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.
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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.