UPDATE #2: Bob Tisdale has responded also in his post
Tamino Misses The Point And Attempts To Distract His Readers
UPDATE: I understand that Tamino’s real name is Grant Foster.
There is a new post at the weblog Open Mind [which is certainly a misnomer]
Tisdale Fumbles, Pielke Cheers
which disparges the weblog post by Bob Tisdale
and my and Anthony Watts’ responses in our posts
An Excellent Multi-Decadal Global Climate Model Hindcast Evaluation By Bob Tisdale
Santer’s “17 years needed for a sign of climate change” compared against the IPCC models
The claim on Tamino’s weblog is that
Apparently Tisdale just doesn’t understand that when you average across a large number of models, you wipe out most of their natural variability. If you then look for variability in that multimodel mean you won’t find it. Tisdale really fumbled the ball — again.
However, Tamino does not understand the significance of the Tisdale analysis. He presents the figure
and then states that
Note that the individual model runs show much more variability than the multi-model mean. In fact they show variability comparable to that shown by the observed data.
However, since to my knowledge the GISS runs were not completed as an initial value problem, Tamino does not tell us how much of varaitions in the trends over time are from the prescribed forcings and how much from the internal dynamics from the model. Since he presents all of the models with a similar behavior in the trends, this suggests an external forcing is affecting each of the model realizations. He needs to clarify why this similar behavior occurred.
Tamino is correct that model realizations of nonlinear geophysical systems always produce more variations than their ensemble average. In weather forecasts, attention is given both to the ensemble mean and the realizations in terms of prediction of weather patterns.
However, Tamino does not seem to appreciate that if the ensemble average is so poor, that the GISS model, as a tool to provide realistic climate projections for impact assessments decades into the future, is “potentially” only of value in predicting a long term slow change of SSTs. A simple global energy balance model would be just as good for that purpose. Tamino confirms what we have been reporting (e.g.see) on the fatal limitations of the IPCC models for impact studies. The impact community does not know which realization to use for their impact study, even if one of those forecasts were actually correct.
Tamino is telling us [even though he does not realize it] that the IPCC AR4 prediction below is than useless, except for the multi-decadal trend [which is also failing] as shown in Bob’s figure below.
Moreover, the challenge in using the multi-decadal global climate models is to provide skillful predictions of the CHANGES in the statistics of the variability and time and space of variables such as SST. Bob Tisdale, by examining the ensemble result has provided a valuable new analysis.
Instead of being insulting, Tamino should have contacted Bob Tisdale to work with him to produce a mutually agreed to paper.
Unfortunately, Tamino writes
Certainly the models need more work. Certainly they should be examined with a critical eye. Just as cleary, Bob Tisdale is not the right person to do this. Neither is Roger Pielke Sr.
It is this type of disparagment that continues to plague climate science. It is too bad Tamino could not rise above this.
Climate Science: Roger Pielke Sr. 