Overpeck notes the problems with attribution statements
Dec 16, 2014
Bishop Hill in Climate: Models

FiveThirtyEight has an amusing article about the competing explanations for the California drought. A bunch of NOAA scientists have reported that it's all down to natural variability, noting that they are pretty sure of their results:

This is the first study to show that a West Coast dry pattern could be triggered by warmer water anomalies in the tropical western Pacific. Seager said researchers feel “pretty confident” about the association because it shows up in all their models. (One objective of the study was to look for factors that could help predict future droughts.)

This seems to me to be a fairly hilarious example of the fallacy I lampooned in this posting a few months back.

But of course reporting that bad weather is down to natural variability rather than the global warming bogeyman is never a good thing for some prominent people and so we also have all The Disreputables hauled out to criticise Seager et al. But this doesn't mean that what they said was not without interest. Take Jonathan Overpeck for example:

They’re assuming that our climate models capture variation and change perfectly and that you can use these climate models to determine whether what we see is due to human causes or natural variations.

Well I couldn't agree more. All attribution statements about climate change depend on GCMs and an assumption that they capture change perfectly, despite all evidence to the contrary.

So can we now just all agree that the IPCC's statement on attribution - that most of the observed change in climate is down to mankind - is simply unsupportable?

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