This is a repost of two articles from John Graham-Cumming’s blog. I watched with interest earlier this month where he and a colleague identified what they thought to be a math error related to error calculation when applied to grid cells. It appears now through a journalistic backchannel that the Met Office is taking the issue seriously.
What I found most interesting is that while the error he found may lead to slightly less uncertainty, the magnitude of the the uncertainty (especially in homogenization) is quite large in the context of the AGW signal being sought. John asks in his post: “If you see an error in our working please let us know!” I’m sure WUWT readers can weigh in. – Anthony
The station errors in CRUTEM3 and HadCRUT3 are incorrect
I’m told by a BBC journalist that the Met Office has said through their press office that the errors that were pointed out by Ilya Goz and I have been confirmed. The station errors are being incorrectly calculated (almost certainly because of a bug in the software) and that the Met Office is rechecking all the error data.
I haven’t heard directly from the Met Office yet; apparently the Met Office is waiting to write to me when they have rechecked their entire dataset.
The outcome is likely to be a small reduction in the error bars surrounding the temperature trend. The trend itself should stay the same, but the uncertainty about the trend will be slightly less.
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Something odd in the CRUTEM3 station errors
Out of the blue I got a comment on my blog about CRUTEM3 station errors. The commenter wanted to know if I’d tried to verify them: I said I hadn’t since not all the underlying data for CRUTEM3 had been released. The commenter (who I now know to be someone called Ilya Goz) correctly pointed out that although a subset had been released, for some years and some locations on the globe that subset was in fact the entire set of data and so the errors could be checked.
Ilya went on to say that he was having a hard time reproducing the Met Office’s numbers. I encouraged him to write a blog post with an example. He did that (and it looks like he had to create a blog to do it). Sitting in the departures lounge at SFO I read through his blog post and Brohan et al.. Ilya’s reasoning seemed sound, his example was clear and I checked his underlying data against that given by the Met Office.
The trouble was Ilya’s numbers didn’t match the Met Office’s. And his numbers weren’t off by a constant factor or constant difference. They followed a similar pattern to the Met Office’s, but they were not correct. At first I assumed Ilya was wrong and so I checked and double checked has calculations. His calculations looked right; the Met Office numbers looked wrong.
Then I wrote out the mathematics from the Brohan et al. paper and looked for where the error could be. And I found the source. I quickly emailed Ilya and boarded the plane to dream of CRUTEM and HadCRUT as I tried to sleep upright.
Read the details at JGC’s blog: Something odd in the CRUTEM3 station errors
kadaka (08:42:28) :
Yup, it took Zeke all of one or two days to figure out how to do spatial averages. He was unnecessarily intimidated by it at first, and needed a pointer on how to work out the surface area of a grid box given the coordinates of the corners. This stuff isn’t that hard.
kadaka (08:07:31) :
“Besides, “everybody” is not getting the same result anyway.”
Really? Exactly who has found that the station drops are ensuring a warming bias to the global record? Where is this analysis?
kadaka (11:33:24) :
It really doesn’t much matter how you slice it. The main differences between Tamino and GISS are:
– how the offset is computed when combining anomalies
– the grid box dimensions
– Tamino is not using any adjustments, and is not using USHCN for the US, so he’s using purely raw data everywhere
whereas the ccc guys do just what GISS does. Zeke on the other hand uses yet another method for combining stations (and one that I think needs to be improved, by the way). GISS, CRU and NCDC also go about all these things in their own way.
But the conclusion on the question of station drop is not sensitive to these differences in implementation.
kadaka (10:53:44) :
You’re reduced to arguing about release numbers?
kadaka (11:33:24) :
Oh, and you keep saying the details of Tamino’s method are missing. Yet you can’t identify which.
Anybody with a familiarity with the subject should be able to pretty well reconstruct Tamino’s version, based on what he’s said. In the cases where I was unclear on what he did, I asked and he clarified. He’s said what data he is using. He’s said how he’s combining duplicates. He’s said how he’s combining stations. He’s said what sort of grid he’s using, and how he’s combining those. He might not have said what he did about relatively empty grid boxes; I don’t remember. But again, you don’t even need to use Tamino’s exact version. You could use Zeke’s. You could use the ccc’s. Either which way, the conclusion is there.
Paul Daniel Ash (11:24:21),
You shouldn’t fabricate statements when they’re so easy to check. Who do you think you are, Dan Rather? Here’s your misrepresentation:
“Smokey says you better get busy on proving that.”
Smokey said no such thing, nor was it implied. What I said, verbatim, was, “keep in mind that skeptics have nothing to prove. The promoters of any new hypothesis have the burden of showing that it explains reality better than the long held theory of natural climate variability. So far, CO2=CAGW fails; natural variability prevails.”
Anthony has nothing to prove; as I clearly stated, it is the promoters of the CO2=CAGW hypothesis who have that burden.
By attempting to re-frame the debate in order to score a minor point, you not only lost the point, but by prevaricating you exposed your own mendacity.
Next time, make sure you’re quoting others accurately. It will help you avoid being exposed as a deliberate inventor of fabricated assertions.
Smokey (09:55:29) :
No, there is indeed a new hypothesis here: that stations from cold locations were intentionally dropped, and that this would somehow “ensure” a warming bias to global trends.
If something is “ensured”, doesn’t that mean that the people putting forth the hypothesis should have done some analysis to back this up?
If you think the skeptics have nothing to prove, to you that means they can just say whatever they like, without having a firm basis?
carrot eater (11:18:43),
There is no new station hypothesis as stated in your first paragraph. That is a fact, not an hypothesis.
Scientific skeptics never have anything to prove, in any discipline. They can certainly offer proof if they like, but it is not required. What is required is that those putting forth a new hypothesis like CAGW have the obligation under the scientific method to fully cooperate with anyone who wants to replicate their experiments or validate their assertions.
If that requires their code and the raw temperatures, and every change made in converting raw to adjusted temps, it is not up to the promoters of the new hypothesis to refuse — without simultaneously discarding the scientific method. All data and methodologies must be scrutinized for error. That is how science arrives at the truth [or as close to the truth as we can currently get].
So no, skeptics have nothing to prove. It is the purveyors of the CAGW hypothesis who have the burden of showing that their model explains reality better than natural climate variability.
So far, they have failed. If there were truth to the CAGW hypothesis, transparency and cooperation with skeptical scientists would immediately rescue it. But the ongoing stonewalling of information means they got nothin’.