Comparitive Criticism of Temperature Reconstructions
Posted by Jeff Id on November 20, 2008
It’s good to be back. In China the internet is amazingly slow for any websites which might have political meaning due to intense censorship. The censors err on the side of caution. While I wasn’t blocked, after several ten minute logon times to my own blog I gave up posting. However, China’s multi-billion dollar internet censorship program allows my site but our left wing American blogs (Tamino or Real Climate) won’t allow on topic posts which dispute their claims – think about that one.
Well today, I want to pass by my bashing on Tamino, as entertaining as it was for me and move back to Mann et Real Climate. I had the opportunity to read a paper on tree ring growth and a second one which was a simplified climate reconstruction by Craig Loehle some time ago. This is the third paper of his which I have read. There is uniqueness in his open style which I feel deserves the highest regard from the scientific community. I am working on a post relating to the details in his article.
Instead of the intentional complication of simple issues, a pet peeve of mine, he writes to the complexity level required to express a result. So many scientific papers obfuscate simple results to perpetuate intellectual appearances and in some extreme cases for obfuscation of questionable results. Dr. Loehle does the opposite; his papers put the facts on the table with a minimum of extraneous statistics. I read the replies to his simple and reasonable climate reconstruction for a second time yesterday on Climate Audit from Nov 07 they are quite interesting. One climate scientist made the mistake of underestimating Dr. Loehle and jumped in with both feet looking for an easy kill. It didn’t work out so well for him.
Without getting into the specific nuances of the discussion which transgressed over several critical comments and Dr. Loehle, readers should not underestimate the Dr’s mathematical understanding or abilities. It’s really quite impressive to see a scientist publishing in climatology these days and hold back on the total onslaught of math simply because it isn’t required. Something Mann should understand.
Skip this paragraph if you already read climate science articles, CA is too complicated for the casual reader so I need to do explanation here.
Mann 08 employs something called temperature proxies. Temperature proxies are measurements assumed to be reasonable stand-in’s for thermometers. Since only 400 years ago our thermometers couldn’t do anything worth reading, we can’t use their data. (we even have strong reason to question today’s measurements). So we use proxies. Proxies consist of dozens of different measurements which are theorized to possibly be related to temperature, isotope ratios in ice, mollusks, speleothum (cave stalagtites) and a variety of tree ring measurements including tree ring widths.
This article is supposed to be about proper scientific method, I just felt it was important to give some background.
Mann 08 is one of the most difficult to understand papers I have read. This group assembled a set of mathematical techniques which are not typically used, have not been independently verified to be effective and employ data which is as questionable as any I have ever imagined. Instead of verifying whether tree rings, speleothum or whatever rusty historical document are accurate temperature reconstructions, he simply piles them together and applies spooky statistics to divine the meaning. After studying the data myself I understand quite well now that his group is unable to achieve high temperature rises in recent years as compared to history by using standard methods, so unverified methods are used.
In comparison Dr. Craig Loehle was able to take pre-calibrated non-tree ring temperature proxies and average them. Not too difficult to understand, he gets the following temperature curve.
Note that the medevial warming period in the above graph is much higher than today, an inconvenient result for CO2 guys. Dr. Craig Loehle is a tree expert to give the shortest explanation. Yet he chose not to use trees in the above reconstruction claiming in other publications that trees are not good thermometers. We must keep in mind that this is in direct conflict with his own best interests. A tree expert who used trees for reconstruction could surely receive nice support from the global warming community. His paper on tree rings in general is the subject of another post I am working on. A link to the Climate audit discussion which contains the Loehle papers publication (corrections were made later) is here.
I read this paper in one one hundredth the time it has taken to review Mann 08. It is clear, sensible and has flaws which are clearly discussed. In my admittedly limited experience it is the first reconstruction that I feel may actually represent historic temperatures. I actually got a chill when I finished the paper, feeling that I was seeing temperature history for the first time. Look at that beast of an ice age in 1600. Unfortunately, it cannot be fully trusted as actual temp, simply because the quantities of proxies are not sufficient. This doesn’t mean that the curve above isn’t close to actual though it may even be as close as the error bars indicate.
In comparison, Mann 08 uses initially questionable data which has not been calibrated to temperature (tree rings), chops the end off of nearly every proxy and pastes fake temperature data on the end as a replacement (the most hideously egregious data fabrication I could have previously imagined) calibrates the fake data to temperature using methods which amplify recent trends compared to history and then throws away anything which doesn’t fit his pre-determined conclusion. This asinine method is how the latest hockey stick was made.
If I worked in this field you would have to put a gun to my head to get me to put my name on it. I thought for a moment of marketing hockey stick toilet paper made from actual tree rings.
I believe now that these math and scientific method errors are done with intent (the ends justify the means) but that is a subject of another post. I just wanted to point out that simplified rational temperature reconstructions are available, the results are inconvenient for the IPCC, Real Climate and Tamino.
The climatology community MUST reject this kind of work to retain any sort of credibility. I brought it up with the Tamino crowd and they simply refused to address the obvious and (I believe) intentional errors in methodology. I tried to address the issues with Real Climate and my posts were simply deleted. So far other scientists seem to have avoided reference this ridiculous false paper but until and unless this work is rejected the climatology community has no credibility in my eyes.