For those who don’t know, Ross McKitrick of the University of Guelph co-authored the first paper with Steve McIntyre debunking Michael Mann’s first Hockey Stick paper, MBH98. Ross wrote this essay in today’s Financial Post, excerpts are below. Please visit the story in that context here and patronize their advertisers. – Anthony
Flawed climate data
Only by playing with data can scientists come up with the infamous ‘hockey stick’ graph of global warming
Ross McKitrick, Financial Post
Friday, October 2, 2009
Beginning in 2003, I worked with Stephen McIntyre to replicate a famous result in paleoclimatology known as the Hockey Stick graph. Developed by a U.S. climatologist named Michael Mann, it was a statistical compilation of tree ring data supposedly proving that air temperatures had been stable for 900 years, then soared off the charts in the 20th century. Prior to the publication of the Hockey Stick, scientists had held that the medieval-era was warmer than the present, making the scale of 20th century global warming seem relatively unimportant. The dramatic revision to this view occasioned by the Hockey Stick’s publication made it the poster child of the global warming movement. It was featured prominently in a 2001 report of the U.N. Intergovernmental Panel on Climate Change (IPCC), as well as government websites and countless review reports.
Steve and I showed that the mathematics behind the Mann Hockey Stick were badly flawed, such that its shape was determined by suspect bristlecone tree ring data. Controversies quickly piled up: Two expert panels involving the U.S. National Academy of Sciences were asked to investigate, the U.S. Congress held a hearing, and the media followed the story around the world.
The expert reports upheld all of our criticisms of the Mann Hockey Stick, both of the mathematics and of its reliance on flawed bristlecone pine data.
…
Most of the proxy data does not show anything unusual about the 20th century. But two data series have reappeared over and over that do have a hockey stick shape. One was the flawed bristlecone data that the National Academy of Sciences panel said should not be used, so the studies using it can be set aside. The second was a tree ring curve from the Yamal Peninsula in Siberia, compiled by UK scientist Keith Briffa.
…
But an even more disquieting discovery soon came to light. Steve searched a paleoclimate data archive to see if there were other tree ring cores from at or near the Yamal site that could have been used to increase the sample size. He quickly found a large set of 34 up-to-date core samples, taken from living trees in Yamal by none other than Schweingruber himself!Had these been added to Briffa’s small group the 20th century would simply be flat. It would appear completely unexceptional compared to the rest of the millennium.
Combining data from different samples would not have been an unusual step. Briffa added data from another Schweingruber site to a different composite, from the Taimyr Peninsula. The additional data were gathered more than 400 km away from the primary site. And in that case the primary site had three or four times as many cores to begin with as the Yamal site. Why did he not fill out the Yamal data with the readily-available data from his own coauthor? Why did Briffa seek out additional data for the already well-represented Taimyr site and not for the inadequate Yamal site?
Thus the key ingredient in most of the studies that have been invoked to support the Hockey Stick, namely the Briffa Yamal series, depends on the influence of a woefully thin subsample of trees and the exclusion of readily-available data for the same area. Whatever is going on here, it is not science.
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elmer (22:23:19) :
Except the instrumental record on its own doesnt look like that:
http://www.cru.uea.ac.uk/cru/data/old-temperature/hemglob.gif
You will notice that the instrumental record curve goes about 0.5 C above the average, whereas your “paleontology” curve soars about 1 degree over the “paleontology” average.
This is more an artifact of reconstruction and plotting than factual.
It was a graph like this that Al Gore used, with a lift to reach the top end, with suitable gasps from his audience, in his “inconvenient truth” lectures.
Joel,
You deserve the Nobel Patience Prize.
brazil84: It seems to me that your argument seems to boil down to this – Even though the nature of the opposition to the scientific consensus was very much the same for the issue of smoking and the issue of evolution, it is really different because in those cases there really was good evidence and in this case there isn’t. Since you have set yourself up as arbiter of what is good evidence or not, ignoring what scientific authorities think, it is absolutely impossible for me to argue against this. You will believe what you want to believe.
brazil84 says:
In neither case is there one best piece of evidence. (As an example, the epidemiological studies that show a correlation between smoking and cancer suffer the problem of all epidemiological studies, that it is hard to show that the correlation means causation and that all other potential factors have been controlled for.)
I think it is relevant to the charge that Wegman was given. And, it is probably also relevant to the general tone of the report and the fact that it went off on this tangent on Mann’s scientific social network. It is also relevant to the fact that in the scientific community this report has essentially been ignored in favor of the NAS report since the NAS is known to approach these issues in a non-partisan manner rather than being commissioned by one political party.
Richard says:
I know this claim has been made but I think it is a re-writing of history. As I remember (and the folks at RealClimate agree with and show a screen capture of http://www.realclimate.org/index.php/archives/2009/09/hey-ya-mal/ ), Al Gore used the lift to demonstrate the dramatic rise in CO2 levels since the industrial revolution. The plot in question was thus the plot of CO2 and temperatures over the last several hundred thousand years as determined from ice cores (with the recent CO2 levels from direct measurement and projected levels into the future).
” It seems to me that your argument seems to boil down to this – Even though the nature of the opposition to the scientific consensus was very much the same for the issue of smoking and the issue of evolution, it is really different because in those cases there really was good evidence and in this case there isn’t”
No, you’ve missed the point yet again. Look, it’s very simple:
Just tell me what this “good evidence” in favor of CAGW is in a few sentences.
“In neither case is there one best piece of evidence. (As an example, the epidemiological studies that show a correlation between smoking and cancer suffer the problem of all epidemiological studies, that it is hard to show that the correlation means causation and that all other potential factors have been controlled for.)”
All you are saying here is that the best piece of evidence might have some weaknesses. So what? It’s still the best piece of evidence.
Anyway, the fact that you have evaded my question demonstrates my point.
______________
“You will believe what you want to believe.”
I think you are just projecting your own wishful thinking here. I believe what the facts show me regardless of my personal wishes. I used to believe in CAGW until I learned how to think critically.
_______________
“I think it is relevant to the charge that Wegman was given. And, it is probably also relevant to the general tone of the report and the fact that it went off on this tangent on Mann’s scientific social network. It is also relevant to the fact that in the scientific community this report has essentially been ignored in favor of the NAS report since the NAS is known to approach these issues in a non-partisan manner rather than being commissioned by one political party.”
But if as you claim, Wegman is no longer relevant, then so what? What do any of these things matter?
Joel Shore:
I have just watched it and, unless my eyes are deceiving me, you’re wrong.
In this case, the study showed not only a strong dose-response, but showed a rr (relative risk) of around 20 at P=0.01. As epidemiological studies go, this is the platinum standard. I will agree that even such high-quality results do not denote causation but, when compared to climate science – chalk and cheese.
EricH (03:06:52) :
When will the apologies start coming for the offence caused to, and vilification of, all the “so called” climate deniers? When will George Bush Jnr. be deified for holding out for so long against signing the Kyoto Accord?
Don’t hold your breath. I can’t see it happening in my life time.
Sorry EricH I think I understand your intent and agree with your summation, but…
George W Bush didn’t sign Kyoto because he couldn’t sign it. It was already signed by Bill Clinton, or more accurately, by one of his aids assigned to the UN. Clinton did this some 800 days before the end of his tenure as President but took no further action. He did not send it ot the senate for ratification. If Kyoto was as big a deal as Al Gore makes it out to be, why did he not encourage then President Clinton to pass it to the senate? Likewise, Obama could send the treaty to the senate now, as a signed treaty.
I’m not a “W” fan, but the story of his “not signing Kyoto” is a red herring used by the AGW crowd. More accurately, one could say that Bush failed to pursue Kyoto, but then so did Clinton and Gore.
Joel Shore (07:14:58) :
Richard says:
“It was a graph like this that Al Gore used, with a lift to reach the top end, with suitable gasps from his audience, in his “inconvenient truth” lectures.”
I know this claim has been made but I think it is a re-writing of history. As I remember (and the folks at RealClimate agree with and show a screen capture of http://www.realclimate.org/index.php/archives/2009/09/hey-ya-mal/ ), Al Gore used the lift to demonstrate the dramatic rise in CO2 levels since the industrial revolution. The plot in question was thus the plot of CO2 and temperatures over the last several hundred thousand years as determined from ice cores (with the recent CO2 levels from direct measurement and projected levels into the future).
The “re-writing of history” is what Al Gore did not me. If all Al Gore wanted to show was the rise of CO2 in the last 50 years he could have used a different graph not showing the ice core temperatures.
1. On the basis of that graph he makes the claim: When there is more CO2 the temperature gets warmer – Implying the CO2 drives temperature – False
2. From that claim and logic, he implies that since CO2 has “gone through the roof”, requiring a hydraulic lift to reach the top of the graph, the temperatures will too.
In my post I had said that graphs are an artifact of plotting, depending on what you take as your baseline, whether you are plotting percentages or absolute values, the scaling you use.
In this case he is plotting parts per million of CO2 in the atmosphere, and then claiming the tail wags the dog. If he took the absolute values from a 0 baseline the CO2 would show as a dead straight line parallel to the X-axis.
Joel Shore (07:14:58) :
PS In that artifact of a graph that Al Gore has shown, besides that ridiculous dramatisation of Al Gore ascending on a hydraulic lift, it appears he has also fudged the Y-axis and X-axis scale.
The axis scale needs to be kept constant over the whole graph.
I maybe mistaken but it appears that the Y-axis for the current period is to a different scale.The CO2 appears to be last few years have been used to a different scale on the Y-axis. Visually, it appears to be over double that at the peak figures of around 29 ppm at the end of the ice-ages and the X-axis at the end also seems to have been stretched out for the current period compared to the previous 800,000 years.
The CO2 appears to, in last few years, have been used to a different scale on the Y-axis. Visually, it appears to be over double that at the peak figures of around 290 ppm at the end of the ice-ages and the X-axis at the end also seems to have been stretched out for the current period compared to the previous 800,000 years.
Richard says:
You are changing the subject. My point is that now people are making the claim that Al Gore used the lift to demonstrate the Mann Hockey Stick curve. The fact is that it had nothing to do with the hockey stick curve.
It is not false. In fact, both of them drive each other. It is admittedly not accurate to imply, however, that the temperature will rise as much as the ice core data correlating temperature and CO2 suggest, since it is estimated that only about 1/3 of this temperature rise was due to CO2…and also, the temperature dependence on CO2 is expected to be logarithmic rather than linear.
That is just plain wrong. CO2 levels have gone up almost 40% during the industrial revolution. That means if the graph starts at a distance of 1 from the bottom; it will go up to ~1.4, which won’t look parallel to the x-axis no matter how you plot it. And, in fact, plotted on the timescales of several hundred thousand years, it will look basically completely vertical, just as Al Gore showed. (And, as near as I can tell from RealClimate’s screen capture, his graph for CO2 does start at 0, or at least pretty close.)
You are mistaken. Note however, that there are two points on that graph, one at today’s levels and one at a projected level (for 50 years hence, I think, although it is hard to read).
Peter says:
I am confused then … Why does the RealClimate screen capture show him on the lift in front of the graph that I described?
Joel Shore (18:16:40):
Al Gore’s “graph for CO2 does start at 0, or at least pretty close.”
Okey dokey. Now let’s take a look at some other graphs that have a zero y-axis: click1, click2, click3.
Not too scary, are they? That’s why the alarmists use charts like this: click. They are deliberately designed to scare the scientifically illiterate populace. That’s why they don’t work around here.
Joel Shore (18:16:40) :
Richard says: “.. On the basis of that graph he makes the claim: When there is more CO2 the temperature gets warmer – Implying the CO2 drives temperature – False”
It is not false. In fact, both of them drive each other.
According to the AGW hypothesis. If this is true however please explain the warmer MWP than the CWP, most of the warmer Holocene interglacial period and the little ice age on the basis of CO2 as the main driver of the temperatures.
Richard: Well, most scientists do not believe that the MWP was warmer than the late 20th century, although obviously the issues with temperature reconstructions make it difficult to assert that with a high degree of confidence.
But, the more general answer to your question is that the world is not so black-and-white. CO2 is the main driver of temperatures when it changes rapidly while other things (such as orbital parameters) don’t change very much. And, CO2 is not the main driver of temperatures when it is nearly constant while other things are changing.
During the glacial – interglacial oscillations, the understanding is that the trigger for glaciation and de-glaciation was provided by orbital changes. However, these orbital changes resulted in almost no change in global mean annual radiative forcing…They just changed the distribution of the radiative forcing in latitude and seasonality. Hence, almost all the temperature change was as a result of feedbacks. The most important feedback was simply the change in albedo from the growth and shrinkage of the land ice sheets (and, to a lesser extent changes in vegetation) and this accounted for about half the temperature change. Changes in CO2 levels accounted for about one third of the temperature change, with a little bit more added by the other greenhouse gases, and these greenhouse gas changes also likely played an important role in synchronizing the change in the two hemispheres. Changes in aerosol loading in the atmosphere contributed a bit too (maybe 10-15%).
During the Holocene (and up until the industrial revolution), CO2 levels have been pretty constant and so much of whatever temperature change has occurred is likely due to the changes in orbital parameters (which is a slow change over thousands of years) and changes in solar irradiance or volcanic activity.
Joel Shore (19:14:13) : Richard: Well, most scientists do not believe that the MWP was warmer than the late 20th century, although obviously the issues with temperature reconstructions make it difficult to assert that with a high degree of confidence.
Firstly how can you say that statement is correct. Has any poll been conducted among scientists with the question “do you believe that the MWP was warmer than the late 20th century”? Naturally since they are scientists they will also have to asked the question why do you believe as you do. Secondly beliefs are not a substitute for the truth.
I presume that you yourself are a scientist? (I am not). If you believe that, why do you, specially when you also say that there is not a “high degree of confidence” in that statement.
Why I believe it was warmer is
1. Because people who lived during the period left sagas that could be taken as a “proxy” clues (a better one than Briffa’s) that it was indeed so
2. The ice-core records of Greenland say so.
3. There is other evidence that says so.
4. The IPCC itself said so till 2001
5. The National Academy of Sciences still says so in some of its crucial publications as well as the Woods Hole Oceanographic Institution.
In fact the only evidence which says to the contrary is the temperature reconstructions of Mann, Briffa et al, which, as you point out, have “issues” with their confidence.
CO2 is the main driver of temperatures when it changes rapidly while other things (such as orbital parameters) don’t change very much. And, CO2 is not the main driver of temperatures when it is nearly constant while other things are changing.
Where is the evidence for this? It certainly does not show up in the records of the past 10,000 years.
During the glacial – interglacial oscillations, the understanding is that the trigger for glaciation and de-glaciation was provided by orbital changes. However, these orbital changes resulted in almost no change in global mean annual radiative forcing (unproven assumption. You simply do not know the radiation of the Sun to any accuracy before the satellite era)…They just changed the distribution of the radiative forcing in latitude and seasonality. Hence, almost all the temperature change was as a result of feedbacks. The most important feedback was simply the change in albedo from the growth and shrinkage of the land ice sheets (and, to a lesser extent changes in vegetation) and this accounted for about half the temperature change. Changes in CO2 levels accounted for about one third of the temperature change, with a little bit more added by the other greenhouse gases, and these greenhouse gas changes also likely played an important role in synchronizing the change in the two hemispheres. Changes in aerosol loading in the atmosphere contributed a bit too (maybe 10-15%).
The ice core records show the CO2 kept going down when temperatures started rising to take us out of the ice ages and kept rising when we plunged into them, so CO2 was not a driver either of the rise in temperatures nor could it save us from repeatedly plunging into them.
During the Holocene (and up until the industrial revolution), CO2 levels have been pretty constant and so much of whatever temperature change has occurred is likely due to the changes in orbital parameters (which is a slow change over thousands of years) and changes in solar irradiance or volcanic activity.
Since the temperature fluctuations have been far more rapid than the “slow change over thousands of years” that you are attributing to orbital parameters.
Since the temperature fluctuations have been far more rapid than the “slow change over thousands of years” that you are attributing to orbital parameters that statement cannot be true
It has become icy cold here. The weather ignores global warming
Joel Shore (19:14:13) :
Richard: Well, most scientists do not believe that the MWP was warmer than the late 20th century, although obviously the issues with temperature reconstructions make it difficult to assert that with a high degree of confidence.
Joel can you please explain:
What you mean by a “scientist”?
How you know that most scientists do not believe that the MWP was warmer than the late 20th century?
How you decide the degrees of confidence with which you make your speculative assertions?
Thanks in anticipation.
S
“Firstly how can you say that statement is correct. Has any poll been conducted among scientists with the question ‘do you believe that the MWP was warmer than the late 20th century’? ”
That’s a good point, but it’s worth noting that like most warmists, Joel Shore is attempting to divert the discussion into a debate over how many scientists believe what.
Why didn’t he say something like “the evidence indicates that the Medieval Warm Period was less warm than now.”?
Because that would invite a request to explain and provide such evidence.
And what exactly is the evidence that the MWP is cooler than the present? Primarily, it seems that a small group of carefully selected trees grew at least as much between 1950 and 1990 as some other group of carefully selected trees during the Medieval Warm Period. And how exactly were these thermomoter trees selected? Nobody really knows except for a few “scientists” who assure us we can trust them despite their demonstrated lust for shrouding their work in secrecy.
It’s completely unsurprising that warmists want to shift the debate into scientist counting contests since the actual evidence on their side is thin — to put it mildly.
Richard says:
Well, “most scientists” was a shorthand for saying that most of the peer-reviewed papers in the field have said that the current period is likely warmer, as has the IPCC in the last two assessment reports, and the NAS in its report on temperature reconstructions (with some caveats in regard to not being able to assign a degree of certainty to the statement).
(1) Local records tell us only what happened at that location, not what happened globally (let alone the amount of synchronicity in the times at which the different parts of the globe experienced their warmest temperatures during the broad period of time defined by the MWP).
(2) Do you have quotes from the earlier IPCC reports? My impression is that the first report had a schematic graphic taken from Lamb that did seem to show a warmer MWP than at the end of the period, which was before the modern (post 1970) warming, but that if you extended it to temperatures up to the present would have it about the same as the MWP. And, at any rate, this was only schematic since noone had attempted to do a globe-wide or hemispheric-wide reconstruction. And, while the Mann et al. work was pioneering, I don’t think they were the first ones to suggest that the warm periods identified in different areas sometime during the broad period of the MWP appeared to be asynchronous.
(3) Where do the NAS and Woods Hole make these claims? Here is the NAS report on temperature reconstructions: http://books.nap.edu/catalog.php?record_id=11676
As I noted, it is hard to tell during that period since CO2 has been quite constant.
It is strange that the people who have written the papers that have provided this data don’t seem to agree with your conclusions. One problem is that you are likely taking the data well beyond where it can be taken. You do know that the temperature data from ice cores is a proxy for that given location (or region)…and there are various issues with it and, in fact, at least one paper that talks about important corrections that must be made during (I believe) the drop in temperature from interglacial into glacial periods? You also have to look at temperature behavior in both hemispheres since one tends to warm or cool before the other. (And, in fact, I believe that the one that does so more slowly actually does not have a lag between the temperature change and CO2 change.)
What I am referring to are the general triggers for the glacial and interglacial transitions, as well as, for example, the gradual cooling on the Arctic over the last ~8000 years that the recent temperature reconstruction showed.
brazil84 says:
I didn’t say that because I like to attribute statements on scientific issues that I haven’t worked in, or carefully examined and analyzed the data myself, to the scientists who actually have. (Some people, by contrast, seem to think they are experts on something because they have read Steve McIntyre’s and his cohorts’ accounts of it.)
According to the National Academy of Sciences report: “Presently available proxy evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900. The uncertainties associated with reconstructing hemispheric mean or global mean temperatures from these data increase substantially backward in time through this period and are not yet fully quantified.” ( http://books.nap.edu/openbook.php?record_id=11676&page=3 ) Of course, some further progress in that quantification has been made since the report was issued in 2006)
“I didn’t say that because I like to attribute statements on scientific issues that I haven’t worked in, or carefully examined and analyzed the data myself, to the scientists who actually have.”
I’m a little confused . . . are you saying that you have no personal evaluation of the evidence on this point?
“Presently available proxy evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900. The uncertainties associated with reconstructing hemispheric mean or global mean temperatures from these data increase substantially backward in time through this period and are not yet fully quantified”
So it’s basically like I said. The primatey evidence that the MWP was cooler than the present is that a small group of carefully selected trees grew at least as much between 1950 and 1990 as some other group of carefully selected trees during the Medieval Warm Period. And how exactly were these thermomoter trees selected? Nobody really knows except for a few “scientists” who assure us we can trust them despite their demonstrated lust for shrouding their work in secrecy.
And by the way, notice that in response to a question about evidence, Joel Shore responded with a quote summarizing conclusions of various authorities.
Here is my attempt to boil this down into layman’s terms.
http://minnesotansforglobalwarming.com/m4gw/2009/10/the-mystery-of-hockey-stick-chart-revealed.html
Feel free to comment If I got any part of this wrong
P.S. By the way Joel Shore, you never answered my earlier question:
Just tell me what this “good evidence” in favor of CAGW is in a few sentences.
Is it possible for you to answer this question by simply summarizing the evidence? Or will you simply appeal to authority again?