Friday, July 08, 2005

More on alarmism

I mentioned some time ago that I didn't really think there was much alarmism in the climate science debate (by which I mean a similar style, but diametrically opposing viewpoint, to the sceptics who do not admit the reality of the IPCC-defined consensus on climate change). According to my viewpoint, on the one hand we had the rational, honest, fair scientists who put the evidence dispassionately, and on the other hand there are the sceptics who lie and cheat to advocate their politically-motivated agenda.

Of course I've always realised that this is somewhat naive and over-simplified (William Connolley has a nice analysis of some borderline scaremongering from FoE, for example, but they are not front-line scientists), but I thought it was basically correct. However, recently I've been rather surprised - and more than a little disappointed - at some statements from scientists who clearly should know better. I recently wrote about the Andreae, Jones and Cox paper here, complaining about how they place an unreasonably alarmist focus on the theoretical possibility of extremely high (~10C) climate sensitivity - a possibility that can be effectively ruled out by alternative analyses (and Gavin Schmidt at RealClimate draws a similar conclusion here).

Now it's the turn of the project and in particular Tim Palmer from ECMWF. Tim Palmer gave a talk on global warming at the Royal Society back in April, and a video recording of it is availble on the web here. He describes the results thusly (about 1/3 of the way through the lengthy recording):
It's a sort of probability distribution of global disagrees with IPCC 2001 in a very key and important aspect...the collective probability of all these members in the tail [~10C warming] is 10% or so
This is wrong and will have seriously misled the audience. The CPDN team were quite careful in their description of their results. Read their paper carefully (you have to look in the Methods section for the crucial comment), and you will see that they actually do not claim that these results have any sort of probabilistic interpretation - the "exciting" aspect of their results is merely that they managed to find climate sensitivities of 11C in a GCM (to which I say big deal, I can get a runaway greenhouse with our model, but never mind). In fact, this experiment was essentially a (rather expensive) fishing trip in which they went looking for the most extreme model results they could possibly generate. People who are heavily involved in probabilistic climate prediction will spot this and realise that the paper is not claiming too much. But of course the media and general public see the distribution and draw the obvious conclusion. SCARY GLOBAL WARMING COULD KILL US ALL!

Either Tim Palmer was fooled by the spin himself, or he gave a deliberately misleading presentation. Frankly, I'm not sure which is worse. I don't think that simplifying things for the sake of the audience is an acceptable excuse, because the simplification is in fact a serious distortion of what their results mean.

As for where that leaves my search for an alarmist to bet against, it's not so clear. Palmer and Andreae were talking about climate sensitivity (steady-state response to doubled CO2) rather than temperatures directly. This is not directly measurable and different values will not lead to substantially different global temperatures over the next few decades. Moreover, they are only talking about a fairly small probability anyway (even though it should be much much smaller).

So their exaggeration is not quite at the same level as the sceptics who deny the immediate reality of global warming and make predictions which will be clearly proven wrong in a few decades at most. OTOH these scientists are supposed to be the "good guys" and should be competent and honest. The tactic seems to be that the stuff in the peer-reviewed literature is just about ok (potentially misleading, but defensible), but then it is spun out of all reasonable proportion in the press releases and public presentation. Colour me disappointed.

1 comment:

Anonymous said...

Actually, many of the septics are now denying catostrophic climate change, or some similar term. Apparently they now accept AGW, but not that it will cause significant problems.