Rearranging The Deckchairs

Frank O'Dwyer's blog

Bishop Hill - 'Not Entirely Open About Negative Feedbacks'

Bishop Hill has responded to my earlier post about his accusations against IPCC scientists in a comment here.

[Frank] suggests that the IPCC is being open about negative feedbacks from boundary layer clouds.

I think the answer is,”not entirely”. The Klein and Hartmann paper is discussed in Bony et al and I cover it in Hockey Stick Illusion too:

Later in the same paper, Bony had noted the findings of two earlier researchers, Klein and Hartmann, who had observed a correlation between cloud cover and temperature stability in the tropics. This, Bony reported, ‘leads to a substantial increase in low cloud cover in a warmer climate … and produces a strong negative feedback’. So once again, there was an unequivocal case being made that the feedback from boundary layer clouds is both strong and negative – tending to cool the Earth rather than warm it.

It is a mystery to me that Bishop Hill does not go on accuse himself of engaging in ‘charlatanry’, or at least ‘not being entirely open about negative feedbacks from boundary layer clouds’ here.

Because the above is yet another inaccurate summary from him of what Bony et al 2006 says. In this case, a wildly inaccurate representation of what Bony et al has to say about the Klein & Hartmann Paper, which is this (my emphasis):

Klein and Hartmann (1993) showed an empirical correlation between mean boundary layer cloud cover and lower-tropospheric stability […]. When imposed in simple two-box models of the tropical climate […] or into some GCMs’ parameterizations of boundary layer cloud amount […], leads to a substantial increase in low cloud cover in a warmer climate […] and produces a strong negative feedback.

Note the conditions - the strong negative feedback is seen only when the results of Klein & Hartmann are imposed in certain models.

Furthermore Bony et al immediately goes on to say:

However variants of lower-tropospheric stability that may predict boundary layer cloud cover just as well as the Klein and Hartmann (1993) parameterization, would not necessarily predict an increase in boundary layer cloud in a warmer climate.

So in addition to this strong negative feedback being seen only in certain models, it may not exist at all.

It is hard to see how Bishop Hill gets from an effect that may or may not exist, and then only according to some models, to this:

there was an unequivocal case being made that the feedback from boundary layer clouds is both strong and negative