Monday, November 30, 2009


Clarification on Climategate

If you want to follow this stuff on the cutting edge, the site to visit is ClimateAudit, which is run by Steve McIntyre, the intrepid outsider who caught Mann with his pants down on the "hockey stick" graph. (Actually ClimateAudit is overwhelmed right now with new visitors because of Climategate, and so McIntyre is placing his new posts at a mirror site, here.)

The problem with McIntyre is that he shares Ludwig von Mises' expectations on the knowledge of the reader. Just as Mises would make one-off comments about Bohm-Bawerk's capital theory or the Weber-Fechner physiological law, so too does McIntyre assume all of his thousands of readers are totally familiar with the history of climate science and just want McIntyre to give them the actual freaking computer code to replicate Jones graph from 1999. (!!)

So anyway, that's why you have me here. Lately my purpose has not been to invent new material but to translate the work of other giants into a version that you, the unwashed masses, can understand...

Now that I've made the opening funnies, let's get down to business. I had been aware of this (vaguely) but it didn't really hit me until a commenter at ClimateAudit said it explicitly. To set the context, PaulM first said:
Steve I really think you need to explain things more clearly for the thousands of new readers who are now reading your blog. Most of them will not understand this. I’ll have a go, please correct:

The green line is tree-ring data on the left. On the right it has been smoothly merged into temperature data. This is Michael Mann’s trick, that he falsely claims is never done. The reason they do it is to hide the fact that otherwise the green tree-ring data curve would go down in the late 20th century rather than up, showing that the tree-ring data is useless at representing temperature. Hence “hide the decline”.
Then to endorse this take (which I endorse as well, for what that's worth), Calvin Ball said:
Paul, that’s my take. And I agree that this is important for the masses to get; the popular interpretation of “hide the decline” is somehow concealing the lack of warming over the past decade. This is completely wrong, but it’s catching on.
Does everybody get what he's saying? When Jones said in the infamous CRU email that he used "Mike [Mann]'s Nature hide the decline," he was NOT talking about a decline in actual global temperatures that thwarted the claims of global warming.

On the contrary, he was talking about a decline in the proxy for global temperatures based on tree ring observations. So what happens is that from 1960 on, the proxy starts dropping while the actual temperatures go up. (See the divergence in this post.) Ironically then, if actual global temperatures had NOT risen in the last half of the 20th century, then there would be less of a problem to "hide."

Now you might ask, "Huh? Why do they need to hide the decline in a proxy of temperature, when we already know the actual temperature post-1960?"

Good question; I'm glad you asked. The answer is that to make the claim that the warming of the 20th century is unprecedented in the last x years (I don't remember the actual number the alarmists use, but it's big)--meaning it must be due to human activity and not natural variability--we need to know what the global temperature was, say, 800 years ago. And unfortunately all the educated people back then were busy copying the Bible by hand, rather than setting up temperature stations (and being careful to filter out the Monastery Heat Island effect).

So in order to demonstrate that the 20th century warming is unusually rapid, the climate scientists have to construct a proxy of global temperatures going back before the period of modern instrumentation. One of these series is based on tree rings.

Now you see the problem. If the tree-ring proxy diverges sharply from actual recorded temperatures from 1960 onward, then we can't trust it when it tells us that temperatures have been fairly stable before modern economic growth. Hence the claims of the alarmists are undercut.

In conclusion, Jones was not trying to "hide" the lack of global warming since 1998, as many people are probably concluding. So the problematic phrase in his email is "hide," not "the decline."

(I am pretty sure my explanation above is correct, but by all means if someone thinks I have botched a particular point please bring it to my attention.)


Say, I haven't been following but has Silas gotten uppity about any of this yet?
You are right, IMO, as I have been following the two groups bickering since it started.
I say you are right.
The idea is that if you «stitch» two different data set ( be it tree ring and thermometer or a new thermometer technolology with the old one ) the overlap part of the data has to say the same thing or else stop and find the error...
That is science...

You talk about Mises here.
I would like to point an interesting correlation: almost everybody who accept global warming are Keenesian ( or are «would be» if they knew about it), and most Austrians are sceptics...
(Note: no scientific data here, just observation...)

If true, that would point to an epistemological cause here, no ?
And wouldn't that be reality against whish ( whim could be a better word ) as an axiom ?
It is more devastating.

Tree ring proxies are used to create the hockey stick graph, and the hockey stick graph was concocted to dispute this simple argument that AGW is wrong:
(ie warming before 1910 cannot possibly be explained by human CO2 emissions, which were tiny before 1945)

Tree rings are rubbish (eg do not show post-1960 rise in temps)
=> hockey stick is rubbish
=> simple proof comparing timing of human emissions and temperatures is true
=> AGW is rubbish.

It will take a while for people to figure this out, and the alarmists will try hard to distract and obscure.
People should definitely read up on the history of the hockey stick battle. It's interesting in itself and you'll learn a lot about the cast of characters involved in this hack/leak.

For instance, from the hacked/leaked CRU documents it is the emails of Michael Mann which are amongst the most frequently flagged up by all the big oil funded denialists commenting in blogs and what have you. Yet, as shady as some of that stuff is it is mild when compared to what was leaked inadvertently by Mann himself. Google "Mann Censored folder" for the goods. You'll get a good insight on why he and some of his colleagues might not be keen on the idea of releasing data.
Want to see real science replying to pseudo-science ?
See the reply today of Lubos Motl to Scientific American.
( )

Quite interesting...
Great post Bob. I admit I'd accepted the popular interpretation of "hide the decline" as well, and I'm firmly a geekonosphere follower.
@TAYLOR: My complaints have always been about how libertarians react *conditional* on AGW being true, which has likewise always been appalling.

If you can't understand the differece between that position and defense of the behavior shown in the CRU emails, that should help explain why I'm reluctant to bother responding to you.

It's truly amazing and a testament to the patience and honesty of all those libertarians that anyone bothers to respond to you in the first place. Seeing as how most of us don't have your entire intellectual framework, including all relevant conditionalities and related circumstances, committed to memory, replying to your criticisms is usually good for nothing more than an invitation to have one's intelligence and motives immediately called into question and rebuked.

Take me, for example... I've read a whole lot of your posts and I had no idea you made all your arguments based upon the condition of AGW being true. I guess I must've missed your original position paper, likely published before I was even a loving glance between my parents. So many people are so often confused and frustrated by what you have to say, I often wonder if it's because your wisdom is that great, or your explanatory prowess is that weak.

Now, I was going to observe that what I find appalling is that you, as a libertarian, would ever suggest that government redistribution be a solution to any problem like AGW, if it were true, but I am sure that in even saying something like that I'd only reveal the careless nonchalance with which I've previously examined your arguments and contingent conditionalities and I'd rather not do that right now. I fear my self-confidence so thin at this point I couldn't take the verbal lashing.

As a long time reader of ClimateAudit, I can tell you that your description of "hide the decline" is largely correct. Much of the contention in the proxy battle has been the seeming desire to obliterate all evidence of any warmer period than the present.
I agree with that the divergence of the tree ring temps with the real temps undermine the tree rings being used as a proxy. However, other proxies were being used (e.g. ice core data). How do these match with recent temps? Do they give us an idea of temps from centuries ago?
it has been covered so many times before. Not including a referral in a comment like that could be the writer's way to help its audience do some conscious thinking, not obvious knowing.
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