Angry in the Great White North

Phil Jones is the former head of the Climate Research Unit at the University of East Anglia.  He stepped down in the wake of the Climategate revelations, including the bombshell email in which he describes using a "trick" to "hide the decline".

The BBC asked Phil Jones to explain himself.  Here is Phil Jones' answer regarding the trick:

Q - Let's talk about the e-mails now: In the e-mails you refer to a "trick" which your critics say suggests you conspired to trick the public? You also mentioned "hiding the decline" (in temperatures). Why did you say these things?

This remark has nothing to do with any "decline" in observed instrumental temperatures. The remark referred to a well-known observation, in a particular set of tree-ring data, that I had used in a figure to represent large-scale summer temperature changes over the last 600 years.

The phrase 'hide the decline' was shorthand for providing a composite representation of long-term temperature changes made up of recent instrumental data and earlier tree-ring based evidence, where it was absolutely necessary to remove the incorrect impression given by the tree rings that temperatures between about 1960 and 1999 (when the email was written) were not rising, as our instrumental data clearly showed they were.

This "divergence" is well known in the tree-ring literature and "trick" did not refer to any intention to deceive - but rather "a convenient way of achieving something", in this case joining the earlier valid part of the tree-ring record with the recent, more reliable instrumental record.

I was justified in curtailing the tree-ring reconstruction in the mid-20th Century because these particular data were not valid after that time - an issue which was later directly discussed in the 2007 IPCC AR4 Report.

Am I the only one who thinks this doesn't make sense?  I mean, it would seem that the tree ring data is considered valid until the appearance of instrumented records.  But then the instrumented records show one trend (temperature going up) while the tree rings show a different trend (temperature going down).  So at that point, the tree ring record is considered invalid.

But doesn't this put the tree ring data prior to the appearance of instrumented records in serious doubt?!

If I was using Method A to measure something, then switched to a superior Method B, I would still expect Method A and Method B to agree with each other.  If they didn't, then one of my methodologies is giving me bad data.  If I conclude it was Method A, then I would have to throw out all the Method A data collected.

I can't just summarily declare Method A to have suddenly gone bad with the appearance of Method B.   That doesn't make sense.  On the other hand, scientists try mightily to explain the divergence.  To the layman, it just sounds like arm-waving.

I think I understand the problem for climatologists.  Tree ring data is their primary record for temperature prior to the thermometer.  If they declared that tree rings do not provide reliable data on temperature (too many variables, like moisture content, soil conditions, changes in light conditions when beavers gnawed down the next tree over), then they would have little paleo-climatological information to go on.  Then how could they declare the global temperatures have been going up?

The answer, of course, is that they couldn't.

Phil Jones hasn't explained away the "trick". It's still a piece of logical nonsense.