Last week I ribbed Dana Nuccitelli and Gavin Schmidt over the former's comparing the mean of the Aldrin paper to the mode of Lewis's. Here's the quote:
One significant issue in Lewis' paper (in his abstract, in fact) is that in trying to show that his result is not an outlier, he claims that Aldrin et al. (2012) arrived at the same most likely [i.e. the mode] climate sensitivity estimate of 1.6°C, calling his result "identical to those from Aldrin et al. (2012)." However, this is simply a misrepresentation of their paper.
The authors of Aldrin et al. report a climate sensitivity value of 2.0°C [per the paper, the mean] under certain assumptions that they caution are not directly comparable to climate model-based estimates. When Aldrin et al. include a term for the influences of indirect aerosols and clouds, which they consider to be a more appropriate comparison to estimates such as the IPCC's model-based estimate of ~3°C, they report a sensitivity that increases up to 3.3°C. Their reported value is thus in good agreement with the full body of evidence as detailed in the IPCC report.
I was somewhat taken aback when Nuccitelli subsequently denied having done this:
Me: @dana1981 And you can't really duck the fact that you compared mean to mode. @ClimateOfGavin @wattsupwiththat
Nuccitelli: @aDissentient You have a strange definition of the word "fact", but that's not news.
Me: @dana1981 You are denying comparing mean to mode?
Nuccitelli: @aDissentient Sure. While we're at it, I'm also denying that the moon is made of cheese.
In the comments, Tom Curtis is remonstrated about Nuccitelli accusing Lewis of misrepresenting the match between his PDF and Aldrin's,
Dana correctly describes Lewis as claiming that the mode (most likely climate sensitivity) of his result is identical to the mode of Aldrin et al, but then incorrectly calls that claim a simple misrepresentation. It is not a misrepresentation. The modes of the two studies are identical to the first decimal point.
Now it has all changed. Look at the Skeptical Science page again (bold emphasis added):
One significant issue in Lewis' paper (in his abstract, in fact) is that in trying to show that his result is not an outlier, he claims that Aldrin et al. (2012) arrived at the same most likely climate sensitivity estimate of 1.6°C, calling his result "identical to those from Aldrin et al. (2012)." However, this is not an accurate of their paper.
The authors of Aldrin et al. report a mean climate sensitivity value of 2.0°C under certain assumptions that they caution are not directly comparable to climate model-based estimates. When Aldrin et al. include a term for the influences of indirect aerosols and clouds, which they consider to be a more appropriate comparison to estimates such as the IPCC's model-based estimate of ~3°C, they report a sensitivity that increases up to 3.3°C. Their reported value is thus in good agreement with the full body of evidence as detailed in the IPCC report.
This seems to be a result for Tom Curtis. However, he then goes on to make a very strange point:
[Lewis's claim] is...misleading in that it is an apples and oranges comparison. Given that other studies report the mean, in comparing with other studies the mean should be reported, or it should be made absolutely clear that not only are you reporting the mode, but that the authors you are reporting on reported the mean.
The idea that comparing mode to mode is "apples to oranges" is pretty strange. To say it is "misleading" is again absolutely extraordinary when one notes that the IPCC doesn't consider means either - it reports medians and modes. This is only natural to do so when considering skewed distributions since the mean is strongly influenced by outliers.
The other reason for using the mode is that it is largely unaffected by choice of prior, so by using it one can better understand what the Lewis paper means, namely that the Lewis and Aldrin approaches give the same best estimate of climate sensitivity, but the adoption of the objective Bayesian approach gives a more constrained estimate.