So the critical question then becomes: what is the lukewarmers' range? Consensus scientists estimate climate sensitivity at about 3C, but concede that it might be 1.5C, 4.5C or even higher (and very unlikely to be much lower). What range do lukewarmers think is plausible?
So far, to my knowledge, no self-identified lukewarmer has been persuaded to answer this question. They will find it difficult. Because they have positioned themselves as participants in the scientific debate, they can hardly claim 100% confidence in X climate sensitivity, no error bars. If they are reasonable, they have to accept they they are as fallible as the rest of the scientific community, and although they think the climate sensitivity is 1.5C (say) it might be 1.0C, or 2.0C, or even (gasp!) 3.0C (where the consensus puts it).Time has moved on Tom Curtis pointed out in the comments
Being fair to the lukewarmers, some including Nic Lewis and Steve Mosher have indicated uncertainty ranges (sort of). The first problem is that Lewis' uncertainty looks an awful lot like dogmatism given how tight his uncertainty interval is relative to that of the IPCC. The second problem is that Mosher's range looks more like a con job.
Specifically, Mosher has said: "ECS is not less than 1.2C ( or basically a no feedback value however you want to calculate it And the probablity of it being less than 3C ((Hmm I’ve prolly said 3.2 in a couple places) is greater than 50%."
The IPCC does not give a PDF, but from their statements it is clear that any distribution maximally coherent with their claims must have a strong right skew. Assuming that their likely range is centrally placed, ie, that it is as unlikely to be below the range as it is above it, that means the modal value is around 2.5 to 2.8 C and the median is likely to be very close to, and possibly below 3 C. So, in an attempt to give a range for a purportedly distinct position, Mosher appears to simply redefine the IPCC as "lukewarmers".Today, the twits guided Eli to a piece on skepticism by Nassim Taleb, keeper of the black swans. Black swans keepers are, of course, the opposite of Luckwarmers, who, in their way are the Émile Coués of the science blog world
Taleb looks at the effect of ignorance on estimates of probability
The introduction in general in any field with potential iatrogenics of any new element without available track record (hence model uncertainty) fattens the left tail.
Some straight applications
• Skepticism about climate models should lead to more precautionary policies in the presence of ruin. It is incoherent to doubt the mean while reducing the variance.Which pretty much kills Nic Lewis's squeezed prior and
• "Mitigating" policies aiming at reducing risks –say geoengineering– in fact are likely to increase such risk.
• Conservatism is a dominant strategy in the tails.Taleb elaborates
In thin-tailed domains, an increase in uncertainty changes the probability of ruin by several orders of magnitude, but the effect remains small: from say 10−40 to 10−30 is not quite worrisome. In fat-tailed domains, the effect is sizeable as we start with a substantially higher probability of ruin (which is typically underestimated).He also makes an interesting point about such issues as GMOs
For standard statistical theory doesn’t allow "acceptance", it only allows "failure to reject". Even when someone in prose says "accept that" he mathematically means "failed to reject at some significance level...", i.e., baring a tail event. Similarly, when someone is indicted, he is treated as innocent unless proven otherwise. This principle is adopted by scientific journals (remember from section 1.3 that statisticians are the "evidence" police and their evidence is "up to" a tail event that is not specified in impact). This is a very big thing and it is ironic.
For the majority of biologists involved in the GMO debates against the precautionary principle don’t appear to be aware of the central fact that
evidence = ”barring a tail event”
and argue they have "evidence there can’t be a tail event".