A shift in climate 'forcing' led to demise of Laurentide ice sheet 9000 years ago

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

A study of the demise of the Laurentide Ice Sheet that once covered Canada may help scientists better understand shrinking ice fields today -- like this melting ice margin in Greenland. CREDIT Courtesy of Oregon State University

A study of the demise of the Laurentide Ice Sheet that once covered Canada may help scientists better understand shrinking ice fields today — like this melting ice margin in Greenland. CREDIT Courtesy of Oregon State University

From OREGON STATE UNIVERSITY:

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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183 thoughts on “A shift in climate 'forcing' led to demise of Laurentide ice sheet 9000 years ago

  1. Certainly all those woolly mammoths farting could do no good for forcing.

      • 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

  2. Just another “kick”. Can there be no end to the vapid musings surrounding the wonder molecule?

    • ‘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.’

      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.

  3. 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.

  4. 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.

      • 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.

      • 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?

      • 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.

  5. 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.

  6. well at least the pseudo-science of how our planet’s climate operates is settled.
    CO2 – The Magic Molecule.

  7. 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.

  8. ‘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.”

  9. “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

    • 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

  10. ‘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.

  11. 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.

      • 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.

  12. “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.

  13. He says that big shifts were due to “very small changes in radiative forcing”. Are the changes in forcing statistically significant?

  14. 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

  15. 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!

  16. “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.

  17. 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.

  18. “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.

    • 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.

  19. If the levels of CO2 were not as high as todays levels, why is the ice not melting rapidly, if what they claim is true?

  20. The paper must be bunkum. Both sea level rise and a number of coastal sediment proxies show that the Laurentide melting was underway ~19000 years ago, and was essentially gone by 9000 ya, despite the Younger Drayas event, which cause (lake Aggasiz breaching the ice dams of the St. laurence) shows the disappearance was from melting and a sharply negative mass balance.
    It is as if the author is unaware of Greenland ice, coastal sediment core, moraine dating (like in Wisconsin), and all the other hard physical evidence concerning the event. If his point was some inferred CO2 tipping point, then it is a massive fail.

  21. Either the paper is trash or it is sadly misrepresented in the press release.
    ‘What we found was that during most of the deglaciation, the surface mass balance of the Laurentide Ice Sheet was generally positive,’ Ullman said.
    Oh, sure, they must of found it stuck to the underside of someone’s desk at Oregon State. Maybe they used a model, aka guess work. All the rest of the press release is a fairy castle built on this make-believe premise.
    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.
    I didn’t know anyone had cored the Laurentide ice sheet and left the results lying around for Oregon State to find.

  22. Love this:
    “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”
    This was my fault. I had just bought a second SUV back in 7000BC.

  23. Thre’s good news here,
    “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.”
    Solar intensity is down, so CO2 increase is keeping us from slipping into the next ice age 🙂

  24. About 10,000 years ago, all three Milankovitch cycles were working in harmony to melt the Laurentide ice sheet as well as the Eurasian icesheet. It was all about the Sun, fellas, and CO2 had virtually nothing to do with it; and btw, the beginning of this melting started about 20,000 years with a few setbacks along the way.

  25. Funny, glacial calving used to be a sign that a glacier was stable or growing, but now, through the magic that is “climate science” presto chango – it means just the opposite.

  26. The latest fad is the “attribution study” where an expert pronounces that something was caused by CAGW. Today’s California Water News carries an article about an attribution study linking extreme weather with CAGW:
    http://www.usatoday.com/story/weather/2015/06/22/extreme-weather-climate-change-global-warming/29124803/
    Extreme weather events linked to climate change, study says
    Excerpts:
    “We have a new normal,” said lead author Kevin Trenberth, a scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., and two fellow scientists. “The environment in which all weather events occur is not what is used to be: all storms, without exception, are different.”
    […]
    One expert, Martin Hoerling of the National Oceanic and Atmospheric Administration, who was not involved in the study, criticized that there’s no new research in Trenberth’s study, and that it’s basically an op-ed piece. “The issue of how climate change affects weather is much more complicated,” than expressed in the piece, Hoerling said.
    “It is important to emphasize that extreme events are not borne of high vapor vapor and warm oceans alone,” Hoerling said.
    […]
    Another expert, meteorologist Michael Mann of Penn State University, also not involved in the study, calls it “a useful contribution to the ongoing discourse on climate change and extreme weather.”

    • How can climate change affect weather? Climate is average weather over a fixed period. For the climate to change, the weather has to change first. Climate change is the result of a change in the weather.
      These people are caught up in their failure to understand their own jargon.

  27. Anthony – your advertisers are getting out of control. They interrupt reading your stuff , both visually, orally, and by shifting your text in the middle of reading it. Takes away from concentration what you have posted, even interferes with writing this reply.

  28. ” ‘It just might be that the ice sheet needed an added kick from something like elevated CO2 levels to get things going,’ Ullman said. ”

    So just a little kick from that magic molecule CO2 ended the Wisconsin Glacial Episode. What do they suppose caused the beginning and end of the Nabraskan, Kansan, and Illinoian glacial periods?

  29. https://stevengoddard.wordpress.com/2015/06/22/obama-continues-his-siege-against-reality/#comments
    The Northwest passage will be blocked, not due to ice, but due to lowering sea levels as the ice sheets build. Even in this ice thickness picture you can see the ice sheets starting to build as the ice retreats from the Northern Russia region. Warm water from the Atlantic is moving in from the passage between Greenland and Europe. The Atlantic is cooling while the Arctic is warming. It couldn’t be more obvious that this is the end of the Holocene. This is all laid out by Ewing and Donn (1956 Science). The US and Russian military know it. Russia will have the arctic region, and Alaska, which is one of the few places to survive the change from interglacial to glacial. People really need to be talking about this, especially here.

    • Nice graphic. I don’t believe I’d realized (or, I’d forgotten) that there was still so much of the ice sheet left only 7,000 years ago. An additional pane, or two, illustrating the full extent of the ice sheet – what, some 29,000 yrs ago, or so, would have been a nice addition to the graphic. Thanks

    • There’s a major lake (Lake Agassiz) missing northwest of Superior in that graphic and 7 KYA Lake Agassiz was continuous with Lake Ojibwe to the east and which drained into the St. Lawrence river east of Lake Ontario. There was no ice in the area indicated 7,000 KYA. You can only wonder where they get this kind of information(?).

  30. I have no doubt CO2 was elevated back then. Greening and “insecting” was likely quite rapid as ice sheets everywhere retreated, resulting in ever increasing CO2. Additionally, something else was outgassing and that would be the oceans. When warm waters rise to the surface and sit there, they not only pump heat into the atmosphere, they pump CO2 into the atmosphere.
    If this were my investigation, I would be looking for clues about the Arctic Oscillation, why it was stuck for such a long time in one phase, and why it rather rapidly switched to another regime. When it is negative Arctic blasts inundate Canadian territory, freezing its tootsies off. It seems reasonable that ice ages in the NH are characterized by the AO being stuck in negative (along with orbital forcing and other factors). But what goes one way on Earth tends to swing back eventually but not smoothly, and not in equal measures. A positive AO would bring melting temperatures to this very same region and would start in the western part of the Laurentide Ice Sheet which is EXACTLY what has been found. It seems to me that the only thing having enough energy to build and sustain, and then to destroy such large environments is an oceanic-atmospheric teleconnection regime that creates global changes and that are unique to each area of the globe (IE some areas are much colder while other areas are much warmer at the same time when these global regimes are in charge). I think CO2 just rides the tail of these regime shifts.
    http://serc.carleton.edu/vignettes/collection/58451.html
    http://www.climate.gov/news-features/event-tracker/how-polar-vortex-related-arctic-oscillation

    • P.G., I agree. And the largest shift in insolation occurs between northern hemisphere (NH) and SH, where one cools as the other warms. The oceans become major conveyors of such heat changes around the globe.

      • donb @ 11:15 am
        I would like to understand the bi-polar earth affect. Right now we have the Arctic “heating” and the Antarctic “cooling”. Does this happen on Mars also? Elsewhere? Mars is bi-polar but annually. I can understand how the earth would be bi-polar based on changes in orbit and when perihelion occurs. But no one seems to talk about that. Yet, it shows up on so many graphics of the earth’s temperature.
        Maybe someone can point me to some reading.
        Thanks.
        Per Willis:
        https://wattsupwiththat.files.wordpress.com/2015/06/decadal-temp-trends-uah-msu-tlt-v6-flat.png?w=720&h=636

      • I would look at the AO and AAO indices for further elucidation. That said, there are lots of differences between the poles thus they may react differently to oceanic and/or atmospheric oscillations and regime shifts.

  31. “‘What we found was that during most of the deglaciation, the surface mass balance of the Laurentide Ice Sheet was generally positive,”
    How do they know that I wonder? It requires knowing the thickness of the icecap, cloudiness, the local lapse rate and the amount of precipitation. There are no reliable proxies for any of these, so it is “models all the way down” as usual.
    By 9,000 years ago the Laurentide Ice was already mostly melted. It had been melting for about 10,000 years. The Eurasian icecap was already all gone. I hope that was allowed a negative mass balance a bit earlier by the models, since it didn’t have any ocean to calve into the last couple of milleniums.

  32. Solar TOA insolation in the Northern Hemisphere reached a maximum about 9400 years ago and has been slowly decreasing. But the total decrease (~40 watt/m^2 at 65N) probably was too slow to trigger this early melting.
    The mass sheet mass balance is maintained by precipitation rate, which depends on open oceans and ocean currents in the North Atlantic and Arctic. Such currents change. If this precipitation (snow) abruptly decreased, then warm temperatures of NH solar insolation maximum could produce rapid melting. NH cloud albedo may also have been involved.
    Melting from small changes in CO2 seems unlikely.

    • The run up to the peak of solar TOA isolation happened well before 9400 years ago. Roughly 13,000 years ago, perihelion occurred in the beginning of June. It took thousands of years for it to pass the solstice and trail off into latter July.

      • Orbital eccentricity peaked about 15,000 years ago; orbital obliquity peaked about 12,000 years ago; but climatic precession peaked later. The NH is still in insolation decline from that peak. The month of the peak cannot be determined because of slight changes in orbits of the planets.

      • “The NH is still in insolation decline from that peak”
        ..
        Not true.
        Perihelion is currently in the first week of January.
        The last time perihelion was on the December solstice was in 1246 AD. It is advancing toward the March Equinox at the rate of about one day every 58 years. So the NH is not declining, it is on the rise.

      • donb: “Orbital eccentricity peaked about 15,000 years ago”
        eccentricity has a periodicity of 100,000 years and we are near the minimum of eccentricity now. So there is no way eccentricity “peaked” 15,000 years ago unless you mean the minimum is the peak.

      • NH insolation at 65N depends not only on axial precession (cycle time just under 26,000 years), but also on the tilt of Earth’s axis, which varies over 21.5-24.5 degrees. These BOTH contribute to insolation, and not just where the axis is pointing. Earth’s tilt reached a maximum 9500 years ago.

      • donb: ” orbital obliquity peaked about 12,000 years ago”
        Obiquity changes 1 degree about every 6833 years. We are currently at 23.5 degrees and declining so that would put the peak of obliquity (24.5 degrees) only 6833 years ago. 12,000 obliquity was closer to what it is today but increasing.

      • To Tom. I mean a peak in insolation produced by eccentricity interacting with other orbital parameters. You are correct that eccentricity is a 100,000 yr plus cycle. However, in considering NH insolation, it is the interaction of ALL parameters that produce the result.
        Because Earth is near the minimum in eccentricity, its effect on precession etc., over the next few 10s of thousands of years will be to dampen swings in insolation. Thus, Earth is unlikely to experience a major glaciation anytime soon.
        Of course, insolation is only part of the reason Earth has glaciations.

      • Tom. I think we are comparing apples and oranges. You and Joel are discussing orbital changes individually. When I refer to a maximum or minimum, I mean the effect on solar insolation at 65N. This depends on interactions of all parameters and will not be in phase with any one.

  33. National Science Foundation (actually,National Fr**dulent Science Foundation)with support from the National Aeronautics and Space Administration (NASA) (actually, Never A Straight Answer) sarc/
    Science for Sale. Sad.

  34. ‘It shows just how sensitive the system is to forcing, when it might be solar radiation or greenhouse gases.’
    It shows nothing of the sort. Glaciation and deglaciation are driven by summer solar isolation at high northern latitudes, which in turn drives the rate of change of ice volume, not ice volume itself. These phenomena are not amenable to treatment as a matter of climate sensitivity as in greenhouse gases. The statement is specious. See for example Fig 2 in
    http://earthweb.ess.washington.edu/roe/Publications/MilanDefense_GRL.pdf

  35. Look fellows and fellins since we have this no increase in surface temperature but an increase of CO2. Where is all that famous back radiation going? Or not going?
    By the way this paper is garbage.

  36. Notice how strong the Sun is today on June 23, 2015 at the margins of where those glaciers were 14,000 years ago.
    The Sun was almost exactly just as strong at the summer solstice 14,000 years ago.
    The glaciers were melting furiously at this time of year and all the rivers were flowing south at tremendous rates and new lakes were appearing out of nowhere. The Mammoths had to be very careful or they would drown. The humans who moved in 500 years later, also had to know what they were doing or their camps would be in the middle of a new river or lake.
    Why did the glaciers melt back 14,000 years ago. Go stand in the Sun right now and it will be very clear.

    • “The Sun was almost exactly just as strong at the summer solstice 14,000 years ago. ”
      If you are addressing insolation remember that because the periodicity of Precession is 23,000 years, summer solstice in the northern hemisphere was closer to perihelion 14,000 years ago rather than closer to aphelion as it is today.

  37. There is a large submerged city off the west coast of India that was larger than any city built for another 5000 years. Maybe if the ice sheet hadn’t melted we may be much more advanced!

  38. Folks, this is a news report written by a journalist who quite likely could not identify Antarctica on a map where it wasn’t at the bottom and colored white. I assume that the study authors had some data of some sort to base their conclusions on. Unfortuately the nature of the evidence has been entirely lost in this writeup. Until someone finds either the paper itself or an intelligent summary of its content, discussion this looks to me to be a complete waste of time.

  39. 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.
    Ummm…. question. WHY didn’t Greenland respond? Same sunlight, same forcings, same CO2. A giant counterexample right in their own claims.

    • Greenland, like Antarctica, is surrounded by water. That may be the key factor in the ice sheet there not melting.

      • How do the glaciers know they are surrounded by water? The factors cited were solar, forcings and CO2.

      • “What we found was that during most of the deglaciation, the surface mass balance of the Laurentide Ice Sheet was generally positive”
        There was no link to the actual research so I still haven’t read what the evidence for this is. It doesn’t seem likely though. There were areas south of these ice sheets that were a lot wetter eg. SW USA, North Africa, middle east. The wind patterns meant that the ice sheets were in a sort of rain shadow. Siberia now gets about the same average precipitation as semi-arid regions and the Antarctic.
        Also, dynamic suggests that the terminus of glaciers were melting quicker but much of the drainage of the ice sheet in the south was down the Mississippi as a river not glaciers ending in a bay. Surely then, there is some evidence that the ice sheet in the NE US didn’t start to recede until late? All the evidence points to the ice sheet receding from the south to the north with proglacial lakes forming and bursting their dams.
        I would go with greater rainfall. It takes a lot of energy to melt ice and if the precipitation is rain not snow, then the pools of water on the ice absorb more radiation rather than reflect it. A lot of summer rain when shallow pools of water are more likely to dry out than freeze over seems like a better reason than the ice flowing to the sea quicker.

      • Robert B, I believe you hit the nail on its head. Early March cold rain will melt snow pack. Watch out for flooding if the ground is still frozen,

    • WHY didn’t Greenland respond?

      Today we can sunbathe where there used to be a mile of ice. Almost nobody is sunbathing in Greenland at any time of the year. The conditions aren’t nearly the same.

  40. Yes. Glaciers must have precipitation, and both are surrounded by water, whose evaporation is carried above them by prevailing wind. In contrast, Alaska is located far from prevailing winds carrying moisture from the north Atlantic. And when the Arctic ocean was frozen in the last glaciation, much of Alaska remained unglaciated, in sharp contrast to Canada.

  41. Wouldn’t it be nice if the PR people who write these releases recognised that all journal articles are contributions not decisive works that end discussion. It cannot be said that the authors ‘found’ what they propose. Rather, they ‘suggest’ that this is what happened.
    Yes, I know it’s a small point…

  42. It is a fact that there is cyclic climate change in the paleo record with a periodicity of 1500 years plus or minus 500 years. In the last 15 years climatologists have confirmed that cyclic changes are global. The cyclic changes occur during the interglacial period and during the glacial period. One of the surprises in the climate record (Discovered in 1993 by analysis of the Greenland Ice Sheet Project 2 ice core, paleo climatologists did not trust project 1’s ice core analysis and hence drilled another core at an ideal location, 30 miles from project 1’s location, to confirm project 1’s analysis) is the discovery of very large abrupt climate change events.
    The abrupt climate change events are capable of and do end and start the interglacial periods (Interglacial periods start and end abruptly not gradually). There are dozens of different observational and analysis results that support the assertion that the cyclic abrupt climate change is caused by cyclic changes to the solar cycle which in turn is caused by/trigger by the motion of the sun by the large planets which explains what regulates the period of the cycle.
    http://www.agu.org/pubs/crossref/2003/2003GL017115.shtml

    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.

    The cyclic change to the sun when it occurs, causes a small, medium, or very large change to the earth’s climate. The observational fact all of the climate changes – small, medium, and super large – occur along the same series in time (imagine a sequence in time where the size of the next in the sequences varies in dependence on what happens to the sun) for the next 1500 year plus or minus 500 year climate change and the fact that there are small, medium, and immense cosmogenic isotope changes that correlate with the cooling and warming events are a couple of the observations that supports the assertion that the sun is causing the cyclic climate changes.
    Early indication of the start of cooling will be expansion of deep blue in this diagram. It will be interesting to see how the cult of CAGW initially tries to spin away abrupt cooling.
    http://www.ospo.noaa.gov/data/sst/anomaly/2015/anomnight.6.22.2015.gif
    The strongest cyclic climate changes are called Heinrich events which is a idiotic naming conversion. A cyclic physical event should not be named after the person who discovered the event. Use a naming convention that provides information concerning the cause of the event. Heinrich events initiate and terminate interglacial periods.
    The small and medium cyclic climate changes are called Dansgaard-Oeschger events. Again an idiotic naming convention. (Wally Broeker started the idiotic naming convention and sent the climate community off into left field with suggestion that North Atlantic Drift current could somehow cause a Heinrich event. (It is an order of ten too small.)
    If and when the planet starts to unequivocally cool, I will present in serial form a Coles note summary of what is happening and its theoretical implications.

    • Great stuff – – that’s exactly what my gut came to realize simply through studying the history a bit. Do you have a link to the actual study – would appreciate.

  43. “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.”
    Whaaaat?? Only at Oregon State would MORE accumulation result in LESS mass. Perhaps that only happens during deglaciation?? Wow – I am glad I graduated from the UofW! Perhaps the Physics department at OSU needs to be notified that the Climatology dept has discovered a new law of physics – one where adding more mass results in less total!
    I assume only that the quote was correct.
    And this is PhD work??

  44. ‘It just might be that the ice sheet needed an added kick from
    something like elevated CO2 levels to get things going,’ Ullman said.
    Yes, it just might be, maybe, perhaps, possibly.

  45. [quote] …the massive Laurentide ice sheet that covered Canada during the last ice age initially began shrinking through calving of icebergs, [/quote]
    How can a shrinking ice sheet calve icebergs?

    • The last glaciation greatly lowered sea level and exposed continental shelf (bare land), on which glaciation formed. As ice melted and the sea rose, this ice was broken into the sea.

      • That process may work for coastal areas, but in places like Pennsylvania, Ohio, Indiana, Illinois, Wisconsin, Iowa, and the Dakotas, for example, it would not.

      • There is considerable evidence that glaciation in the US melted from south to north over time, and as you infer, this was due to Temperature and increasing solar insolation, not the sea.

  46. As it is clear that CO2 always lags temperature changes, it is ingenuous to pretend that it triggered anything back then. As temperatures crashed while atmospheric CO2 was still high, it is clear that CO2 not only cannot cause warming but also cannot maintain warmth when CO2 is high.
    Also, experts in ice core analysis indicate that there is 30–50% losses of CO2 during the traumatic micro fracturing during the depressurization of ice core retrieval. If you back calculate, at 40% losses, what the CO2 might have been originally, we get CO2 concentrations the same or much higher than now and quite similar to the direct CO2 chemical bottle data that shows that CO2 has been high during three periods of the last 200 years and as high as 550 ppm (400 ppm at present) (200 years of direct chemical CO2 bottle data by Ernst Beck)

    • I am glad you posted this. I was questioning the ice core level of CO2 as presented. It only seems logical that CO2 levels were higher than what the ice cores represent for the exact reason you state. A 32 F bottle of coke retains most of the CO2 injected into it, however a warmer bottle will boil over with CO2. The oceans are similar in their retention of CO2. Warmer = less CO2 (or any other gas)

  47. There is no real evidence that CO2 has any effect on climate. It is just conjecture. If greenhouse gases added to global warming then H2O has got to be the culprit. For significant amounts of CO2 to enter the atmosphere, large volumes of water need to warm up. But for H2O all that is needed to wa
    rm up is the surface of the water and the air. The claim is that H2O is a positive feedback to the climate effect of increased levels of CO2. But if H2O provides such a positive feedback it must provide a positive feedback to increased levels of itself. Positive feedback systems are inharently unstable yet the Earth’s climate has been inharently stable for at least the past 500 million years, enough for life to evolve. Besides being a greenhouse gas, H2O is a major coolant in the Earth’s atmosphere which is a major reason why the feedback effect of H2O must actually be negative and hence mitigate the effects of other greenhouse gases on climate. If CO2 actually affected climate it would have to do so by changing the radiometric thermal insulation qualities of the atmosphere. The increase in CO2 that has been observed would cause an increase in the natural lapse rate in the troposphere but that has not happened.

  48. It always surprises me these people ignore altitude when discussing icesheet gain and loss. As ice accumulates, surface altitude increases and it gets colder, hence more snow. As ice mass is lost, the reverse happens. Two strong +ve feedbacks.
    Stopping the ice accumulation feedback and initiating the ice loss feedback requires a relatively short period of sudden ice loss (and of course other factors have to be conducive, particularly orbital forcings) in perhaps as little as a century or two.
    What could cause sudden rapid ice loss over a short period?
    My pet theory is that as ice accumulates, sea levels fall and coastal swamps/bogs dry out, becoming susceptible to lightning initiated fires, and we know from current experience, these can burn for decades.
    Atmospheric black and organic carbon levels rise and get deposited on the ice, reducing its albedo and initiating melt. Some gets washed off by meitwater, but most doesn’t and over years accumulates on the surface of the ice and is exposed at peak summer melt, causing accelerated ice loss, reducing altitude and reaching the point where other factors can continue the melt, as rising sea levels extinquish the fires.

    • I hope that graphs right. Huntsville, Al has had a string of 19 days at or above 90F and nine straight days at or above 95F. The extended forecast doesn’t look much better for us.

  49. I only needed to see that the “study” was funded by the National Science Foundation to know what the conclusions would be; so I stopped reading at that point.

  50. hey , i belong to a couple climate change debate sights on facebook. im surely in the minority going up against all these warmists folk and could use some help . if anyone that can debate with some real technical knowledge should join up . this site (wattsupwiththat) is constantly under ridicule and not taken seriously . they have like one or 2 guys that actually study some type of climate science just spewing madness and my technical knowledge can only go so far so any help would be appreciated .i think 1 site is invite only so id have to invite you . get at me at emmdigital at gmail

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