Bishop Hill Moonshine 2
Aug 28, 2014 Climate: sensitivity In my post about Keith Shine's contribution to the All-party Climate Change Group briefing on AR5 I said that Prof Shine had failed to discuss the divergence between model and observational estimates of climate sensitivity. In fact the report on which I had based this statement (and which I quoted in the original piece) misrepresented what Shine said. There is an audio file available here (H/T Richard Betts) which shows that a significant chunk of the talk was in fact given over to a consideration of the two main approaches to estimating climate sensitivity. Shine described the pros and cons of the various approaches as follows:
...state-of-the-art climate models, which are our embodiment of the laws of physics as applied to the atmosphere...
...a mixture of observations and simple models. Now you might think using observations were a better way of doing things but the problem is that there are a lot of things going on at the same time in the climate system - the internal variability, the aerosols - and there is also a lot of debate about how you should do your statistics to estimate the climate sensitivity.
I'm not sure I detect any question marks over the reliability of the models. No mentions of fudge either. And the remarks about debates over statistics are grossly misleading. The IPCC has been engaging in PR rather than science: showing a series of studies that all use flat priors in ECS is equivalent to repeated shouting "We already know that climate sensitivity is high". It's propaganda, not science.
So I'm not sure that Prof Shine is giving the politicians a fair assessment here. It looks more like an attempt to pooh-pooh the observational estimates.
Still, if you think this is bad, wait until you see the next post.
Reader Comments (9)
'which are our embodiment of the laws of physics as applied to the atmosphere...'
Spherical chicken in vacum at work alert
You cannot do cause and affect if you little idea of what the affect is and a poor idea of the cause no matter how well you apply the laws of physics . There is after all a good reason they cannot do a weather prediction 72 hours ahead worth a dam and why they so often get weather prediction on a shorter time scale dead wrong , even with the same ‘laws of physics as applied to the atmosphere’ in play
knr, is it not traditionally a spherical cow?
I think the GHG theory is flawed.
The surface of the earth cannot be considered to be a black body radiator because the atmosphere is opaque to the IR photons. You have to go to an altitude above most of the clouds, water vapour and other GH gases in order that the black body can actually radiate through a transparent atmosphere.
So the GHG effect is to raise the altitude of the black body surface and the lapse rate determines the black body temperature. (about -18 Celsius at an altitude of 5km which is above about 95% of the water in its various phases).
If we had no IR absorbing materials in the atmosphere then the black body radiative surface would coincide with the actual surface temperature, freshly warmed by solar visible light. That would give a black body temperature of around 15 Celsius.
There is no greenhouse warming. It is due to the mistaken belief that the black body surface is below the opaque to IR part of the atmosphere.
'...there are a lot of things going on at the same time in the climate system....'
Well - whoop-de-doo. And there was us thinking the only thing affecting climate was BLOODY CARBON DIOXIDE....
That 'climate sensitivity' can usefully be estimated is something that even climate sceptics seem to believe in.
So far as I can see, it is based on a whole raft of unverified (and probably unverifiable) assumptions - right down to the assumption that an ultimate increase in global average temperature is a single-valued deterministic function of atmospheric CO₂ level.
I wonder if I am the only person who regards estimating climate sensitivity as the equivalent of clairvoyancy.
Although it has two flavours - clairvoyancy A (based on using the outputs of climate models as its starting data) and clairvoyancy B (based on the use of observational data as its starting point) is it anything other than clairvoyancy no matter which flavour you look at?
Martin: I prefer clairvoyancy B and I think Nic Lewis and others are right to be pursuing it. But I also agree with Essex and McKitrick that there's no reason to expect an obscure statistic, globally averaged temperature anomaly, to obey equations connecting it in a fundamental way with any set of inputs. Immature science. But, given what the IPCC has cooked up, Lewis is right to improve the recipe, for the linear approximation we call sensitivity isn't anything like as scary as we were led to believe.
Richard - - Yes I agree that it makes some sense to take a dodgy computation from model outputs and say "If you were to do the computation again, but getting the probability theory right, this is what you would get - less scary than the result you got from applying incorrect probability theory".
The Essex McKitrick objection to the use of a statistic that has no physical meaning as the basis of a computation is just one of a long list of reasons why I think the whole thing is expletive.
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Schjrodinger's Cat - The Bish detests discussions of radiative physics on his threads. In a moment I'll kick off a discussion thread because I want to ask you for more info.
'Specious' - that's the word that came to mind upon reading Prof Shine's words as reported above. Kininmonth and Lupo note that 'Whereas the breaking of simple rods under strain is easy to model and predict, earthquakes, which are also a breakage problem but occur in a complex setting of inhomogeneous rock, are not predictable.'
The link is to a pdf file of the report 'Global Climate Models and Their Limitations', which is part of 'Climate Change Reconsidered II: Physical Science' reachable here: http://www.nipccreport.org/reports/ccr2a/ccr2physicalscience.html
No, Martin. I said something similar yesterday, comment 50 at August 27 3:57 AM on the first Moonshine thread, in response to Exergonic Man.