“Hide the decline”: why it’s dishonest

Needless to say, the biggest news story in the world of global warming in the past week has been the hacking of the East Anglia Climate Research Unit. When the news first broke, the big headline was an email by Phil Jones from 1999 and one damaging line:

“I’ve just completed Mike’s Nature trick of adding in the real temps to each series for the last 20 years (ie from 1981 onwards) amd from 1961 for Keith’s to hide the decline.”

This line has prompted much debate, with some on the right claiming this is fraud or that it’s proof the global warming alarmists are adding fake data or whatever. This line of thought has been attacked, with Real Climate leading the way:

The paper in question is the Mann, Bradley and Hughes (1998) Nature paper on the original multiproxy temperature reconstruction, and the ‘trick’ is just to plot the instrumental records along with reconstruction so that the context of the recent warming is clear. Scientists often use the term “trick” to refer to a “a good way to deal with a problem”, rather than something that is “secret”, and so there is nothing problematic in this at all. As for the ‘decline’, it is well known that Keith Briffa’s maximum latewood tree ring density proxy diverges from the temperature records after 1960 (this is more commonly known as the “divergence problem”–see e.g. the recent discussion in this paper) and has been discussed in the literature since Briffa et al in Nature in 1998 (Nature, 391, 678-682). Those authors have always recommend not using the post 1960 part of their reconstruction, and so while ‘hiding’ is probably a poor choice of words (since it is ‘hidden’ in plain sight), not using the data in the plot is completely appropriate, as is further research to understand why this happens.

Others have said it’s just a way to make the data look pretty, or that “trick” is just the natural jargon. Needless to say, the truth is a bit more complicated.

Here’s the gist of it in a simplified manner (a more scientific explanation can be found here. You discover that tree ring length corresponds fairly well with temperature. In other words, you can measure tree ring width, plug it into some equation, and get an average temperature for that year. Now you can keep doing this, going back a couple thousand years, and recreate the temperature profile throughout that time. Hooray!

Only one problem. When you do it for the most recent 30 years or so, you find that the temperature you get out of the tree rings is lower than the actual measured temperature. In other words, tree ring length doesn’t keep increasing with increasing temperature, but instead starts to decrease. So now, your temperature profile starts to curve downward in the 20th century instead of still going up. Alas and alack! What to do?

Well, just cut out the tree ring data at the end and replace it with the actual temperature data. What’s wrong with that? It’s more accurate, right? We should always use the most accurate data, correct? So we use the “trick” of splicing in real data with tree rings in order to “hide the decline” that shows up erroneously with the tree ring data. Perfectly legitimate, right?

No. What happens if you don’t do that? If you don’t do it, then one can plainly see the divergence between tree ring width and temperatures. One can plainly see that the calibration (ie, equation used to convert tree ring width to temperatures) does not hold for the entire range of temperature data you wish to study.

And why is that important? Because some stupid, amateur scientist might look at it and say, “Hey, wait a minute! If your tree ring reconstruction can’t possibly find high temperatures, how do you know there weren’t high temperatures in the past? Maybe there were high temperatures, but the trees didn’t grow that well, just like what’s happening now. So this reconstruction doesn’t actually tell us anything about past temperatures!”

To which the intelligent, establishment scientist replies: “Duh, of course that’s not true. If it were, then we couldn’t scare the public into giving us bazillions in funding.”

And so to avoid the possibility of people correctly recognizing the faults of bristlecone pine reconstructions, an additional data set is included to hide the faults.

That is why it’s dishonest. And while RealClimate claims that everyone knows about this already, the fact is that they not everyone knew about this back then (the email is dated from 1999). This was an attempt to hide the fact that their reconstruction was not robust, and to hide the inevitable conclusion that they couldn’t prove that the MWP did not exist.

Is it fraud? Probably not. Some clues to what they did were probably buried in the fine print. They weren’t completely hiding it (“hiding it in plain site”, as RC calls it, is probably more accurate). But it’s still very, very unethical. Why? Because even though the truth is still available, it’s hiding one of the most important pieces of information possible from the bristlecone pines: the fact that they probably can’t detect warm periods in the past even if they did occur. It’s why they aren’t usually used in reconstructions nowadays.

This email is not a shocking revelation. We’ve known about this for years. However, it does suggest that the original hockey stick authors were aware of what they were doing by “hiding the decline”. It’s just more proof that the politics of global warming have overrun the science.

So all things considered, this particular email is not all that exciting in the overall scheme. What’s more important is the bullying and disrupting of the peer review process. I’m still reading up on all of this, so maybe that’s a post for another time. In the mean time, I’ll direct you to Bishop Hill, who is one of the best writers on chronicling the global warming saga. If you’ve never read his post on Caspar and the Jesus paper, I strongly suggest it. It shows just how corrupted the scientific process has become for global warming.


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