torsdag 8 oktober 2009

Wrong but Useful for Policymakers?

                                   Keplers model of the Solar System: Wrong but useful?

The article Errors of Omission in The Economist about climate models starts by repeating the well-known story:
  • BUMBLEBEES cannot fly—or so physical models are said to have shown. That the insects routinely become airborne demonstrates the shortcomings of some theoretical accounts of the world. 
  • But one of the strengths of the scientific method is that, when presented with evidence that discredits their theories, scientists are forced to concede that their models are wrong and endeavour to learn from the failure. In science, observation always trumps theory, no matter how elegant the theory might be.
This may sound fine, but is not true, as shown in Why Bumblebees Can Fly. What is true is that state-of-the-art science of aerodynamics has not been able to explain Why It Is Possible to Fly
but has has not learned from the failure and has not come up with a theoretical model which fits with observations.

But why is the bumblebee failure brought up in the context of climate models? Yes, you are right, because state-of-the art climate models model the climate as little as aerodynamics models model bumblebee flight.  

The logic is thus that: Look, we have been able to build airplanes using wrong models of flight, and therefore we should be able to handle climate change with wrong models of climate. 

In the related article Wrong but useful Gavin Schmidt concludes:
  • All climate models are wrong, but some of them are useful, and by working more closely to answer the questions that are actually being posed by policymakers, we can make them more useful still.
  • However, climate models – appropriately used – might have a vitally important part to play in breaking through some of the log jams now hampering policymakers.
So climate models are wrong but yet somehow useful, maybe by the same magic that makes 
wrong models of bumblebee flight useful? We also see the argument that the models can be twisted to fit policymakers. But this is not science. It is politics,  but politics based on wrong models can be wrong politics and wrong politics is not right for the people.

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