It seems that the author of the recent paper in Nature (Shakun et al ) says that the Earth’s wobble was a contributor for ending the ice age, but won’t go so far as to call it the trigger. But I’m not even sure he can claim much of anything, because Willis has found some serious issues with the Shakun et al paper which you can read about here. It seems to me, based on the proxies and methods used, Shakun is just making a SWAG. Of course we’ll know more about the certainty as the paper is dissected in greater detail – Anthony
From National Public Radio- Shake It Off: Earth’s Wobble May Have Ended Ice Age
(h/t to WUWT reader Paul Bell)
by Christopher Joyce NPR
When viewed from outside and looking down onto the Earth from the north, the direction of precession is clockwise. When standing on Earth looking outward, the axis appears to move counter-clockwise across the sky. Image from mydarksky.org (original image with the NPR story could not be used due to licensing issues - Anthony)
But exactly what caused the big thaw isn’t clear, and new research suggests that a wobble in the Earth kicked off a complicated process that changed the whole planet.
Ice tells the history of the Earth’s climate: Air bubbles in ice reveal what the atmosphere was like and what the temperature was. And scientists can read this ice, even if it’s been buried for thousands of years.
But when it comes to the last ice age, ice has a mixed message.
The conventional wisdom is that carbon dioxide increased in the atmosphere starting about 19,000 years ago. Then the ice melted. The logical conclusion? The greenhouse effect.
But the Antarctic was getting warmer even before CO2 levels went up. So which came first in the Antarctic, warming or CO2?
“The problem is, [the Antarctic is] just one spot on the map, and it’s a dicey way to slice up global climate change by looking at one point,” says Jeremy Shakun, a climate scientist at Harvard University. So he went way beyond the Antarctic — he collected samples of ice, rock and other geologic records from 80 places around the world and found that CO2 levels did, in fact, precede global warming.
Here’s his scenario for what killed the ice age, which was published in the journal Nature this week.
About 20,000 years ago, the Earth — the whole planet — wobbled on its axis. That happens periodically. But this time, a lot more summer sunlight hit the northern hemisphere. Gigantic ice sheets in the Arctic and Greenland melted.
“That water is going to go into the North Atlantic, and that happens to be the critical spot for this global conveyer belt of ocean circulation,” Shakun says.
The conveyer belt is how scientists describe the huge, underwater loop-the-loop that water does in the Atlantic: Cold Arctic water sinks and moves south while warm water in the southern Atlantic moves north.
The trouble is that the sudden burst of fresh meltwater didn’t sink, so the conveyer belt stopped.
“It’s like, you know, sticking a fork in the conveyer belt at the grocery store,” Shakun says. “The thing just jams up; it can’t keep sinking, and the whole thing jams up.”
So warm water in the south Atlantic stayed put. That made the Antarctic warmer. Eventually, ocean currents and wind patterns changed, and carbon dioxide rose up out of the southern oceans and into the atmosphere.
Eric Wolff, a climate scientist at the British Antarctic Survey, isn’t convinced a wobble was the trigger — the planet had wobbled before and not melted the ice. But he says whatever did start the process during the ice age, the subsequent increase in CO2 created a runaway greenhouse effect worldwide.
“The CO2 increase turned what initially was a Southern Hemisphere warming into a global warming. That’s a very nice sequence of events to explain what happened between about 19,000 and 11,000 years ago,” Wolff says.
But that’s a process that has taken about 8,000 years. And Shakun’s research found that the amount of CO2 it took to end the ice age is about the same amount as humans have added to the atmosphere in the past century.
Rapidly increasing CO2 from 200 to 250 ppm is not much of a ‘forcing’,
on a log scale it’s only a third of a doubling, worth but a quarter-degree C,
a mere ‘contribution’ indeed.
Obviously the heat that melted all that ice was solar, not miniscule sky-warming.
It would certainly be nice to know that adding CO2 would keep the next glacial from occuring, for humanity’s sake, but let’s see what the skeptics say about this paper.
Yes, it must be CAGW and CO2 or the plan falls apart.
I believe the “trigger” that flips the system into the other state is Arctic summer ice. If you get enough summers of too little Arctic ice melt, maybe even Hudson Bay ice melt, the system flips into the stable cold state. It probably takes a volcanic eruption at just the right time of year at just the right place. In conjunction with a solar magnetic minimum, maybe even likely. It isn’t so much, in my opinion, the insolation being the trigger as it is there not being enough insolation to completely recover from the triggering event. Once enough ice builds, the insolation is not enough to get completely back to conditions before the event.
I believe we have been seeing that condition over the past 2000 years. Each cold period a little cooler than the one before and each subsequent warming period fails to recover to the level of the previous one. I would expect to find, if the data were available, that the Arctic sea ice for the past 2000 years has overall been trending upwards with some major variation along the way.
I’m still not sure how CO2 levels could be different to a meaningful degree in spots around the globe at the same time (unless you’re standing right next to a volcano that goes off). So either the Antarctica samples are dated wrong or those for the study are.
“Eric Wolff, a climate scientist at the British Antarctic Survey, isn’t convinced a wobble was the trigger — the planet had wobbled before and not melted the ice. But he says whatever did start the process during the ice age, the subsequent increase in CO2 created a runaway greenhouse effect worldwide.”
WTF! Where? In computers? I guess he must have fogotten the oceans rusted a while back, all due to O2.
If this had started a “runaway greenhouse effect” then why is the world not much hotter than it is? Clearly something has prevented this from happening – a mechanism for stabilising the climate.
“The trouble is that the sudden burst of fresh meltwater didn’t sink, so the conveyer belt stopped…. But that’s a process that has taken about 8,000 years….”
What a mess “sudden” means “8,000” years?
“But this time, a lot more summer sunlight hit the northern hemisphere. Gigantic ice sheets in the Arctic and Greenland melted…..So warm water in the south Atlantic stayed put. That made the Antarctic warmer. Eventually, ocean currents and wind patterns changed, and carbon dioxide rose up out of the southern oceans and into the atmosphere.”
So the Northern Hemisphere warmed first (increased insolation) but that didn’t warm the earth (somehow) that had to wait for the antartic to warm.
“So warm water in the south Atlantic stayed put. That made the Antarctic warmer. ”
Wait a minute, if the south atlantic was already warm, how dit it warm up and release more CO2.
“That’s a very nice sequence of events to explain what happened …”
This whole thing is a self-confessedly rube goldbergian mess!!!
“And Shakun’s research found that the amount of CO2 it took to end the ice age is about the same amount as humans have added to the atmosphere in the past century.”
If Shakun is right, is this not good news? Forestalling the next ice age would be man’s greatest achievement, n’est-ce pas?
oh ok….
that explains the runaway glaciation when Co2 levels are sky high
Unless I am missing something, Shakun’s theory that the “ice age” ended because of CO2 necessarily requires that the glaicers melt before the CO2 is released. If so, doesn’t the theory refute the stated conclusion? If the glaicers have melted (and, not incidently, antartica has warmed) hasn’t the “ice age” already ended? Isn’t a relative absence of ice what defines the end of an “ice age”?
Of course, it stands to reason that temps might continue to rise after the ice is gone. It also makes some that portion of the increase in CO2 (caused either directly by the warming which melted the ice or by an interruption in Ocean circulation patters) would occur before the temps reach their inter-glaicial maximum. It even makes sense that, in some portions of the world, temps might lag as the process of melting the ice and warming the Oceans would both require enormous amounts of energy. Isn’t the more natural inference that the Milankovitch cycle caused the temp increase directly and all of the other observed effects followed from that single cause?
Crosspatch,
Nice post, and one with which I completely agree. It isn’t so hard to see that we’ve been heading downward in fits and starts for 6,000 years now since the Holocene Optimum. I too agree that since we are currently only a few W/m2 above that required for a prolonged ice age (and will be at that minimum insolation for another 8,000 more years, it would only take a relatively minor event to flip us into the cold climate state.
crosspatch says:
April 6, 2012 at 10:35 am
But why the regularity of interglacials during what has been a million plus years of ice age? The regularity certainly hints at a cyclical process (Milankovitch cycles etc) with perhaps volcanic events being common enough to help the process if occurring at a time when the events would reinforce the cyclical process. And there is much we do not know about long term variability in the solar process.
But the Antarctic was getting warmer even before CO2 levels went up. So which came first in the Antarctic, warming or CO2?
What came first at the start of the ice age?
I quite like Fred Hoyle’s theory – ice ages end when a large comet or asteroid strike in an ocean somewhere vaporises a few billion tons of seawater. The extra water vapour triggers global warming.
“The problem is, [the Antarctic is] just one spot on the map, and it’s a dicey way to slice up global climate change by looking at one point,””
Correct me if I’m wrong, but the CO2 proxy is from “just one spot on the map”.
Robert Austin says:
April 6, 2012 at 10:58 am
Ho boy, you are SO right, Robert! I figure were I live here in Idaho, a return to an Ice Age will result in temperatures where the average lows every month but one will be below freezing! And the exception? July–where it will be just one degree above freezing (and that’s the AVERAGE–the actual temps will probably get below freezing every week). Looking back on my pack of seeds for garden planting, I don’t recall a single one that gave me a 1- or 2-week growing season. Not a single one!
The next Ice Age, as Anthony pointed out, will be diastrous, an extreme counter point to the current reprieve:
The last big ice age ended about 11,000 years ago, and not a moment too soon — it made a lot more of the world livable, at least for humans.
So, by this scenario, the first event is that the Northern polar areas heated and melted the Arctic ice caps, then this stopped the ocean conveyors (a ludicrous inference IMO), and this caused the Southern oceans to heat, and so released CO2. So the release of CO2 is the last thing to happen. And this is reported as that it *precedes* the warming? This is beyond pretzel logic.
It would be really nice to see some hard figures here instead of hand-waving.
How many kilojoules of energy would be required to melt kilometer thick ice down to the latitude of New York? Where did all that come from – given all we are told about TSI being constant.
Where did all the CO2 come from after a ‘little Milankovitch wobble? Going from not enough to warm the planet to current day levels -when poleward of 50 deg N/S latitude is ice covered (so no plants) the oceans are freezing (literally) and without any SUVs or coal fired power stations – takes some kind of leap of faith.
As almost all the proxies that are used in the paper seem to disagree in every metric where is the certainty of the timing, temperature and quantity of CO2? Another leap of faith?
If that relatively minor amount of CO2 was enough to melt all that ice why did it stop? Why didn’t the Earth warm “until the oceans boiled away” (Jim ‘the hat’ Hansen).?
So every ~3.5 precession cycles, the ice melts, life thrives for almost half a cycle, then it refreezes. I’ve always found this cycle interesting. Upon hearing the Arthurian legend several times and variations, it occurred to me there is an allusion to the precession cycle in the story. if one considers the king to be the guiding ‘star’ for a country where the land and king are ‘one’. With Uther Pendragan as Arthur’s father, the star went from the constellation Draconis to Ursa Minor. There is disputed etymology that the name Arthur has roots in a term for ‘bear-king’. If so, this myth holds information from a few thousand years earlier, when the pole star was in Draconis.
Don’t worry: Soon this paper will be withdrawn. What Shakun is implying can’t be true.
He also needs to explain how ice ages start with this theory if CO2 has such a big impact on climate.
Robert Austin says:
No…It is not good news that we have put such a large amount of CO2 into the atmosphere that we are not only indefinitely postponing the next ice age which we would otherwise gradually go into on a timescale of thousands to tens of thousand of years but are also likely to cause a dramatic and significant warming from the current state perhaps of about the same magnitude as the warming from the glacial period to now and over a timescale of decades to a few centuries!
Derek says:
Who says it started a runaway greenhouse effect? It didn’t…and neither is it expected to in the current anthropogenic case. (The only climate scientist I know of who is talking about the possibility of a runaway greenhouse effect is Jim Hansen and that is for the situation where we really go to town burning almost all conventional fossil fuels and maybe a lot of unconventional sources like tar sands to boot. In that case, the rise in CO2 levels will be much more larger than occurred between the last glacial period and now…as well as much, much more rapid.)
This discussion is missing the obvious point — remember that water vapor is a much stronger greenhouse gas, and water frozen deep inside glaciers stays there, never turning into water vapor. So, a little warming produces some glacier melt, which produces more water vapor, which produces more melt, and so on. The CO2 contribution to all this is a sideshow. (And obviously this process works in reverse during the onset of an ice age.)
———–
Correct me if I’m wrong, but the CO2 proxy is from “just one spot on the map”.
———–
Willis Eschenbach has just now clarified this in a separate post … CO2 is well-mixed across latitudes.
So *THAT’S* OK.
Much appreciation to Willis/WUWT for confirming the main features of the Shakun et al analysis.
The finding of Lindzen and Choi that the planet’s feedback response to a change in forcing is negative (clouds in the tropics increase or decrease to reflect more or less energy off into space which) removes the forcing amplification which is required to try to explain why the weakest of the orbital parameters eccentricity can cause the 100 kyr glacial/interglacial cycle.
http://www.leif.org/EOS/2009GL039628-pip.pdf
“On the determination of climate feedbacks from ERBE data
Richard S. Lindzen and Yong-Sang Choi
Program in Atmospheres, Oceans, and Climate
Massachusetts Institute of Technology
Climate feedbacks are estimated from fluctuations in the outgoing radiation budget from
the latest version of Earth Radiation Budget Experiment (ERBE) nonscanner data. It
appears, for the entire tropics, the observed outgoing radiation fluxes increase with the
increase in sea surface temperatures (SSTs). The observed behavior of radiation fluxes
implies negative feedback processes associated with relatively low climate sensitivity.
This is the opposite of the behavior of 11 atmospheric models forced by the same SSTs.
Therefore, the models display much higher climate sensitivity than is inferred from
ERBE…”
The discussion is pointless and goes in circles as there are multi incorrect mechanisms posited to explain what is observed. Naturally when the mechanisms are incorrect, the proxies are misinterpreted or in this case due to the extreme AGW paradigm manipulated to try to save the incorrect mechanism.
Insolation changes, due to orbital changes, are not the cause of the glacial/interglacial cycle. Temperature changes cannot and do not cause of the observed glacial/interglacial atmospheric changes in CO2. The long term reduction in atmospheric CO2 is not due to the Himalayas forming.
The theoretical assumed mechanism what controls and varies atmospheric CO2 is incorrect. The posited cause of the glacial/interglacial cycles (changes in summer insolation at 60 degree latitude north is incorrect.)
Look at figure 3 which is Greenland Icesheet temperature over the last 12,000 years Vs atmospheric CO2.
The planet warms and cools during the Dansgaard-Oeschger cycles. The Dansgaard-Oechger climate change is not an event. It is a cycle. It is a cycle.
Question 1: What the heck causes the Dansgaard-Oeschger cyles? That is rhetorical question. As I know what causes it. Hint there are cosmogenic isotope changes each and every time during the Dansgaard-Oeschger cycle. The late Gerald Bond was able to track 23 cycles. The same suspect is always at the scene of the crime. It is the bloody sun.
The assumed model for the sun is fundamentally incorrect. The sun cyclically causes a very sever climate change. The paleoclimatic data unambiguously shows there are cyclic abrupt climate changes such as the Younger Dryas. The paleoclimatic specialist refer to the Younger Dryas as Heinrich event 0. The Heinrich event is not a stupid event it is cycle. It is a cycle. An event is something that occurs randomly due to for instance comet impacts. A climate cycle requires a cyclic forcing function. A cycle is something that will happen again. All of the past interglacials ended abruptly.
The cyclic Heinrich abrupt climate change cycles are not caused by CO2 changes. The Dansgaard-Oeschger cycle is not caused by CO2 changes.
Question 2: Why the heck does CO2 not change during the Dansgaard-Oeschger cycle? Planetary temperature increases and decrease. That also is rhetorical question.
The planet cooled during the Holocene interglacial period. Why does CO2 gradually rise? Temperature is decreasing.
http://climate4you.com/images/GISP2%20TemperatureSince10700%20BP%20with%20CO2%20from%20EPICA%20DomeC.gif
http://climate4you.com/
http://arxiv.org/abs/physics/0612145v1
The Antarctic climate anomaly and galactic cosmic rays
Borehole temperatures in the ice sheets spanning the past 6000 years show Antarctica repeatedly warming when Greenland cooled, and vice versa (Fig. 1) [13, 14]. North-south oscillations of greater amplitude associated with Dansgaard-Oeschger events are evident in oxygenisotope data from the Wurm-Wisconsin glaciation[15]. The phenomenon has been called the polar see-saw[15, 16], but that implies a north-south symmetry that is absent. Greenland is better coupled to global temperatures than Antarctica is, and the fulcrum of the temperature swings is near the Antarctic Circle. A more apt term for the effect is the Antarctic climate anomaly.
http://www.agu.org/pubs/crossref/2002/2000PA000571.shtml
On the 1470-year pacing of Dansgaard-Oeschger warm events
The oxygen isotope record from the Greenland Ice Sheet Project 2 (GISP2) ice core was reanalyzed in the frequency and time domains. The prominent 1470-year spectral peak, which has been associated with the occurrence of Dansgaard-Oeschger interstadial events, is solely caused by Dansgaard-Oeschger events 5, 6, and 7. This result emphasizes the nonstationary character of the oxygen isotope time series. Nevertheless, a fundamental pacing period of ∼1470 years seems to control the timing of the onset of the Dansgaard-Oeschger events. A trapezoidal time series model is introduced which provides a template for the pacing of the Dansgaard-Oeschger events. Statistical analysis indicates only a ≤3% probability that the number of matches between observed and template-derived onsets of Dansgaard-Oeschger events between 13 and 46 kyr B.P. resulted by chance. During this interval the spacing of the Dansgaard-Oeschger onsets varied by ±20% around the fundamental 1470-year period and multiples thereof. The pacing seems unaffected by variations in the strength of North Atlantic Deep Water formation, suggesting that the thermohaline circulation was not the primary controlling factor of the pacing period.
Atmospheric CO2 does not change significantly when temperature changes. There is an estimated maximum change of 30 ppm in CO2 for the total temperature change from glacial/interglacial and visa versa. Due the change in ocean salinity atmospheric CO2 increases when there is there is more ice in the ice sheets. As the vast regions of the biosphere is covered by ice and there is massive reduction in rainforest (roughly 30% of the Amazon is converted from rainforest to savanna) there is massive reduction in vegetation which increases the amount of the CO2. The total net change in atmospheric CO2 due to ice sheets forming causing a saltier ocean and the reduction in vegetation is no net change in atmospheric CO2 and likely an increase in atmospheric CO2. (Volcanic input continues yet there is a reduction in vegetation to remove the CO2.)
There is no explanation as to what causes the reduction of 80 ppm to 100 ppm of atmospheric CO2 during the glacial/interglacial cycle. That is the so called Holy Grail of the carbon cycle specialists.
http://www.up.ethz.ch/education/biogeochem_cycles/reading_list/sigman_nat_00.pdf
A reasonable estimate for ice age ocean cooling of 2.5C in the polar surface and 5C in the low-latitude surface leads to a CO2 decrease of 30 p.p.m.v., with the low-latitude and polar temperature changes playing roughly equivalent roles in this decrease. It has recently been noted that ocean general circulation models predict a greater sensitivity of CO2 to low-latitude surface conditions than do simple ocean box models like CYCLOPS17. However, the significance of this observation is a matter of intense debate.
An opposing effect on atmospheric CO2 to that of glacial/interglacial temperature change is provided by the increased salinity of the glacial ocean, due to the storage of fresh water on land in extensive Northern Hemisphere ice sheets. Based on the approximately 120m depression of sea level during the last ice age18, the whole ocean was about 3% saltier than it is today. All else being constant, this increase would have reduced the solubility of CO2 in sea water and raised atmospheric CO2 by 6.5 p.p.m.v. Taking the estimated temperature and salinity effects together, we would expect the atmospheric CO2 concentration of the ice age world to have been 23.5 p.p.m.v. lower. Folding in the effect of a 500 Pg C transfer from the continents to the ocean/atmosphere system, we are left with an 8.5 p.p.m.v. decrease in CO2 (Table 1). There are uncertainties in each of these effects, but it seems that most of the 80±100 p.p.m.v. CO2 change across the last glacial/interglacial transition must be explained by other processes. We must move on to the more complex aspects of the ocean carbon cycle.
Timing of abrupt climate change: A precise clock by Stefan Rahmstorf
Many paleoclimatic data reveal a approx. 1,500 year cyclicity of unknown origin. A crucial question is how stable and regular this cycle is. An analysis of the GISP2 ice core record from Greenland reveals that abrupt climate events appear to be paced by a 1,470-year cycle with a period that is probably stable to within a few percent; with 95% confidence the period is maintained to better than 12% over at least 23 cycles. This highly precise clock points to an origin outside the Earth system; oscillatory modes within the Earth system can be expected to be far more irregular in period.
You have to love the way “Climate Scientists” muddies the waters. When the MWP and LIA don’t fit the “CO2 dominates” meme, the Hockey Team is on hand to rewrite history.
When the Arctic and Antarctic ice cores show CO2 lagging temperature Shakun shows up to claim the opposite. These people are shameless.
This paper does not present a credible argument to show that CO2 preceded the warming at the end of the last ice age. The arcane explanation of heating in the N H that melted the ice and caused warming means that hemispheric and then global warming preceded the CO2 release. This is not complicated, is it? It gets warm and the CO2 appears. Well, we knew that already from the Antarctic ice cores. Greenland too if anyone bothers to remember, right?
I doubt the paper will be withdrawn. Keep your expectations low. The title and claim are too valuable to the team. We will hereafter have KR quoting it as ‘proof’ that the ice cores are unreliable indicators of historical events, but models are OK.
The re-run about a fresh water deluge stopping the AMO is amusing. The stupid, it hurts, it hurts! We have been told repeatedly that such an event is waiting just around the corner as Greenland melts and when it does, it will cause an ice age!! Guys, you gotta get your fairy tales aligned.
Wouldn’t the ice core record show correspondingly higher temps in the polar regions than the equatorial regions, like some suggest is occuring now in the arctic, due to the present CO2 warming???
The ocean currents are not a conveyor and complete stoppage of North Atlantic drift current is not capable of causing the Northern Hemisphere cyclic abrupt climate changes which are referred to a Heinrich “events”. (Should be called Heinrich cycles rather than events as there is a cyclic forcing function that is capable of causing a Younger Dryas climate cooling period.
Seager explains why complete stoppage of the North Atlantic drift current is not capable of plunging Europe back into an ice age in this article in American Scientist and in this peer reviewed journal.
The point of my comment is changes in ocean current are not capable of causing Dansgaard/Oscherger climate cycles (Bond Events) and they are most certainly also not capable of causing Heinrich climate cycles. (The Younger Dryas abrupt climate change period at 12,900 years BP (before present) is the last Heinrich event.)
http://www.sciencedaily.com/releases/2009/05/090513130942.htm
Cold Water Ocean Circulation Doesn’t Work As Expected
The familiar model of Atlantic ocean currents that shows a discrete “conveyor belt” of deep, cold water flowing southward from the Labrador Sea is probably all wet.
A 50-year-old model of ocean currents had shown this southbound subsurface flow of cold water forming a continuous loop with the familiar northbound flow of warm water on the surface, called the Gulf Stream.
“Everybody always thought this deep flow operated like a conveyor belt, but what we are saying is that concept doesn’t hold anymore,” said Duke oceanographer Susan Lozier. “So it’s going to be more difficult to measure these climate change signals in the deep ocean.”
http://www.americanscientist.org/issues/id.999,y.0,no.,content.true,page.1,css.print/issue.aspx
The Source of Europe’s Mild Climate
The notion that the Gulf Stream is responsible for keeping Europe anomalously warm turns out to be a myth
“If you grow up in England, as I did, a few items of unquestioned wisdom are passed down to you from the preceding generation. Along with stories of a plucky island race with a glorious past and the benefits of drinking unbelievable quantities of milky tea, you will be told that England is blessed with its pleasant climate courtesy of the Gulf Stream, that huge current of warm water that flows northeast across the Atlantic from its source in the Gulf of Mexico. That the Gulf Stream is responsible for Europe’s mild winters is widely known and accepted, but, as I will show, it is nothing more than the earth-science equivalent of an urban legend.
Recently, however, evidence has emerged that the Younger Dryas began long before the breach that allowed freshwater to flood the North Atlantic. What is more, the temperature changes induced by a shutdown in the conveyor are too small to explain what went on during the Younger Dryas. Some climatologists appeal to a large expansion in sea ice to explain the severe winter cooling. I agree that something of this sort probably happened, but it’s not at all clear to me how stopping the Atlantic conveyor could cause a sufficient redistribution of heat to bring on this vast a change.”
http://www.atmos.washington.edu/~david/Gulf.pdf
“Is the Gulf Stream responsible for Europe’s mild winters?
By R. SEAGER, D. S. BATTISTI, J. YIN, N. GORDON, N. NAIK, A. C. CLEMENT and M. A. CANE
It is widely believed by scientists and lay people alike that the transport of warm water north in the Gulf Stream and North Atlantic Drift, and its release to the atmosphere, is a major reason why western Europe’s winters are so much milder (as much as 15–20 degC) than those of eastern North America (Fig. 1). The idea appears to have been popularized by M. F. Maury in his book The physical geography of the sea and its meteorology (1855) which went through many printings in the United States and the British Isles and was translated into three languages. …
In summary, the east–west asymmetry of winter climates on the seaboards of the North Atlantic is created by north-westerly advection over eastern North America and by zonal advection into Europe. The Pacific Ocean has an analogous arrangement with meridional advection being an especially strong cooling over Asia. Since western Europe is indeed warmed by westerly advection off the Atlantic, we next assess how the surface fluxes over the Atlantic are maintained….
In conclusion,while OHT warms winters on both sides of the North Atlantic Ocean by a few degC, the much larger temperature difference across the ocean, and that between the maritime areas of north-western Europe and western North America, are explained by the interaction between the atmospheric circulation and seasonal storage and release of heat by the ocean. Stationary waves greatly strengthen the temperature contrast across the North Atlantic and are themselves heavily influenced by the net effect of orography. In contrast, transport of heat by the ocean has a minor influence on the wintertime zonal asymmetries of temperature. Even in the zonal mean, OHT has a small effect compared to those of seasonal heat storage and release by the ocean and atmospheric heat transport. In retrospect these conclusions may seem obvious, but we …
The LAST ICE AGE, the Karoo Ice Age, ended 260 million years ago. The CURRENT Ice age, referred to as the Quaternary Glaciation, began 2.58 million years ago and is still ongoing (in fact, if it’s anything like the previous ice ages, this one is just getting started and has at least a hundred million years to go, maybe 300 million years). This article is actually talking about the most recent “glacial period”, which did in fact end about 11,000 years ago. But the current ice age did not end then, and will not be considered to have ended until the polar ice caps and the last of the mountain glaciers have all melted. (The global warming alarmists, of course, make that sound like the end of the world, but in fact, it will be a return to the “natural” state of the planet. Over its entire 4.5-billion-year history, less than 700 million years (about 15%) was part of an ice age.)
Though we are still in an ice age, we are in a “glacial minimum” or “interglacial”, during which the ice sheets characteristic of an ice age shrink back to cover only the areas near the poles and the highest mountains. The current interglacial period would be expected to end (without anthropogenic contributions to atmospheric CO2) in about 15,000 years, but if we keep increasing CO2 (up to at least 750 ppm), we could put it off another 35,000 years. So our great(x600)-grandchildren through our great(x2000) grandchildren will avoid the TRULY catastrophic return to hard-core ice-age conditions if we can just continue pumping CO2 into the atmosphere. Personally, I hope the experts are wrong and we can throw the planet out of the ice age entirely with CO2 emissions (possibly supplemented with some methane). Unfortunately, however, even if it’s possible, it will take several millenia to be realized. So you and I will never live to see the wonder and glory of an ice-free planet. Just our bad luck to be born in the unusual time of an ice age. But if we can convince the world to not be so near-sighted, and instead think of generations thousands of years in the future, we can make this world a better, more natural place than it will otherwise be.
well let me understand..
1) the Earth — the whole planet — wobbled on its axis. That happens periodically. But this time, a lot more summer sunlight hit the northern hemisphere. Gigantic ice sheets in the Arctic and Greenland melted.
why did it melted suddenly so much? each summer ice melts without stopping the Golfstream? There was the theory that the Younger Dryas has seen a sudden freeze through an outburst of melted water due to a sudden break of a meltwater lake. but only melting ice…
And did it not cause return to the ice age that time?
– this point is already very weak
2) so water in the Atlantic stayed put. and that warmed the Antarctic
How did warm water staying put in the Nord Atlantic warm the Antarctic? It did not change the currents around the Antarctic? So what warmed the Antarctic?
3) Eventually, ocean currents and wind patterns changed, and carbon dioxide rose out of the southern oceans and into the atmosphere.
? Why? I mean ok, the currents changed but why did the ocean released CO2? Then tend to do it so when they are upset?
4) “Eric Wolff, a climate scientist at the British Antarctic Survey, isn’t convinced a wobble was the trigger — the planet had wobbled before and not melted the ice. But he says whatever did start the process during the ice age, the subsequent increase in CO2 created a runaway greenhouse effect worldwide.”
Ah, ok I see it. So something triggered the output of CO2 from the ocean, be it warmer waters or “something else” not defined and then CO2 started warming the planet.
5) “The CO2 increase turned what initially was a Southern Hemisphere warming into a global warming. That’s a very nice sequence of events to explain what happened between about 19,000 and 11,000 years ago,” Wolff says.
Whatever warmed the Southern Hemisphere did not warm the Northern Hemisphere, but the CO2 dunit. And whatever warmed the Antarctis warmed only there locally.
I got it now, the Antarctic warming was only local like the MWP in Greenland.
D. Cohen says:
“… remember that water vapor is a much stronger greenhouse gas, …”
Not true. Gram-for-gram, carbon dioxide is 30 times as powerful a greenhouse gas as water vapor. The only reason water vapor is so much more important than CO2 is because there’s hundreds of times more of it in the atmospehere. (By the way, methane is between one and two orders of magnitude stronger than CO2, but between 2 and 3 orders of magnitude less common in our atmosphere.)
Regards,
Trevor
Water vapour is the most “potent greenhouse gas” with numerous absorption bands across a widw spectrum and at some 50 – 60 times the concentration of CO2.
If the backradiation “greenhouse” hypothesis is correct logic dictates the effect should be most pronounced in areas where the concentration is greatest – that is humid tropical locations.
Any cursory summary of temperature records shows the surface air temperature of tropical deserts – where the water vapour concentrations are extremely low – is nearly 10 or more degrees C above similar tropical locations where the water vapour concentration is nearly concentrated.
Besides the Moon indicates our atmosphere and oceans REDUCE the heating effect of the solar radiation during the day.
This is an interesting paradox – lower local “greenhouse gas” concentrations resulting in higher temperatures – for my two cents worth this alone casts serious doubt over the “greenhouse effect” hypothesis.
NPR???
The article is horribly written. It’s phrased like they’re talking to 5-year-olds, contains inconsistencies, and it makes numerous factual errors.
As for Shakun, nothing more than Winston hard at work at the Ministry. They just pretend the entire science of Geology does not even exist.
If you really want a shock, pour through some of the comments over at NPR.
Frightful.
“The proxy database provides an opportunity to explore what triggers
deglacial warming. Substantial temperature change at all latitudes
(Fig. 5b), as well as a net global warming of about 0.3 uC (Fig. 2a),
precedes the initial increase in CO2 concentration at 17.5 kyr ago,
suggesting that CO2 did not initiate deglacial warming.
“The identification of orbital frequencies
in the marine 18O/16O record, a proxy for global ice volume, in the
1970s demonstrated that glacial cycles are ultimately paced by astronomical
forcing.”
Source: Shakun et al., Nature 2012
Let’s give the guy a break. He got published, didn’t he?? And isn’t that the name of the game?
I think the most interesting thing is that they have had to use a change in the Earths orbit as the CAUSE of a temperature change, by what ever mechanism.
Next all they have to do is examine the ice-core dust record.
This isn’t science it is pseudo science and deserves just as much attention as any of work of fiction.
Milankovic cycles would start N. Hemisphere land warming, melting permafrost relapses huge quantities of methane, enhancing the warming process. From time to time concentrated plumes of methane are ignited by lightning releasing into atmosphere large volumes of CO2.
Ice Age Cycle progress:
Milankovic– increased insolation– land warming-permafrost melt– methane release and burning– steep rise of atmospheric CO2– proliferation of vegetation (source of the next cycle’s methane)– reduction of CO2– Milankovic– reduced insolation– land cooling– permafrost formation.
Oh goody ,I’m running straight out and burning heaps of tree limbs to prevent the next Ice Age .
“… Shakun is just making a SWAG. …”
Perhaps “Onager estimate” is better phraseology than super wild-ass guess (SWAG).
on·a·ger (from dictionary.reference.com)
noun, plural -gri [-grahy], -gers.
1. a wild ass, Equus hemionus, of southwestern Asia.
2. an ancient and medieval military catapult for throwing stones.
REPLY: Scientific Wild Ass Guess
-Anthony
Shakun and “the cause” are certainly aware of how devastating the “Co2 follows temperature” really is. So do many lukewarmers. Capitulation on Co2 will come back to bite many. The desperation of those who are fully invested in the Co2 drives temperature theory will drive them to more specious claims like this one. The debate is exactly where I stated it is.
I think I like Onager estimate. It sounds much more learned and is definitely obfuscatory.
Which seems to be a prequisite of the alarmist side.
Joel Shore says:
April 6, 2012 at 12:54 pm
Sorry, Joel–that’s just not true. Palynologists have found the transition from interglacials into full blown Ice Ages happen in a few years at most. The process is surprisingly rapid.
So your “…to tens of thousand of years.” for transition into an Ice Age is just supposition–unless you wish to discount what researchers have found on the subject (which, of course, would be no surprise).
Trevor says:
April 6, 2012 at 1:42 pm
I don’t believe that, Trevor. My understanding as a geologist is that these “interglacials” of which you speak last from 11,000 to 12,500 years, and we’re at LEAST 11,000 years into this one (maybe as much as 12,000 years by some estimates). That would mean (without any contribution from man) we should expect onslaught of the next resurgence in just 500 to 1,500 years.
I have been sitting back and observing the commentary on Shakun2012 and wondering if anyone will get stuck into it with ye old “evil eye”. Sadly, I have only seen a few near misses.
We will initiate the discussion with this quote from “Abrupt Climate Change, Inevitable Surprises”, Committee on Abrupt Climate Change, National Research Council, ISBN: 0-309-51284-0:
“Recent scientific evidence shows that major and widespread climate changes have occurred with startling speed. For example, roughly half the north Atlantic warming since the last ice age was achieved in only a decade, and it was accompanied by significant climatic changes across most of the globe.”
The thinking side of the paleoclimate community awaits an answer as to what sort of CO2 source could erupt at each and every ice age termination, typically at or slightly after each glacial maximum (the coldest part) to deliver such a tipping point. With most life on the planet subdued at such a time, we need something that can produce the most awesome climate effect known in Pleistocene time then about half a precession cycle later relax back to the cold glacial state at a time when CO2 levels remain higher than at the so-called tipping point at the terminations.
Can you have it both ways?
A 50 or so ppm rise in CO2 can do this? Yet by the time the interglacial goes kaput the CO2 levels are higher than at the termination tipping point! That’s called a “gotcha.”
The danger of that argument is completely lost on the warmists. OK, so CO2 is the culprit at the terminations, how do we slip into the next ice age then? And the end-game argument of all anthropogenic time follows right on its heels. OK, so haven’t we already “geo-engineered” our way out of the next glacial then? Surely you don’t really mean to worship nature by doing the one thing you think you now know, turn off the heat, and make sure nature continues with whatever State the next continental terminal morrane ends up in. Because if you really are a naturalist, then surely you cannot deny the earth its next ice age can you? I mean it is natural, nature, you know………
Be careful, be very, very careful using CO2 as the agent provocateur of the glacial terminations if you are a true warmist. Doing so emasculates any and all arguments for taking it out of the atmosphere at the 11,715th “hour” (year) of this interglacial. Because if it is so powerful a GHG to terminate a 90kyr old ice age, then it is powerful enough to keep us out of all of them from here on. By your very own logic you just found your “sustainable” climate.
Now that you have your agent provocateur you need to come up with an explanation for its average ~1470 year (the millenial variability you hear so much about) bursts of CO2 productivity to produce these “Large, abrupt climate changes have repeatedly affected
much or all of the earth, locally reaching as much as 10°C change in 10 years……….Similar events, including local warmings as large as 16°C, occurred repeatedly during the slide into and climb out of the last ice age.(NRC, 2003)” and then just go to sleep again. There were 25 D-O events during the Wisconsin Ice Age. D-O 19 scored that 16°C rise.
So given all the assumptions inherent in this argument above, given that we don’t know what causes all of these phantom bursts of CO2, isn’t this just going to keep on happening with known effects far beyond anything the climate science community has yet horrified us with?
Because if they are going to just keep on happening, and if researchers who have documented traces of the D-O cyclicity throughout the interglacials themselves are right, then this is all just a silly bugger’s game isn’t it. Every 1,000 to 4,000 years (documented D-O range in the Wisconsin) some mystery burst of CO2 will bounce the climate regardless of what you think needs to be done. Since we really don’t know what causes these cyclical phantom CO2 outbursts, how successful do you think you will be setting ye old thermostat?
Some of us are good, but none of us are gods, yet.
So be careful what you wish for. Removing that pesky temp-leads-CO2 argument, that warmists the world over have hated since 2003, bequeaths a lobotomy to your argument to remove it, especially at a possible end extreme interglacial.
Otherwise the Precautionary Principle must undergo a sex-change…………….
Just sayin’
He does not use tree rings as temperature proxies. Is not that an improvement? And is there value in the comparison of the used proxies showing that they have a strong correlation between each other? I mean, digging through this, maybe the “CO2 precedes” is just an add-on to the original intent, or most important scholarship, i.e., the kind of speculation that gets you funding these days? IOW, drop the CO2 “precedes” temps business, is there value in this multi-proxy exercise nevertheless?
Gail Combs’ explanation and links re ice age ‘triggers’ on an earlier thread is pretty convincing to me:
Milankovitch cycles, combined with the current situation of continental drift.
See the ‘tutorial linked here:
http://www.sciencecourseware.org/eec/GlobalWarming/Tutorials/Milankovitch/
Note slide 7 of 9: Precession AND Eccentricity
Right now the northern hemisphere experiences winter when the earth is at its closest point to the sun.
13,000 years ago, the northern hemisphere winter was being experienced at the time earth was at its furthest point from the sun in its orbit.
It seems obvious that variations in insolation related to the larger land mass in the Northern hemisphere would have major effects on the earth’s climate.
(by the way, seems to me the article implies the ‘wobble’ is a sudden occurrence, rather than the fact it is an ongoing thing)
Going with Markx here.
It has always been my understanding that the last several glaciation cycles have been governed by the eccentricy cycle, not the precession cycle. That is what that 110,000 year periodicity to ice ages comes from.
There is also a chance that we will have an extended interglacial this time due to the 400,000 year cycle.
It reads to me like a fore-gone conclusion, and a search for evidence to support that conclusion.
The Begin/End interglacials occur & trend much too abruptly to be caused by a slow build-up of albedo, that argument needs to be abandonded now or we’re setting ourselves up for disaster, via not being prepared. The process is abrupt, and it appears to be moderated heavily via celestrially modulayed magnetic and/or geomagnetic perturbational force superimposed on precessional alignment.
Eccentricity cycles do PACE the glacial-interglacial periodicity/length/spacing, but precession & amplitude seem to provide a threshold at which solar magnetic/geomagnetic processes (also influenced by celestial bodies) perturb the kinetic processes that distribute heat across the globe. The PDO/AMO cycle both follow the beat of the magnetic Hale Cycle.
This is evident in the 22yr hale cycle driving the PDO/AMO oscillations..once that gains scientific acceptance the rest could fall into place. The Holocene Interglacial may not even have 10yrs left…we complete the 25,800yr cycle in 2017, we began the entrance to galactic peak in 1980, peaked in 1998, and will close out in 2017..this cycle involves the Sun/Earth directional relativity to the galactic plane.
pardon above typos^^^
Global Warming not hot enough? Climate Change not severe enough?
No problem: Just cook up a new hypothesis, can of fresh paint and and some dire warnings.
Oh, and last but not least, cherry pick the reinforcing data.
And never, ever, look at the rest of the planets in the Solary SYSTEM.
It’s the Earth, man and nothing else. In the Great Void, Earth stands alone.
And on that lone planet:
http://www.robertb.darkhorizons.org/seaice.anomaly.Ant_arctic.jpg
Kinda off topic, but the folks who do the sea level data are getting very far behind again. One wonder’s if the news is not good out there in accelerated sea level rise land.
Global warming alarmists have a near-perfect track record:
All of their dire predictions have failed to materialize.
l think its changes in the jet stream that lead to the forming of the ice sheets.
lt would help to explain the sudden changes in climate.
The subject study bears the same fingerprints you find on the vast majority of AGW supporting works. A conclusion is reached after statistically teasing a signal out of data that should rightly be classified as “noise”. In this case, the horrendous “scatter” of the temperature proxies rendered them useless for defining global average temperature versus time within the 800 year window required to establish whether CO2 drove temperature or the reverse was true. Garbage in and garbage out.
William Astley says:
April 6, 2012 at 1:16 pm
There is no explanation as to what causes the reduction of 80 ppm to 100 ppm of atmospheric CO2 during the glacial/interglacial cycle.
The difference in seawater pCO2 in steady state with the atmosphere gives a change of 16 ppmv/°C. By far enough to explain the increase/decrease over the glacial – interglacial transitions and back. Vegetation acts in opposite ways, which gives an overall average change of 8 ppmv/°C.
@Rosco
>Water vapour is the most “potent greenhouse gas” with numerous absorption bands across a widw spectrum and at some 50 – 60 times the concentration of CO2.
Correct.
>If the backradiation “greenhouse” hypothesis is correct logic dictates the effect should be most pronounced in areas where the concentration is greatest – that is humid tropical locations.
Well, remember that the absorption works both ways. The heat may not be able to get to the ground as efficiently because of easy cloud formation.
>Any cursory summary of temperature records shows the surface air temperature of tropical deserts – where the water vapour concentrations are extremely low – is nearly 10 or more degrees C above similar tropical locations where the water vapour concentration is nearly concentrated.
In the daytime, yes. That same region cools dramatically at night because of a lack of water vapour and clouds to insulate it. Southern Africa has an interesting real life experiment with the weather. In summer it is warm, moist and the temperature variation is small day-to-night. In wonder when the air is really dry, the daytime temperature is almost the same, a bit colder, but at night the termperature drop is dramatic. A day-night change in summer might be 8-10 deg C and in winter 25-28 is common. It can be 0 C in the morning and 25 in the day but only if the air is really dry.
If changing CO2 cause a noticeable difference, there would be a change in the pan evaporation rate, which has not budged in 100 years (based on more than 20,000 observations stations on farms – every farmer has one).
Ah, CO2! The things you don’t do for us!
“Air bubbles in ice reveal what the atmosphere was like and what the temperature was. And scientists can read this ice, even if it’s been buried for thousands of years.”
Nevermind that air bubbles in ice are not hermetically sealed little gas time capsules in which the composition of the gas never changes.
Crispin in Johannesburg says:
April 7, 2012 at 2:34 am
……..
Your observations should be remembered when the Svensmark’s cloud albedo effect is considered, usually the night time effect is totally ignored. btw the latest Forbush effect confirms cloudiness decline :
http://www.vukcevic.talktalk.net/Ap-Cl.htm
****
William Astley says:
April 6, 2012 at 1:16 pm
Question 1: What the heck causes the Dansgaard-Oeschger cyles? That is rhetorical question. As I know what causes it. Hint there are cosmogenic isotope changes each and every time during the Dansgaard-Oeschger cycle. The late Gerald Bond was able to track 23 cycles. The same suspect is always at the scene of the crime. It is the bloody sun.
****
OK, but the cosmogenic isotope changes in the ice-cores have to pass thru & be “processed” by the atmosphere/weather before getting into the ice. The amount of isotopes can doubtless be affected by the state of the climate (warm, cold, wet, dry, etc). How do we establish cause & effect? The isotopic change may be the result of the climate & not changes in the sun itself.
Maybe these university types should read real books, not just on line stuff! my geography classes in the late 1960s studied the effects of the ice sheets over southern England in the last ice age, I do not recall them calling them the Greenland ice sheet, Eurasian maybe, so this is another serving of make some facts fit the result we want! Forget the fresh water idea does he not thing tilting the ice sheets towards the sum would obviate the thermal gradient that drives todays conveyer ? and how does he know that conveyer was working under the ice? Also the ocean levels were over 36 meters less back then, how did that effect the ocean dynamics. Like most of the climate scientists I only have little idea of the whole picture but this theory has holes a layman (who has been here on earth for nearly 60 years, can read and still has a memory ) can see clearly. This does noteven aspire to a nice try.
RockyRoad says:
Cite? There have been some rapid climate changes, although I believe the current thinking is that they were probably not global ones…and not to my knowledge the descent from an interglacial into an ice age, something that requires the growth of ice sheets, which is not a horribly fast process.
If CO2 is the driver of the ice ages now, then the CO2 sensitivity is 10.0C per doubling. Maybe Shakun et al didn’t realize this is what they were really saying.
There is a really tight fit of this formula to the ice core temperatures (noting that polar temperatures change by about twice the global temperature change through polar amplification).
260 ppm is the base value at 0.0C in this chart with 20.0C per doubling matching the ice core temperature numbers pretty closely.
http://img651.imageshack.us/img651/4122/co220cdoublinglast800k.png
So, if CO2 was the driver of the ice ages (which this paper is effectively insinuating) and the ice albedo was just a feedback of that, then we are in big trouble.
The LAST ICE AGE, the Karoo Ice Age, ended 260 million years ago. The CURRENT Ice age, referred to as the Quaternary Glaciation, began 2.58 million years ago and is still ongoing (in fact, if it’s anything like the previous ice ages, this one is just getting started and has at least a hundred million years to go, maybe 300 million years).
And we have no friggin’ idea why the last ice age occurred, why the current ice age is occurring, why the last one quit, why the current one began with a gradual depression and then converted over to an approximately bistable oscillation with an approximately periodic cycle. Blaming it on precession of the poles, orbital resonances, CO_2 or albedo feedbacks — all of it is possible, but none of it seems particularly plausible. I suspect that we are missing an elephant in the room, a major variable that controls the climate against which the rest are mere perturbations. Maybe even a herd of elephants. We’ll see.
rgb
Galane says:
April 7, 2012 at 4:10 am
Nevermind that air bubbles in ice are not hermetically sealed little gas time capsules in which the composition of the gas never changes.
In fact the air bubbles are tightly sealed in so far that any migration trough the ice can’t be measured in a laboratory, can be estimated for “warm” ice cores (-23°C for Siple Dome), based on remelt layers to be in the order of 2 years over a few thousand years or 20 years over 70 kyr, but is undetectable for the “cold” ice cores like Vostok and Dome C (-40°C) over resp. 420,000 and 800,000 years.
One exception is the CO2 levels in Greenland ice cores. The deposit of sea salt + carbonates is not a problem in itself (neither in the Antarctic coastal cores), but in Greenland there are frequently highly acidic dust deposits from Icelandic volcanoes, in combination with carbonates that forms CO2 in situ.
joeldshore says: April 7, 2012 at 6:47 am
“RockyRoad says: …. the transition from interglacials into full blown Ice Ages happen in a few years at most. The process is surprisingly rapid.
Cite? …..”
http://www.wunderground.com/resources/climate/abruptclimate.asp
This is a pretty pro-AGW article – but does say massive warming occurred on occasion In a decade:
“crosspatch”, there are some simple checks on your thesis:
– was the MWP not as warm as the RWP?
– what has Artic ice actually been like in the past two millenia, including during the MWP, circa 1900, and circa 1940? There have been many reports on this blog from the latter two times, albeit they may be snatches of data as comprehensive reporting was not available (whereas satellite is today).
It is up to you to check into them to support your thinking. As stated, your post is hardly even a theory, more like a fantasy.
markx: I agree there have been some abrupt climate changes in the past, but
(1) I think it is generally believed that they are regional changes…i.e., the global temperature does not change by that sort of several degC amount in such a short time period.
(2) The warmings tend to be more rapid than the coolings…and especially coolings from interglacial states. This is presumably because the growth of ice sheets is a fairly slow process, whereas they can break up more rapidly.
Bill Illis says:
Well, I don’t think it is quite as simple as that. But, this does dovetail with a point that Hansen has been making, which is that the calculation based on the last glacial maximum (LGM) that puts the climate sensitivity at about 3 C per doubling does assume that ice albedo is a forcing rather than a feedback. Hansen argued that when one considers ice albedo to be a feedback rather than a forcing, the value one gets is more like 6 C per doubling…and hence that this is the more appropriate number for our current situation, at least over the long term when ice sheets have fully responded (which Hansen has also argued might be considerably faster than some have predicted).
However, other scientists have expressed skepticism that the ice-albedo feedback will be nearly as large going from the current interglacial state to a warmer state than it is going from the glacial to interglacial state. And, my impression is that Hansen himself has backed off at least somewhat on this 6 C per doubling estimate.
joeldshore says:
April 7, 2012 at 3:24 pm
———————-
Assuming this is the same Joel Shore,
If CO2 is the forcing, then the sensitivity is 10.0C per doubling and ice albedo is a 100% feedback having no impact on temperatures.
– Now if temperature is leading the temperature changes, then one might say this is more likely.
Or the Ice Albedo (caused by the Milankovitch Cycles) is the primary forcing and CO2 is a 100% feedback and has no effect on temperatures.
– This is closer to what we used to think when the Ice Albedo was leading the temperature change and CO2 lagged behind by 800 years.
– In this case, each 1.0C drop in temperatures causes a decline of 16 ppm in the CO2 levels but then Ice Albedo alone is driving the temperature change. The Earth’s Albedo merely has to increase from 0.300 (let’s say 10,000 years ago but is 0.298 today) to 0.350 in the ice ages.
Or CO2 could be a forcing for 3.0C per doubling and Ice Albedo could be a forcing for the other 3.4C temperature change in the ice ages.
– But how can BOTH be a simple straight forcing. If both are driving temperatures down, then they are a combination of forcing and feedbacks. More Ice, temperatures fall, the ocean absorbs more CO2, vegetation grows slower leaving leaving less CO2 cycling in the Carbon cycle, less CO2. On the other hand, less CO2, temperatures fall, more Ice.
– In fact, less CO2 causes temperatures to decline which means that oceans absorb more CO2 which leads to less CO2 and so on.
– More Ice, less CO2, temperatures decline and now there is more Ice.
– Now we have a “quandary”. Both are a combination of forcings and feedbacks and feedbacks on the feedbacks. The math no longer works and Hansen’s Ice Age forcings paper is WRONG.
– Okay, Now we are getting somewhere.
The math actually works if CO2 is 1.5C per doubling and the Milankovitch Cycles changed the Earth’s Albedo to 0.330 by itself. Now both can be a forcing and a feedback and we have glaciers down to Chicago (where they have no business being even in an Ice Age).
It doesn’t even matter which is leading which.
William Astley….take a look at the D/O and Heinrich cycles more closely, especially the period 50,000-30,000 BP when for some reason the record is much more clearly defined….firstly, the T rise is very steep, like within a few decades, and the fall more slow….second: if you average the peaks you get one answer about periodicity, but look more closely for an 8:5:3:2:1 ratio…you can see it by looking at the width of each peak at about half-amplitude. This is a quasi-fibonacci series…how to explain that!!!???
And if you plot all of these as ‘warming events’ against the CO2 record, for Greenland, there is no correlation to CO2 changes, either for rate of change or amplitude of change.
On the causation: whilst I agree that changes in the ‘conveyor’ cannot account for the T changes (which are far too rapid), we must not confuse the conveyor and deep water circulation, with the gulf-stream and its northward extensions of warm water into the Arctic…which is wind driven. Changes in meridional winds certainly ARE capable of effecting major temperature changes in the Arctic…just look at the T variations in greenland or iceland when the wind is coming from the south and when sea currents are strongly driving into the Norwegian Sea….and look what happens in Eurasia when there are ‘blocking high pressure systems’ that deflect the winds into more zonal patterns. Climate is, after all, mostly an extension by percentage of weather patterns….and all we need to study is happening right now…..
I can’t believe Shakun said his research vindicates Al Gore. Did he actually say that in his paper or in a newspaper article?
“The last big ice age ended about 11,000 years ago”
Wrong. We are currently in same the ice age of 11,000 years ago. The ice age is expected to last about another 40million years, until antartica moves off the south pole.