23 Nov 2008

Trusting the Model Over the Measurements?

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This may shock some readers, but I really do try to keep abreast of the work of the “real climate scientists” and not get trapped in a corner listening to various skeptics argue whether Al Gore is evil or just crazy. Since one of the latest snarky things is for skeptics to point out that the world hasn’t warmed in the last ten years (despite large increases in CO2 concentrations), I was interested to read the latest post at RealClimate which took on this (alleged) canard.

Anyway, the writer says:

Confusion has continued regarding trends in global temperatures. The misconception ‘the global warming has stopped’ still lives on in some minds. We have already discussed why this argument is flawed. So why have we failed to convince 😉 ?

The confused argument hinges on one data set – the HadCRUT 3V – which is only one of several estimates, and it is the global temperature record that exhibits the least change over the last decade. Other temperature analyses suggest greater change (warming). Thus, one could argue that the HadCRUT 3V represents the lower estimate, if a warming could be defined for such a short interval.

A comparison with other temperature analyses, such as the NASA/GISS…reveals differences. We can also compare with model-generated data (re-analyses), keeping in mind that one must be very careful with these data since they are not appropriate for studying long-term climate change (they give a misrepresentation of trends – at least on a local scale). Nevertheless, information from independent data suggest an increase in global mean temperatures even over the last decade.

(Note that the figure above comes from one of the comments in the RealClimate thread, and note that the source is GISS, run by Hansen. I.e. I’m not taking the graph above from the Michael Crichton estate.)

I really am trying to not jump to conclusions here. I know some of Free Advice’s readers are on “the other side” so to speak, so by all means, please explain if I’ve missed something here.

However, it seems to me that what the writer above is saying, is that we shouldn’t take seriously the skeptic claim that “global warming has stopped” (for the last ten years), because (a) only one set of measurements shows this, and (b) such a halt in warming doesn’t fit our models.

Now point (a) is fine, and point (b) isn’t terrible, subject to a caveat. And yet, the caveat the writer gives is NOT, “Of course, these are just models, and in the long-run the data must trump the models.” I admit I don’t really understand what the stated caveat is, but I’m pretty sure it’s not pointing out the obvious danger in ignoring temperature readings (over the course of ten years) because they don’t match what your model predicts.

Like I said, I am trying to be fair. I suppose one could argue that I have done an analogous thing in my cynicism regarding the BLS’s inflation figures. But even there, I have not been saying, “I think inflation is higher than the BLS is admitting, because look at the money supply and I believe Milton’s theory!” Rather, I have been saying, “I think inflation is higher than the BLS is admitting, because no matter how I manipulate the government’s own gas price data, I can’t get the ‘seasonally adjusted’ fall that the BLS reports (back in April), and because the BLS’ own yr/yr increases suggest far more inflation than their seasonally adjusted, annualized rates.”

And you can be darn sure that if ten years go by and gold has never broken $1000,* I will admit that I was waaaay the heck wrong in my forecasts.

By the way, in case you are entirely new to all this stuff: The main reason the graph above annoys the proponents of the theory of manmade global warming is that 1998 was unusually warm. I.e. there was a huge spike from 1997 to 1998, and so it’s natural that temperatures fell immediately after it. Gavin Schmidt I think gives a better first pass at the “why hasn’t the globe warmed in ten years?!” attack than the guy I linked to in this post. But the guy above amazed me for how casually he relies on “model-generated data.” In my line of work, I think that would be a contradiction in terms. You’ve got the data, and you’ve got your model. The model is supposed to fit the data, or predict the future data, but not generate it.

* The one out I grant myself is if the government takes over the gold market again, and declares an official price. Then my predictions would of course refer to the black market price of gold.

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