I don't pretend to be an expert in mathematics, statistics or climate models but I'm going to make a short comment on 'Wondering' Willis Eschenbach's latest foray into fitting an equation to the outputs of climate models.
He's done this before on WUWT as he says, here and here. What Willis does is fit a linear equation to climate model outputs. Fortunately he doesn't go so far as make projections or predictions.
Willis' closing derogatory comments are nonsense. He writes:
Does this mean the models are useless? No. But it does indicate that they are pretty worthless for calculating the global average temperature. Since all the millions of calculations that they are doing are functionally equivalent to a simple lagged linear transformation of the inputs, it is very difficult to believe that they will ever show any skill in either hindcasting or forecasting the global climate.Climate models might not be perfect but they are far from useless and are used for much more than surface temperature. Indeed they used not just to make climate projections but increasingly to forecast weather on a seasonal basis. (More about POAMA here.)
Willis shows some skill with Microsoft Excel. However he demonstrates a remarkable lack of understanding of climate forcings and climate models for someone who's been writing about them for so long.
To save you a Google search, let me point you to Tamino's explanation in case anyone is under the false impression that Willis' mathturbation™ is anything other than an exercise in curve-fitting after the event. Here are some excerpts. They are just as relevant in this case as they were to Willis' previous articles.
The first excerpt relates to Willis' adjustment for volcanic forcings:
Let me translate: the actual forcing didn’t fit his preconception, so he changed it to a fake forcing.
What he doesn’t do is make the connection: that the short-lived volcanic impulses have reduced impact, not because the GISS modelE treats them differently from all the others, but because they are short-lived and there’s more than one time scale for the model’s climate system response. There is for the real climate system, too — a potent argument for the fundamental soundness of the GISS modelE.
Bottom line: if you put in enough parameters, and fake the data because otherwise your model isn’t very good, you can get an excellent fit to the GISS modelE output. But it’s nothing but curve-fitting; the work of Willis Eschenbach and Paul_K is an outstanding example of mathturbation.
There’s no justification for them to fake the forcing, physical or mathematical. There’s no investigation of “effective forcing” to see how different forcings might actually have a different impact (in part because of feedbacks). That’s an effort which has been pioneered by James Hansen and colleagues. To contribute meaningfully, you’d have to do some actual science other than make an ad hoc change to the forcing data so you can impugn the results of somebody’s climate model.
For once Eric Worrall is spot on when he writes:
May 21, 2013 at 10:01 pm HIlarious Willis...
Feel free to add your tuppenthworth
or maybe we should just ask Kenji :D
Postscript: McIntyre's a dill, too23 May 2013: In case anyone still harboured the false impression that The Auditor, Steven McIntyre knew what he was talking about when it comes to climate science, this comment from him should settle the matter. Steve can't tell the difference between a curve-fitting exercise in Excel and a simple coupled climate model. He is most impressed by Wondering Willis' fancy fudginations and has some wonderings of his own:
Steve McIntyre says:
May 22, 2013 at 9:55 am Willis, nice spotting with the digitization and the fitting of the function. That there was a relatively simple relationship between model forcing and model global temperature is something that has been chatted about from time to time, but the fit here is really impressive. Wigley and Raper’s MAGICC program, used in past IPCC studies, also emulated key model outputs from forcings: I wonder if it does something similar.
According to this page, no. MAGICC is a suite of models not a fudged curve fit, which is hardly a surprise. (But hey, who cares? Now The Revered Auditor has elevated Wondering Willis' curve fitting fiasco to the level of 'real proper science' in the minds of the deluded Dismissives. Doesn't matter that he's talking through his hat.)
You can read more about MAGICC and its history here.