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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If CO2 doesn’t drive climate change, then what’s the point?
Nick Stokes (02:00:26) :
That’s absurd. Amplification is exactly what feedback (and its sign) is about. From Wiki:
Negative feedback feeds part of a system’s output, inverted, into the system’s input; generally with the result that fluctuations are attenuated.
In contrast, positive feedback is a feedback in which the system responds in the same direction as the perturbation, resulting in amplification of the original signal instead of stabilizing the signal.
Unlike you, I learned my control theory from a textbook and many, many hours of study towards a few degrees, not Wikipedia. “Positive” and “negative” refer to the sign applied to the feedback term, nothing more, Nick. Try not to be so ignorant of the facts and re-read that quote, in particular the part that says “Negative feedback feeds the part of a system’s output, inverted,…” In other words, NEGATIVE means the feedback is INVERTED, or in simpler terms, negated.
Get off your collective high horses. You guys really do not understand these concepts.
Mark
Oh, and, btw, if you would care to get into a discussion of the gain of a system we can go there too. For a simple single pole system:
y(n) = x(n) + ay(n-1)
the transfer function for a positive results in a gain of 1/(1-a) for lowpass signals. Test #1: figure out why. For a negative, the gains works out to be 1/(1-a) for highpass signals. Test #2: figure out why. Both have gain and attenuation, but it is frequency dependent.
That’s what happens when you read the Wiki and think you understand what is, to any engineer, basic concepts.
Mark
“results in a gain of 1/(1-a) ”
This is true whether a is positive or negative (which determines whether the feedback is positive or negative). In your system, the open loop gain is 1. And if a is negative the gain is less than 1 (attenuated); if a is positive but less than 1, the gain is greater than 1 (amplified). Exactly what Wiki, Simon and I are saying. And if you want to introduce frequency dependence, the phase shift just makes a complex, but doesn’t really change the principle.
BTW, I did not learn these ideas from Wiki. I have a PhD in mathematical control theory.
I should add, a must be less than unity for stability.
Mark
Mark T (07:41:51)
Mark you have to be a little careful applying words definitions and concepts from one scientific field (control theory in engineering for example) to another (climate; Earth’s energy “budget”) where the meanings of words may not be exactly the same.
In fact control theory, while an excellent subject, is not the most appropriate analogy for addressing the Earth’s energy budget arising from changes in forcings, since this doesn’t really contain predominant elements of “control”. In fact, the effects of changes in forcings is probably best understood in relation to changes in the equilibrium temperature that results from changes in the forcings with amplifications due to feedbacks.
So, for example, any enhanced atmospheric warming (from enhanced solar irradiation, for example, or enhanced greenhouse gas concentrations) results in a water vapour feedback that can be expressed mathematically to give a total response that is similar to the form of the equation you posted:
e.g. If the solar change (or enhanced greenhouse forcing) results in a 1 oC change, and the resulting water vapour feedback adds an additional x of additional warming then the total warming from the primary forcing (enhanced solar or greenhouse) + water vapour feedback is something like 1 + x + x^2 + x^3 + x^4 …
which is 1/(1-x).
The result is an amplification of the effect of the primary forcing and the shift of the earth’s equilibrium temperature to a new (higher) value. Obviously the water vapour feedback doesn’t “feedback” to affect the solar forcing (it does have a slight “engineering style” feedback into the CO2 forcing since enhanced warming recruits a small amount of additional CO2 from ocean/terrestrial sources).
One can add in albedo feedbacks which are also positive feedbacks. These will result in an enhanced amplification of the temperature response to the primary forcing, whether in a warming or cooling direction. One needs also to consider the extent to which the various feedbacks (amplifications) are, or are not, effectively self-limiting. For example the albedo feedback may be dominated by the retreat (in a warming world) of sea ice, but once the ice retreats back to the continental margin, the contribution of the albedo feedback will wane.
In short the use of the term “feedback” must be considered in relation to the subject at hand. We are interested in the thing and not the word that may be used to describe it!
Are there ice core plots of Methane and temp?
“Are there ice core plots of Methane and temp?”
Try
http://www.exploratorium.edu/climate/cryosphere/data2.html
If memory serves, methane responds more quickly to the temperature change than CO2 but also lags the temp.
OT but intresting: an article about 385 million year old tree fossils. Next-to-last paragraph:
This was also a significant moment in the history of the planet. The rise of the forests removed a lot of Carbon Dioxide from the atmosphere. This caused temperatures to drop and the planet became very similar to its present-day condition.”
Link: http://www.sciencedaily.com/releases/2007/04/070418130435.htm
foinavon:
I understand the climate science perversion of the word, and it stems from a lack of understanding of basic control theory, whether they are consistent or not. However, I was directly addressing Nick’s assertion which was in direct reference to the control theory use of the word feedback, which he clearly misread (he chided me for saying negative referred to the sign of the feedback term, yet failed to notice that the Wiki quote actually agreed with me!).
As to the rest of what you state, it is immaterial to my point (and quite frankly, not in contradiction to what I said, either). Control theory still applies, even if they (climate scientists) do not use it correctly. As I noted, it is frequency dependent. Their perverted used of the term is actually correct if the proper frequencies are noted (which depends upon the delay in the feedback path). To date, I have not seen anyone that quotes the Wikipedia article demonstrate a clear understanding of this, however.
And, I disagree that the term “feedback” must be considered in relation to the subject at hand, or at least, that the subject is not at least fundamentally still control theory at its heart. Terminology is invented so that people that understand the theory are able to communicate with each other. I understand that there is no “control” in this particular system (though any self-regulating systems has some measure of “control”), but that does not mean that the analysis methods and terminology does not apply.
Mark
“he chided me for saying negative referred to the sign of the feedback term” Really? Where?
As I said above, frequency dependence does not change the basic properties of positive/negative feedback. In your expression the gain is 1/(1-a). Taking account of phase shift (so a is complex), it’s still the case that if the real part of a is negative, the absolute value (magnitude) of gain is less than one; conversely, if the real part is positive (but less than 1) the absolute value of gain is positive.
I don’t see how climate scientists are getting this wrong. In fact, there’s an earlier comment on this thread by Bill Illis criticising a recent Hansen paper in which he continues to carefully examine the lags in the feedback response.
Um, no, a is not complex, a is a constant in my example. Again, you express your ignorance of the subject matter.
Sorry, but you are completely off base when you say “frequency dependence does not change the basic properties of positive/negative feedback.” Look up the phrase “bode analysis.” While you’re at it, perform a frequency response of these two equations, one positive and one negative:
y(n) = x(n) + 0.9*y(n-1),
y(n) = x(n) – 0.9*y(n-1)
clearly frequency matters, contrary to your ill-informed opinion. Shall I post plots of the responses? When you mention 1/(1-a) and then apply +/- a to the gain you are doing it incorrectly. 1/(1-|a|) is actually the result (sorry if that was not clear), in one case at DC in the other at higher frequencies (depends upon the delay element in your equation).
I don’t see how climate scientists are getting this wrong.
Because YOU don’t understand. Listen, Nick, you know yourself that you don’t have a background in this, yet you continue to argue it from a position of ignorance, why?
Mark
Constant a would imply a linear feedback, i.e., a constant slope. A logarithmic response would show up as a slowly decreasing value for a, approaching zero, or no more feedback.
Mark
Mark,
I’ve been reluctant to get into this juvenile casting of aspersions on knowledge and qualification (particularly inappropriate here) but it’s hard to avoid. Your original disparagement of Simon was contradicted by explicit quotes from Wikipedia. And this is standard undergrad stuff where Wiki errors won’t last long. You keep bizarrely misquoting me – I still don’t get the negative chiding, and I didn’t say frequency doesn’t matter.
Then you come up with something like this: gain is 1/(1-|a|). That just shows complete lack of understanding. The sign (pos or neg) of the feedback is the sign of a. This expression says that the gain is the same whether a is pos or neg. That may be in line with your original assertion, but it’s absurd. It says that feedback always increases gain.
ps I don’t have a problem with your use of a discrete example.
I should point out that the equations above would need to be generalized into continuous time variables rather than discrete. It’s just easier to visualize using discrete equations. Discretization merely causes the “spectrum” of the analysis to repeat at intervals of the sampling period.
Mark
Steve’s thesis, that CO2 does not force (initiate) glaciation cycles, stands. That is, changes in CO2 have not caused changes between glacial and interglacial periods.
So this at least limits the power of CO2 to change climate. And one cannot use the glaciation history to “Prove” the power of CO2.
All of this, by itself, does not disprove AGW. But it is up to the AGW proponents to prove their theory, it is not the burden of anyone else to disprove AGW unless it was previously considered proven.
Steve’s thesis as you have stated it has been the accepted science for at least 30 years, so that’s hardly new news.
And, what one can do is use the glacial – interglacial cycles to estimate the climate sensitivity, i.e., the global temperature response to a given change in forcings. And, what one finds if one adds up all of the forcings and compares it to the estimated temperature change, then one gets a result of 3/4 +-1/4 C / (W/m^2). [FYI, this calculation also tells us that about 1/3 of the temperature change between the glacial and interglacial cycles is due to changes in CO2 levels…with maybe another 10% due to the other greenhouse gases and most of the result due to the change in albedo due to changes in ice sheets and vegetation.]
Since doubling CO2 creates ~4 W/m^2 of forcing, that corresponds to a climate sensitivity of between 2 and 4 C for a doubling of CO2.
And, as Hansen has pointed out, this calculation counts albedo changes due to ice sheet expansion or contraction as a forcing, not a feedback. In our current “experiment” where we are increasing CO2, these will act as a feedback, which will tend to further increase the climate sensitivity…although there is some debate about how much and how quickly these feedbacks will act.
Joel Shore
“Since doubling CO2 creates ~4 W/m^2 of forcing, that corresponds to a climate sensitivity of between 2 and 4 C for a doubling of CO2.”
and then there’s this
http://www.john-daly.com/artifact.htm
The conclusion of this research was
“the absorption is 0.054 W/m2 – and not 4.3 W/m2.
This is roughly 80 times less than IPCC’s radiative forcing.”
I understand enough chemistry to understand that the bottom line is that the absorption spectrum of CO2 is already saturated. All radiation in these frequencies is absorbed within 10 m of the Earth’s surface. No amount of CO2 can absorb frequencies that have already been extinguished. In other words, all the energy that CO2 can possibly absorb is already being absorbed.
“And, as Hansen has pointed out, this calculation counts albedo changes due to ice sheet expansion or contraction as a forcing, not a feedback.”
Seriously, I don’t understand…does that mean it counts more than it would as a feedback?…less?….the same? Is it counted in the 4.3 w/m2?
It looks as if that 4.3w/m2 needs a little propping up or something. Maybe some Red Bull.
Jeff Alberts (09:49:16) :
Are there ice core plots of Methane and temp?
My post above – thefordprefect (17:22:56) – contains links to plots of most ice age entries/exits with ch4 and co2 levels fom epica ice cores. The same core data has dust values which will also affect ice age. These are available but not plotted above.
Mike
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”
It is an all too prevalent misconception that albedo alone will effect the temperature of a radiantly heated ball . I recently implemented the basic Stefan-Boltzmann equation for gray balls and only differences in albedo towards and away from sources of heat make any difference . See http://cosy.com/Science/TemperatureOfGrayBalls.htm .
Bob,
I think that the source of your confusion is that you are assuming that the same emissivity should be used for both absorption and emission. However, these occur at very different wavelengths (i.e., the solar radiation is strongly weighted in the visible and near ultraviolet and infrared whereas the earth’s emission is in the far infrared) and hence that is not the case.
As a general hint, if you find yourself in disagreement with well-settled science, rather than immediately questioning the science you should first question your own understanding.
@Steven Goddard
I have now checked EPICA Vostok and Fuji data. All seem to show that exit from low temp period is co-incident with CO2 increase.
EPICA and Vostok also have dust data. In general the increases in temperature are at a similar time to reduction in dust. However, CO2 increase is better synchronised to temp increase.
You claim that there is no synchronicity between CO2 and Temperature. So I was wondering if you are using the same data as me. Could you give a link to the data you are using please?
Have you checked the plots I made (see post above – thefordprefect (17:22:56) ) from data at this location http://www.ncdc.noaa.gov/paleo/icecore/antarctica/domec/domec_epica_data.html
EPICA Dome C Ice Core Data is more detailed and longer than the Vostok data that I could find. Would you agree that CO2 seems to drive the exit from a cold period?
Mike
Mike,
As I said above, there’s fairly widespread agreement now that CO2 does not look like an Ice Age initiator, partly because of its lagging phase. It was never part of the AGW argument that CO2 would be responsible, although since the cause of Ice Ages has not been clear, people have looked at it. Sec 2.4.1 of the AR3 2001 summarises the evidence at that time – there is more now. They say, for example:
Prefect,
I said nothing of the sort. What I said is that there is no correlation between CO2 levels and the direction which the temperature is moving. It is trivial to prove this. Pick any CO2 level on the ice core graph and count how many times that level correlated to downwards and upwards movements in temperature. You will find that the two quantities are equal, meaning there is 0% correlation between CO2 level and the temperature trend.
If you are going to comment, please take the time to read what I said more carefully.
Steven Goddard (21:15:12) :
Apologies for not understanding you report.
But now you have really confused me with your statement above.
1). Do you mean that if you chose a CO2 level that occurs when the temperature is changing there are as many positive temperature transitions as negativ? – But surely mathematically there must always be as many positive transitions as negative?
2). Or do you mean that if CO2 is increasing and is at a particular % it is as likely to be cooling as warming?
3). Or do you mean that when CO2 is –
above x% it is as often cold as hot
below x% it is as often hot as cold
If you mean the latter I will have a look at my EPICA results tonight and see if there is a transition CO2 level at which cold is prevalent
Mike
Prefect,
If the climate is cyclical, then there will be an equal number of rising and falling transitions. The claim from Hansen, Gore etc. is that the climate has reached a “tipping point” where it is moving exponentially upwards. Whether or not they are correct about the tipping point, the ice core data provides no evidence to support their claims – and Al Gore was grossly incorrect in his usage of the giant ice core plot in his movie.
The point is that the ice core data is irrelevant to the argument. All that it shows is that CO2 follows temperature.
Sandw15 says:
All because you can find something on the internet doesn’t make it right. The objection about the CO2 bands already being saturated is discussed here in the historical context: http://www.aip.org/history/climate/co2.htm (search on saturated). The fact that the forcing is around 4 W/m^2 is so universally agreed to be scientists, even skeptics like Richard Lindzen and Roy Spencer that it is way out in the weeds to try to argue otherwise.
Think about it. The calculation that gets the climate sensitivity of ~3/4 C per (W/m^2) from the ice age – interglacial transition includes in the W/m^2 the forcing due to changes in ice sheets and the resulting albedo change. However, when we are talking about calculating the climate sensitivity to changes in CO2, that is the only forcing that we are including. So, changes in the albedo due to such land ice sheet changes will then produce additional “forcing” that we haven’t really counted because it is part of the feedback process. This will cause some additional temperature change.
Looks like we’ll have to wait a little longer for global CO2 measurements. Apparently the launch of the Orbiting Carbon Observatory ran into some problems.
NASA Climate Change Satellite Has Troubled Launch
Sandw15 (19:06:53) :
No, that’s incorrect:
If one considers longwave IR emitted from the Earth’s surface, the wavelength/energy of the emitted wavelength has to be considered, since the absorption coefficient (k) is inversely related to the wavelength of the absorption band. The transmisivity, t, (absorbtivity = 1-transmisivity) of a column of air is given by:
t = e^(-k*p*l)
where k is the absorption coefficient, p is the partial pressure and l is the path length.
since the absorption coefficients for the absorption bands of the greenhouse gases are known[***], we can calculate the pathlength required to effectively absorb all of the radiation at that energy/wavelength.
For 99% absorption, the pathlength of the 4-5 micron absorption band of CO2 is 625 metres at current atmospheric CO2 concentrations
and for the ~14-20 micron absorption band, CO2 at 385 ppm is still unsaturated at 7,800 metres of altitude.
likewise for the 12-20 micron infrared absorption band of water at 0.4%, water vapour is still absorbing at 1,700 metres.
So the radiation is certainly not absorbed within 10 metres of the Earth’s surface!
(iii) Thus, at current atmospheric greenhouse gas concentrations, the absorption bands aren’t saturated; enhancement of the concentration of greenhouse gases, particularly at higher altitudes [see (iv)], is effective in trapping more of the longwave IR emitted from the Earth’s surface.
(iv) In any case, the altitude of absorption of IR emitted from the Earth’s surface isn’t that important. A key element of the greenhouse effect is the altitude of emission of longwave IR into space. This has to happen for radiative balance between incoming radiation and outward radiation.
As greenhouse gases are added to the Earth’s atmosphere, the radiation of IR into space is suppressed at any altitude (especially altitudes far from the Earth’s surface). So the radiation emitted to space from (say) 5 km is suppressed by enhanced CO2 concentrations, and so the altitude of mean radiation to space is increased. Since an increased altitude in the troposphere is at a lower temperature, the efficiency of radiation to space is decreased. The troposphere must warm in order to restore radiative balance. Since the surface and troposphere are strongly coupled, the warming of the troposphere is transmitted to the earth’s surface (and vice versa).
[***] This has been well known for more than half a century. See for example:
RM Goody and GD Robinson (1951) Quart. J. Roy. Meteor. Soc. 77, 151-185
Steven Goddard (06:24:14) :
Hansen doesn’t say that the “climate has reached a “tipping point” where it is moving exponentially upwards” (what is “it” btw, that is “moving exponentially upwards”?). Hansen iseems to be pretty explicit about what he says. He considers that the Earth can’t support a significant Greenland ice sheet at CO2 levels above 450/500 ppm at equilibrium (likely to be achieved on the millenial timescale). He considers that the climate sensitivity is likely to be a good bit higher than 3 oC, once the extremely long time scale ice dynamics are factored into the analysis. In another context he considers that burning all of the fossil fuels would result in truly catastrophic consequences and these might well involve non-linear effects that could be considered “tipping points” (e.g. massive die-off of tropical rainforests; massive release of methane from deep-sea clathrates as oceans warm…that sort of thing).
We may as well address his views in the context of what he actually says/writes!
And in fact the ice core data is highly relevant to the argument. One can’t inspect the ice core data visually and infer lack of effects of greenhouse gas levels from an absence of obvious visually-apparent signatures. One of the facts of life of modern science (since the mid 19th century at least) is that we can address phenomena that aren’t revealed by simplistic visual inspection. The ice age cycles have to be addressed in terms of a full consideration of the radiative forcings, feedbacks and amplifications. Everyone knows very well that changes in greenhouse gas levels don’t instigate transitions between glacial and interglacial periods. That’s the result of Milankovitch cycles. However the Milankovitch cycles produce puny changes in insolation and their effects can only produce the observed record once ice sheet dynamics and greenhouse gas forcings are included in the analysis. In terms of the record these contributors are pretty much “mixed together”. So while increases in atmospheric CO2 driven by Southern hemisphere sea ice retreat may lag the temperature rise recorded in Antarctic cores by 800 (+/- 600) years, that doesn’t mean that rising CO2 levels don’t contribute to the subsequent 4000-ish years of warming through a glacial-interglacial transition….and vice versa in a cooling transition.
If one wants to understand these phenomena, all of the evidence needs to be considered. It’s helpful to know, for example, that while temperature changes precede CO2 changes in Antarctic cores, the rise in atmospheric CO2 levels occurs in advance of warming in the tropics (probably) and in the high Northern latitudes (very likely).
http://icebubbles.ucsd.edu/Publications/CaillonTermIII.pdf
(and subsequent work has reinforced that conclusion)
http://www.sciencemag.org/cgi/content/abstract/1143791
Steven Goddard (06:24:14) :
If the climate is cyclical, then there will be an equal number of rising and falling transitions.
Surely this depends on your stating and finishing times?
… the ice core data provides no evidence to support their claims – and Al Gore was grossly incorrect in his usage of the giant ice core plot in his movie.
Cannot comment on this as I have not watched the film, sorry.
The point is that the ice core data is irrelevant to the argument. All that it shows is that CO2 follows temperature.
but this is just not true. If you look at the EPICA core data then CO2 levels rise just at the point where the temperature begins to rise from the lows. The point at which temperatures start falling is more messy but CH4 and/or CO2 frequently begin to fall at that time. Dust during low temperature periods is often elevated.
If you would have a look at the EPICA data I think you should agree that CO2 rise and temp rise ar synchronised.
Mike
As Foinavon has pointed out:
The ice age cycles have to be addressed in terms of a full consideration of the radiative forcings, feedbacks and amplifications.
Dust/CO2/CH4/clathrates/O3/H2O/NO2/Insolation/ etc/etc need to be looked at to fully explain ice age cycles. But from looking at EPICA data CO2 could be one reason for the exit from an ice age.
One need also to understand that the ice core data is a very coarse set of data with most records being separated by 1-10,000 years. Not good for deciding which came first – heat or CO2
Mike
Eight glacial cycles from an Antarctic ice core
The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years. For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago (Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long—28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future.
http://www.nature.com/nature/journal/v429/n6992/abs/nature02599.html
Wondering Aloud (15:47:06) : I assume you are refering to the plots in my post:
thefordprefect (17:22:56).
The data is not cherry picked – it is the data from EPICA ice core from the reference given
Scaling is changed to get a suitable period on the plot nothing more.
I have requested the original author look at this ice core data as it is longer and more detailed than the Vostok core. I would have expected him to download and plot the data himself rather than relying on my plots. If you disbelieve mine then it is a simple matter to replicate the plots yourself.
Anyway, in all but one the plots (which include all the ends of cold periods in 800000 years as far as I am aware) CO2 is in sync with the rise in temp.
The exception is at 722000 years bp in plot
http://img27.imageshack.us/img27/634/iceageco2ch4650740et7.jpg
Allowing for the granularity of the data (as much as 2000 years between points) I would suggest the temp and CO2 are increasing in synchronism. (remember that the graphs have their time scales reversed – earlier is to the right of the plot – scale is years before present [1950])
I am not suggesting that CO2 or CH4 are the only forcings in operation but CO2 is certainly one of them.
Mike