Guest post by Steven Goddard
There are still people who insist that changes in CO2 can explain the pattern of glacial and interglacial periods. This article will present several arguments demonstrating that is incorrect, based on the ice core data below.
Click for larger image
The most obvious reason is that CO2 lags temperature. Changes in ocean temperature have driven the changes in atmospheric CO2, as explained here. CO2 is not the driver.
Now consider the earth 20,000 years ago. Temperatures were low – about 8C cooler than the present. Due to the cold ocean temperatures, levels of atmospheric H20 (the primary greenhouse gas) were low. CO2 levels were also low, at about one half current levels. The earth’s albedo was very high due to extensive ice cover which had much of North America and Europe buried in ice. Using the popular “CO2 and feedbacks explain everything” theory, all of these negative feedbacks should have driven earth further and further into an irrecoverable ice age. Cold ocean water should have continued to absorb more CO2 from the atmosphere.
Atmospheric H2O should have continued to decline due to lower vapor pressures over the cooling oceans. Albedo should have continued to increase due to expanding glaciers further from the poles. All of these negative feedbacks should have caused temperatures to decrease further, and the death spiral should have continued. But none of these things happened. Instead, the earth warmed very quickly. CO2 was absolutely not the driver, and positive/negative feedbacks had to be in balance.
Consider the earth 14,000 years ago. CO2 levels were around 200 ppm and temperatures, at 6C below present values, were rising fast. Now consider 30,000 years ago. CO2 levels were also around 200 ppm and temperatures were also about 6C below current levels, yet at that time the earth was cooling. Exactly the same CO2 and temperature levels as 14,000 years ago, but the opposite direction of temperature change. CO2 was not the driver.
Now consider 120,000 years ago. Temperatures were higher than today and CO2 levels were relatively high at 290 ppm. Atmospheric H20 was high, and albedo was low. According to the theorists, earth should have been warming quickly. But it wasn’t – quite the opposite with temperatures cooling very quickly at that time. CO2 was not the driver.
If CO2 levels and the claimed lockstep feedbacks controlled the climate, the climate would be unstable. We would either move to a permanent ice age or turn into Venus. Warmer temperatures generate more CO2. Increased CO2 raises temperatures. Warmer temperatures generate more CO2 …… etc. It would be impossible to reverse a warming or cooling trend without a major external event. Obviously this has not happened.
An exercise to get people thinking for themselves. If the temperature at some point in the past was 4C cooler than now and CO2 levels were 240 ppm, was the temperature going up or down? There are ten points on the graph that match those conditions. Half of them have rapidly rising temperatures and half have rapidly falling temperatures. It becomes abundantly clear that there has to be another degree of freedom which is dominant in controlling the glacial cycles.
In the ice core record, temperature drives CO2 – not the other way around. Sometimes the earth warms quickly at 180 ppm CO2. Other times it cools quickly at 280 ppm CO2. Again, CO2 is not the driver of glacial cycles – there has to be a different cause.
UPDATE:
The use of the term “negative feedback” in this article is the commonly understood meaning – i.e. feedbacks that drive temperature down. Technically speaking, this usage is incorrect. From a viewpoint of semantics, a negative feedback would be one that works against the current trend. This semantic difference has no relevance to the logic being presented in the article.
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Steve,
Who are these people “who insist that changes in CO2 can explain the pattern of glacial and interglacial periods”? I don’t think they include any regular climate scientists that I know of. There is a view that CO2 provides positive feedback to a change already under way.
“Atmospheric H2O should have continued to decline due to lower vapor pressures over the cooling oceans. Albedo should have continued to increase due to expanding glaciers further from the poles. All of these negative feedbacks should have caused temperatures to decrease further…”
Ummm. Those are positive feedback mechanisms. The feedback signum refers to effect on signal amplitude, not the direction the signal changes.
Way to not read carefully.
Nick Stokes,
Are you asking a serious question? The giant ice core graph was the centerpiece of Al Gore’s movie – in a clear, deliberate, unambiguous attempt to convince the audience that CO2 drives temperature cycles. Nearly every schoolchild in the world has been taught this concept.
Nick Stokes (21:58:40) :
Steve,
Who are these people “who insist that changes in CO2 can explain the pattern of glacial and interglacial periods”?
http://www.sciencemag.org/cgi/content/abstract/289/5486/1897
“Hence, the 100,000-year cycle does not arise from ice sheet dynamics; instead, it is probably the response of the global carbon cycle that generates the eccentricity signal by causing changes in atmospheric carbon dioxide concentration.”
My comment is bascially the same as Nicks. All of the science that I have read says that sun cyles drive the long term glacial cycles and that CO2 provides a positve feedback during the warming periods. It’s not just the simple solubility of CO2 in the oceans. Warming increases rates of bacterial degredation on land and in water, as well as making stronger thermal statification in the oceans. Thus, warming can lead to less CO2 burial in the ocean and more CO2 release from soils. Right now the tundra is a major reservoir of organic carbon. If warming and melting continue, releases from this source will increase.
Of course there aren’t any of these people
This is just a way of trying to give the simple minds among the readers here the impression that there actually is people in the “AGW camp”, the “Alarmists”, “Climate hysterics” or whaetever, that holds this view.
“Science Blog of the year” – Yeah, right!
REPLY: Actually, you got the title wrong. If you are going to criticize, at least do it correctly. – moderator
What is clear from the ice core data is two fold
1. Carbon dioxide trails temperature and so can not be the primary cause as it would violate causality.
2. The idea that temperature increase releases carbon dioxide is reasonable but the second part that this amplifies the signal is clearly not supported by the data in fact the shape and timings of the peaks and cooling portions of the graph falsify this hypothesis as well.
I see reason to think carbon dioxide should help warming however the ice core data really doesn’t support it.
It’s a mystery why we do not get runaway warming or cooling (to a stable state) in the glacial/interglacial cycles.
Something stops and then reverses the warming and cooling on a regular 100,000 year cycle. Although, the length of that cycle changed from about 50,000 years to a 100,000 years around a half million years ago.
Milankovic Cycles have been proposed as the cause, but several problems exist with this (proposed) cause.
http://en.wikipedia.org/wiki/Milankovitch_cycles#Problems
BTW, the CO2 as feedback theory is nonsense.
CO2 declines approximately linearly over the glacial phase of the cycle of about 80,000 years. And similarly it increases approximately linearly over the interglacial. This means CO2 will act as a negative forcing for about half of the time and most crucially for the first half of the glacial/interglacial period (when the two are averaged together).
So rather than being a positive feedback, CO2 is forcing the temperature in the opposite direction to whatever is causing the warming and cooling glacial cycle for the first half of the cycle.
In fact, if one were to ignore (the rather flimsy) evidence that increased CO2 causes warming and decreased CO2 causes cooling, CO2 looks to be a good candidate for driving the glacial cycle. Increasing CO2 progressively cools the climate, eventually overwhelming other positive feedbacks. Ditto for warming.
Steven
Yes, it’s a serious question. Gore showed the plot, as many have done. His main point was that CO2 is now at a higher level than it was during that period. I don’t see anywhere where he said (let alone insisted) that it drove glacial cycles.
It is quite amusing seeing AGW defenders scrambling to claim that “no one believes” CO2 is the driver. It was the AGW camp who attempted to use the ice cores to prove their case, and now they are disavowing any knowledge.
Al Gore stood in front of the giant Vostok Graph in his movie and said “there is one relationship that is far more powerful than all the others and it is this. When there is more carbon dioxide, the temperature gets warmer, because it traps more heat from the sun inside. “
Has he issued a retraction to the hundreds of millions of people who saw the film and believe what he said?
According to the story at this link …
http://www.telegraph.co.uk/earth/environment/climatechange/4734859/Scientists-capture-dramatic-footage-of–Arctic-glaciers-melting-in-hours.html
… we don’t have to worry as the glaciers have just about disappeared already.
REPLY: The title of that video is: ” Scientists capture dramatic footage of Arctic glaciers melting in hours”
I watched the video to the end. What utter unmitigated rubbish. First it was shot and edited like a TV reality show. Second there was no before and after proof in the video imagery showing “a” glacier let alone “glaciers” melting in entirety within a hours, or even days. It’s nothing more than video showing something that happens regularly on glaciers and icefields with seasonal changes. They melt, water runs under them to the base. It is called a “moulin”. Unfortunately many will be drawn in by the slick editing and the danger faced by the intrepid scientists dangling over the abyss. Oh the danger, what brave scientists! Except, other than take a water speed measurement, there was no science in that video, just antics for the camera.
A moulin is nothing new. Admiral (then Lieutenant ) Peary reported on it back in 1897 in the Journal of Geology. Read here.
– Anthony
Molon,
You are technically correct about the use of the term “negative feedback” but most people associate the term “negative feedback” with feedbacks which drive temperatures downward, and associate the term “positive feedback” with feedback that drives temperatures upwards.
I don’t see anyone disputing the logic of the article – so can I take it that the AGW camp agrees that Al Gore’s film was misleading?
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Steven,
If you want to establish your point, you only need to name those who believe that, and quote what they say. Your quote from Gore is just a standard, if a bit oversimplified, statement of the greenhouse effect. It’s not saying CO2 drives glacial cycles.
Steven,
Well done.
I’ve observed over the last several years that very few day-to-day climate change believers, whether strident AGW alarmists or just every day citizens who read papers and watch TV, have any comprehension of the real scientific issues that come into play in a discussion of what climate change is, has been or could be. One of my policy friends questioned me the other day whether we had ANY data, before satellites, to support contentions of medieval warming, the mini ice age or solar cycles going back 250 years. Another penned an email asking whether it was true that its getting cooler, not warmer, and what proof exists. Apparently this person had been exposed to someone who indicated that predicted higher temperatures were not occurring. These are highly educated people who populate high corporate and government public positions responsible for implementing climate change policies, who don’t have a clue about what constitutes climate change. These are people who accept a public consensus that climate change will lead to a host of unimaginably horrible things related to an ever warming planet caused by human waste and avarice, They don’t yet realize that the current CC movement is fueled by a global political – economic ideology, not scientific concern. Its amazing, but our entire national public policy apparatus is now focused on saving us from supposedly increasing global temperatures when our true public policy risk is abrupt cooling and the utter havoc that will cause.
Your post is aimed at scientifically minded individuals familiar with glacial and interglacial cycles. I love it. Though I’m tempted to share your observations (and questions) with the people I cited above, to help educate them regarding the utter lack of scientific justification for our current craze, I hesitate because my fellow day-to-day climate change policy executives have no background to appreciate your observations and the implication of your logic. They have no conception that the IPCC reports are based on a “what if” premise of CO2 causation, rather than a scientifically based conclusion to a legitimate question about what was responsible for late 20th century warming.
So, I take my hat off to you for your clearly written and well thought out post. But I offer the observation that those who understand your work are either part of the choir or, if not, understand that the well educated policy executives in high corporate and public policy positions responsible for implementing new climate change policies have no way to process this information and will not be affected by it. Over the last several years I have identified only three or four individuals, out of the many who populate high corporate and government policy positions, who could appreciate your work. How sad.
Nick,
Al Gore’s claim is incorrect “there is one relationship that is far more powerful than all the others and it is this. When there is more carbon dioxide, the temperature gets warmer”
The Vostok data (which he was standing in front of at the time) disproves his point. 120,000 years ago, CO2 levels were high and temperatures were cooling rapidly. 14,000 years ago, CO2 levels were low and temperatures were increasing rapidly.
The Vostok data shows unequivocally that you can not make any prediction about the direction which temperatures are moving, based solely on the amount of CO2 in the atmosphere. Al Gore was wrong and has misled hundreds of millions of people. Still, he gets invited to give keynote speeches at AAAS.
And let us not forget that during the Ordovician, CO2 levels were 10X current values, and earth had an ice age.
Nick Stokes, the reasonable face of AGW pedantry; it is disingenuous to claim that a lack of CO2 doesn’t cause the ice-ages when AGW is premised on the hypothesis/fairy-tale that CO2 increases cause the opposite of the ice-ages; Arrhenius, who certainly thought a lack of CO2 would ice things up, is quoted with approval in Weart’s classic dystopic piece, “A Saturated Gassy Argument”;
http://www.realclimate.org/index.php/archives/2007/06/a-saturated-gassy-argument/
Keep trying Nick, you may stumble onto something consistent in AGW eventually, even if it is the R2 correlation between CO2 increase and Gore’s increasing wealth.
Now let us focus on the other half of Al Gore’s statement.
“there is one relationship that is far more powerful than all the others and it is this. When there is more carbon dioxide, the temperature gets warmer”
The Vostok data again proves that is incorrect. The most powerful driver has to be something else besides CO2, because whatever is driving the glacial cycles has to overcome and reverse CO2 feedback, as well as H2O, albedo and other feedbacks – all of which are working against a reversal.
Whatever drives glacial cycles must be a very strong force, and it is not CO2.
Steven: “There are still people who insist that changes in CO2 can explain the pattern of glacial and interglacial periods.”
This sentence is badly worded. It appears to be claiming that some people regard CO2 as the sole or primary driver of both glacial and interglacial periods.
It’s not clear who these “people” are, but the standard understanding of the change from a glacial to an interglacial period is that CO2 acts as feedback to a process – perhaps a change in the earth’s orbit — that sets off the initial warming that occurs at the end of an ice age.
http://www.realclimate.org/index.php/archives/2007/04/the-lag-between-temp-and-co2/langswitch_lang/in
If you are arguing that CO2 was not the primary driver of past glacial/interglacial cycles, then you are in agreement with standard AGW theory. The difference between the glacial/interglacial periods and now are:
1) We are not currently emerging from an ice age, and;
2) CO2 is now considered to be acting as a forcing, not a feedback.
Steven,
Gore did precede the quote you’ve given with the caveat “The relationship is very complicated.” And he went on to make a point that, in the context, was overly simplistic. But this falls a long way short of demonstrating your claim that: :There are still people who insist that changes in CO2 can explain the pattern of glacial and interglacial periods.”
Mike Ramsay pointed to a 2000 Science article which does come close to making that claim. Although that is not so long ago, the author clearly was not aware of data showing the phase sequence of heating and CO2 rise – his claim is that both preceded ice volume changes. The IPCC AR3 in 2001 did say that CO2 lagged temperature, which pretty much settled this issue.
You may want to check on what Leif has been saying on various threads here. His field is solar astronomy and he seems to be able to argue convincingly that solar variability doesn’t match the record either.
It isn’t that we know why the climate is varying, I am just darn tired of being told that we do. Things like “an inconvenient truth” do significant harm to science as a whole and as a result to society.
Hi Nick,
Maybe you could add your thoughts on what does drive the Glacial Cycles to support your viewpoint. If you don’t believe it’s CO2 then you would be more aligned with Steve’s post than with the AGW camp !
CO2 is a trace gas, the Atmospheric (incorrectly coined Greenhouse) Effect is not about infared this or that or insulation. It is about boundaries of convective zones (mass) of fluid. AGW violates what we understand of thermodynamics.
How the physics of this whole area of study was supplanted with politics is a ‘case study’ in a sociology class.
Whether that is science or not is another debate.
As far as interglacials and glaciations go … how many people out there understand that we are at the end of an interglacial in what could be called a long ‘ice age’ and it could end at any time like it did many times in the Vostok record. My guess is we have a millenium before the Milankovitch cycle takes over. Not very long considering it took us this whole interglacial for mankind to start hitting his stride. We will need a few centuries like the 20th, in terms of technological development, to deal with evacuating most of North America, Europe, and Northern Asia. Evacuate may be the operative term given that some evidence, even this graph, indicates the onset can be very quick … even a decade. Now that would be a good ‘what if’ for a sociology class.
One need to be cautious with drivers and feedbacks…
Theoretically, there is a positive feedback of CO2 on temperature, as good as ice sheets and vegetation albedo changes are positive feedbacks on some inititial temperature change. To avoid any confusion: a positive feedback strengthens the initial change in the same direction, be it up or down.
Does that mean that a positive feedback always lead to a runaway process? That depends of the feedback factor: As long as the feedback effect is smaller than the original forcing (feedback factor smaller than one), there is no runaway, but only a higher response than from the original cause alone.
Is there a positive feedback of CO2 on temperature measured in the Vostok (or other) ice core(s)? No. Even a 40 ppmv drop at the end of the Eemian (the previous warmer (than current) period doesn’t show a measurable decrease of temperature, while a 3°C/2xCO2 should cause a drop of 0.5°C, according to current models:
http://www.ferdinand-engelbeen.be/klimaat/eemian.html
Temperatures (and methane) are already at minimum and ice sheets again at maximum when CO2 starts to drop, without measurable effect on temperature.
The same is true for the warming from the LGM to the Holocene: There is a clear influence of temperature on CO2 levels, but no measurable influence of CO2 on temperature, as one should expect if CO2 is an important feedback:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/epica5.gif
With thanks to André van den Berg, who provided the graph.
Thus all together, the least one can say is that even if CO2 forms a positive feedback, that is not measurable in the ice cores and far overblown in current GCM’s…
I see no reason to single out Al Gore or even James Hansen. A vast army of people believe that CO2 forces global temperature increases. The CO2 Believers are planning “the largest mass civil disobedience for the climate in U.S. history” on March 2 in Washington DC. The Obama Administration is thick with such folks. It’s hard to find any politician that doubts that CO2 drives global temperature.
And yet the ice record clearly shows that CO2 does not force global temps up or down. Temps fell when CO2 was high, and rose when CO2 was low, and vice versa. That factoid has been demonstrated numerously at WUWT (my personal favorite was the post by Frank Lansner last month).
http://wattsupwiththat.com/2009/01/30/co2-temperatures-and-ice-ages/
I know it flies in the face of The Consensus, but increased CO2 over the last ten years has been accompanied by falling global temperatures. Ipso facto, that theory is wrong. The ice record confirms that CO2 as the climate forcing GHG is bunkum, and in fact throws the entire GHG as a forcer of climate change into question, regardless of whichever GHG we’re talking about.
It does no good, I know, to tell True Believers that the seas are NOT going to boil. Some folks are deeply invested emotionally as well as financially into the End of Creation hysteria. But I tell them anyway, not to bum their trip but out of a slim hope that logic will cure their madness.
A few notes on the previous interglacial 120,000 years ago:
The CO2 level was actually a bit higher than 290 ppm see:
http://www.geol.lu.se/personal/MSR/bjerknes.pdf or:
http://www.geol.lu.se/PERSONAL/DNH/images/RUN2005.pdf
The ice-core record smooths out the short-term changes during the interglacials, and is probably systematically low at least during interglacials (stomatal index measurement give consistently higher results during the Holocene too) .
The temperatures in northern Siberia were MUCH higher than today (on the order of 10 degrees centigrade) and forest extented to the Arctic coast, but no noticeable CH4 release resulted, nor did it during earlier warm interglacials. This strongly suggests that this particular feedback is imaginary.
About the Ordovician glaciation. Not only did it occur at a time of much higher CO2 levels, it may well have been the most severe during the Cenozoic. It is the only glaciation to have caused a mass extinction.
Also the cyclicity of glacial/interglacial is a crucial point. The ice ages are driven by 3 interacting astronomical variables.
1.These are the variation of the earth’s orbital eccentricity. The eccentricity varies between 0 , a perfect circle, and 0.1, at these times the earth sun distance varies between 88 and 98 million miles. Cycle length = 100,000 years
2. Axial inclination , this is currently 23.5 degrees, but can vary between 22.5 and 24.5, cycle length = 41,000 years.
3. Precession of the equinox, this is the variation of the seasons compared with the calender. i.e. in the NH summer solstice occurs in June, but in 13,250 years time NH summer solstice occurs in December. Cycle length = 26,500 years.
An Ice age will happen when the above parameters cause reduced solar heating in the NH summer. Permanenet Snow and Ice moves south , increasing the earth’s albedo. This positive feedback continues to reduce temperature until the ice covers all of Canada, the Northern part of USA large parts of Europe. Typically the average temperature is 5 degrees below what we see today.
Ice ages are a lot easier to start than to end. The is why glacial/interglacial times spans are typically 100,000/20,000 years.
To end an Ice age the sun would have to a maximum heating effect to melt the Ice and reduce the albedo. To do this the axial inclination would have to be near 24.5 degrees, NH summer solstice sun distance near to the minimum of 88 million miles.
2 other points.
Ice ages are a NH only, antartica has little or no influence on this.
Carbon dioxide varies during Ice ages, but is not the driver.
Mike Ramsey (22:34:44)
Your selective quoting of a sigle sentence of Shackleton (2002) misrepresents the theme of the article. Shackleton and the science of 2000 in general recognised the dominant role of Milankovitch cycles as the primary drivers of ice age glacial-interglacial cycles. The question was what factor(s) amplify the rather puny changes arising from variations in insolation due to changes in orbital eccentricity.
A previous study (Imbrie) had proposed that the temporally primary amplification was ice sheet dynamics (albedo feedbacks). Shackleton (the paper you linked to) analyzed deep sea sediments and the new glacial core records to infer a phasing of drivers (Milankovitch orbital eccentricity) and amplifiers (CO2; ice sheet albedo responses) and concluded that the primary amplifier of the weak orbital eccentricity was CO2 rises in advance of albedo effects through ice sheet dynamics.
So Shackleton (2000) can’t really be “recruited” to support the straw man “argument” of the top post. Then as now, the evidence supports CO2 and albedo effects as the primary amplifiers of the orbital variations that drive the ice age cycles (we’d probably reinstate ice age dynamics a little more prominently nowadays since we have a better handle on the relative timings of responses now).
Nicholas J. Shackleton (2000) The 100,000-Year Ice-Age Cycle Identified and Found to Lag Temperature, Carbon Dioxide, and Orbital Eccentricity Science 289, 1897 – 1902
How strong is the evidence that the orbital cycles people keep mentioning are in fact the cause of the glacial cycles? I only ask this because until a few months ago I was convinced they could, now… not so much. We need an explanation for the glaciations ending is the problem, if we haven’t got that we haven’t got much.