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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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?