Multiple, Intense, Abrupt Late Pleistocene Warming And Cooling: Implications For Understanding The Cause Of Global Climate Change

Guest essay by Dr. Don J. Easterbrook

Dept. of Geology, Western Washington University, Bellingham, WA

The results of oxygen isotope measurements from ice cores in the Greenland and Antarctic ice sheets several decades ago stunned the scientific world. Among the surprises from the cores was the recognition of multiple, late Pleistocene, extraordinarily abrupt, intense periods of warming and cooling. The most precise records of late Pleistocene climate changes are the ice cores of the Greenland Ice Sheet Project (GISP) and the Greenland Ice Core Project (GRIP). These cores are especially important because the ages of the ice at various levels in the core have been measured by counting annual layers in the ice, giving a very accurate chronology of climatic fluctuations determined by measurement of annual layers.

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Figure 1. Oxygen isotope fluctuations in the GISP2 Greenland ice core. Red = warm periods, blue = cold periods. Up on the vertical axis is warmer (Plotted from data in Stuiver and Grootes, 1997)

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Figure 2. Temperature fluctuations in the GISP2 Greenland ice core. Red = warm periods, blue = cold periods. (Plotted from data in Cuffy and Clow, 1997 and Alley, 2000)

Figure 1 is the oxygen isotope record from the GISP2 Greenland ice core from 11,000 to 15,000 years before present (BP). Although it is not a direct measure of temperature, the 18O/16O ratio is a proxy for temperature. Figure 2 is the reconstructed temperature record for the same time interval, based on data from Cuffy and Clow (1997), modified by Alley (2000). Comparison of the two different approaches in Figures 1 and 2 shows essential agreement.

The temperature variations shown in Figures 1, 2, and 3 correlate very well with other geologic data that has led to recognition of several named periods of warming and cooling. The named periods of warming and cooling discussed below were established long before the same climatic events were discovered in the ice cores.

[1] Bølling warm period: Abrupt, intense warming 14,500 years ago resulted in sudden wholesale melting of the huge continental ice sheets that occupied vast areas in North America, Europe, and Russia and extensive alpine glaciers in mountainous areas. What made this warming so remarkable was not only its abrupt onset, but also its intensity. Temperatures in Greenland rose 20°F (~12° C), about equal to the total cooling of the late Pleistocene glaciation, to near present-day levels in about one century (Figs. 1, 2). Although this temperature change is for Greenland, simultaneous glacial retreat all over the world indicates that this was a global event. Prior to the ice core analyses, such large swings in temperature were believed to have taken a thousand years or more. This warming event, known as the Bølling (Figs. 1, 2) lasted only a few hundred years, but temperatures rose to near-modern levels.

[2] Older Dryas cold period: At the end of Bølling, temperatures suddenly plummeted about 20° F (~11°C) from the Bølling maximum in a few hundred years (Figs. 1, 2), initiating the Older Dryas cold period, which lasted from about 14,300 to 14,000 years before present (BP). Temperatures returned to near full glacial levels and glaciers halted their rapid retreat.

[3] Allerød warm period: About 14,000 years BP, temperatures once again rose abruptly and the Allerød warm period began. It lasted until 12,800 years BP, but was not as warm as the present or the Bølling. However, the rate of warming was very intense ~8° F (~4.5°C) accomplished in as little as a single century.

[4] Inter-Allerød cold period: Near the end of the Allerød warm period (13-14,000 years BP), temperatures dropped precipitously, ~14° F (~8°C) in about a century (Figs. 1, 2) during a time known as the Inter-Allerød cold period (IACP). Temperatures returned to near full Ice Age levels but persisted for only a few hundred years, so glaciers halted their retreat but did not rebuild to former extents. Just as suddenly as it had cooled, the IACP warmed abruptly 9° F (~5°C) and temperatures returned to Allerød levels.

[5] Younger Dryas cold period: 12,800 years ago, temperatures plunged ~14° F (~8°C) to full glacial levels where they remained for 1300 years during the Younger Dryas (YD). Because of the abruptness, intensity, and duration of the cooling, the YD is the best known of the Dansgaard/Oerscher events. Glaciers, including remnants of the huge ice sheets and alpine glaciers, re-advanced, leaving moraines as footprints of their former presence. Temperatures rose sharply, about 21° F (~12° C) 11,500 years ago, marking the end of the Younger Dryas cold period and the end of the Pleistocene Ice Age. Additional details of the YD may be found at http://wattsupwiththat.com/2012/06/19/the-intriguing-problem-of-the-younger-dryaswhat-does-it-mean-and-what-caused-it/

Radiocarbon and isotope dating of glacial moraines in regions all over the world and abrupt changes in oxygen isotope ratios in Greenland and Antarctic ice cores indicate that the Younger Dryas cooling was globally synchronous. Evidence of Younger Dryas advance of continental ice sheets is reported from the Scandinavian ice sheet, the North American Laurentide and Cordilleran ice sheets, and the Russian ice sheet. Alpine and ice cap glaciers also advanced during Younger Dryas cooling in both the Northern and Southern hemispheres, e.g., many places in the Rocky Mts. of the U.S. and Canada, the Cascade Mts. of Washington, the European Alps, the Southern Alps of New Zealand, and the Patagonian Andes Mts. of South America.

Multiple Climatic events within the Younger Dryas

The Younger Dryas cooling was not just a single climatic event. Climatic warming and cooling occurred not only before and after the YD, but significant climate fluctuations also occurred within the YD. That these were global events that occurred in both hemispheres is shown not only by the ice cores of Greenland and Antarctica, but also in glacial deposits of the major, late Pleistocene ice sheets of the world, all of which experienced multiple moraine-building episodes as did alpine glaciers.

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Figure 3. Oxygen isotope record from the Greenland ice core showing an abrupt temperature drop 12,800 years ago, 1,300 years of cool climate, and sudden warming 11,500 years ago. Up on the vertical axis is warmer. (Plotted from data in Cuffy and Clow, 1997 and Alley, 2000)

Figure 3 shows a plot of oxygen isotope variation within the YD. Temperatures fluctuated up and down at least a dozen times, some brief warming periods reaching near-Allerød levels. That these climatic fluctuations were real and global in extent is shown by multiple YD and IACP moraines in the Puget Lowland of Washington, Loch Lomond in the Scottish Highlands, European Alps, Rocky Mts., Alaska, Cascade Range, Andes, New Zealand Alps, and elsewhere.

Magnitude and rate of abrupt climate changes

How do past temperature oscillations compare with recent global warming (1978-1998) or with warming periods over the past millennia? The answer to the question of magnitude and rates of climate change can be found in the δ18O and ice core temperature data (http://wattsupwiththat.com/2011/01/24/easterbrook-on-the-magnitude-of-greenland-gisp2-ice-core-data/).

We can compare the warming and cooling in the past century to approximate 100 year periods in the past 25,000 years (Fig. 4). Not all of the periods noted here are exactly 100 years̶̶—some are slightly more, some are slightly less, but they are close enough to allow comparison of magnitude and rates with the past century.

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Figure 4. Magnitudes of the largest warming/cooling events over the past 25,000 years. Temperatures on the vertical axis are rise or fall of temperatures in about a century. Event number 1 is about 24,000years ago and event number 15 is about 11,000 years old. At least three warming events were 20 to 24 times the magnitude of warming over the past century and four were 6 to 9 times the magnitude of warming over the past century. The magnitude of the only modern warming which might possibly have been caused by CO2. (1978-1998) is insignificant compared to the earlier periods of warming. (Plotted from data in Cuffy and Clow, 1997 and Alley, 2000)

Implications of multiple Younger Dryas and Inter-Allerød climatic fluctuations

The multiple nature of YD moraines in widely separated areas of the world and in both hemispheres indicates that the YD consisted of more than a single climatic event and these occurred virtually simultaneously worldwide. Ice sheets and alpine glaciers were sensitive to the multiple YD phases.

What can we learn from all of this?

(1) The ice core isotope data were hugely significant because they showed that the Younger Dryas, as well as the other late Pleistocene warming and cooling events, could not possibly be caused by human emissions of CO2 because they occurred thousands of years before such emissions had any effect on atmospheric CO2.

(2) The magnitude and intensity of multiple climatic fluctuations has been up to 20 times larger than warming during the past century.

(3) Single events, i.e., volcanic activity or cosmic impacts, cannot have caused the abrupt Dansgaard/Oerscher warming and cooling events because of the multiplicity of warm/cold events over periods of thousands of years.

(4) The absence of a time lag between the N and S Hemisphere glacial fluctuations precludes an oceanic cause and is not consistent with the North Atlantic Deep Ocean Water hypothesis for the cause of the Younger Dryas.

(5) The abruptness of the climate changes and their multiplicity could not have been caused by slow, Croll-Milankovitch orbital forcing, which occurs over many tens of thousands of years. Since fluctuations to and from full glacial climates occurred over short periods of time, clearly a cause other than the Croll-Milankovitch theory is capable of causing the Ice Ages .

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John Tillman

To anyone with an open mind, these data would be dispositive. The effect of CO2 is negligible, and at least so far during recent decades, beneficial.
Thanks!

I’m thinkin’ that if you correct the spelling in the title folks might take the article a little more seriously.
That’s ‘Pleistocene’ not “Pleisitocene”
[Typo fixed, thanks. — mod.]

Lars P.

Typo in the title: pleistocene not pleisitocene

Yet, even today, there are articles in USA Today referencing climate change due to “heat-trapping” CO2. I can only shake my head with wonder. Mother Nature is beautiful and wonderful, but I hope everyone keeps a key fact in mind: she has a nasty temper.

NucEngineer

Could we see these temperature proxies compared with Be-10 in the ice cores over the same period?

Peter Miller

It just goes to demonstrate what we know about what makes our planet’s climate tick is only a tiny fraction of what we do not know.
This is why non-government geologists are the most sceptical group on the planet. Geologists know that climate change is natural and normal and there is not a thing we can do about it.
This is the greatest fear of the Global Warming Industry that people come to realise that climate change is all about natural cycles and has little or nothing to do with the levels of the supposedly evil gas carbon dioxide.
There are ‘tipping points’ in the Earth’s climate as the post clearly illustrates and with our current level of knowledge, we can only make an educated guess as to why they happen.
This post will be considered as a great heresy by followers of the Global Warming cult, as it clearly illustrates the crass stupidity of their beliefs and the irrelevance of their deeply flawed computer models.
What scares me is it suggests the current inter-glacial cycle started longer ago than I originally thought. That means the next ice age is just that much closer. You just can’t mess with natural climate cycles.

tadchem

The oxygen isotope data shows clearly that temperature variations occurred with a frequency on the order of decades, not centuries. This is far too fast for astronomical influences, but not too fast for oceanic current pattern shifts (PDO, AMO, NAO, or ENSO). There are multiple oceanic patterns which seems to shift independently, but which contribute to global climate simultaneously. The patterns are also far too regular in period to be purely stochastic as would be expected from cosmic rays or material bombardments.
The CO2 is just a smoke screen. The real climate drivers are the heterogeneous but fluid thermal ballast masses in the ocean basins.

Kaboom

The next time someone mentions “unprecedented warming”, enthusiastically hit them about the head and shoulders with some Bølling .

Les Johnson

tadchem: Too fast for astronomical influences? Not too fast for GCR, or solar UV changes, both of which have been linked to climate.

rgbatduke

This data should be incredibly troubling to climatologists everywhere, because it makes it very difficult to describe any rational cause to the fluctuations — but one. If the Earth is a near-critical multistable nonlinear system with attractors scattered all over the place in phase space, that would just about do it. Various parameters such as CO_2 and aerosols might well modulate the landscape on which the poincare cycling occurs, causing attractors to appear and disappear, but the data looks just like what one would expect from a system with near-critical feedback being driven by random noise, so that “insignificant” noise events (butterfly wings) can cause actual CLIMATE shifts in fifty or a hundred years. Or the butterfly can flap its wings differently and things appear, for a moment or two, stable.
Well, maybe two. The one variable whose past behavior we cannot speak to with any degree of confidence is the Sun. Orbits are predictable. Precession is predictable. At the moment, however, we cannot predict the sun from one cycle to the next with any great deal of confidence, certainly not for two or three cycles out. We have sparse data here, but the LIA suggests that a century long pause in solar activity is perfectly capable of causing a rapid plunge in global temperatures (to the lowest in the entire Holocene). Similarly, the increase of solar activity to “normal” or even high levels seems correlated with the recent post Dalton warming. The pause in “even” CO_2 linked warming could be connected with the notable drop in solar activity, possibly presaging another Maunder or Dalton type solar minimum.
We cannot rule out “mere” solar variability as being 100% of the cause of the major variations in the curves above, if the Sun varies from its active to inactive phases with a timescale on the order of a few hundred to a few thousand years, and with a fairly random/noisy variation in cycle strength in between. Neither, of course, can we explain it — we have no reliable data, no verified theory of solar state, no verified theory of how solar state might impact global climate at the proposed level.
There is plenty of science remaining to be done here. It is fortunate that at least a few people are willing to do it even though the results are likely to be as welcome to the worshippers of human caused climate disaster as Galileo’s results were to the then-Catholic church.
rgb

Jim Strom

Ice ages scare me a lot more than warm periods. Just as we are now beginning to plan to avert asteroid hits on earth it seems that we should be giving some thought to engineering projects that can stop the planetary threat of an ice age. They would be huge, of course, and CO2 alone doesn’t pack enough of a punch.

@rgbatduke
You should print that comment out and nail it to the front door of the National Academy of Sciences.

Of the conclusions, number 3 is not necessarily correct about impacts, since it assumes that there could only have been one impact event. Current thinking on the YD impact hypothesis leaves the possibility of more than one at the YD onset. Some in the wider community are considering that, with the nature of the Taurid meteor stream, it is possible that impacts may have occurred repeatedly during the YD. Such events – though barely conceivable (and certainly not conceivable within the current geological Gradualism meme) – could conceivably have also occurred late in the Pleistocene. This is all quite speculative at the moment.
For more on the Taurids, google “Napier Taurids.”
Steve Garcia

None of this means CO2 has no warming effect. It just says that it is not the only thing affecting climate. Whether our current era is mostly, moderately, or only slightly affected by CO2 as opposed to other factors is what needs to be determined.
One other point. I went to Wikipedia to look at the Holocene temperature variations. They have an interesting graph which shows multiple proxies that seem to be up and down but then an average that appears somewhat flat and stable. If this post is based on ice core proxies, it might be that drastic temperature changes would smooth out if multiple proxies were used. However, the reverse might also be the case – that the Holocene itself has had more variation than appears in the Wikipedia graph but when you average the good and bad proxies together you get something that looks to be more stable than it really is.

When I started validating the assumptions of the ‘water’ isotopes of the ice cores, nothing made sense. Take for instance the mystery interval (Denton et al 2006), warming during the cooling.
The problem is the misinterpretation of the isotopes in the ice cores. Here is a work in progress on that: https://dl.dropboxusercontent.com/u/22026080/non-calor-sed-umor.pdf
the abstract : “It’s not the heat, it’s the humidity. The isotope paleo thermometer of the ice cores is a proxy for absolute humidity and hence it cannot be used as an accurate reconstruction for paleo temperatures.
In the precipitation cycle, the dew point at which the first condensation takes place, is the main determining factor for the isotope ratios. Together with the Rayleigh process, it controls the actual decline of the isotope ratios (δ18O and δD) in the precipitation during the path of the moist air mass from the source to the ice sheets. The dew point however, is a direct function of the absolute or specific humidity at the moisture source. Therefore isotope reconstructions ,like for instance in Greenland ice cores, should logically be reconstructions of the humidity, rather than the temperature. This explains previously considered anomalies, like warm Younger Dryas Summers and glacial readvances in the USA and Scandinavia during the the Allerød/Older Dryas oscilations, preceding the transition to the Younger Dryas by a substantial margin. This suggest that it was not the Younger Dryas that was cold but the preceding period, which is at odds with the isotope paleo thermometer of the Greenland Ice Cores.”

Ref. Denton, G.H., Broecker, W.S., and Alley, R. B., 2006, The Mystery Interval 17.5 to 14.5 kyrs ago. Pages News 14, 14-16.

rgbatduke
I imagine Leif will be along any moment now.
I think from observations of sun like stars in other solar systems we know that these stars have a somewhat predictable history and, although they vary in small cyclic ways, they do not turn on and off in drastic ways.

Rud Istvan

Dr. Easterbrooks information ought be dispositive on the very large role of natural variability compared to AGW. But it obviously isn’t because most of the information has been available yet AR5 SOD does not substantially modify AR4 conclusions.
Similarly the MWP and LIA should be dispositive on shorter time frames. They haven’t been because of the efforts of folks like Mann and Marcott to essentially disappear them through various statistical manipulations, including the graphical representations in AR3 and AR4.
Hardening up the realities of natural variation could be one of the most effective counterpoints to AGW, given the increasingly obvious failings of the models and the IPCC to predict this century’s temps. A simple two part graphical explanation for the uninitiated: models wrong, climate variation normal.

Mindert Eiting

Thanks. Beautiful post and easy to understand.

milodonharlani

James Cross:
Does variation by a factor of two in higher energy solar spectra v. lower energy within a not that variable TST count as drastic?
How about the variation in solar magnetic flux? Drastic or not?
IMO it doesn’t take much variation in solar radiation & magnetism to effect big swings in Earth’s climate.

milodonharlani

TSI, sorry.

Stephen Richards

Younger Dryas, as well as the other late Pleistocene warming and cooling events, could not possibly be caused by human emissions of CO2.
I’m not sure about the making of this statement. I don’t think it’s necessary.
Dr Brown, many thanks for all your post and this one in particular. You clarity and precision is a great example to the idiots that pervade the world of climate theology.

It look like TSI for sun like stars doesn’t really change that much unless we are talking about millions of years.
I haven’t given up that there is some solar influence but I think there needs to be some major augmentation mechanism.
I think rgbatduke is closer to be on the right track with “near-critical multistable nonlinear system with attractors scattered all over the place in phase space”.

From this excellent and informative article:

About 14,000 years BP, temperatures once again rose abruptly and the Allerød warm period began… However, the rate of warming was very intense ~8° F (~4.5°C) accomplished in as little as a single century.

Compare that 4.5ºC warming over a single century with the extremely mild, 0.8ºC fluctuation over the past century and a half [and which climate alarmists are incessantly arm-waving about]. In reality, the current climate fluctuation is a non-event.
We have truly been living in a “Goldilocks” climate during the past 150 years: not too cold, not too hot — but just right. And, when observed on a normal chart measured in degrees [rather than in tenths or hundredths of a degree], the minor temperature fluctuations are imperceptible.
Natural variability can abruptly change global temperatures by fully tens of degrees, over just a few decades. That has occurred regularly, and during times when CO2 levels were much lower than now — which deconstructs the CO2=AGW conjecture.
There is a good reason why geologists in particular tend to reject CO2 as the failed cause of recent, very minor global warming: geologists know that the planet has routinely experienced very large temperature fluctuations during times when CO2 was very low. Until recently, the biosphere was starved of harmless, beneficial CO2.
Kudos for this excellent article, which puts the current very minuscule temperature fluctuations into a geologic perspective.

Lars P.

From the article:
“These cores are especially important because the ages of the ice at various levels in the core have been measured by counting annual layers in the ice, giving a very accurate chronology of climatic fluctuations determined by measurement of annual layers.”
As complete ignorant of the ice core science, maybe the question is stupid, have these annual layers been confirmed by a different measurement? How sure is that the layer represent 1 year?
James Cross says:
June 2, 2013 at 1:14 pm
It look like TSI for sun like stars doesn’t really change that much unless we are talking about millions of years.
To my understanding not quite so James, please see the below link:
http://www.spaceacademy.net.au/library/guides/varstar/varstar.htm
“THE SUN AS A VARIABLE STAR
The Sun was long thought to be a invariable star, with its total energy output constant.
However, satellite measurements over the last 20 years have shown that it does vary.
There is a 27 day variation in solar output due to its rotation and the presence of dark sunspots and light areas of faculae (this makes it an extrinsic variable).
There is also a longer (~11 year) variation coincident with the sunspot cycle.
The average periodic change in solar luminosity over a decade is about 0.1 %.
Short term variations, due to the appearance of sunspots, may be on the order of a few times 0.1%.
The Sun has also been found to vibrate or oscillate with a period of around 5 minutes (this makes it an intrinsic variable). The brightness variations due to this vibration are very small.
In the 1970’s John Eddy collected evidence that shows that the solar variations have not been constant over timescales of centuries. In particular, the solar 11 year variation seems to have been absent in the latter half of the 17th century (1650 – 1700). The speculation is that it may also have been stronger at other times in history.
The Sun is a G-type star. Now the average G-type star shows a variability of around 4%. The Sun’s variation of only 0.1% is thus atypical. The question is, will it always remain this low, for if it were to rise to 4%, we would experience very large fluctuations in our climate indeed (the supposed current ‘global warming’ would pale into insignificance!).”

Wouldn’t you think that the sharp temp rise at the end of the Younger Dryas should have been a clue to the fact that the Earth can warm at a rapid rate all on it’s own?

Ian W

James Cross says:
June 2, 2013 at 12:19 pm
None of this means CO2 has no warming effect. It just says that it is not the only thing affecting climate. Whether our current era is mostly, moderately, or only slightly affected by CO2 as opposed to other factors is what needs to be determined.

But what it means is that there is now no support for the argument that anthropogenic CO2 is the ONLY possible reason for the unprecedented rise in temperature 1980 – 1998 as the change in temperatures is not unprecedented. And the preceding changes in temperatures exceeded the twenty years at the end of the twentieth century in size and rate and were not linked to anthropogenic CO2 emissions.
Therefore to apportion current atmospheric global warming causality to anthropogenic CO2 there needs to be empirical evidence of a real world atmospheric temperature rise caused by anthropogenic CO2. There is no such evidence. Indeed as the temperatures have remained flat for more than 15 years there is significant evidence to falsify the hypothesis that anthropogenic emissions of CO2 cause global warming.

DesertYote

Its interesting that the upper paleolithic Magdalenian culture managed to survive with all of this climatic variation. Not only did this culture survive, but these people managed to find the time to produce some wonderful pieces of art.

rgbatduke says: June 2, 2013 at 12:03 pm
……….
…… and one more:
Greenland-Scotland ridge where the warm Atlantic and cold Arctic currents meet in narrow passages. The most critical is Denmark Strait which is bottleneck on the superhighway in the oceans global circulation (WHOI).
Denmark Strait is only 600m deep but it has 800m depth of sediments, mostly of volcanic origin. Although the Island’s active volcanoes number just over 1% of the world’s total, it is estimated that they produced more then 30% of the total lava eruption.
Denmark Strait’s deep cold current (North Icelandic Jet) is a key component of the Atlantic Meridional Overturning Circulation (AMOC), also known as the “great ocean conveyor belt,” which is critically important for regulating Earth’s climate.

Ian W.
I largely agree there is evidence that CO2 is not the only possible reason. The fifteen year flatness does indicate that there is more affecting climate than CO2 but it doesn’t prove CO2 has no effect either. I wonder what would constitute evidence for you.
Regarding the sun again, I would hope Leif would put in an appearance. My statement was that TSI does not change much in decadal cycles. Apparently it hasn’t change much since the Maunder minimum either. So I think you need an argumentation mechanism if it is have a larger climatic effect. We can speculate that TSI might decrease or increase more dramatically in the future or maybe has done so in the past but I haven’t seen any evidence of that on hundreds or thousand year time scale. If you have some evidence, please point it out.

Maybe it’s the solar wind cutting in and out.

Don J. Easterbrook

Here are responses to some of the comments above.
NucEngineer says:
“Could we see these temperature proxies compared with Be-10 in the ice cores over the same period?”
The Maunder, Dalton, 1890-1915, and 1945-1977 cold periods all show 10Be spikes, indicating increased 10Be production (i.e., increased cosmic radiation), which reinforces the Svensmark hypothesis.
Les Johnson says:
tadchem: Too fast for astronomical influences? Not too fast for GCR, or solar UV changes, both of which have been linked to climate.
“I said ‘cosmic impacts,’ not ‘astronomical influences.’ A good argument can be made for solar changes.
feet2thefire says:
“Of the conclusions, number 3 is not necessarily correct about impacts, since it assumes that there could only have been one impact event. Current thinking on the YD impact hypothesis leaves the possibility of more than one at the YD onset. Some in the wider community are considering that, with the nature of the Taurid meteor stream, it is possible that impacts may have occurred repeatedly during the YD.”
The number of warming/cooling events is about two dozen over just the period of 11,500 to 15,000 and there are many older ones going back 100,000 years. Where are the impact craters if these were caused by cosmic impacts? They are too young to be erased by erosion.
1. James Cross says:
“One other point. I went to Wikipedia to look at the Holocene temperature variations. They have an interesting graph which shows multiple proxies that seem to be up and down but then an average that appears somewhat flat and stable. If this post is based on ice core proxies, it might be that drastic temperature changes would smooth out if multiple proxies were used. However, the reverse might also be the case – that the Holocene itself has had more variation than appears in the Wikipedia graph but when you average the good and bad proxies together you get something that looks to be more stable than it really is.”
Take a look at the second graph in
http://wattsupwiththat.com/2013/03/08/marcott-et-al-claim-of-unprecedented-warming-compared-to-gisp-ice-core-data/
which shows a lot of temperature changes during the Holocene, but not as profound as the late Pleistocene ones. And yes, if you add a lot of low precision proxies on a composite curve, they will dampen out the details and mask details of the climatic events.
leftturnandre says:
“It’s not the heat, it’s the humidity. The isotope paleo thermometer of the ice cores is a proxy for absolute humidity and hence it cannot be used as an accurate reconstruction for paleo temperatures.”In the precipitation cycle, the dew point at which the first condensation takes place, is the main determining factor for the isotope ratios. Together with the Rayleigh process, it controls the actual decline of the isotope ratios (δ18O and δD) in the precipitation during the path of the moist air mass from the source to the ice sheets. The dew point however, is a direct function of the absolute or specific humidity at the moisture source. Therefore isotope reconstructions ,like for instance in Greenland ice cores, should logically be reconstructions of the humidity, rather than the temperature. This explains previously considered anomalies, like warm Younger Dryas Summers and glacial readvances in the USA and Scandinavia during the the Allerød/Older Dryas oscilations, preceding the transition to the Younger Dryas by a substantial margin. This suggest that it was not the Younger Dryas that was cold but the preceding period, which is at odds with the isotope paleo thermometer of the Greenland Ice Cores.”
The problem with this concept is that the Greenland ice core 18O and temperature reconstructions (see figs 1 and 2) are nearly identical and both match global glacial advances and retreats. You can’t melt much ice by reducing the humidity.
Lars P. says:
From the article:
“These cores are especially important because the ages of the ice at various levels in the core have been measured by counting annual layers in the ice, giving a very accurate chronology of climatic fluctuations determined by measurement of annual layers.”
As complete ignorant of the ice core science, maybe the question is stupid, have these annual layers been confirmed by a different measurement? How sure is that the layer represent 1 year?
The annual layers are recognized by a greater accumulation of dust during the summer ablation period and these are seen from much greater electrical conductivity. They make a very regular pattern and if you add them up for any known climatic event, they match quite nicely.

Stephen Wilde

I think this analysis suggests that the mix of particles and wavelengths from the sun is far more variable than previously thought and linking that to my proposal that such variations alter the vertical temperature profile of the atmosphere provides a possible solution.
By my proposal such changes alter the gradient of tropopause height between equator and poles so as to allow the climate zones and jets to shift latitudinally.
That alters global cloudiness and albedo to change the amount of solar energy able to enter the oceans to fuel the climate system.
It is clear that the temperature changes are tied to isotope changes that reflect solar behaviour so I commend my proposal for further research.
Such a mechanism explains the thermal amplification of solar variations and detaches many of the observed temperature variations from the Milankovitch cycles.
May I have some money and a suitable tenure please ?
A few years ‘working’ in Boulder, Colorado would be nice 🙂

Brian H

Anthony Watts says:
June 2, 2013 at 12:15 pm
@rgbatduke
You should print that comment out and nail it to the front door of the National Academy of Sciences.

Hear, hear!
It’s enough to make multi-thousand-mile diameter solar reflectors look like a reasonable contingency plan. If the CAGW-Agenda 21 cabal(s) don’t hamstring and impoverish the globe as intended, a few decades or a century or so should make the option available.

Brian H

Clarification: ^^space-borne reflectors, of course.

Allencic

Before I retired from my position as a geology prof I often took my students on field trips out to the glacial deposits exposed in gravel pits west of Ann Arbor. In one very large pit (Killins gravel on Scio Church Road) the pit had a two layered aspect. At the bottom was the well washed sand and gravel that was deposited as the Erie Lobe of the Wisconsinian ice sheet had retreated and the meltwater pouring off the front of the ice laid down thick and economically valuable outwash material. Must have been a time of ice retreat and presumably warmer climate. At a later time the ice readvanced over the outwash gravel and laid down a thinner but very obvious layer of clayey glacial till. The climate must have cooled to get the ice to readvance and then the climate changed or stalled and the melting ice lobe dropped it’s load of till (everything from fine clay to crystalline Canadian boulders as big as a car) on top of the outwash deposits. It’s situations like this that always made be dubious of the notion that the climate could only change for the worse because of man’s actions. What could be more natural than climate change.

Don Easterbrook said:
The problem with this concept is that the Greenland ice core 18O and temperature reconstructions (see figs 1 and 2) are nearly identical and both match global glacial advances and retreats. You can’t melt much ice by reducing the humidity.
You show me one glacial readvance or retreats, or other temperature proxies that matches the ice core isotope temperatures during the last glacial transition and I reply with three at a minimum, but maybe some ten or more that contradict them..
Maybe it helps to read the link to get the idea:
https://dl.dropboxusercontent.com/u/22026080/non-calor-sed-umor.pdf

Doug Procttor

Sir –
Data source, excell spreadsheet style?
I’m interested in data density: although the dating may be by annual ice layers, the oxygen-18 and CO2 sampling will not be at that level. Also, CO2 levels are something like 70-year running averages, due to the ice “breathing” during pressure changes before the vertical permeability is at zero (for practical purposes, anyway). Whatever sampling has been done, trend analysis to get the curves as shown has used some other length of time for smoothing: is it two hundred years, or more? And what happens when you smooth a previously “smoothed” data record – what is the setback error you get on the start date of changes?
As for oxygen-18 data: here the data is taken from the water, not the air. The oxygen isotope data is thus “of the moment”, not a 70-year running average. Still, data density is important, especially if it is not equal to that of CO2. The principal smoothing would simply be that appropriate to the data density.
The more smoothing you get, the more “setback” you create in the time of trend change, i.e. you start a decline (or warming) on a graphical display BEFORE the initiating factor of that change. In modern records, you cause a temperature drop 18 months or so before the volcano erupted that caused the temperature drop. I wonder if this has caused at least some of the disconnect between the CO2 and the isotope-temperature trends in the ice-core data.
The problem is dealing with sharp, threshold-type, acute events within a long-term pattern. The data “corrections” that are done should, but typically don’t, take this stop-start condition into account. Statistical breaks don’t work well for the mathematically inclined as they degrade what are supposed to be seen as “continuous” records that bear consistent manipulation or, in their worst fears, are neither continuous nor general: what you really can get from them is the time and events of that spot. Mannian logic doesn’t work that way.
A reference to the digital data would be useful.

How do they calculate the age of the ice?
By counting the annual layers.
If the ice melted back, 1, 2, 3….n, layers during a thaw
How would they know how many layers it had lost.
Maybe this might account for those sheer vertical drops on the graph?

SittingQuietly-ListeningLoudly

Leftturnandre…
I followed your link to a 503 error. I am interested in the notion you propose, but cannot consider the work in question.

Marc

So, relating to the other thread yesterday on the Schmidt/Taleb debate, and then incorporating Rgbatduke’s comments about the near-critical multistable nonlinear system with attractors scattered all over the place in phase space, I would welcome comments on the following:
I read about Taleb’s views on AGW, and his basic admonition is that it is a bad idea to perturb a chaotic complex system since you can’t possibly predict the downstream effects due to the system’s complex chaotic nature.
So he agrees with us that the models are a joke. But he agrees with them on the “precautionary principle” even though for him it is based on the general principle of unpredictable result, and for the CAGWists it is based on their overconfidence in believing they have insight into what will happen.
One question in this context would be — Is our contribution to CO2 enough of a perturbation to have any material downstream effect in the context of Rgbatduke’s near-critical multistable nonlinear system with attractors scattered all over the place in phase space?
Thanks for any perspective the experts might have on this.

wsbriggs

Leftturnandre says:
Good try, but what is the dew point of air at -40 C? -30C? Nice charts, but drawing the lines doesn’t make them real. Below freezing, H2O molecules can aggregate on a surface without forming clouds first. Frozen fog can plate surfaces, but in the case of frozen fog, we can’t really discuss the relative humidity, just the absolute humidity and that’s not homogeneous – you see the ice crystals in the air give the AH function a stepwise look.
Molecular aggregation is likely the source of the O18 in the ice, and claiming that the humidity was a variable is somewhat fanciful. As long as the molecules aggregated in the air, rather than directly on the surface, what is the change?

John West

How many times have we heard the alarmist fall back position: “It’s the rate of warming that’s different and unadaptable to!”
Well, goodbye unprecedented rate hello pretty much normal.
Now if we can just get the alarmists to acknowledge Henry’s Law maybe we won’t have to listen to the next fall back position.

Sabertooth

“Temperatures rose sharply, about 21° F (~12° C) 11,500 years ago, marking the end of the Younger Dryas cold period and the end of the Pleistocene Ice Age.”
I thought it was called the Quaternary Ice Age and I thought it was ongoing, despite the Holocene Interglacial.

Tom G(ologist)

Scientists of all disciplines can run controlled experiments in labs, and they can simulate responses on computer models, but if it does not, or has not happened out in nature, there’s no basis for saying any experimental or theoretical finding is real.
Geology. The proving ground of all sciences. Has what have created/devised/deduced/theorized actually happened in nature? If not, then we are in the realm of technology – or fantasy.
Thanks Dr. P. Always a treat.

Bill Illis

Thanks Dr. Easterbrook,
I’ve tried pointing people to these other events in the record like the Older Dryas, which I would say started at 14,300 years ago and is a bigger downturn than the Younger version.
There are 28 of these swings in the Greenland ice core record over the last ice age, so there is nothing special about the Younger Dryas.
It is a common feature in the Greenland ice cores and in the ice age climate record. (I think it is more just periods of when the glaciers were advancing and then retreating. There needs to be a very strong push of snow accumulation in the centre load points like the one over Hudson Bay to keep the ice age glaciers moving south. When this accumulation slows, the glaciers melt back because the Sun is just far too strong in Central North America in the summer for glaciers to exist, even in the lowest low points in the Milankovitch cycles).
In any event, the climate can change all its own in very short time periods. If you throw the CO2 record from Antarctica over top, we see nothing but conflicting trends with CO2 rising and temperatures falling and visa versa.

JFD

James Cross – There is a lot of evidence, including the halt in global warming observed from 1980 to 1996 for an almost equal period (and still counting) that carbon dioxide emissions from burning fossil fuels are not the root cause of global warming. The evidence that I find points to natural cycles as causing variations in earth’s climate, especially ENSO. For more than 20 years, especially the last 6 years, I have been looking for evidence that carbon dioxide is the root cause of global warming without finding any. Since you seem to believe that carbon dioxide is the root cause, could you please list some specific directly detailed citations that form the basis of your belief that carbon dioxide caused the observed recent global warming?
The global warming discussion is not whether or not the climate has warmed the last 150 years nor the period from 1980 to 1996, but why did it warm? One cannot address corrective actions until one has first correctly identified the problem. Carbon dioxide may have some influence but perhaps not as much as the new water added to the atmosphere from producing fossil aquifers (no or slow to recharge) to irrigate food and fodder. This new water accounts for 2.6 mm per year of increase in ocean levels.

Steve Keohane

Charles Gerard Nelson says: June 2, 2013 at 3:44 pm
How do they calculate the age of the ice?
By counting the annual layers.
If the ice melted back, 1, 2, 3….n, layers during a thaw
How would they know how many layers it had lost.

Check out the temperatures in the graph, all less than -30°C / -22°F.

Ian H

What this shows is that climate is bistable and when slightly cooler than the climate we are now experiencing, can switch between ice age and non ice age conditions very rapidly displaying huge swings in temperature over a short period of time. We should therefore be wary of the possibility of catastrophic sudden cooling should the climate get much cooler than it is today. The climate however does not seem to be susceptible to instability in the other direction. We are unlikely to see sudden extreme warming from today’s temperatures.
This analysis is qualitative not quantitative. However quantitative analysis is not always superior and can hide a multitude of sins. Those who compute a single sensitivity number for climate are misinterpreting the nature of climatic variation.

Of the conclusions, number 3 is not necessarily correct about impacts, since it assumes that there could only have been one impact event. Current thinking on the YD impact hypothesis leaves the possibility of more than one at the YD onset.

YD isn’t anything really special from all the other cooling events going into the Holocene, except it was the last one of them. More importantly, there is some evidence that YD-like events are not unique to this interglacial.

DesertYote

Sabertooth says:
June 2, 2013 at 4:20 pm
“Temperatures rose sharply, about 21° F (~12° C) 11,500 years ago, marking the end of the Younger Dryas cold period and the end of the Pleistocene Ice Age.”
I thought it was called the Quaternary Ice Age and I thought it was ongoing, despite the Holocene Interglacial.
###
You are technically correct, but the usage of the term “Pleistocene Ice Age” is still common. Some things just seem to get entrenched. Personally, I would like to see the Holocene – Pleistocene division disappear altogether, but that’s not about to happen.