I reported a while ago on Santer’s refusal to provide the T2 and T2LT data as collated. Despite Santer’s rude refusal, PCMDI placed the data online anyway, notifying me that this had been their plan along. I reported on this at the time, but so far haven’t reported on the collated data.
The T2 and T2LT data is now located at http://www-pcmdi.llnl.gov/projects/msu in a reasonably accessible format. I collated the T2 and T2LT “TROP” data sets, each into a time series with 49 columns (representing each of the 49 runs) and as a first cut analysis, took an average of the 49 runs and the count of represented runs up to 2000 (when the population decreases sharply, though a few models are archived up to 2050). This yielded the following interesting graphic:
I was intrigued by the sharp decline in the average of the models around 1960. There were no changes in population at the time (as shown by the count information.)
I cross-checked the data in a couple of different ways, one of which was the following barplot of the maximum value for each of the 49 model-run combinations. The 7th model CNRM3.0_run1 had a very anomalous maximum value of over 13 deg C.
I plotted the values for the 7th model-run combination (from CNRM in France), yielding the following interesting graph, showing some sort of goof in the data as archived. I don’t know whether the error rests with Santer’s collation, with the archiving at PCMDI or with the underlying model. The only thing that we know with considerable certainty is that Santer will say that the error doesn’t “matter”.
When he refused to provide data as collated in response to my original request, Santer had emphasized how easy it was to calculate the T2 and T2LT averages from the terabytes of data at PCMDI:
You should have no problem in accessing exactly the same model and observational datasets that we employed. You will need to do a little work in order to calculate synthetic Microwave Sounding Unit (MSU) temperatures from climate model atmospheric temperature information. This should not pose any difficulties for you. Algorithms for calculating synthetic MSU temperatures have been published by ourselves and others in the peer-reviewed literature. You will also need to calculate spatially-averaged temperature changes from the gridded model and observational data. Again, that should not be too taxing.
Perhaps so. But the operation appears to have enough complexity in it to result in a botched version of the CNRM 3.0 run1 in the PCMDI archive for Santer et al 2008.
UPDATE: Here’s a comparison of averages of GISS AOM (which apparently does not have volcanic forcing) with GISS EH (which does) – both averages of archived T2 tropical troposphere. I must say that I’m a little surprised by the form of the difference between the two – my understanding was that volcanic impacts were held to be fairly transient, whereas there is a notable displacement of GISS EH relative to GISS AOM around 1960. The step takes place at or near the time of the bad CNRM3.0 splice, resulting in a peculiar similarity between the diagram showing GISS EH versus GISS AOM and the the diagram with and without the bad CNRM run.