Thursday, October 01, 2009

Keith Briffa Strikes Back

The Yamal ring-width chronology of Briffa (2000)

My attention has been drawn to a comment by Steve McIntyre on the Climate Audit website relating to the pattern of radial tree growth displayed in the ring-width chronology "Yamal" that I first published in Briffa (2000). The substantive implication of McIntyre's comment (made explicitly in subsequent postings by others) is that the recent data that make up this chronology (i.e. the ring-width measurements from living trees) were purposely selected by me from among a larger available data set, specifically because they exhibited recent growth increases.

This is not the case. The Yamal tree-ring chronology (see also Briffa and Osborn 2002, Briffa et al. 2008) was based on the application of a tree-ring processing method applied to the same set of composite sub-fossil and living-tree ring-width measurements provided to me by Rashit Hantemirov and Stepan Shiyatov which forms the basis of a chronology they published (Hantemirov and Shiyatov 2002). In their work they traditionally applied a data processing method (corridor standardisation) that does not preserve evidence of long timescale growth changes. My application of the Regional Curve Standardisation method to these same data was intended to better represent the multi-decadal to centennial growth variations necessary to infer the longer-term variability in average summer temperatures in the Yamal region: to provide a direct comparison with the chronology produced by Hantemirov and Shiyatov.

These authors state that their data (derived mainly from measurements of relic wood dating back over more than 2,000 years) included 17 ring-width series derived from living trees that were between 200-400 years old. These recent data included measurements from at least 3 different locations in the Yamal region. In his piece, McIntyre replaces a number (12) of these original measurement series with more data (34 series) from a single location (not one of the above) within the Yamal region, at which the trees apparently do not show the same overall growth increase registered in our data.

The basis for McIntyre's selection of which of our (i.e. Hantemirov and Shiyatov's) data to exclude and which to use in replacement is not clear but his version of the chronology shows lower relative growth in recent decades than is displayed in my original chronology. He offers no justification for excluding the original data; and in one version of the chronology where he retains them, he appears to give them inappropriate low weights. I note that McIntyre qualifies the presentation of his version(s) of the chronology by reference to a number of valid points that require further investigation. Subsequent postings appear to pay no heed to these caveats. Whether the McIntyre version is any more robust a representation of regional tree growth in Yamal than my original, remains to be established.

My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data. We do not select tree-core samples based on comparison with climate data. Chronologies are constructed independently and are subsequently compared with climate data to measure the association and quantify the reliability of using the tree-ring data as a proxy for temperature variations.

We have not yet had a chance to explore the details of McIntyre's analysis or its implication for temperature reconstruction at Yamal but we have done considerably more analyses exploring chronology production and temperature calibration that have relevance to this issue but they are not yet published. I do not believe that McIntyre's preliminary post provides sufficient evidence to doubt the reality of unusually high summer temperatures in the last decades of the 20th century.

We will expand on this initial comment on the McIntyre posting when we have had a chance to review the details of his work.
K.R. Briffa 30 Sept 2009

Briffa, K. R. 2000. Annual climate variability in the Holocene: interpreting the message of ancient trees. Quaternary Science Reviews 19:87-105.
Briffa, K. R., and T. J. Osborn. 2002. Paleoclimate - Blowing hot and cold. Science 295:2227-2228.
Briffa, K. R., V. V. Shishov, T. M. Melvin, E. A. Vaganov, H. Grudd, R. M. Hantemirov, M. Eronen, and M. M. Naurzbaev. 2008. Trends in recent temperature and radial tree growth spanning 2000 years across northwest Eurasia. Philosophical Transactions of the Royal Society B-Biological Sciences 363:2271-2284.
Hantemirov, R. M., and S. G. Shiyatov. 2002. A continuous multimillennial ring-width chronology in Yamal, northwestern Siberia. Holocene 12:717-726.

Origonal here.

PS. All Steve's data froma single location? His accusation of cherry-picking is supported by cherry-picked data? The irony abounds.

PPS. All accusations of deliberate scientific misconduct on Mr. Briffa's part will be deleted from the comments. Keep that stuff for the birthers with slide-rulers and spreadsheets over at CA.

RealClimate Strikes back here.


Anonymous said...
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Jason said...
This comment has been removed by a blog administrator.
bigcitylib said...

All accusations of deliberate scientific misconduct on Mr. Briffa's part will be deleted. Keep that stuff for the birthers with slide-rulers and spreadsheets over at CA.

Jason said...

Some facts:

1. The modern temperature spike in his data comes from just 10 trees, selected by presently undocumented means (by either Biffra or his collaborators or both) out of hundreds of other trees in the region which were believed to be temperature proxies and then cored. The vast majority of these other trees are still not available to the scientific community.

2. Biffra's methods assume a normal distribution in the absence of temperature changes, and a substantially linear response to temperature changes. It is impossible for any competent scientist to look at the data from these 10 trees. Look at it yourself: (

3. Biffra refused a continuous stream of requests for this data for many years. Throughout this time he refused to make his data available, even after publishing in journals that required it as a pre-condition of publication. Only after one such journal forced him to make the data available (more than a year after the relevant article was published) did Biffra finally permit his data to be examined.

4. BigCityLib does not permit accusations of deliberate scientific misconduct.

Jason said...

Talking about false accusations, BigCityLib:

All Steve's data is NOT from a single location. Instead he has reused ALL of Biffra's data, and then added a single additional set of data intended to replace the 12 trees in question. He shows the results with and without the 12 trees.

What he proves is that Biffra's result was dependent on his decision to include these 12 cores (more importantly the 10 that extend into recent times), AND exclude results from hundreds of other trees in the area, a great many of them identified ex ante as temperature independent and gathered by the same group.

Steve makes no attempt to suggest that the new graph is a temperature proxy. His point is that the new graph is completely different from the old graph, meaning that the decision to include these 12 trees while excluding all other nearby cores is responsible for an enormous portion of the (supposedly robust) warming shown by recent paleoclimate studies.

Frank said...

All warmers are honest and transparent, and would never knowingly give false or misleading information.

Frank Frank said...

Lysenko, eat your heart out.

The Mound of Sound said...

McIntyre has been nicely shredded at

John Cross said...

A couple of observations:

1) I believe that all data should be open and available.

2) If Dr. Briffa has a selection methodology that he has applied consistently then I don't really know what the fuss is about. If someone else has a different selection criteria then they can use it and publish.

3) If he published his criteria and then violated it, and you can show that he did it deliberately - then you can use words like dishonest. However I don't see that yet.

4) And, of course, this does nothing to change the physics of the CO2 molecule.

Paleoclimatology is interesting and fun to argue over since it requires a great deal statistical analysis. However it is hard to see how it really changes our understanding of AGW.


Jason said...

The Real Climate post makes Real climate look extremely bad.

In it, Real Climate conducts "A RealClimate exclusive investigation" [their words] in which they list a bunch of other studies which do not depend on Biffra's work.

Apparently they didn't notice this post (currently on McIntyre's home page dated September 29th) in which he already explicitly discusses these other studies.


Ti-Guy said...

The first comment is libellous. Better to delete that too, BCL.

...and nuke Fred's house from orbit. Y'know...just to be sure.

John Cross said...

Jason S: Thanks for the link. Could you please point out the place where it is shown that the lack of the Yamal series changes the borehole reconstructions shown on RC. While you are at it, you could also show me how it changes the glacial retreat series.


Jason said...

John Cross,

It is not necessary to find fault with every proxy for the entire paper to be defective. This is because Mann, Briffa and friends have chosen to use a statistical procedure that exaggerates any hockey stick shapes that may be added to the mix.

They could pass in seven pristine proxies, and one hockey stick, and get back a hockey stick.

This is precisely what the folks at Real Climate HAVE done. In almost all of their studies, removing the Bristlecones completely changes the shape, and shows the Medieval Warm Period to be warmer than the present day.

This is very well documented in at CA (which is presently down).

The following is also well documented:

1. The particular Bristlecones used by Real Climate folks were not believed to be a temperature proxy by the person who collected them.

2. They were specifically selected for strip bark trees which are known by the dendro community to be a poor choice for temperature proxies.

3. The same region was recently resampled by Ababneh ( If this bristlecone data is substituted for the data used by real climate, the hockey stick completely disappears.

Jason said...

John Cross,

I didn't mean to suggest that the other series are not broken.

For example, the Borehole series on Real Climate has a sister series (collected by the same guy) which shows that the present day is not as warm as the MWP (HPS97).

There are reasons for preferring the series that RC uses (the HPS97) series is considered to be noisier than boreholes covering a shorter time period.

But there are two important reasons why it doesn't serve RC well:

1. The series on their website doesn't include the MWP, therefore it doesn't tell us anything about whether or not the planet is warmer now than it was then.

2. The borehole series that they have shows the current warming beginning well before the industrial revolution had produced significant emissions.

In sum:

A. There are other boreholes (by the same folks) showing a warm MWP.

B. I'm not sure how a borehole series showing us that the little ice age was cold enhances our understanding of climate. I will gladly stipulate that the little ice age was cold.


C. Removing the borehole data entirely has relatively little impact on the reconstructions. Removing the tree ring data destroys the central conclusion of the reconstructions.

John Cross said...

Jason: My comment was in regards to your statement that Steve had already discussed these other cases.

To that end I am a little confused about your response. Did he discuss them?

In regards to the plaeoclimate reconstructions I stated my thoughts above. Show me how they actually change our understanding of the physics of global warming and I will start to take place. Until then, you have ancient scientists (and others) arguing over ancient data using (some) ancient statistics. I know that some get off on it, but to me the start of global warming can be summed up in three points.

1) We are responsible for all the recent rise in CO2.

2) Co2 will absorb and re-emit longwave radiation.

3) If you shine more longwave radiation on an object it will warm or it will cool less quickly.

If you can show me how our understanding of tree rings changes one of these points, then I am all ears.


PS, if anyone has not already done so, I would encourage you to read the RealClimate post. One of the funniest things I have read in a while.

Jason said...

John Cross,

First I would point out that I actually agree with your points #2 and #3. I think that point #1, while clearly false, is still a reasonable approximation of reality.

I would also point out that there is general agreement as to the degree of warming that should be directly expected from the physics of CO2, and it implies a climate sensitivity to CO2 that is less than half what climate modelers predict.

The current hysteria about climate is largely based on claims that warming caused by CO2 will produce changed weather patterns that result in increased water vapor in the upper atmosphere, but do not result in a corresponding increase in cloud based reflectivity.

Actual surface temperatures over the last 10 years, and tropical tropospheric temperatures over the last 30 years diverge substantially from what these models predict.

That doesn't necessarily prove that their estimates of climate sensitivity are completely wrong.

I simply wanted to note that the straight forward physics of CO2 do NOT imply warming that is at all comparable to that predicted by the IPCC and mainstream climate science. They are making a substantially more complex (and more questionable) argument.

I don't know whether or not it was your intent to imply otherwise.

I actually agree with the part of the argument based on straight forward physics.

I'll save the part about Steve for a separate comment.

Jason said...

John Cross,

Steve addresses all of the multiproxy studies mentioned in the real climate post.

The Ice core graph does not have a link to a specific source (it appears to be an IPCC graph) so I can't positively confirm that he has addressed it. Do you have a reference to the original source?

Steve has already addressed multiple studies including the borehole graph, but it isn't relevant to Steve's analysis.

Steve questions whether or not these multiproxy studies show that the current period is warmer than the MWP. The borehole graph (as previously mentioned) doesn't actually include the MWP.

There is widespread agreement that the little ice age was colder than the medieval warm period. Graphs showing this would appear to be confirming an expectation that the vast majority of commentators already have, so I am not sure I understand its relevance.

If real climate has led you to believe that Steve things the current warm period is colder than (or as cold as) the little ice age, then they have misrepresented Steve's position.

John Cross said...

Jason: Glad that we agree on my 2nd and 3rd points. However, counter to what you expressed, point 1 is the only point that can be proved in a mathematical / logical sense. So I do not agree that #1 is clearly false and I would like to see your argument for it being clearly false.

In regards to the IPCC predictions, I will note that Deep Climate has a good analysis of how well the IPCC predictions have done.

In regards to Steve's work, I am familiar with it and if you look through the records, I was a fairly active poster over at Steve's until the personal attacks on me and the insults became a bit too much. I didn't mean to imply anything about Steve's work, I was pointing out that in fact he did not discuss all the series on the RealClimate post as you had indicated.


Jason said...


The point #1 I am refering to is from this list:

"1) We are responsible for all the recent rise in CO2.

2) Co2 will absorb and re-emit longwave radiation.

3) If you shine more longwave radiation on an object it will warm or it will cool less quickly."

Are you referring to a different point #1, or do you actually believe that #1 "can be proved in a mathematical / logical sense" more easily than #2 and #3?

I'm inclined to think that we are talking past each other unless you tell me otherwise.

As to Deep Climate's comparison, he uses yearly temperatures and the year 2000 (even though AR3 was published in 2001). If he had used 2001 as a starting point (and I believe that predictions should be tested from when they are made), he would have concluded that the IPCC predictions have already been falsified. If had used 2000 and monthly data, and I understand his methods correctly, he also would have determined that the predictions have been falsified, but he probably would have made reasonable changes to his procedure (which I would not object to) and then determined that it was a marginal case (right on the 95% threshold). Either way, less than a decade of data isn't very much to be comparing.

The much longer term failure of tropical tropospheric temperatures to follow the models (which hits directly at the credibility of the models and their supposed adiabatic feedback) is a much more serious problem.

As to Steve's blog posts: I was only considering the RC post to the degree that it attempts to "shred" Steve. To the degree that it contains data which appears to confirm what Steve has written (such as the Huang borehole), I'm not sure how it is even relevant (and never mind that Steve's September 29th post does include multiple multiproxy studies that do include the Huang borehole).

Gerrard787 said...

McIntyre has been nicely shredded at - Mound of Sound

Sadly (for RC) they didn't touch on any of the issues raised by McIntyre.

And RC should stay away from trying to be funny; it doesn't work for Ti and it doesn't work for them.

John Cross said...

Jason: no, I mean what I say. It is actually relatively easy to prove #1. Consider the following. We have good measurements of atmospheric CO2 concentrations and we have good oil and gas production numbers.

If we do the calculations we see that we are putting out about twice as much CO2 as is showing up in the atmosphere. So the various sinks are actually absorbing more than we produce. SO what would happen if we did not produce? Would the sinks stop? While it is possible - I guess, it goes against the laws of physics.

A simple analogy is to consider a bank account. There are multiple people that have access to it (there represent the various sources and sinks). Over the year you contribute $7. At the end of the year the total account is $4 higher than it was at the start. What would be the balance if you had not put in your $7?

In regards to Deep Climate's projection, there is no need to stop at AR3! Why not go right back to Arrhenius ;-)


Jason said...

John Cross,

It is well established in the literature that there are numerous non-anthropogenic sources of CO2.

Indeed it is well understood [and incorporated in to most climate models] that increasing temperatures reduce the solubility of CO2 in the ocean.

It is quite remarkable to me, that you think that all human emissions can be tracked, and all natural sources eliminated in a scientific/logical way (especially when mainstream peer reviewed literature disagrees with you), but that the basic optical properties of CO2, which can be verified in a laboratory, are more difficult to pin down.

John Cross said...

Jason: I have no problem with the points that you raise. The issue is that they don't have any impact on my argument.

The key question is what would happen to the CO2 levels in the atmosphere over the next year if we stopped producing CO2. Would they go up or down? I think that they would go down. If you accept that then you must also accept the fact that any increase in levels over the next year are anthropogenic.

If you think the levels would go up, then you need to ask yourself why? If they go up because of a new source OK, but that is not relevant to this argument since if that had happened in the past, we would see an increase greater than what we had produced. To date we have not seen this.

So, your only out is to propose a new source of CO2 that would not exist if the anthropogenic CO2 was taking place. In fact it has to be even more complex because it could not limit itself. In other words the producetion of anthropogenic CO2 would inhibit its production, but the production of non anthropogenic CO2 would not. I do not know of any such source, but I would like to hear of one if you would care to propose it.

I do like your last statement though. You say especially when mainstream peer reviewed literature disagrees with you. Let me play. I am surprised that you put so much faith in Steve M's work, especially when mainstream peer reviewed literature disagrees with you. You're right, that was fun!


Jason said...

I obviously do not trust mainstream peer reviewed literature.

In fact, I think this current scandal has its most significant impact not on Briffa, but on Science and Nature which failed to use the tools at their disposal to ensure proper peer review (how do you not get a statistician to review a primarily statistical paper) and data disclosure.

As to CO2, we have always agreed that anthropogenic sources are dominant.

But certainly it would not be shocking if anthropogenic emissions suddenly ceased for a year but atmospheric CO2 levels continued to rise for a short while (less than a couple of years).

There are many potential non-anthropogenic sources in the literature. There are probably many unknown sources of CO2 as well. And, of course, there are numerous CO2 spikes recorded in the glacial record that occurred long before human civilization.

But I don't question the dominance of anthropogenic emissions, so you'll have to find somebody who does if you want to debate that.

John Cross said...

Jason: You have been clear enough that you accept that anthropogenic sources are the dominant. However I was very specific when I said ALL and you did not seem to accept that.

Your counter argument is not sensible if you accept the two facts that my argument rests on (i.e. that we can measure atmospheric CO2 concentrations relatively accurately, and that we can measure oil and gas production relatively accurately).

If you accept those then how can you say that if we stop emitting CO2 it will still rise? There would obviously have to be a new source involved - so what would that new source be and why would it only show up after we stop?


Jason said...

John Cross,

Natural (non-anthropogenic) sources certainly can and do have an enormous impact on atmospheric CO2.

Here is the first Wikipedia graph I googled:

Obviously the CO2 spikes at 130,000 and 15,000 years ago were not caused by anthropogenic activity. They were caused by natural processes.

In this case it appears that significant non-anthropogenic episodes of global warming increased ocean temperatures, reducing the solubility of CO2 in the earth's oceans, and thus increasing atmospheric CO2.

BTW, it is certainly not the case that we can accurately measure human CO2 emissions. We try our best, but the IEA and other organizations that measure CO2 emissions acknowledge that this is more art than science.

We _may_ be able to measure oil and gas production accurately (I've never looked into it), but you can not effectively predict annual atmospheric CO2 levels from oil and gas production alone (go ahead an try it for yourself).

(You can, of course, show that both are going up. But that's not the same thing as being able to add up all the carbon taken out of the ground, and determine how much will wind up in the atmosphere, which is what I understand you to be saying.)

John Cross said...

Jason: your facts are correct, but they have nothing to do with my argument. Yes, there are natural sources and sinks, yes, these change over time. But as long as we are producing more than is showing up in the atmosphere it is not relevant.

In regards to calculating the CO2 produced, we don't need 5 significant figures since it appears that about only 1/2 of what we produce shows up in the atmosphere.

If you would show some good faith (like retracting your previous statement) I would be happy to walk through the numbers with you if you like. But the argument is to take the production of oil and gas, take some appropriate percentage that is converted to CO2 and then do the chemistry. High school stuff.


Jason said...

I think we are still talking about this:

"We are responsible for all the recent rise in CO2"

If it is true there are numerous non-anthropogenic sources then this statement is false.

Since we agree on the big picture (That recent increases in atmospheric CO2 are dominated by anthropogenic sources) and we seem to be talking past each other in what may or may not be a semantic argument, I think we are best off letting this thread die.

John Cross said...

Jason: your statement "If it is true there are numerous non-anthropogenic sources then this statement is false." does not make sense. As we both know there are both sources and sinks.

The only relevant question is what will the CO2 level do if we stopped producing? If you can argue that it would rise then you may have a point. Logic and science dictates that it will fall in which case it is obvious that we are responsible for the increase.

It really is that simple which is why I am able to make such a strong statement.


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