I wonder what caused a shift in ‘radiative forcing’ 9,000 years ago? Good thing that it happened though, or we would likely not have the civilization we have today.
Sudden shift in ‘forcing’ led to demise of Laurentide ice sheet
CORVALLIS, Ore. — A new study has found that the massive Laurentide ice sheet that covered Canada during the last ice age initially began shrinking through calving of icebergs, and then abruptly shifted into a new regime where melting on the continent took precedence, ultimately leading to the sheet’s demise.
Researchers say a shift in ‘radiative forcing’ began prior to 9,000 years ago and kicked the deglaciation into overdrive. The results are important, scientists say, because they may provide a clue to how ice sheets on Greenland and Antarctica may respond to a warming climate.
Results of the study, which was funded by the National Science Foundation with support from the National Aeronautics and Space Administration (NASA), are being published this week in Nature Geoscience.
David Ullman, a postdoctoral researcher at Oregon State University and lead author on the study, said there are two mechanisms through which ice sheets diminish — dynamically, from the jettisoning of icebergs at the fringes, or by a negative ‘surface mass balance,’ which compares the amount of snow accumulation relative to melting. When more snow accumulates than melts, the surface mass balance is positive.
When melting outpaces snow accumulation, as happened after the last glacial maximum, the surface mass balance is negative.
‘What we found was that during most of the deglaciation, the surface mass balance of the Laurentide Ice Sheet was generally positive,’ Ullman said. ‘We know that the ice sheet was disappearing, so the cause must have been dynamic. But there was a shift before 9,000 years ago and the deck became stacked, as sunlight levels were high because of the Earth’s orbit and CO2 increased.
‘There was a switch to a new state, and the ice sheet began to melt away,’ he added. ‘Coincidentally, when melting took off, the ice sheet began pulling back from the coast and the calving of icebergs diminished. The ice sheet got hammered by surface melt, and that’s what drove final deglaciation.’
Ullman said the level of CO2 that helped trigger the melting of the Laurentide ice sheet was near the top of pre-industrial measurements — though much less than it is today. The solar intensity then was higher than today, he added.
‘What is most interesting is that there are big shifts in the surface mass balance that occur from only very small changes in radiative forcing,’ said Ullman, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. ‘It shows just how sensitive the system is to forcing, when it might be solar radiation or greenhouse gases.’
Scientists have examined ice cores dating back some 800,000 years and have documented numerous times when increases in summer insolation took place, but not all of them resulted in deglaciation to present-day ice volumes. The reason, they say, is that there likely is a climatic threshold at which severe surface melting is triggered.
‘It just might be that the ice sheet needed an added kick from something like elevated CO2 levels to get things going,’ Ullman said.
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Certainly all those woolly mammoths farting could do no good for forcing.
and CO2 increased
===============
9000 years ago, CO2 levels were at record lows. The only thing this study shows is that LOW CO2 levels CAUSED the melting of the Ice sheet and the end of the Ice Age. What the CO2 record shows is that Ice Ages ALWAYS happen when CO2 levels peak!
http://www.skepticalscience.com/graphics/CO2_history_1024.jpg
No CO2 until 0 AD? Absurd! The Vostok ice cores show CO2 leading temp changes for 450,000 years.
Jim “No CO2 until 0 AD? Absurd! The Vostok ice cores show CO2 leading temp changes for 450,000 years”
Really? Surely you mean CO2 lags temps..
ferdberple
June 23:
“9000 years ago, CO2 levels were at record lows.”
_____________
That’s not what the Vostok data (blue line) shows. The last low point on the Vostok data is actually at ~ 17,695 years before present (b.p.), where ‘present’ means, by convention, 1950.
The last date in the Vostok data that pre-dates 9,000 years b.p. is at 10,123 years b.p. CO2 concentrations by then had risen abruptly from the previous low point (182.2 ppm) to 261.6 ppm. So in the 7,572 years between the low reported at 17,695 and 10,123 years b.p., CO2 concentrations had risen by around 80 ppm.
This is consistent with what the scientists are saying when they are paraphrased: “…a shift in ‘radiative forcing’ began prior to 9,000 years ago and kicked the deglaciation into overdrive”.
Vostok data are here: http://cdiac.ornl.gov/ftp/trends/co2/vostok.icecore.co2
Just another “kick”. Can there be no end to the vapid musings surrounding the wonder molecule?
I know where I would like to be aiming my kick at these swilling rogues…
It’s a ‘magic’ molecule!
The highly unstable switch from glacial to interglacial is clearly different from the quasi-stable states either side. It is wilfull misdirection to suggest that any observed behaviour during the transition applies to current climate.
Viewing the bistable pattern of behaviour it is strongly suggestive of the presence of a positive feedback. The subsequent stability of the Holocene clearly demonstrates that the positive feedback is constrained by a more powerful negative feedback : the Planck effect
Once at the upper limit and constrained by Planck, the only way it can go unstable is downwards, back into glaciation. That will be just as abrupt and unstoppable as it has ever been.
http://www.jstor.org/stable/3886350?seq=1#page_scan_tab_contents
Stop it, you know he wasn’t a Climate Scientist.
I agree. The statement you quoted is ambiguous, and perhaps intentionally so.
Shifts of ocean currents do it. Then warm Gulf Stream and warm rains do the melt, followed by ice ungrounding letting the warm water enter the arctic ocean as today. At that point the upper bound is reached and we have a stable interglacial.
If it ‘just might be’ then what lesson is there really for us here. Naturally calving of the ice stopped when the part over the sea disappeared, and yeah not only does mass balance change positively when snow is accumulating faster than melting but mass balance also changes negatively when it is melting faster than that added. Boy oh boy we sure have to reach into every cranny of self-evident sciencey stuff to match the name of the institution you are in.
It also ‘just might be’ that the aliens used their super-blaster heat ray gun. I have just as much proof as the CO2 theory.
Grin. 🙂
Keep increasing CO2 and the next Ice Age won’t happen. Tax CO2 out of existence and we can blame the next ice sheet onslaught on government stupidity. We’re doomed!
So they should be grateful for good ole CO2 as the saviour of the Earth, RockyR. Oddly, when you talk about solar hibernation and the threat of another LIA, they get even more angry. You’d think they’d be glad of the reprieve.
Thanks Niven and Pournelle
http://www.amazon.com/Fallen-Angels-Larry-Niven/dp/0743471814/ref=sr_1_1?s=books&ie=UTF8&qid=1435157689&sr=1-1&keywords=niven+pournelle+fallen+angels
If the warmists had their way they wouldn’t be happy until we are in another ice age, and even then they would blame CO2. (Hey can’t be seen to be “dithering”. That would affect their “trustworthiness” which trumps (no pun intended) scientific accuracy.
That theory, that rising CO2 levels and decreasing sea ice precede a glacier building period, was put forth in 1956. So yes, even if we enter a full blown ice age, it was predicted by Science!
It is very much possible that indeed the extra heat being trapped by greenhouse gasses builds reserve energy into the oceans. And like a battery, the oceans build up reserve until a critical point is reached. At that stage, cloud cover becomes continuous and cooling the upper troposphere. Since the ocean has enough reserve energy, it keeps on producing clouds even though there is not much heat coming in. These storm clouds are what causes the glaciers to form in the North.
The misconception about Ice Ages is that the Earth must be colder for it to happen. The reality is, you need a lot of energy to transport that amount of water from the ocean to the land in the form of ice. And so, the Earth might actually need to reach a tipping point in heat reserve for Ice Age to trigger.
Ewing and Donn may end up being right after all
http://harpers.org/archive/1958/09/the-coming-ice-age/
Wouldn’t that be ironic?
Its the temperature of the oceans that matters, and the surface to boot. Quite a lot of energy can be stored with the oceans below 2000m being 1°C warmer (enough to melt the Laurentide ice sheet) but that is not going to make more clouds.
Very interesting theory, Paul. Has it appeared earlier and/or elsewhere? And who else subscribes to it?
So what happened to Ewing and Donn?. That Harpers article is one of the best I have read , and of course because it is 60 years old I give it more credence than anything out today.
It seems so counter-intuitive, but is really thought provoking.
What happened? Where did we change? Did these guys die and no one continued the work? Was it discredited?
Does any one know?
Best I can tell, they died.
In reply to self (why so few levels of reply?) Methane Hydrate is what I was looking for.
Also the only sequitur for Ewing and Donn I can find so far is the phrase: “However, the Ewing-Donn theory turned out to have fatal errors, and most scientists continued to doubt that such swift changes were possible.” from aip.org
Sea floor cores from under the current sea ice areas showed they were never ice free, which pretty much killed the theory of an ice free arctic. So because one part of their theory was dismissed, the whole thing was thrown out.
Paul
There is support for your idea of a short warming peak before glacial inception from William McClenney who posts here from time to time on the subject of glacial-interglacial switching, e.g.:
http://wattsupwiththat.com/2014/05/29/glacial-inception/
One paper he quotes shows strong coral reef palaeo-evidence from the Bahamas that at the end of the last interglacial, sea level actually rose 2m briefly before a much larger fall signaling glacial inception:
https://www.researchgate.net/publication/249518169_Rapid_sea-level_changes_at_the_close_of_the_last_interglacial_%28substage_5e%29_recorded_in_Bahamian_island_geology
Here it is called the climate “madhouse” in between the greenhouse and the icehouse.
Thanks for that link to the 1958 Harper’s article, which was good reading, even after I noted, with mild astonishment, that the author is none other than Betty Friedan, the Grand Witch of the modern Feminist movement, alleged closet Marxist-Stalinist, co-founder & 1st president of NOW, and author of The Feminine Mystique from 1963 “… often credited with sparking the second wave of American feminism in the 20th century.”
Back to Ewing and Donn, has their work also been overturned with respect to the sharp pink-gray divide at 11,000 years ago they found in their ocean floor sediment coring? Even if their idea about he Arctic Ocean being ice free is wrong, that means only that we have to keep looking for the mechanism.
I’m no expert on this, but searching Google books turns up a plethora of information, including an awesome 1960 LIFE issue.
As far as I know from the icecore-data, the rise of CO2 was always 800 to 1000 years after the beginning of the rising of the temperature and always the temperature first sunk and than the CO2, so CO2 can’t be the driver of the lost of the laurentian iceshield.
HelmutU,
The rise in CO2 lags behind the rise in Antarctic temperature. But it leads the melting of Arctic ice and the rise in Arctic temperature.
It certainly does not during the early part of the last glaciation when temperatures led CO2 by up to 5,000 years.
Take a look at 20,000 years after the Eemiam temperature peak (128,000 BCE), the most recent with no possible human influence yet with highly resolved phase between temperature and CO2, and explain the multi-thousand-year lag of CO2 behind temperature.
The Greenland data match the data from Antarctica. There is no hemispheric inversion. The driver for increased atmospheric CO2 at the end of the Pleistocene is warmer ocean surface temperatures. The lag might be explained by increased CO2 uptake as vegation biomass increases and areas that were formerly savannah and grassland acquire denser vegetation as the climate improves for plants. The phenomenon is global.
tty, R Taylor,
I wrote: “The rise in CO2 lags behind the rise in Antarctic temperature. But it leads the melting of Arctic ice and the rise in Arctic temperature.”
You seem to be disagreeing, yet I see no contradiction between what you wrote and what I wrote. So I don’t see your point.
look at the record of CO2 and temperature. ICE Ages end when CO2 is lowest and begin when CO2 is highest.
Nowhere do we see high levels of CO2 ending Ice Ages or low levels of CO2 causing Ice Ages. Climate science has it backwards.
Well how about; as the arctic is warmer, the hydrates (I think I have that right) that lay under the ocean floor bed start to release methane? There is something about these releasing huge amounts of methane and this is a worry for the AGW people as they see it as a forcing of more greenhouse heating.
This would result in gases concentrations lagging temperature changes.
You can see I am no scientist, but someone here will be able to eek out my meaning.
It had nothing to do with GHG effect which follows the climatic change.
well at least the pseudo-science of how our planet’s climate operates is settled.
CO2 – The Magic Molecule.
CO2 – The taxable Molecule.
If they decide to tax O2 would that be at 2/3 the price of CO2 or 1/2 price?
It’s a desperate effort to link the climate then with now. And as usual, the wild speculation that maybe CO2 had something to do with the deglaciation then, causing a “big shift in the surface mass balance” then, so the same thing “could” happen today. Utter nonsense, of course.
It’s the only way to get published nowadays. Mention CO2 and you’re with the “in” crowd.
The same institution that fires descent from the consensus rights a 6th grade paper of :
http://wattsupwiththat.com/2012/06/11/climate-skeptic-instructor-fired-from-oregon-state-university/
“Results of the study, which was funded by the National Science Foundation with support from the National Aeronautics and Space Administration (NASA), are being published this week in Nature Geoscience.” All experts in agenda driven propaganda.
The same institution that fires dissenters (see here: http://wattsupwiththat.com/2012/06/11/climate-skeptic-instructor-fired-from-oregon-state-university/) from the consensus, writes a 6th grade paper. …there…that’s a little bit better writing…after lots of coffee… 🙂
‘What is most interesting is that there are big shifts in the surface mass balance that occur from only very small changes in radiative forcing,’ said Ullman, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. ‘It shows just how sensitive the system is to forcing, when it might be solar radiation or greenhouse gases.”
“But there was a shift before 9,000 years ago and the deck became stacked, as sunlight levels were high because of the Earth’s orbit and CO2 increased.”
nope…CO2 levels were stable for few thousand years before 9,000
Latitude,
CO2 rose from about 190 ppm 17 kyr ago to about 270 ppm 10 kyr ago.
CO2 has never been “stable” at any time scale that we can measure. The green curve is CO2 in the Vostok ice core:
No flat spots at all during the last 450,000 years. What IS notable is the dust. It is inversely correlated with temperature increasing as the planet chills and decreasing as it warms.
How does anybody know in any detail what happened 9,000 years ago? Besides the earth is only 6,000 years old.
No , the earth is only 36 years old. Nothing happened before 1979. There were no “super” storms or flooding or droughts or massive snowstorms or heat waves or tornadoes or hurricanes (they were just small ones, not like Katrina that regularly hit the US every year now) . It was a perfect world were nothing changed much, AND then bam co2 changed everything! Just wait!! In 15 years there will be disasters!!! (of some kind, not really sure, but panic now. We need a different kind of government to protect us from out selves. The UN says a communist government like China is perfect) .. SARC
Volcanoes, there’ll be VOLCANOES . . .
Yes and AGW will be responsible for those too. See when it gets warmer, I mean hotter, then the earth’s crust expands thinning out mantle allowing volcanoes to erupt. Do I get a grant now?
Then how can I be 60?
Spooky Physics, same logical as CAGW. It’s worse than we feared, some people are in denial that they are older than 39.
‘What is most interesting is that there are big shifts in the surface mass balance that occur from only very small changes in radiative forcing,’
Wouldn’t the “big shifts” caused by “very small changes in radiative forcing” also imply that sunspots and related cycles would have a significant effect.
More “tosh” from the echo chamber.
It’s been pretty-well established that temperature leads CO2 by 600-800 years in the paleo records.
yes and the lag was PREDICTED by the theory.
read your Hansen
Mosh, which paper by Hanson do you recommend to see this prediction in print? Can you provide a link, please?
Us Canadians were avid SUV drivers back then, we needed to be to outrun the polar bears
Us Canadians were avid SUV drivers back then, we needed to be to outrun the polar bears
Back then Polar bears were the SUV’s.
What’s hoseur for “giddyup”?
What’s hoseur for “giddyup”?
****************************
giddyup-aye
That’s “eh” not “aye” 🙂
EH is the proper Canadian spelling of the phrase EH. I’m not upset just Canadian 🙂
the french canadians here (maine) near border have more of an aye than an eh sound. slightly more drawn out and seems to be combo of canadian eh and maine ayuh.
course anything with french canadian accent is weird anyways especially when mixed with mainer accent lol
What’s hoseur for “giddyup”?
****************************
giddyup-aye
=====================
while in NY, they say:
aye-giddyup
thus:
NY = 0 – Canuck
proving NY less than zero.
“the french canadians here (maine) near border have more of an aye than an eh sound.”
Southern Canadians.
“It shows just how sensitive the system is to forcing”
“Forcing” meaning exactly what? Climate geniuses have used it in the past to mean a secondary effect. It appears this genius is using to mean a primary effect.
Whatever.
He says that big shifts were due to “very small changes in radiative forcing”. Are the changes in forcing statistically significant?
As i understand it, CO2 levels nine thousand years ago and today are at extremely low levels compared to earth’s past. Yet these low levels of CO2 might create forcing that tips the system and caused the ice sheets to melt? They present absolutely no evidence that such is true but have no qualms about making such a speculation.
How about this. The ice sheet form a blanket over the earth’s surface preventing heat from the earth’s core from radiating out into space thus warming the ground beneath the glaciers and causing them to melt from below. I have no proof of this whatsoever but I am sure it is as likely as CO2 above the glaciers causing them to melt. In fact probably more likely.
Eugene WR Gallun
You are on to something because Ice under pressure(such as the bottom of a mile thick ice sheet) has it’s melting point lowered. http://www.pnas.org/content/105/39/14779.full also https://youtu.be/gM3zP72-rJE
The thin layer of water at the bottom of (in this case the Laurentide) ice sheet is what helped it to move across land, and glaciers to move downslope.
glaciers to move downslope.
==================
look at any map. it is all downhill from Canuckistan to the US. The ice sheet didn’t melt so much as it moved to warmer climes. Once it reached Kentucky, it fried.
It’s possible, the chickens in Kentucky are fried.
These papers are completely daft. A study of how we came out of an ice-age is supposed to tell us anything about what might happen in the interglacial period when we don’t have the same ice?
This study might tell us what is likely to happen the next time we come out of a glacial period in around 90,000 years, but until then it is completely useless.
It’s a bit like research studying how a boat sinks – and then saying that can tell you how a boat at the bottom of the sea will sink into the mud IT’S ALREADY SUNK – IT CAN’T SINK AGAIN!
False analogy. Straw man argument too.
Scottish Sceptic,
By your argument, all science is completely useless.
sounds like you are upset about semantics.
settling into the mud vs sinking into the mud.
“Ullman said the level of CO2 that helped trigger the melting of the Laurentide ice sheet was near the top of pre-industrial measurements — though much less than it is today. The solar intensity then was higher than today, he added.”
Who counted the spots? LOL
It’s not the spot count it is based on orbital fluctuations. 10,000 years ago NH summer solstice was at perihelion along with maximum obliquity. So the solar intensity as stated by Ullman is really insolation increases in the NH. If he is that flippant about this terminology, perhaps he is just as flippant about the 9,000 year figure and the supposed CO2 forcing way back then.
I wonder what the grant application said prior to the start of the study.
The report is about the demise of Laurentide ice sheet. Still the date of 9,000 years ago seems odd. In Washington State, Cascade glaciers and the Puget Lobe had a much earlier demise. Image:
http://rocky.ess.washington.edu/areas/Puget_Lobe/
The ice reached its maximum about 13,500 years ago and had melted back to the US-Can border by about 11,000. My dates here are approximate. I don’t have time to look up the best accepted timing. Mountain glaciers in the area had somewhat different sequences.
Thus, a “a shift in climate ‘forcing’ ” at 9,000 years ago sounds odd.
Agree. My understanding was that the current configuration of the great lakes (which were under a mile of ice at the last glacial maximum) has been essentially unchanged for 12,000 years, which is not possible if the Laurentide ice sheet still existed 9,000 years ago.
The Laurentide began disappearing ~19 millenia ago and was essentially gone by 8 millenia ago. Sea level rise shows this. The most rapid melting was meltwater pulse 1a which began about 15 millenia ago.
John F. Hultquist wrote: “Thus, a “a shift in climate ‘forcing’ ” at 9,000 years ago sounds odd.” But the article says “before 9,000 years ago”.
My guess is that the imprecision in the language is courtesy of some press office hack.
“Sudden shift in ‘forcing’ led to demise of Laurentide ice sheet”.
They do not really say that in the article, so your headline is misleading.
Either way, the melting process probably took a while.
I smell a rat! How could Oregon State’s researchers know there was a shift in the radiative forcing if this shift began 9000 years ago?
Retroactive anthropogenic CO2 made outa tachyons.
Does our evil know no bounds?
Mark, I often wake up at night thinking about the damage we’ve done to the galaxy by blasting rf carelessly into space.
I’ve been blasting Metallica into space for about 10 years now. I haven’t heard any complaints from the Galaxy, but it drives my neighbors bonkers.