New paper confirms the climate was warmer 1000 years ago

Fig. 1. The geographical locations of all the 91 proxies in Table 1 (top) and of those that correlate significantly with their local temperatures (from HadCRUT3v) in the period beginning in 1880 and lasting to the final year of each individual proxy (bottom). The resolution (annual, annual-to-decadal, decadal) is indicated with the symbols. Proxies that reach back to at least 300AD are indicated in blue.

Mike Mann will have a twitfest on Twitter trying to knock this one down. Data from 91 Northern Hemisphere proxies was used to reconstruct temperature. See reconstruction graph (figure 5) below.

Via The GWPF:

A new paper, looking back at the climate of the past two thousand years, published in the journal “Climate of the Past,” will either cause something of a stir, or provide confirmation of what some regard as having already emerged from the peer-reviewed scientific literature. The title of the paper is, “The extra-tropical Northern Hemisphere temperature in the last two millennia: reconstructions of low-frequency variability,” by B Christiansen of the Danish Meteorological Institute and F C Ljungqvist of Stockholm University.

The climate of the past few hundred years is of clear importance because it allows scientists to put today’s warm period into context, and provides some evidence of the influence of the quantity of greenhouse gasses that mankind has injected into the atmosphere. In much literature and during many debates statements to the effect that it is warmer now than it has been for thousands of years are frequently used.

As the authors point out the major problem with reconstructing the climate of the past few thousand years is that the so-called instrumental period – for which we have direct measurements – only stretches back as far as the middle of the 19th century. To overcome this researchers in this paper compile an impressive number of temperature proxies situated in the extra-tropical Northern Hemisphere. There are 91 in total, comprising ice-cores, tree-rings (density and width), lake and sea sediments, historical records, speleotherms, and pollen. All of them go back to 1500 AD and 32 go back as far as 1 AD.

The reconstruction of past climate has improved significantly in the past few years due to the availability of more proxies and better statistical analysis. The authors acknowledge this and point out the differences that are emerging from the reconstructions conducted about a decade ago. They mention two such reconstructions performed by Michael Mann that they say, perhaps typically for the period, show little variability. They add they display, “little evidence for previous temperature anomalies comparable to those of the 20th century.” The authors conclude that previous climate reconstructions “seriously underestimate” variability and trends in the climate record of the past two millennia.

This new analysis shows that the warming we have seen in the late-20th century is not unprecedented, as can be seen in figure 5 (from the paper). Seen in the reconstruction is a well-defined peak of temperature between 950–1050 AD. They also find that the first millennium is warmer than the second.

Fig. 5. Reconstruction of the extra-tropical NH mean temperature (C) based on the gray-shaded proxies in Table 1 reaching back to at least 300 AD. Calibration period 1880–1960AD. Only proxies with positive correlations and a p-value less than 0.01 are used. The included proxies are given in the legend. Thin curves are annual values; thick curves are 50-yr smoothed. Red curves show bias and confidence intervals for the 50-yr smoothed values. From ensemble pseudo-proxy studies mimicking the reconstructions, we have calculated the distribution of 50-yr smoothed differences between reconstructions and target. The biases and the upper and lower 2.5% quantiles are calculated from these distributions. In the figure the biases (full red curves) have been added to the real-world reconstructions. Likewise, the upper and lower quantiles have been added to the real-world reconstructions (dashed red curves). The green curve shows the observed extra-tropical (>30 N) annual mean temperature. The yellow curve show the temperature average over grid-cells with accepted proxies. Both curves have been centered to zero in 1880–1960 AD.

The researchers conclude:

“The level of warmth during the peak of the MWP (Medieval Warm Period) in the second half of the 10th century, equaling or slightly exceeding the mid-20th century warming, is in agreement with the results from other more recent large-scale multi-proxy temperature reconstructions.”

Ljungqvist et al. also show that, “on centennial time-scales, the MWP is no less homogeneous than the Little Ice Age if all available proxy evidence, including low-resolution records are taken into consideration in order to give a better spatial data coverage.”

In conclusion this impressive piece of research makes a significant contribution to a growing body of evidence that both the global extent of the MWP, and the temperature was similar, or even greater than the Current Warm Period, even though the atmospheric CO2 concentrations today are some 40% greater than they were during the MWP.

Some argue that without anthropogenic greenhouse gasses the world would have cooled in the past few decades. That might be the case, but the statement that it is warmer now than it has been for thousands of years is untrue. The rate of warming seen recently is also not unprecedented.

In the context of climate sensitivity – the real world climatic reaction to increasing greenhouse gasses – and climate model uncertainty, it is an interesting question to ask: if Nature alone in the past can produce temperatures like those we see today, why can’t she do so again?

=============================================================

The link to the journal is here. Abstract below.

The extra-tropical Northern Hemisphere temperature in the last two millennia: reconstructions of low-frequency variability

B. Christiansen1 and F. C. Ljungqvist2

1Danish Meteorological Institute, Copenhagen, Denmark

2Department of History, Stockholm University, Stockholm, Sweden

Abstract. We present two new multi-proxy reconstructions of the extra-tropical Northern Hemisphere (30–90° N) mean temperature: a two-millennia long reconstruction reaching back to 1 AD and a 500-yr long reconstruction reaching back to 1500 AD. The reconstructions are based on compilations of 32 and 91 proxies, respectively, of which only little more than half pass a screening procedure and are included in the actual reconstructions. The proxies are of different types and of different resolutions (annual, annual-to-decadal, and decadal) but all have previously been shown to relate to local or regional temperature. We use a reconstruction method, LOCal (LOC), that recently has been shown to confidently reproduce low-frequency variability. Confidence intervals are obtained by an ensemble pseudo-proxy method that both estimates the variance and the bias of the reconstructions. The two-millennia long reconstruction shows a well defined Medieval Warm Period, with a peak warming ca. 950–1050 AD reaching 0.6 °C relative to the reference period 1880–1960 AD. The 500-yr long reconstruction confirms previous results obtained with the LOC method applied to a smaller proxy compilation; in particular it shows the Little Ice Age cumulating in 1580–1720 AD with a temperature minimum of −1.0 °C below the reference period. The reconstructed local temperatures, the magnitude of which are subject to wide confidence intervals, show a rather geographically homogeneous Little Ice Age, while more geographical inhomogeneities are found for the Medieval Warm Period. Reconstructions based on different subsets of proxies show only small differences, suggesting that LOC reconstructs 50-yr smoothed extra-tropical NH mean temperatures well and that low-frequency noise in the proxies is a relatively small problem.

The paper is not paywalled and be read in its entirety here. (PDF)

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Notice that the bulk of warming occurred in the first half of 20th century and present warm peak is not different from that in 1940s. Sorry, no anthropogenic fingerprint there..

Brian D Finch

When I was twelve, I knew it was warmer a thousand years ago than it is now..
But then, I was reading the Viking sagas. Perhaps Michael Mann should do likewise.

RB

“That might be the case, but the statement that it is warmer now than it has been for thousands of years is untrue. The rate of warming seen recently is also not unprecedented.”
That one tree Mann loves so much has a great deal to answer for!

BrianSJ

Nice big dip at AD540 – should please Mike Baillie and catastrophists.

ferd berple

Reconstruction of the extra-tropical NH mean temperature (C) based on the gray-shaded proxies in Table 1 reaching back to at least 300 AD. Calibration period 1880–1960AD. Only proxies with positive correlations and a p-value less than 0.01 are used.
================
This still leaves open the question of selection bias which has been shown to create hockey sticks.
Just because a proxy correlates during the period 1880-1960 doesn’t mean it will continue to correlate outside this period. The correlation could simply be accidental, which means that the selection process is amplifying the noise instead of reducing it.
This was the criticism of the Mann methodology and the more recent Southern hemisphere hockey stick that was withdrawn prior to publication after the problems were identified on Climate Audit.
It is a statistical error that is well recognized in fields outside of climate science, such as statistics. Formally it is known as “Selection on the Dependent Variable”. It is a statistical no-no. It is like division by zero, you can prove anything true. 3/0 = 2/0, therefore 3=2.

ferd berple

correction:
It is like multiplication by zero, you can prove anything true. 3*0 = 2*0, therefore 3=2.

A slightly different way to look at
http://www.colderside.com/Colderside/Temp_%26_CO2.html
with the same result. – – – All you have to do is juxtapose the 280 ppm CO2 flatline with land temperature over the past thousand years. Then it is stunningly obvious that the any linkage between temperatures and CO2 is clearly absent from the recent record.

Mike should have had his twitfest back in April when this article actually came out :-p

ob

new? if you call 6 to 12 months new. Did Mann try to knock the previous C&L or L papers down? I can’t remember? C&L12 isn’t too different from some of the previous reconstructions. Furthermore, if you look at their Figures 2,3 and 10, you see that their results are far from claiming “universal northern hemispheric warmth”. You also see the obvious mismatch with the observations. The most important point of the paper is: It shows that we really don’t understand the origin of the century of (regionally rather extreme) warmth at the change of the millennia.

Inconvenient.

it is a shame that we are only now rediscovering what we already knew decades ago. Climate is hugely variable with these apparent peaks and troughs and todays temperatures are nothing out of the ordinary.
We must assume that the non warming of today over historic temperatures is because the concentration of co2 ceases to matter after around 280/300 ppm. In other words that apears to be the high spot of the logarithmic curve.
tonyb.

Their plot looks much like what I found in just the ice core data. See slide 49 in http://www.kidswincom.net/climate.pdf. Atributing the temperature rise since 1850 solely to anthropogenic emissions is not statistically probable because the rise in anthropogenic emissions is covarient with natural longterm cycles that the authors are attempting to identify. Quantifying the relative contributions is more difficult. http://www.retiredresearcher.wordpress.com.

DaveA

That’s easy to sort out. The crew at SkS have a little trick to deal with misbehaving MWPs; see what they did to Ljungqvist’s last effort.

Ferd

One thing that strikes me about this proxy is the speed of the temperature increase 1000 years ago. We have been told that it is not just the warming but the rate of increase that is alarming.
It seems from the graph that the warming 1000 years ago, looks just like the modern warm period.

Alan the Brit

Anybody who read history either professionally, or as an ameteur, or was taught it in schools, who is 40+ years of age, knows it was warmer a thousand years ago than it is today! People have short memories indeed! It is really something when in a 16 year old’s science GCSE paper they get a multiple choice question about what burning fossil fuel causes, of course the box against “Global Warming” is the required answer. Frankly, the question is generally irrelevent as the question is one of many in the examination, & is indeed only there to promote the propaganda of AGW into vulnerable & easily shaped young minds! In this country brainwashing with political propaganda is illegal, just don’t tell the Guvment that & never mention it to the 13 year long Imperiously Socialist New Labour from 97-2010!

beng

****
The level of warmth during the peak of the MWP (Medieval Warm Period) in the second half of the 10th century, equaling or slightly exceeding the mid-20th century warming….
****
I don’t think that’s going far enough. Greenland & other N Atlantic regions (at least) were much warmer during the MWP than now.

vboring

If you look at it like a stock chart, there is a range-bound downward trend line. Around 1950 the curve breaks the trend and escapes the range. If I were a momentum investor, I’d buy that stock.

Juice

So…proxies are ok now.

jayhd

There is so much anecdotal evidence of both the Medieval Warm Period and the Little Ice Age, both in contemporaneous accounts and literature, that Mann’s work should have been called into question just based on that evidence. The fact that it wasn’t, the fact that it was embraced whole heartedly by the majority of climate scientists and the greenie leftists, shows just how unscientific climate science is.

Vince Causey

But they didn’t use the sacred bristlecones, and nor did they process the data with the holy algorithm of Mann.

Steve Keohane

As others have mentioned above, it is too bad that what we used to know is now a revelation in the context of the false Mannian climate perspective that is the alleged current consensus..

JS

Ooooops. Yamal is there and prominent. Fortunately, the methodology apparently doesn’t mine for hockey sticks does’it? I’m wondering what weights is assigned to Yamal?

Go Whitecaps!!!

I bet Craig Loehle is pleased with this study. High 5s.

Jim Clarke

Juice says:
October 17, 2012 at 8:05 am
So…proxies are ok now.
Proxies and anecdotal evidence are all that we have and both have their limitations. Yet, using a wide variety of proxies over a wide area with good statistical analysis makes proxies more valuable and scientifically meaningful. When they match with the anecdotal evidence, proxies become even more reliable.
The problem with Mann and the Team is not that they used proxies, but that they primarily relied on tree rings and very bad statistical analysis. Plus they simply dismissed the anecdotal (historical accounts) evidence that indicated they were wrong. Oh…and Mann was extremely arrogant and obnoxious in defending his horrible science work!

Don E

I recall a divergence controversy on the location of Viking North America settlement during the MWP based on narratives. Their estimate of latitude, they sailed by latitude, put the settlement in Massachusetts or maybe a little north. The description of the flora and fauna put it in New Jersey or a little south. This difference has never been reconciled which made the search for physical evidence of the settlement even more difficult.

ericgrimsrud

There are three factors that affect the temperature of the Earth: the intensity of solar radiation, the albedo and the greenhouse effect. Various events that have occurred on Earth (such as volcanoes or the lack of volcanoes just to mention possibility) can affect at least two of these variable. We do not know as well as we do today what was happening over the entire planet say 1,000 or so years ago. So it is therefore quite possible that temperatures were either higher or lower than today and it is also very possibly that we cannot know why because of a lack in relevant information concerning the past. From the Ice Core Record, however, we do know that CO2 levels did not differ then from their preindustrial levels – so just perhaps a warming was caused by lower particulate matter in that atmosphere, a possibility that we cannot assess because of a lack of information concerning that period.
My points is: today we know many times more about existing conditions and events around our planet. We do not have comparable knowledge concerning the past – only bits and pieces in comparison. Thus we should not let our lack of understanding of past climates diminish our confidence in what we do know about our present climate and that of the last 100 years during which modern science bloomed and has provided an unprecedented abundance of information pertaining to climate.

This study is excellent confirmation of what geologists have been saying for years based on the oxygen istotope measurements made by Stuiver and Grootes (1997) on the Greenland GISP ice cores. The past really is the key to the future! In order to understand where climate is heading, we need to know where it’s been. This study should put to rest any doubts about the natural variability of climate, independent of CO2. Most of the warm and cool periods show up well in the ice core record and have been confirmed by historic records, both human and glacial.

Crito

if AGW is true, should we not see a drop in warming in Europe following the Black Plague in the 1st half of the 14th Century? Just askin

Juice says:
October 17, 2012 at 8:05 am
So…proxies are ok now.

OK proxies are OK. Bad proxies, such as Mann used, aren’t.

JamesS

Juice says:
October 17, 2012 at 8:05 am
So…proxies are ok now.

A tad disingenuous, don’t you think? The original hockey stick proxies were twelve trees from one site in Siberia, and the addition of one particular tree created the blade. This paper uses “91 in total, comprising ice-cores, tree-rings (density and width), lake and sea sediments, historical records, speleotherms, and pollen.” The samples were also taken from all over the extra-tropical Northern Hemisphere. Apparently they also did not tack on the observed temperature record when the proxies diverged from what they wanted to see.
I have my doubts about proxies as well; however, when you use so many different kinds from around the globe, I’d hope that you’d get something other than red noise.

Ockham

“The reconstruction of past climate has improved significantly in the past few years due to the availability of more proxies and better statistical analysis.”
Isn’t this pretty much what you get with Mann’s data when short-centered principal component analysis is not used?

Don J. Easterbrook says:
October 17, 2012 at 8:59 am
This study is excellent confirmation of what geologists have been saying for years based on the oxygen istotope measurements made by Stuiver and Grootes (1997) on the Greenland GISP ice cores. The past really is the key to the future! In order to understand where climate is heading, we need to know where it’s been. This study should put to rest any doubts about the natural variability of climate, independent of CO2. Most of the warm and cool periods show up well in the ice core record and have been confirmed by historic records, both human and glacial.

Former geology student here…. Yep!. It always annoyed me that the climate gurus were so insistent to swipe away all evidence of the past based on sound geologic methodologies, and substitute that with their own brand of short-term /short sighted science. Note that I’m not referring to all of climate science and scientist, but the ones who came to dominate the political landscape… You know the names.
PS. Just wanted to throw this out, that I agree with this post by Gavin. We can only be effective if we make sure we also are skeptical of claims that might favor our skeptic bent.

Pamela Gray

Fred, your equation’s proof says that 0 = 0, not 3 = 2. Regardless if you divide or multiply by 0. The integer 3 or 2 can be replaced with x = any value, because the value of that integer doesn’t matter. They could even be the same value. Therefore, when your calculation is simplified, it will be 0 = 0. The “logic” your statement tried to use is not logic but is an emotional trick that can be played on simpler minds.

Joe

ob says:
October 17, 2012 at 7:31 am
The most important point of the paper is: It shows that we really don’t understand the origin of the century of (regionally rather extreme) warmth at the change of the millennia.
We can be pretty sure that it wasn’t SUVs or power stations 😉 Apart from that, how dare you suggest that something affecting climate might be “not understood”? Remember, the whole of current climate science is built on “it must be … because we don’t know what else it might be”.

Pamela Gray

In standard published research, inclusion criteria are set to determine which studies merit meta-analysis. That Mann’s study was not is an idictment against it. Burn!

more soylent green!

Somehow, all the climate variation up to 1979 or so was natural. Everybody knows that.

wayne

Most people think a Warm Globe is a better globe, and they are right. The warming of the globe ended years ago.

Chris Edwards

Alan the Brit, I fit that demograph, I was lucky enough to attend a grammar school before the left killed them, we were taught, from print (that is why the lefts big heroes burned all the old thought books) about the Romans growing grapes over all of England and the Vikings naming Greenland, and not because they were colourblind ! Then we had lithographs of the thames ice fairs climate changes without our help! I have noticed the lack of common sense in most things green (not the least when I lived in Cornwall and we had one of our usual gales the only thing stationary in the whole county was the wind turbines !)

Luke

I think that was kind of his point Pamela. The analogy was that you can prove anything true if you use faulty logic. If I choose to only analyze data with a strong statistical correlation to x, should I be surprised that the logical conclusion is analyzing the data shows it has a strong statistical correlation with x. If I use the 3*0 = 2*0 example to prove 3=2, it is faulty logic. It may be different faulty logic than confirmation bias, but both are still logical fallacies in the end.

richardscourtney

ericgrimsrud:
Your post at October 17, 2012 at 8:50 am repeats a falsehood that you know is a falsehood because I have explained the matter to you on two other WUWT threads. I won’t bother to refute it again.
STOP SNOWING THREADS WITH FALSEHOODS THAT YOU KNOW ARE FALSEHOODS.
Richard

Mann doesn’t need to have a twitfest. He can claim
1. New data, new view. Mine was valid with the data I had.
2. If not for my prodding, this new work would not have been done. I initiated Good Things.
3. Yesterday doesn’t matter. Today the situation is different. Yesterday the sun did what human beings are doing today.
4. I have research grants pending to expand on my previous work. Talk to you later when I have gone beyond what doofus has done. I expect validation of what I did.
5. It’s all in my book. Buy another today.

KnR

This work is not a problem for Mann, there is always the fall-back of claiming that becasue the data does not cover ever square inch of the planet it means nothing , of course proof of ‘the cause ‘ only requires one magic tree but that is the way climate ‘science ‘ works .

Tenuk

Juraj V. says:
October 17, 2012 at 7:06 am
“Notice that the bulk of warming occurred in the first half of 20th century and present warm peak is not different from that in 1940s. Sorry, no anthropogenic fingerprint there.
Yes… and no need to invoke the special ‘Nature Trick’ as perfected by the IPCC CAGW consensus cabal of climatologists.
It is also becoming obvious that without some serious ‘bending’ of the modern instrument global temperature data-sets that real temperature is much cooler than indicated. We are already over the global peak and on the toboggan ride of the decline. All the extra CO2 seems to have had little or no impact.

The Earth and the sun do it together.
From the paleomagnetic data (far more accurate then tree rings) it is possible to go back 2 millennia with an error of plus/minus 25 years around 0 BC. We don’t exactly know intensity of the solar activity (10Be and C14 are both affected by precipitation – climate factor, with a danger of circular reasoning).
Thus to take an even solar output (Dr. S would approve) than we are left with the paleomagnetics as a single factor giving reasonable correlation
http://www.vukcevic.talktalk.net/LL1.htm
In the more recent times we have good sunspot count and the accurate geomagnetic records (actual measurements initiated by Gauss) from which a more accurate reconstruction is possible:
http://www.vukcevic.talktalk.net/GSC1.htm

Joe

ericgrimsrud says:
October 17, 2012 at 8:50 am
[…] My points is: today we know many times more about existing conditions and events around our planet. We do not have comparable knowledge concerning the past – only bits and pieces in comparison. Thus we should not let our lack of understanding of past climates diminish our confidence in what we do know about our present climate and that of the last 100 years during which modern science bloomed and has provided an unprecedented abundance of information pertaining to climate.
Eric, there’s a huge logical disconnect in your statement.
While we may well “know many times more” about current conditions, the conditions that (by your own admission) we DON’T know about from the past are still able to influence climate by as much, if not more, than the recent warming. Since that demonstrate clearly that we DON’T know about all the natural factors capable of producing such warming, the logical conclusion is that information like this seriously damages any confidence we can have about what’s happened recently.
Remember, the only reason the science places such high confidence on the effect of CO2 is because there’s “no natural explanation” for warming of this speed or magnitude. Clearly, if this work withstands scrutiny, there ARE natural explanations. The fact we don’t know what they are, or how they work, doesn’t mean they don’t exist!

Pete Claybourne

My word. The GWPF are on fire.

Jeff Condon

I want to caution everyone about these results. Besides the fact that there is no such thing as a reasonable temperature proxy that I am aware of, there is a clear pattern of regressomatic sorting in this curve.
The curve is nonsense.

Lars P.

ericgrimsrud says:
October 17, 2012 at 8:50 am
There are three factors that affect the temperature of the Earth: the intensity of solar radiation, the albedo and the greenhouse effect… Thus we should not let our lack of understanding of past climates diminish our confidence in what we do know about our present climate and that of the last 100 years during which modern science bloomed and has provided an unprecedented abundance of information pertaining to climate.
Pretty simplistic way at looking at the climate. You ignore for instance ozone variability. Ozone is warming from direct solar radiation influencing the energy budget of the atmosphere. Ozone can be influenced by natural variation or by solar UV – which can have huge variations even with stable solar radiation intensity.
You ignore the multidecadal natural oscilations like AMO
http://upload.wikimedia.org/wikipedia/commons/b/b4/Atlantic_Multidecadal_Oscillation.svg
or Arctic Oscilation or ENSO.
What do you mean with albedo? Hopefully not an “albedo constant” – see also Earthshine project:
http://www.bbso.njit.edu/Research/EarthShine/
The albedo is variable and we do not know many factors that are influencing it, let alone measure it properly.
Yes we know more then in the past, but our knowledge is far from being complete, as Richard explained you before, repeating again something that has been shown to you to be wrong does not make it right. So trying to understand what caused the climate variability in the past does have a lot of importance for our understanding of what can cause the climate variability today.

Pamela Gray

Luke, meta-analysis studies set inclusion criteria on study design, not study outcome. That is if they are attempting to be blind to study results. To get a good idea of study criteria for meta analysis done well, visit:
http://ies.ed.gov/ncee/wwc/DocumentSum.aspx?sid=19

Duster

ericgrimsrud says:
October 17, 2012 at 8:50 am

My points is: today we know many times more about existing conditions and events around our planet. We do not have comparable knowledge concerning the past – only bits and pieces in comparison. Thus we should not let our lack of understanding of past climates diminish our confidence in what we do know about our present climate and that of the last 100 years during which modern science bloomed and has provided an unprecedented abundance of information pertaining to climate.

That is not a well-taken point. The idea that we “know” more about the present is mistaken. We have more contemporary measurement. The principle of uniformitarianism has not been suspended, so while Lyell argued that we could, based upon observations of present geological processes, understand much about the past, the converse must be true as well. Any processes operating in the past must also be operating now. No physics or chemical laws have been recently suspended in nature.
In order to sort out natural effects from anthropogenic effects, we need to understand HOW those natural effects operate. Any evidence of a recent anthropic effect must be superimposed upon the standing natural signal. The sole justification that Mann and the team had for stating that recent warming was “unprecedented” was founded on the assumption that they had actually discovered the signal of anthropic influence and had a valid physical theory to explain it. This is why in the Climategate emails there is concern that the MWP is not disappearing neatly in new data. If it doesn’t vanish with “better” data, then the argument that current warming is unprecedented is unsupported under the uniformitarian principle. If the rates of change are not importantly different between past and present episodes of warming, then rate changes or speeds are not “unprecedented” either. In short, there is then no demonstrable evidence of an anthropic signal in the climate and climate proxy data.
The fact is that over any geological span of time there is no indication of a strong correlation between CO2 and temperature that indicates a causal linkage, other than evidence that warming oceans discharge CO2 and cooling oceans absorb it, which is what ice core data appears to show during the Pleistocene. At significantly longer or shorter time frames even that mostly vanishes into the effects of other, not so well identified processes at other scales.