13 Sep 2008

Faith in Climate Models Is Non-Falsifiable

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Suppose you supported the global climate models touted by the IPCC, and because of this you also supported giving the government power to implement trillions in new taxes. But then, a new model came out that showed a regional impact was the exact opposite of what the global model predicted. Specifically, the global model predicted water shortages in the Middle East, but the regional model instead predicted rainfall increases of 50%.

I’m not sure what I would do, but I don’t think I would say, “The best science is confirmed by replication, and these models (and data used for input and confirmation!) are working in the right direction.”

People who put faith in these climate models are not subjecting that faith itself to scientific scrutiny. They are assuming that “We need to base policy on the best available evidence” (which is a tautology) but then leap to, “We need to base policy on the best available models.” The latter does not follow. Surely governments in the Middle Ages shouldn’t have enacted policies on the basis of the best climate models of the day.

Now my observation above doesn’t by itself prove that governments should never listen to climate modelers; maybe at some point their advice becomes useful. I personally don’t think we’re there yet. However, my view of whether we’ve crossed the threshold isn’t relevant to this post. Rather, I am just pointing out that very few proponents of the IPCC set up an independent benchmark for validity* and then test whether the current crop of climate models gets over that objective bar. Instead they usually give a smart alecky answer like, “Well if we wait for certainty we’d never do anything! ‘Oooh, how do I really know the sun warms the planet?’ Take a hike, Mr. Know-Nothing.”

* And note that I am saying validity for use as a policy input. Of course you can independently measure how close the predictions are to observed temperatures. But the real question is, “Are we confident enough in these models that we are going to completely revamp the tax code based on them, or delay the electrification of Africa based on them, … ?”

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