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Thou shalt extrapolate

John Cook, of Skeptical Science fame, has an article in The Age, in which he is very rude about Bob Carter:

A Yiddish proverb states ''a half truth is a whole lie''. By withholding vital information, it's possible to lead you towards the opposite conclusion to the one you would get from considering the full picture. In Bob Carter's opinion piece on this page yesterday, this technique of cherry-picking half-truths is on full display, with frequent examples of statements that distort climate science.

One bit of the article that stuck out at me was this:

[Carter] has long hung his hat on the proposition the climate has been cooling since 1998. But with 2005 and 2010 being the hottest years on record, he resorts to cherry-picking which dataset to use. Rather than use temperature records that cover the entire globe, he opts for datasets that do not include the Arctic region, where warming is the strongest. These temperature records underestimate recent warming and are the darling of those who wish to deny global warming is happening.

Now this is interesting. As readers here know, there are almost no temperature stations in the Arctic and the gaps are therefore infilled by extrapolation.

Now, I don't know about you, but I'm not sure that it is reasonable to get on one's high horse complaining about somebody who prefers to look at, you know, actual data rather than the outpourings of a mathematical model.

Certainly, to accuse them of half truths seems, well, extreme.

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Reader Comments (223)

Lucy Skywalker's work with John Daly's data is well worth a look on this:

Jun 28, 2011 at 11:10 AM | Unregistered Commenternot banned yet

We may all pick cherries (the complexity of climate and editorial limitations leave few other options) but we say real ones taste better than those produced by software.

Jun 28, 2011 at 11:11 AM | Unregistered CommenterRichard Drake

It was predicted that there would be a rude reply to Prof Carter after The Age gave him space yesterday

Shades of the Guardian in action again, get an evil denier up to write something reasonable and then beat him up.

I think they call it "engaging with the skeptics".

Jun 28, 2011 at 11:27 AM | Unregistered CommenterChris

Interestingly, the story in the Age (which is certainly the Gruniad of the Antipodes) has a poll on the question: 'Do you think tackling climate change should be a priority for Australia?' These polls are unscientific, because they tend to reflect the readership of the website, who self-select. But a poll on the website of Pravda on the Yarra that is running at 53% to 47% against with more than 14,000 voting is interesting.

Jun 28, 2011 at 11:35 AM | Unregistered CommenterAynsley Kellow


the tab heading to that article even labels Carter "Climate Change Denialist Bob Carter". Nice.

They can't help themselves can they.

Jun 28, 2011 at 11:35 AM | Unregistered CommenterSimonW

That article seems broken anyway - the title seems to refer to some kind of poll, but the only one on the page is the one at the bottom -theirs - where the majority don't seem to support Mr Cook.

Jun 28, 2011 at 11:38 AM | Unregistered CommenterChris

I visited the 'Climate Sceptic' blog and was very disappointed with the standard of science displayed there. Mr Cook is no sceptic but seems to be making an attempt to be a player in the alarmist camp and his not infrequent attacks on reputable scientists are beyond parody. To anyone who can think logically and do basic arithmetic, most of his presentations and arguments are not just error-riddled but quite juvenile.

Jun 28, 2011 at 11:48 AM | Unregistered CommenterAlexander K

Error alert1 Don't know what I was thinking, but I should have titled the blog I wrote about 'Sceptical Science'.
Mea culpa!

Jun 28, 2011 at 11:49 AM | Unregistered CommenterAlexander K


Pravda on the Yarra ...

Great. There's something about the way you Aussies deal with such tribute bands that suggests that "53% to 47% against" is only gonna grow. My aunt (who's lived in Melbourne since the 1950s) has been saying recently that I must emigrate. I'll see what I can do to increase the favourable stats :)

Jun 28, 2011 at 12:05 PM | Unregistered CommenterRichard Drake

Skeptical Science: Winner of the Most Inappropriately Named Blog Award 2011, 2010, 2009, 2008 ...

Jun 28, 2011 at 12:20 PM | Unregistered CommenterSimon from Sydney


I voted yesterday, and then the proportions were more like 80-20 if not higher in favour of the "no it should not be a priority" argument - so it has moved the other way if anything.

Jun 28, 2011 at 12:21 PM | Unregistered CommenterChris

Funny that. Whenever I've looked at Skeptical Science it has always appeared as a bunch of half truths craftily assembled to make a case about reality. There sure is an awful lot of information unhelpful to the warmist cause being suppressed. There is no point in quoting a proverb unless one means to apply it and make comparisons. By the same token, therefore, Skeptical Science would appear to be a "whole lie". I don't wish to be rude by saying this, I'm simply holding John Cook to the same standard he applies to everyone else.

Jun 28, 2011 at 12:25 PM | Unregistered CommenterScientistForTruth

Who can forget

which turned out to be 75 of 77.

He's still selling the t-shirt though :)

Jun 28, 2011 at 12:32 PM | Unregistered CommenterChris

The NASA GISS temperature record uses extrapolation to fill in the areas not covered by weather stations. However, the European Centre for Medium Range Weather Forecast combine satellite data, weather stations, ship measurements, buoys and weather balloons to create a reanalysis record that covers the Arctic region using empirical data.

Jun 28, 2011 at 12:34 PM | Unregistered CommenterJohn Cook

Ooops Maybe thats a different survey :S

Jun 28, 2011 at 12:34 PM | Unregistered CommenterChris

Chris, the 97% consensus is based on two studies - the Doran et al 2009 survey which you refer to and Anderegg et al 2010 which uses a different methodology and a much larger sample size to arrive at the same answer.

Jun 28, 2011 at 12:36 PM | Unregistered CommenterJohn Cook

John, I realised after posting. Identical results though - hence the, er, skepticism ;-)

Jun 28, 2011 at 12:47 PM | Unregistered CommenterChris

John Cook:

The NASA GISS temperature record uses extrapolation to fill in the areas not covered by weather stations. However, the European Centre for Medium Range Weather Forecast combine satellite data, weather stations, ship measurements, buoys and weather balloons to create a reanalysis record that covers the Arctic region using empirical data.

John, I feel I should record that before looking at Bishop Hill this morning I took a small punnet of cherries from my kitchen - one of my favourite fruit - and was just starting to enjoy them when I came across this post. So your words in The Age and the Bishop's commentary seemed a bit of a gift.

But thank you for the point you make - and the polite way it is made. And of course any combining of data by the European Centre for Medium Range Weather Forecast is done by software. The crucial matter is what the code is doing, whether that is optimal and what the error and uncertainty are. We need great trust in such software, which is why I'm sure you agree that all such code should be open as a matter of course.

Jun 28, 2011 at 12:53 PM | Unregistered CommenterRichard Drake

Cook is merely following rule one of climate science/religion . Which is when the models and reality differ in value , its reality that is wrong .

Jun 28, 2011 at 12:55 PM | Unregistered CommenterKnR

@ John 2 - But now I look more closely at it it, the more it seems fishy....

Jun 28, 2011 at 12:55 PM | Unregistered CommenterChris

Perhaps Mr Cook can explain what 'Skeptical Science' is sceptical of?
It doesn't seem to be AGW.

Jun 28, 2011 at 1:03 PM | Unregistered CommenterJames P

Dear Dr/Mr Cook,

You don't feel the slightest twinge of hesitation in quoting Anderegg et al for your purposes?

That paper received more than 4 replies. Going by climate sciences standards of rhetoric, that would mean that it is 'completely demolished', 'debunked', eviscerated' etc, isn't it?

Secondly, the paper's conclusion is that the 'skeptics+deniers' camp does not possess expertise or academic standing, as evaluated by their method of publication metrics. The paper does not assess or come to the conclusion you have drawn above in your post (and on your website). The study assesses publication metrics of those who participated in the IPCC fourth assessment who are automatically assumed to have 'signed up to the consensus'.

From their materials and methods section:

We defined CE researchers as those who signed statements broadly agreeing with or directly endorsing the primary tenets of the IPCC Fourth Assessment Report that it is “very likely” that anthropogenic greenhouse gases have been responsible for “most” of the “unequivocal” warming of the Earth's average global temperature in the second half of the 20th century (3). We compiled these CE researchers comprehensively from the lists of IPCC AR4 Working Group I Contributors and four prominent scientific statements endorsing the IPCC (n=903...)

It then states in their abstract:

Here, we use an extensive dataset of 1,372 climate researchers and their publication and citation data to show that (i) 97–98% of the climate researchers most actively publishing in the field surveyed here support the tenets of ACC outlined by the Intergovernmental Panel on Climate Change, ...

I hope the circularity of this logic, and in claimsmaking doesn't escape you.

Indeed, the paper's conclusions as stated in the abstract are probably sound (within the bounds of its own logic, and if one accepts its numerous glaring flaws in methodology). But it is very cleverly worded to sound as its exact inverse, a trap which you have fallen for, Mr Cook, in your careless reading.

It is a consequence of your butterfly-collection approach to science. Please don't dessicate and shrinkwrap science papers and put them up on display - as you do on your website - and call it 'skeptical' or 'science'.

Jun 28, 2011 at 1:13 PM | Unregistered CommenterShub

Mr. Cook is sceptical of science.

Jun 28, 2011 at 1:14 PM | Unregistered CommenterEdim

Lubous Motl spent some re-butting the "Getting skeptical about global warming skepticism" section in John Cooks site.

I personally have not spent much time at Mr Cooks site, the use of the D word being totally inappropriate IMHO. If the science he is preaching is so strong then there would be no need for the abuse.

Jun 28, 2011 at 1:27 PM | Unregistered CommenterJack Cowper

Shub, I watched the video of the dreadfully unfunny comedian from your link, and he reminded me of an Englishman, a university professor who had emigrated to New Zealand in the 1960s, who flatly refused to attend any live theatre in NZ on the basis that 'he had seen the best productions in the world, in London's West End and wouldn't bother with inferior stuff the Colonials probably put on'. The same bloke wondered out loud in the University staff club as to why he didn't seem to be enormously popular with NZ students'
Or perhaps the comedian was being ironic and both me and the audience didn't realise the joke was us.

Jun 28, 2011 at 1:44 PM | Unregistered CommenterAlexander K

John Cook

Good to see you posting here.

Is there anything about the AGW science decreed by Hansen/Mann/HockeyTeam/IPCC etc that you are sceptical about, or are you cherry picking those that you support?

Jun 28, 2011 at 1:48 PM | Unregistered Commentergolf charley

Lucy Skywalker's work with John Daly's data is well worth a look on this:...
Interesting that her links to Tamino's comments don't work.

Jun 28, 2011 at 1:53 PM | Unregistered CommenterMike Jackson

A question - is the reporter complaining about Carter using the HadCRU dataset rather than GISS? There are many others who do so without being criticized by Cook.

Jun 28, 2011 at 2:01 PM | Unregistered CommenterSteve McIntyre

James, to me, the heart of skepticism is reliance upon evidence. Skeptics don't just take someone's word for it - they investigate and consider the full body of evidence. So my approach is to consider all the evidence - I don't believe there is "their evidence" and "our evidence" - there is only the full body of evidence.

This philosophy is reflected in my article about Bob Carter who utters half-truths such as "global warming stopped in 1998" or "CO2 is beneficial to plants" - when you consider the full picture, you realize reality is actually the opposite to the picture Carter was painting.

Jun 28, 2011 at 2:03 PM | Unregistered CommenterJohn Cook

Can I please ask those readers who are of an angry disposition to park their anger at the door - it's nice to have John Cook come here and engage and I'm keen that this thread does not deteriorate as others have done in the past.


Jun 28, 2011 at 2:09 PM | Registered CommenterBishop Hill

John Cook:

... the 97% consensus is based on two studies - the Doran et al 2009 survey which you refer to and Anderegg et al 2010 which uses a different methodology and a much larger sample size to arrive at the same answer.
Doran is so breathtakingly idiotic that even a layman like me can see where its failings lie. Start with 10,000 scientists of whom only 30% bother to reply, making the exercise self-selective and therefore dubious from the start: then eliminate and eliminate and eliminate until you reduce the number to 79 and claim from that "97% believe ..." Come on, John, how stupid do we have to be?
As far as Anderegg is concerned, the numbers may be bigger but the inevitable conclusion is going to be the same. You might as well say that 97% of practising Catholics believe murder is sinful.
And since it is already well-established (not least by certain email exchanges between prominent climate scientists) that concerted efforts have been -- and probably continue to be -- made to ensure that papers that contradict the paradigm do not see the light of day it is hardly surprising, as that well-known neutral observer Oreskes rather patronisingly puts it, that "those who don't agree, are, unfortunately—and this is hard to say without sounding elitist--mostly either not actually climate researchers or not very productive researchers."
When the handful of "productive" researchers spend their lives up each others backsides there is little room for anyone else. Personally I take the view that there are climatologists considerably more expert, experienced and better qualified than Mann, Jones, Briffa and the other members of "The Team" combined and we have read frequently and at length of the difficulties they have in getting work published. And you don't need to be a sceptic to fall into that camp, witness the Pielkes among others.

Jun 28, 2011 at 2:19 PM | Unregistered CommenterMike Jackson

Anderegg et al? Puhleeze! You gotta be kidding, Cook! LOL!

Jun 28, 2011 at 2:20 PM | Unregistered CommenterSimon Hopkinson

.. Sorry.. MR Cook. :o)

Jun 28, 2011 at 2:21 PM | Unregistered CommenterSimon Hopkinson

NB: Bish.. mine is not anger. It is incredulity. It's difficult to be angry while guffawing. :o)

Jun 28, 2011 at 2:23 PM | Unregistered CommenterSimon Hopkinson

Mr. Cook, you seem to be saying CO2 does not benefit plants, so I checked your website to clarify.

You seem to be saying CO2 benefits plants in a controlled environment, but that other effects of climate change around the world "have had, and will have" more abiding adverse effects.

"A rise in CO2 levels is not the only consequence of climate change, and it is these other effects that have had and will have more abiding adverse effects on plant growth around the world."

if you did indeed "investigate and consider the full body of evidence" how could you have missed Liu et al, research which shows warming and elevated CO2 are not combining to destroy the planet’s vegetation. Quite to the contrary.

Jun 28, 2011 at 2:48 PM | Unregistered CommenterFrosty

John Cook – thanks for your participation. About those studies:

The flaws in the Doran paper are well known: (A) it used a hopelessly inadequate sample size (79 respondents) and demographic (nearly all from N America) and (B) in any case, most sceptics would agree with both its propositions: (1) that the world has warmed since the 1700s and (2) that mankind contributed. It made no mention of GHG emissions.

Anderegg is more sophisticated than the hopeless Doran. But there’s a basic problem: it’s concerned with whether or not respondents agree that ““anthropogenic greenhouse gases have been responsible for “most” of the “unequivocal” warming of the Earth’s average global temperature over the second half of the 20th century”. The only scientists qualified to evaluate that are those engaged in detection and attribution (both difficult and uncertain). Yet the research was not confined to such scientists.

And the research itself is flawed. First, the total number of “climate researchers” who accepted the above statement was, according to the paper, 903 and the total who did not 472. In other words, 66% - not the much-claimed 97%. The researchers got their 97% by restricting their findings to researchers “most actively publishing in the field” – in other words, the paper’s findings do not cover all “climate scientists”. Further, it wasn’t an opinion survey but an analysis of scientists who signed pro/anti statements – not perhaps the most useful of documents. And, again, it was essentially confined to N America. In other words, it’s almost wholly valueless as a measure of opinion.

So neither “survey” is evidence of a consensus among climate scientists about the dangers of AGW. But, of course, the overriding point is that science is not done by consensus or by majority vote.

Jun 28, 2011 at 3:06 PM | Unregistered CommenterRobin Guenier

John Cook on Revkin, (complete with photo) -

"I studied physics at university and majored in astrophysics in my post-grad honors year. After completing my studies, I went into real world (a sorely needed break from academia) and I’ve been working from home for just over a decade now"

So working from home is the real world. If only sheep shearing and coal mining was so tough. I wouldn't really class completing a first degree as being in "academia" either. Perhaps you do.

"post-grad honors year" - A 1st will get you a stab at a PhD. A 2A probably would, but would certainly get you a guernsey for a Masters. A 2B, thanks for coming and for a 3rd you merely have to fog up a mirror held in front of your mouth. So what honours in Physics were you granted John? Perhaps you got a first or an upper second and had good reasons to leave. Fair enough, I know many that did just that.

However, as it stands you have no post-graduate qualifications, no peer reviewed publications and are looked upon as a mere zeolot by fellow physicists I know in Oz.

Jun 28, 2011 at 3:14 PM | Unregistered CommenterGrantB


Lubos Motl ripped this guy to shreds

And he has taken down the photo too.

Jun 28, 2011 at 3:21 PM | Unregistered CommenterFred Bloggs

Let's follow up on Frosty's point, John.
Are you saying that CO2 only benefits plants in a controlled environment because if so I'd like to see your evidence since it appears to overturn "the wisdom of the ages"?
More importantly, can we have some evidence of the effects of climate change that "have had and will have" adverse effects on plant growth? This seems to me to be very speculative.

Jun 28, 2011 at 3:25 PM | Unregistered CommenterMike Jackson

Half truths.

Why does John Cook opst a short bio of himself describing himself as a "physicist" on his blog, but a cursory search on the interweb reveal that he ommits to include the fact that he has spent his time since graduating as a cartoonist (and at times childminder according to his own words)?

Is it because such ommission help to craft the reality he wants to paint?

Jun 28, 2011 at 4:13 PM | Unregistered CommenterGeckko

I don't see how ship and weather balloon measurements can contribute to a mean temperature record, surely the sampling is too random and sparse?

Jun 28, 2011 at 4:16 PM | Unregistered CommenterRyanS

Cook engages in half truths himself. Just one small comment: yes, CO2 is a plant fertilizer, yes you get more food and output with more CO2, everything else equal -- Cook agrees there.

But then he says that plants need water, and CO2 will (he implies) reduce water availability. Leaving aside that there will be more precipitation, but that we don't know how the patterns will change, Cook should know that with more CO2, plants respire less water and therefore need less water. So, everything else equal in a higher CO2 world, not only would you get more crop yield, but you would also need less water to do it. Maybe marginal lands will become productive!

All is to a degree speculation, without knowing (how can we?) how rainfall patterns and amounts will change, but as a matter of first order impressions -- I hope you are listening, Mr. Cook! -- more CO2 is good for lowering water use, or producing more with the same amount of water.

No more half truths, sir!

Jun 28, 2011 at 4:27 PM | Unregistered CommenterJohn

Maybe marginal lands will become productive!
Vraiment! Is it not the case that the Sahara is currently in retreat, for example?
This doom-mongering drivel that there is nothing but a down-side to increased CO2 or even to global warming itself is really starting to get a little boring.

Jun 28, 2011 at 4:40 PM | Unregistered CommenterMike Jackson

First I would ask that commenters dispense with the attacks on John Cook, as Bishop Hill requested. They are not productive, and it's not relevant to this discussion that Lubos Motl wrote an article attacking Skeptical Science, for example. I have my own opinions of Motl, his blog, and his article (and they're not good), but it's irrelevant here.

Secondly, Carter states five so-called "facts" in his articles, each of which is a half-truth at best (some are outright lies), and the 'cooling since 1998' claim is just one of them. Probably not even the worst.

Thirdly, it's a fact that the Arctic is the fastest-warming region of the planet's surface, and it's excluded from the HadCRUT analysis. It's also ironic that CRU was attacked so fiercely by "skeptics" after "climategate", and now appears to be their exclusive temperature dataset choice.

Regardless, every dataset including HadCRUT shows a warming trend since 1998. GISS, the European reanalysis, and NOAA NCDC all show 2005 and 2010 hotter than 1998. Carter is wrong on this point.

Jun 28, 2011 at 4:50 PM | Unregistered Commenterdana1981

Unfortunately, "big data" science is, at its essence, a process of reduction. PCA, regression, etc, etc are all data reduction techniques. The choices made during the reduction process can have a large impact on the results. In many cases, you can get any answer you want by the choices you make. Having said that, the arctic data is synthetic to begin with, so I don't think it is accurate to say that using a dataset that does not contain added synthetic data equals "cherry picking". Seems like just the opposite to me.

Jun 28, 2011 at 4:51 PM | Unregistered Commentermpaul

WRT John Cook:

The NASA GISS temperature record uses extrapolation to fill in the areas not covered by weather stations. However, the European Centre for Medium Range Weather Forecast combine satellite data, weather stations, ship measurements, buoys and weather balloons to create a reanalysis record that covers the Arctic region using empirical data.

By which I take it John means this from here although I may be wrong and he does not provide a link.

If this is the correct reanalysis, it appears (to my eyeball) to be in good agreement with HADCRUT, GISTEMP, UAH and RSS for the period 1998 - present.

The decadal trends for that period are (degrees C):

GISTEMP 0.12 (0.123)

HADCRUT3 0.0 (0.006)

UAH 0.05 (0.049)

RSS 0.03 (0.031)


- Carter is incorrect to state that GATA has fallen from 1998 - present

- The satellite measurements for TLT are arguably the most truly global and representative (despite their lack of full polar coverage) and show no significant warming trend.

- HADCRUT3vgl shows no trend and GISTEMP is known to derive its positive trend from Arctic interpolation.

- The ECMWF GATA (surface) reanalysis may support the higher trend exhibited by GISTEMP.

- If so, both are contradicted by the satellite measurements of TLT which suggests methodological problems with the surface-based reconstructions.

- It is as potentially misleading to claim that significant warming has occurred over this period as it is to claim that GATA indicates cooling.

- Everyone should be very careful not to over-interpret a short time-series.

Jun 28, 2011 at 4:52 PM | Unregistered CommenterBBD

I have my own opinions of Motl, his blog, and his article (and they're not good), but it's irrelevant here.
Then what's your point, exactly?

Jun 28, 2011 at 4:55 PM | Unregistered CommenterMike Jackson

"Everyone should be very careful not to over-interpret a short time-series."
That's a point I can certainly agree with BBD on. Trends are positive, but not statistically significant since 1998. However, they're certainly not negative, as Carter asserts.

Jun 28, 2011 at 5:00 PM | Unregistered Commenterdana1981

John Cook, I do not know where you have been posting from, but if it is bed time where you are, that is understandable.

I have just had a quick flick around your site, and I am confused about your beleif or not in the Medieval Warm Period. You seem to support the findings of MBH98, that included the scrubbing of the MWP from the historical record, but are happy to support authors on the MWP when discrediting ideas about the sun being the cause of climate change.

Do you intend to review your debunking of the sun's influence in the light of recent reports concerning the sun's variable output?

Jun 28, 2011 at 5:00 PM | Unregistered Commentergolf charley

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