Today’s post is complementary to MMH10, which, as readers obviously realize, is in Ross’ excellent style. There has been a kneejerk reaction from climate scientists that the article is “wrong” – typically assuming that we have neglected some trivial Santerism (which we haven’t).
This post is NOT – repeat NOT – an explication of MMH10. Let me repeat another point – Santer’s ensemble results don’t hold up with additional data using his own method. So this result doesn’t depend on the validity of the MMH10 method.
Some of the defences of the Santer results are based on the idea that the standard deviation of an “ensemble mean model” should be huge relative to the standard deviation of realizations of any given model. Unfortunately, the precise meaning of an “ensemble mean model” ishard to pin down in precise statistical terms.
I thought that it would be useful to try to pin the concept of “ensemble mean model” down in statistical terms. As I was doing so, I did the simple boxplot diagram presented here that provided interesting results and made me think more about the stratification issue. But this post is not an elucidation of the MMH10 algebra, which comes at things from a different perspective. ’ll try to figure out a way of presenting the MMH10 algebra in a friendly version as well on another occasion.
UPDATE Aug 13 – there was a mistake in the collation of trends that I used in this post -which was (confusingly) supposed to help clarify things rather than confuse things. I used trends calculated up to 2099 instead of 2009, which ended up making the within-group standard deviations too narrow. I’ll rework this and re-post. However, I’m going to Italy next Tuesday and am working on a presentation so the re-post will have to wait. This has also been a distraction from the MMH issues so let’s focus on them.