‘the best available evidence’

I have come across  an essay about ‘science communication’ which has drawn a long and most illuminating discussion, and I recommend both. I saw a reference to the essay first in Judith Curry’s ‘Climate etc’ website, and she was of the same opinion. At its core is one of the frustrating aspects of the ‘climate change’ issue: the puzzle over why we have the positions we have about it.

The essay was written by Dan Kahan, and published on the website of the Cultural Cognition project at Yale Law School. You can read it here. Kahan explains his purpose like this:

When I address the sources of persistent public conflict over climate change … it seems pretty clear to me that those with a practical interest in using the best evidence on science communication are themselves predominantly focused on dispelling what they see as a failure on the part of the public to credit valid evidence on the extent, sources, and deleterious consequences of anthropogenic global warming.

That is, like some other writers I have come across in the past, he saw the issue as demonstrating a poor sense of the best way to communicate science. But you will see at once that he is on the orthodox side. When chipped by some sceptics for his apparent bias he argued that they too needed to know how better to communicate what they saw as the science. Both sides, as he sees it, don’t understand science communication. The commentary that followed his essay got to be quite fascinating, with luminaries from both sides taking part.

How would the sceptics fix the science-communication problem, he asked. In later comments he used two phrases that really raised my eyebrows: he referred to ‘the failure of valid, compelling, widely available science to quiet public controversy’, and half a dozen times to ‘the best available evidence’.

I thought it was a  remarkably interesting discussion, and I took part in it to say so. As I wrote a little time ago here,  there is an abundance of evidence to support almost any view you like to put forward on global warming. I asked Kahan what did he happen to regard as the best available evidence. As if to answer my question (though he had already written it), he supplied a new essay on exactly that question. And the new essay produced some more highly readable and absorbing debate, much of it at a high standard.

The answer was, I think, a bit limp. I could summarise it like this: first, he can’t explain quite why, but he knows good evidence when he sees it and second, the best evidence passes the usual scientific tests — good argument, excellent confirming observations. Well, I’d certainly agree with the second, and I guess we all feel intuitively that our judgment of evidence, as of most other things, is pretty good, even if we can’t explain how we reached our judgment very persuasively to another person.

My feeling is that we have to do better than this. In the case of global warming, there have been predictions, and it is increasingly the case that the observations don’t support the predictions. Why didn’t Kahan see that as at least ‘good available evidence’? I would argue that it is also increasingly clear that the global circulation models are not good at predicting anyway, and that the evidence we have about climate is scanty. Put all that together, and one starts to doubt almost any claim made about ‘climate change’ by the orthodox.

Yes, but … the orthodox might say, and go on to talk about the risks we might be running, about runaway warming, massive sea-level rises and all the rest of the scary stuff. Indeed we might, but that is not good enough a reason to go down the path of carbon taxes and RETs. Public policy demands good solid cost-benefit analysis, and a real feeling for opportunity costs. I do not regard the Garnaut or Stern Reports as having provided anything like that, and in fact no one now refers to them, even from the orthodox side.

As several commenters pointed out to Kahan, it didn’t seem to occur to him that science-communication wasn’t the problem, and that sceptics were not accepting his invitation to fix it because they saw it as irrelevant. It is not communication but the Science, and Nature, that are the issue, and Nature does not seem to be obeying Science, which suggests that Science hasn’t got it right yet.

Kahan also seemed to me to miss the point that although there is an orthodoxy, and one can describe it and the people and organisations that support it, the sceptics are a heterogeneous lot, often old, retired, poor and, most important, largely unorganised. That governments and the media have begun to back off their earlier insistence that we are all doomed unless we ‘combat climate change’ may be due a little to sceptical pressure, but the main reasons, I think, are the continuing global economic crisis and the temperature pause.

Anyway, these essays are well worth reading, and so is Judith Curry’s blog on the essays. The comments on Kahan’s essays are better, though, than the comments on Climate etc..