Andrew Montford has a post about the errors in Lennart Bengtsson’s rejected paper. I haven’t seen the paper, and nor – I think – has Andrew Montford. All we have access to is a copy of one of the reviewer’s reports. What Andrew takes issue with is this comment from the reviewer
Even more so, as the very application of the Kappa model (the simple energy balance model employed in this work, in Otto et al, and Gregory 2004) comes with a note of caution, as it is well known (and stated in all these studies) to underestimate ECS, compared to a model with more time-scales and potential non-linearities (hence again no wonder that CMIP5 doesn’t fit the same ranges)
Andrew’s issue is that
What struck me – a humble blogger, a mere accountant, a grubby scribe, as my detractors are occasionally wont to say – is that the Kappa model is not actually used in Otto et al (or indeed Gregory 2004). So here we have an expert reviewer who seems to be less familiar with the details of the relevant studies than I am.
Well, I’m slightly confused, as I thought that the reviewer was referring to models based on this kind of energy balance formalism
where N is the system heat uptake rate, F is the change in forcing, and is the climate sensitivity paramter (in Wm-2K-1). One can rewrite this – as in Otto et al. (2013) – to estimate the transient climate response (TCR) and equilibrium climate sensitivity (ECS) – which should probably be called the effective climate sensitivity
All the the reviewer is pointing out is that these are linear equations and that is essentially a constant. Hence this formalism doesn’t capture – as the reviewer points out – potential non-linearities.
Normally I might just assume that Andrew Montford was simply wrong, but Nick Stokes – in the comments – seems to partially agree. Am I missing something here? As I see it, all the papers mentioned do essentially use simple energy balance models (which I assume are often referred to as a model), therefore the reviewer is essentially right; but maybe there’s some subtlety that I’ve missed. Having said that, I would argue that it’s all somewhat irrelevant, since his point was more about potential non-linearities – that these models can’t capture – rather than specifically about the name of the model used.