Wednesday 25 November 2009

Mining The Source Code

In the last post we saw that accusers are willing to quote mine the released CRU emails, selectively taking a choice phrase at face value and missing the preceding and proceeding context in the longer email.

Now we will see them doing similar with some of the released CRU source code. The released source code included source for some of CRU's surface temperature record and source code for some proxy work.  No climate model source code was released as far as I know, although that hasn't stopped many of the accusers rampantly assuming there has been - presumably either confusing or not knowing the difference between temperature records and climate models.

This post concerns the an accusation which is now spread far and wide all over the internet.

Here is one example:

Here's the code and comments in question:

; Apply a VERY ARTIFICAL correction for decline!!
valadj=[0.,0.,0.,0.,0.,-0.1,-0.25,-0.3,0.,- 0.1,0.3,0.8,1.2,1.7,2.5,2.6,2.6,$
2.6,2.6,2.6]*0.75 ; fudge factor
if n_elements(yrloc) ne n_elements(valadj) then message,’Oooops!’

The accusers point to the words "very artificial", "fudge factor" and to the nature of what is being done. 

yrloc is assigned a 20 element array, the first value starts at 1400, the second at 1904 and the rest increment by 5 until 1994. Ie 1400, 1904, 1909, 1914, ... 1994. They are obviously years.

valadj is another 20 element array, you can see the values it is assigned above in the line "fudge factor". The 'Oooops!' message is displayed if the number of elements in the yrloc and valadj arrays are different. They shouldn't ever be according to the code, this line was probably added in as a first pass safety check and not subsequently removed.


I have to guess a little here (I don't know IDL), but I think this is producing an array yearlyadj to hold an adjustment value for every year since 1400, derived by interpolating yrloc over valadj

Despite so many accusers citing this snippet of code, they amazingly fail to mention (or perhaps notice?) that directly following this snippet is:


The top line contains yyy+yearlyadj. This is the only place where the previously created adjustment array is used, I presume (I don't know IDL, the language used here) that yyy contains each years temperature data and that this is adding the adjustments to the temperature data to produce the plot. But notice at the start of that line is a semi-colon. That line is commented out, inactivated. The lines that are used instead do not contain the use of yearlyadj and therefore do not apply the adjustment, they only plot yyy.

Of course it would be trivial to switch the comments around and activate the adjustment, but as the accusers are relying on a face-value interpretation of the source code they should fall by such silliness.

They haven't even shown their quoted adjustment was used, let alone what it's purpose is. A proper analysis of this would require knowing what the adjustment was based on (it clearly isn't arbitrary), why it was done (perhaps nothing more than an experiment), and not to forget - whether it was even used at all in published results.

It's not difficult for me to point out why the accusations of fraud are misplaced. All I have to do is point out that they have insufficient evidence. Come back with better, if you can. I am surprised they haven't picked up on the mispelt "artifical", surely that beggars belief - true scientists wouldn't spell words wrong! Quick to the blogs!

Isn't it surprising some of the same people who demand so much evidence when faced with the science behind manmade global warming are surprisingly relaxed at placing accusations of fraud with such a dearth of evidence?

Tuesday 24 November 2009

Trenberth on Travesty

Before I start let me make it clear why I am not using the word "skeptic" to describe the manmade global warming skeptics who using these emails to push accusations of fraud. It's because their behavior is anything but. They feign skepticism and claim to be analyzing the emails, but what they are really doing is quote mining them. I will simply refer to them below as the accusers.

"The fact is that we can't account for the lack of warming at the moment and it is a
travesty that we can't."

This is often the only quote accusers will pull from that email. A quote mine if I have ever seen one. Quote mining is the practice of pulling juicy quotes out context of the larger body they reside in and then presenting those out of context quotes as an argument. It is not a new trick (!) by any means. As wikipedia explains on the subject, "Scientists and their supporters used the term quote mining as early as the mid-1990s in newsgroup posts to describe quoting practices of certain creationists"

Well guys, here we go again.

Lets look at the context in the rest of the email. The most damning thing against the accusers is that a good part of the context is found right before that quote, in a reference to a paper of Trenberths. In fact from my reading, this paper is central to Trenberth's email.

Here it is:

An imperative for climate change planning: tracking Earth's global energy.

The abstract:

"Planned adaptation to climate change requires information about what is happening and why. While a long-term trend is for global warming, short-term periods of cooling can occur and have physical causes associated with natural variability. However, such natural variability means that energy is rearranged or changed within the climate system, and should be traceable. An assessment is given of our ability to track changes in reservoirs and flows of energy within the climate system. Arguments are given that developing the ability to do this is important, as it affects interpretations of global and especially regional climate change, and prospects for the future."

Immediately you start to get a feeling that Trenberth's quote has been taken out of context somewhat. But wait until you see the part immediately following the quotemined phrase:

"The CERES data published in the August BAMS 09 supplement on 2008
shows there should be even more warming: but the data are surely wrong. Our observing
system is inadequate."

The context is now clear. Trenberth is talking about the travesty of the observation system and our inability to see where the heat is going from year to year. It is well known and public that there are problems in recent years with the global climate observation system ( Problems are more of a rule in any complex field of science rather than an exception.

The accusers cherrypicked a phrase from Trenberth's email thinking they had found some hidden truth, when in fact Trenberth had already published about this. These kind of accusers will analyze only until they get an argument they want. The quotemine above provided them with the argument so they looked no further.

The accusers exploit the private nature of these emails to claim these emails represent the uncovered real thoughts of the scientists. This cuts both ways, if you are going to exploit the privacy of the emails to claim "this is what the scientists really think!" then you are forced to accept the emails contain what the scientists really think. 

So what do accusers make of the bulk of the email material which runs counter to their views? In the Trenberth exchange for example, what do accusers make of the fact that even behind closed doors the scientists are saying long term warming signal exists and short term cooling is noise? I would have thought the accusers would have been quite interested in learning this as it contradicts their beliefs that this was just some excuse that scientists couldn't possibly believe. But no they aren't interested in that kind of "what scientists really think".

Overall I think the emails are inconvenient revelations for the accusers, although unfortunately quote-mining is a particularly effective method of propaganda and no easy counter exists.