an attempt to develop equations to explain ice ages in a rigorous manner. I am finding the book quite useful, so at least I do not find Saltzman’s effort to be pointless…
Comment by David B. Benson — 23 Feb 2007 @ 8:01 PM
In Reply to Robert’s Comment 67 to my comment 66. “How about this one?
“… (All researchers agree that the very, very rapid field changes could not possibly be due to changes in the earth’s core. If the problematic data is correct, the earth’s magnetic field is not generated in the core.)”
Attached is a link to a summary that provides papers and a discussion of the salient scientific issues.
Physical issues with explaining rapid field changes:
1. Did the very, very, rapid geomagnetic field changes occur? Yes three papers, two different authors confirm, the event happened.
2. How rapid is the observed geomagnetic field change of 6 degree/day. Current field change is 0.5 degree per year.
3. Physically, why is it difficult to explain this rapid change? If the geomagnetic field change was caused by changes in core, the outer core fluid velocity would have needed to increase a 1000 times (what is the physical reason for a 1000 times increase?) or there would need to be a more complex field configuration in the core than is currently used in computer models. (i.e. A theoretical configuration of core currents which is believed to be physically not be possible. No mechanism to move the core fluid to create the observed pattern.)
4. Regardless and most important, the mantle is slightly conductive, rapid changes in the core magnetic field would create currents in the mantle that would resist the changes. Based on the theoretical geomagnetic field computer models (Which are all incorrect as the geomagnetic field is not generated in the core. Other theoretical problems with core as source, such as what is driving the core fluid motion? Heat flux problem.) it is believed (and it is stated in paper’s) that reversals take a couple of 1000 years to complete.
5. As the sea floor sediment proxy data, filter’s the geomagmetic field changes, everyone assumed field changes took 1000′s of years to complete.
Re #126: Steve Bloom — With pleasure. The late Professor Satzman, with colleagues, develop a system of three first order nonlinear differential equations to represent ice mass, carbon dioxide and ocean temperature, all globally. Using reasonable values for the parameters, the model is tuned to naturally resonate at a 100+ ky period. Then orbital forcings are added. The result gives a qualitatively good match to the most recent four ice age cycles, according to the 1990s data that they used.
They then go on to somewhat more sophisticated models which assume a secular downwards trend in carbon dioxide over the last 5000 ky. Running this model gives quite a decent, but qualitative fit, for the entire Late Cenezioc ice age. The fits for the latest 700 ky are quite respectable.
The conclusion is that the ice age cycles occur because the climate system has a natural period of about 100 ky. The orbital forcings just set the phase. I interpret his view as implying that eccentricity has essentially nothing to do with the cycle length.
I am such an amateur at this that I am not in a position, yet, to suggest revising his constitutive equation for the rate of change of ice mass. But either I am missing something or his equation is overly simple. Either way, he has done a most impressive piece of work in reducing the climate system into a form which can be expressed with only 4 free parameters. (9 for the longer term model.)
It is interesting to note that in this work, even the carbon dioxide feedback does not suffice alone to quickly end the major glaciations. There is a calving effect included once there is sufficent bedrock depression. With this, the modeled ice masses quickly and appropriately decay.
Comment by David B. Benson — 24 Feb 2007 @ 6:04 PM
Satzman did interesting work but ultimately it was a blind alley because the equations that he and his colleagues were solving could not have been rigorously derived. Their counter-argument would be the same point that I keep trying to make here: the GCMs are even worse, actually much worse because in addition to arbitrariness of parameterizations and complexity they use a lot more “free” parameters.
[Response: Not so. The difference between GCMs and more heuristic models is precisely because they include more real physics that can be indpendently measured. The number of 'free' parameters is actually not that great, and since only a handful are used to tune the models 'holisitically' the arbitrariness is limited. As time goes on, assumptions that were initially made are tightened up based on real observations, and as that has happened simulations have got better - and that is not because they are better 'tuned'. It is in some sense optimistic, but the principle that drives GCM development - that improvements in basic physics lead to improvements in climatology - seems in fact to be empirically true. - gavin]
Re #128: Sashka — Most important, I committed a typo. His name was Barry Saltzman. The book is cited in an earlier post of this thread.
I, at least, find this work useful in obtaining a fairly rigorous derivation of equations which approximately describe ice age climate. There are simplifying assumptions, of course. But of greatest interest are two assumptions. (1) Carbon dioxide feedback is important. (By now I suppose most are convinced of the reality of this.) (2) Earth’s climate has had a natural period of about 100 ky for about 900 ky and a shorter period before that. Saltzman and coworkers offer an explanation of this shift in natural period.
Being a relative new-comer to amateur paleoclimatology, I am impressed with how well they did without the consumption of vast quantities of computer resources. The paper by A. Abe-Ouchi et al. linked in a comment earlier on this thread seems to largely confirm that Saltzman and his colleagues are correct.
Of course, there may still be debate regarding the existence of a long natural period for ice age climate, since it seems to be much longer than the periods for any of the feedbacks and forcings (other than the trivial variations due to eccentricity). This is an interesting question still, at least for me.
Comment by David B. Benson — 26 Feb 2007 @ 1:21 PM
A good deal of research focuses on the roughly 100 ky “cycle” not actually being a period, but being a “characteristic timescale.” Essentially, the system exhibits stochastic behavior, but because of the nature of the beast, this leads to major deglaciations on a roughly 100 ky timescale. Carl Wunsch and colleagues are probably the strongest proponents of such a viewpoint.
The “shorter period” which precedes the mid-Pleistocene transition is 41 ky, and is most assuredly due to the cycle of changes in earth’s obliquity (axial tilt); there’s no doubt.
As for eccentricity forcing, its importance is an idea which is indeed out of favor, but by no means dead.
Gavin, it’s not only the number of free parameters. The functional form of the closure hypotheses is not justifiable, for example, neither for momentum nor property turbulent fluxes on subgrid scale. To be clear, I don’t blame anybody it’s just the problem is too darn hard. But I disagree with your optimistic assessment. You are giving the impression that GCMs develop towards some ultimate truth. In reality the GCMs do improve incrementally but they are doomed to be off-mark. BTW, while I’m stating my own position, this is more or less what I heard Saltzman’s people in person. While they were more active you must have had a chance to rebuff their claims face-to-face.
David, you’re mistaken. Gavin is absolutely correct in referring to this kind of models as heuristic, as opposed to rigorous.
Re #130: tamino — Thank you for hinting that I ought to look into Carl Wunsch’s work. I don’t mind stochastic models, but I do prefer deterministic ones when I can get them.
Re #131: Sashka — It depends on what one means by rigorous. In other fields what are developed, rigorously from simplifying assumptions, are useable constitutive laws since the microscale and mesoscale physics and chemistry are too messy for actual applications. I view what Saltzman and colleagues have done in the cited book as a form of constitutive law for ice age climate.
Anyway, it sounds better than heuristic. :-)
Comment by David B. Benson — 26 Feb 2007 @ 4:40 PM
I went to Carl Wunsch’s publications page and found
Eli Tziperman et al. Consequences of pacing the Pleistocene 100 ky ice ages by nonlinear phase locking to Milankovitch forcing
PALEOCEANOGRAPHY vol. 21, PA4206, 2006.
Therein the four authors careful define what they mean by nonlinear phase locking and then point out that model identification is impossible by comparing model runs to the proxy data. All even partially realistic models will phase lock, they state. So it is not possible to even to distinguish those nonlinear models which have a natural period from those which would be static without Milankovitch forcing.
Comment by David B. Benson — 26 Feb 2007 @ 5:51 PM
Re 92 and 105: First I just want to reitterate more generally what 105 said – Milankovitch cycles have had climate signals, in ice ages or otherwise, – well probably ever since the Moon formed, although the signal from times past will not always reach us, but I’ve read of evidence of Milankovitch precession cycle forcing of monsoons in lakes in Pangea (PS over geologic time the periods of some of the Milankovitch cycles have changed as the Moon recedes from the Earth due to tides). There have not and will not always be ice ages because the Earth can be just too warm or ill-conditioned to respond in that manner (The Earth might also become too cold to have interglacials within an ice house period – though I’m not sure if that has ever happenned outside the Proterozoic snowball/slushball episodes).
Why sometimes ice house and sometimes not – As far as I’m aware:
Faster sea floor spreading, presumably associated with more volcanic activity at subduction zones, and/or other increases in volcanic activity or geologic outgassing, or faster oxidation of exposed fossil organic C (as in shales) – greater geologic CO2 emissions (I think another way of looking at the inorganic part is that any given region of sea floor has less time to accumulate carbonate minerals from chemical weathering, so that C reservoir could shrink while others, including the atmosphere, can grow).
The silicate + CO2 -> different silicate + carbonate chemical weathering rate tends to increase with temperature globally, and so is a negative feedback (but is too slow to damp out short term changes) – but chemical weathering is also affected by vegetation, land area, and terrain (and minerology, though I’m not sure how much that varies among entire mountain ranges or climate zones) – ie mountanous regions which are in the vicinity of a warm rainy climate are ideal for enhancing chemical weathering (see Appalachians in the Paleozoic, more recently the Himalayas). There is also an idea that mountain glaciers, and repeated continental glaciation and deglaciation, may actually enhance chemical weathering by their mechanical weathering, even though the cold climate generally inhibits it.
Organic C burial – affected by topography and climate (wind driven upwelling and dust fertilization by wind may favor burial in the ocean, while a wet climate on flat land may favor burial on land (as in peat bogs)).
In the above and in other ways, the arrangements of the continents and oceans.
Re 130: Isn’t there an idea of a threshold, that the eccentricity cycle’s modulation of the precession cycle is such that some but not all obliquity cycle peaks occur in tandem with a precession cycle forcing strong enough to end an ice age.
Also, one idea I’ve read of is that through ice age after ice age, the bedrock would be scraped bare of looser material, which might have lubricated the ice sheets. As that lubrication might be lost after several ice ages, the ice would not spread as fast, it would build up into thicker sheets, and the higher elevation of the ice surface would cause it to be colder than otherwise and so less likely to start melting.
I also read once of an idea that ecological succession could play a role, that in some forested areas with enough moisture, bogs would start to take over. There may be influences on the C cycle, but the part I remember well is that this would make winter snow more reflective as it would be on a flatter surface, as opposed to snows upon trees.
I’m curious about the mechanisms responsible for the CO2 feedback in glaciation and deglaciation. What I’m aware of is that:
CO2 is less soluble in saltier water, but more soluble in colder water, and the second effect would win out for globally averaged changes. But for the reduction of atmospheric CO2, the surface ocean CO2 must also have fallen even given the greater solubility.
Likely less biomass in the ice ages, too. It may be reasonable to expect less C in soils, so the C increase must have been in the deeper ocean.
I’m vaguely aware that faster deep water formation could be a factor. I also know that wind driven upwelling and fertilization of phytoplankton by dust could also be factors.
What I’m wondering about is –
What happens to the C stored in soil underneath a young ice sheet? I’m thinking it wouldn’t decay right away. It would be buried, and then eventually carried to the margins of the ice sheet. There, it may still be quite cold, so I’m imagining that much of it may have stayed in moraines (providing a convenient source of CO2 during deglaciation) or been washed into the ocean (perhaps decaying later during warming?) This C was out of the atmosphere before glaciation, so it doesn’t directly help accelerate the glaciation, but could it have accelerated deglaciation? Of course, once in an interglacial, the boreal soil C must be stored up again…
What might the significance of methane hydrates be?
Any thoughts? (PS I was recently paging through “Earth’s Climate Past and Future” by Ruddiman)
Also, I was wondering – how certain is the prediction that the next ice age, absent anthropogenic effects, will start in 50,000 years?
Re 122 – if the magnetic field is weak than it’s direction could change faster with the same vector change in the field.
Pat — You have some good insight into this. I recommend highly that you look at the 1981 paper by Walker et al. that first came up with the idea of the carbonate-silicate feedback. Here’s a link to it:
Re #134: Pat — From orbital forcing theory, some state that future climate ought to have a stab at an ice age (stadial) in 20 ky and again in another 30 ky. Some opine that the first is too weak a forcing, hence 50 ky.
All of the above ignoring anthropogenic effects, of course.
Comment by David B. Benson — 28 Feb 2007 @ 1:43 PM
Re 122 – also, if a magnetic pole where nearby, small movements could cause large directional changes in the horizontal component of the magnetic field, although the horizontal component should be quite small in that case.
I am an elementary school science teacher. Having read this article and other articles on ice ages and climate changes in the past, it is apparent to me that climatologists are still wrestling with the causes of such changes. If we do not fully understand the mechanisms of past climate changes, how can we be sure that the current rise in global temperature is primarily anthropogenic rather than primarily natural? Is is possible that both factors are working together?