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« An objective Bayesian estimate of climate sensitivity | Main | Grantham style »
Tuesday
Apr162013

Another paper finds that climate sensitivity is low

Nic Lewis has had a paper published in Journal of Climate. It's a reworking of the Forest et al 2006 paper on climate sensitivity, but removing the warm bias of Forest's uniform prior, as well as dealing with some data issues.

A detailed reanalysis is presented of a ‘Bayesian’ climate parameter study (Forest et al., 2006) that estimates climate sensitivity (ECS) jointly with effective ocean diffusivity and aerosol forcing, using optimal fingerprints to compare multi-decadal observations with simulations by the MIT 2D climate model at varying settings of the three climate parameters. Use of improved methodology primarily accounts for the 90% confidence bounds for ECS reducing from 2.1–8.9 K to 2.0–3.6 K. The revised methodology uses Bayes’ theorem to derive a probability density function (PDF) for the whitened (made independent using an optimal fingerprint transformation) observations, for which a uniform prior is known to be noninformative. A dimensionally-reducing change of variables onto the parameter surface is then made, deriving an objective joint PDF for the climate parameters. The PDF conversion factor from the whitened variables space to the parameter surface represents a noninformative joint parameter prior, which is far from uniform. The noninformative prior prevents more probability than data uncertainty distributions warrant being assigned to regions where data responds little to parameter changes, producing better-constrained PDFs. Incorporating six years of unused model-simulation data and revising the experimental design to improve diagnostic power reduces the best-fit climate sensitivity. Employing the improved methodology, preferred 90% bounds of 1.2–2.2 K for ECS are then derived (mode and median 1.6 K). The mode is identical to those from Aldrin et al. (2012) and (using the same, HadCRUT4, observational dataset) Ring et al. (2012). Incorporating forcing and observational surface temperature uncertainties, unlike in the original study, widens the 90% range to 1.0–3.0 K.

1.6°C, again and again  - there really is quite a lot of evidence for low climate sensitivity now, isn't there?

[Full disclosure - I made some (relatively minor) editorial suggestions in the drafts.]

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Reader Comments (51)

Although the sensitivity keeps getting lower (don't panic, don't panic), it's all still based on climate models which use fudge factors and have no physical validity.

Apr 16, 2013 at 9:00 AM | Registered CommenterPhillip Bratby

Good.

The war for more sanity, more calm and reasoned analysis about climate variation is being waged on many fronts. Here we see a sortie into one of the engine-rooms of the alarmed ones - what will remain for most an inaccessible zone of mysterious terminology and rabbits appearing out of hats. We see a palpable hit on the generation of suitably alarming statistical intervals. For this raid, if I may be permitted to push this vivid imagery a little further, I'd recommend a medal.

Coming back down to my more mundane world, I can merely say, well done Nic Lewis!

Apr 16, 2013 at 9:47 AM | Registered CommenterJohn Shade

Philip: ...it's all still based on climate models which use fudge factors...

Does that matter? Pointing out that climate mumbo jumbo is flawed is surely a step in the right direction: and a big one.

Apr 16, 2013 at 10:01 AM | Unregistered Commenterssat

Really there's no need for all this statistical flummery. Here's my estimate: take the globalwarmmongers' preferred value (3C) and halve it, => 1.5C. Easy, ain't it?

The logic is that the "climate scientists" aren't madmen, or honest fools, who might be wrong by a factor of ten or a hundred - they consciously lie, so they opt for a value that is just on the edge of plausibility.

Apr 16, 2013 at 10:04 AM | Unregistered Commenterdearieme

ssat: Absolutely, these are all small steps in the right direction. Nic lewis is to be congratulated, but I presume the paper won't get into AR5.

Apr 16, 2013 at 10:10 AM | Registered CommenterPhillip Bratby

Well done Nic Lewis. I'm glad you made the effort to get your work published in a high-profile (for jobbing scientists) journal.

Apr 16, 2013 at 10:20 AM | Unregistered Commentertilting@windmills

Two thoughts...

1. Why the focus on 90% confidence, as opposed 95% (not reliable enough?) It's still early. I don't have access to the paper yet ;-)

2. Even with a lower climate sensitivity, the prospects of a more than doubled CO2 are quite real-- even triple, yes? Is it not but a small victory for the world unless we can find that climate sensitivity reduces with increasing CO2 beyond certain/various threshold? It does seem the lion-share of the newer sensitivity studies are coming up with lower ranges-- perhaps the first change in prevailing climate understanding that would have the big names in the field acknowledging a backing-away from higher-dire thoughts to lower-dire thoughts?

Apr 16, 2013 at 10:32 AM | Unregistered CommenterSalamano

If this keeps up we will eventually get to a position where all the scientists finally realise that the earth and its climate is going to do what it will and there is nothing mankind can do about it. What are they going to do then, apologise for all the trouble they have caused?

At least if we get to that state, they could then look at reducing energy poverty through out the world.

Apr 16, 2013 at 11:08 AM | Unregistered Commenterivan

I do not think they will ever apologise, ivan. They will claim good intentions. They will claim widespread consensus. They will claim raising the general issue was a good thing. But the reality of the great harm they have done in numerous ways will remain and I hope it will be thoroughly recorded, analysed, and used to motivate further research into how we got into this pathetic state of worldwide acute alarm over carbon dioxide in the first place.

Any apologies that might be forthcoming would be incidental to that larger picture, although they might help a little with increasing the rate at which remedial, and possibly pastoral, work is done in such places as schools and universities.

Apr 16, 2013 at 11:25 AM | Registered CommenterJohn Shade

Re: Salamano

If a doubling of CO2 increases temps by 1.5C then a tripling will increase it by around 2.4C.

Apr 16, 2013 at 11:31 AM | Unregistered CommenterTerryS

I would actually argue that the post's titel is somewhat misleading. Rather it should say:

Antoher study finds that the GCM-model-implied value of 'equilibrium climate sensitiviy - ECS' is lower than previously reported if skewing bias is removed, and some other data-issues are adressed.

I am quite (=very) skeptical to both the idea that a GCM can resolve or clearify anything more than demonstrating how this particular model responds to changes in input data and initialization. And would say that this 'optimal fingerprinting' is basically a slightly more advanced form of 'curve fitting'.

Futher, I think that ECS (or any 'climate sensitivity) are at best simplified emegring properties under the same stated preconditions. Of descriptive value at best, but hardly explaining anything in the physical world, or contributing to it's understanding

Apr 16, 2013 at 11:38 AM | Unregistered CommenterJonas N

Salamano -
"Is it not but a small victory for the world ?"
Well, yes. At the current rate of increase of ~2 ppm/year, we'll reach CO2 doubling by the end of century; with greater economic growth one can presume that emissions will increase and that point will be arrived earlier. However, it's also true that the equilibrium response, according to the models, takes centuries, and the prompt response (TCR) will be perhaps 1 K if the equilibrium response (ECS) is 1.6 K.

The victory is not that all danger disappears. Rather, it's that the situation is not dire; we don't have "100 months to save the world", or whatever. Rash attempts to enforce large immediate reductions in CO2 are not warranted. I find myself, however, drawn to the perspective of Pielke Jnr (and others) that it would be wise to fund research into alternative energy sources which will eventually -- say, by the end of the century -- be able to displace fossil-fuel energy. Or at least in large part.

The idea that "it has all blown over" seems to me as excessive a response to the current state of affairs, as the "we're all doomed" reaction to global warming.

Apr 16, 2013 at 11:44 AM | Registered CommenterHaroldW

Apr 16, 2013 at 11:08 AM | Unregistered Commenter ivan

And that is exactly what we 'sceptics' have been saying for a generation. For nothing except verbal abuse.

Apr 16, 2013 at 11:46 AM | Unregistered CommenterJimmy Haigh.

Despite rising atmospheric CO2 levels temperature has not risen as assumed even with 1.6C sensitivity. So perhaps this 1.6C figure should be 0.0C.

Apr 16, 2013 at 11:52 AM | Unregistered CommenterJohn Marshall

The ideologues won't listen.

They are locked in a world which regards unguided individual efforts as dangerously disruptive and where only ideological compliance can lead to a better life for the collective planet.

Apr 16, 2013 at 12:28 PM | Unregistered CommenterRick Bradford

I tend not to believe (especially with climate science) anything I can't read and understand for myself.

I can't read Nic Lewis's paper because it seems to be paywalled.

Climate Science seems to generate its own terminology more that other fields. To me, the abstract seemed incomprehensible at first reading. I started to attempt to decode it into language that I could make sense of. Here is my attempt at the first sentence.

"A detailed re-analysis is presented of a ‘Bayesian’ climate parameter study (Forest et al., 2006) that estimates climate sensitivity (ECS) jointly with effective ocean diffusivity and aerosol forcing, using optimal fingerprints to compare multi-decadal observations with simulations by the MIT 2D climate model at varying settings of the three climate parameters. "

TRANSLATION:

"I present a reanalysis of the study by Forest et al, 2006. Their study estimated the following:

- the eventual temperature rise due to a doubling of CO² (ie the climate sensitivity)

- ocean diffusivity (which represents vertical mixing in the ocean by a simple parameter)

- the effect of atmospheric aerosols on so-called "forcing" (their effect in producing an imbalance between incoming solar energy and outgoing infra-red radiation).

Forest and co compared physical observations over several decades with the results obtained by running a climate model computer program for various values of these three parameters. They used "optimal fingerprints". This is Climate Science jargon for using a regression method to find the combination of model parameters that results in the model's outputs being the best match to the observed data."


Then the 3rd and 4th sentences:

"The revised methodology uses Bayes’ theorem to derive a probability density function (PDF) for the whitened (made independent using an optimal fingerprint transformation) observations, for which a uniform prior is known to be noninformative. A dimensionally-reducing change of variables onto the parameter surface is then made, deriving an objective joint PDF for the climate parameters. "

To make sense of this I think I'd have to read the paper. He seems to be filtering the observation data to eliminate correlation between values at different times ("whitening") and then reducing the dimensionality (sounds like principle components analysis to me), finishing up with an estimate of the joint probability density function for the three parameters (rather than just three estimated values, I'd guess).

[Dunno what an "an objective joint PDF" is. The antithesis of a "subjective" joint PDF, where the investigator's "judgement" is involved perhaps?]

Am I on the right track? If my translation is correct, it's reasonably down-to-earth stuff, once the Climate Science terminology has been penetrated.

BUT...
It's all dependent on a computer climate model. For me, complicated unvalidated computer climate models are, at best, an expensive form of guessing, at worst, an expensive form of self-delusion. So, whether their use shows we are all due to fry or whether nothing much is going to change, I find it hard to take anything produced by their use seriously.

Apr 16, 2013 at 12:36 PM | Unregistered CommenterMartin A

TerryS, how did you get your tripling (I got nearly the same number) and a quadrupling would give 3.12C. I wonder if we're using the same, easily available simple sum?

Apr 16, 2013 at 12:40 PM | Unregistered Commentergeronimo

If a doubling of CO2 increases temps by 1.5C then a tripling will increase it by around 2.4C.
Apr 16, 2013 at 11:31 AM TerryS

Out of curiosity, how do you know that?

The logarithm formula certainly seems very firmly embedded in climate science folklore but is there any evidence it represents reality?

Apr 16, 2013 at 12:56 PM | Registered CommenterMartin A

The 'realists' may be falling into a trap here. The sceptics are already saying "Climate sensitivity is lower, so the recent 'pause' is only to be expected/predicted. But we still need to do all the daft things we are doing at the moment, because thermageddon is still coming, just a bit more slowly than we thought."

Apr 16, 2013 at 12:57 PM | Unregistered CommenterColonel Shotover

Nic's paper is likely to be mentioned in IPCC AR5, since the draft version of the paper was cited in the IPCC 2nd order draft, chapter 10 verse 10.8.2.1. But in true IPCC style when referring to a sceptic paper, they disparage it, even suggesting that he made a mistake:

Lewis (2012) reanalyzed the data used in Forest et al. (2006) using an objective Bayesian method and find that use of a nonuniform prior lowers the upper limit of ECS. However, this author also presents two very different results based on differently processed versions of the data used in Forest et al. (2006), one of them unpublished, suggesting this may arise from a data-processing error. Hence neither the latter results nor Lewis (2012) are shown here until these differences are resolved.

It's a bit hard to find since discussion of CS is scattered across the various chapters, including Ch7 and Ch12. It will be interesting to see whether the final version acknowledges these reduced estimates. The draft version does not, with Ch12 declaring solidarity with AR4:
Despite considerable advances in climate models and in understanding and quantifying climate feedbacks, the assessed literature still supports the conclusion from AR4 that climate sensitivity is likely in the range 2–4.5°C, and very likely above 1.5°C.

Apr 16, 2013 at 1:00 PM | Registered CommenterPaul Matthews

I tried:

if ECS = 1.5 C
2xCO2 = 1.5

z log (2) = 1.5

z is approximately 5

5 log (multiples of CO2) = temp rise in C
5 log (3) = 2.4 C

Apr 16, 2013 at 1:06 PM | Unregistered CommenterJit

The psychology of do-gooding environmentalists has been remarked upon at length, but not of the theoretical method developers as such. The old engineering maxim "If it looks right, it is right" applies to the theoretical side of science too. Physicists often believe in their theories-of-everything for no deeper reason than admiration for the beautiful equations that emerge. That a Higgs particle might actually be detected by independent observation does not surprise them, since it already existed sufficiently to be intellectually satisfying.

How many aspects of the CGMs are there simply because they ought to be there in some sort of introspective aesthetic judgment, quite apart from any implication for practical reality? For their best loved ideas to survive the method developers must sometimes be psychologically unable to credit contradictory data.

____


The mad mind has a tendency to float away, given the gentlest push. The above excursion followed from reading the estimate of

Apr 16, 2013 at 11:31 AM | TerryS

I checked it and got (3 ln 3) / (2 ln 2), which has a certain mesmerising quality!

Oh, well, that’s enough dreaming for today!

Apr 16, 2013 at 1:11 PM | Unregistered CommenterMark Well

All of that probability jargon is so much learned idiocy, as Philip Bratby--the very first commenter above--seems to "get". Anyone who thinks they can get to the heart of the matter through such ornate, but empty, advanced mathematical rhetoric (that is irrelevant, immaterial, and incompetent, in the immortal words of Perry Mason) is an incompetent fool--and climate scientists all fit that bill, like it or not. The bare facts, comparing CO2 to temperature, have long indicated an insubstantial CO2 climate sensitivity (and indeed, a CO2 level dependent upon the temperature, not vice-versa), and the definitive evidence, of a proper Venus/Earth temperatures comparison, over the full range of Earth tropospheric pressures, shows the CO2 climate sensitivity is zero. There will be no sanity, much less real progress, in climate science until that is properly confronted and generally accepted.

Apr 16, 2013 at 1:12 PM | Unregistered CommenterHarry Dale Huffman

Philip Bratby
"Nic lewis is to be congratulated, but I presume the paper won't get into AR5."

Thank you. I think that the paper probably will be cited in AR5 WG1.

Paul Matthews
"But in true IPCC style when referring to a sceptic paper, they disparage it, even suggesting that he made a mistake"

It wasn't a question of making a mistake, rather that at the time I submitted the paper Dr Forest had not published any data or computer code. It was therefore impossible to be sure which version of the two unpublished datasets from related studies, both of which were stated to use the same data as Forest 2006, was correctly processed. As it turned out, neither were, but the one that remained unpublished at the time the second draft of AR5 WG1 came out had worse misprocessing. So the IPCC comment was fair enough.

Apr 16, 2013 at 1:16 PM | Unregistered CommenterNic Lewis

Nic, thanks for clarifying, I thought the IPCC wording was not very clear.
Is there a freely available preprint version of your paper?

Apr 16, 2013 at 1:38 PM | Registered CommenterPaul Matthews

Nic,

This is interesting in that you are taking on the modellers on their own ground and showing their conclusions to be suspect.

Have you analysed sensitivity based on empirical evidence - as far as possible without involving models? It's a little out-of-date now (1992) but, as I'm sure most people here know, John Daly had a striking comparison of half-a-dozen such approaches... http://www.john-daly.com/miniwarm.htm . They're very much "back-of-an-envelope" (or even postage stamp)" estimates but the results for sensitivity are similar and low (about 0.2 degrees). It might be particularly worth looking back now at the arguments in the light of the last decade-plus of effectively unchanged temperatures.

I realise that your field is more maths than physics but I wonder whether some of Daly's outlines could be used to show that models - even with your reanalysis - are still likely to be significantly over-estimating sensitivity.

Apr 16, 2013 at 2:03 PM | Unregistered CommenterSimon Anthony

If 1.5C is the climate sensitivity to CO2 doubling then:

Tripling = 1.5 x log2(3) = 2.4
Quadrupling = 1.5 x log2(4) = 3.0
Quintupling = 1.5 x log2(5) = 3.5
Sextupling = 1.5 x log2(6) = 3.9

Apr 16, 2013 at 2:34 PM | Unregistered CommenterTerryS

Martin A
'Climate Science seems to generate its own terminology more that other fields. To me, the abstract seemed incomprehensible at first reading. I started to attempt to decode it into language that I could make sense of.'

Sorry about that. There is a tight word limit for an abstract and there were a lot of points I wanted to get in, so the language is indeed dense.

'He seems to be filtering the observation data to eliminate correlation between values at different times ("whitening")'

Correct, but correlations in space as well as time are eliminated.

'and then reducing the dimensionality (sounds like principle components analysis to me),'

There is a form of principal components analysis involved at an earlier stage, which reduces the dimensionality of the observational variables, but not down to the number of parameters (three). It is the second stage reduction, to the three parameter dimensions, that is referred to here.

'finishing up with an estimate of the joint probability density function for the three parameters (rather than just three estimated values, I'd guess).'

Correct. Marginal PDFs for each parameter are then derived from their joint PDF.

'Dunno what an "an objective joint PDF" is. The antithesis of a "subjective" joint PDF, where the investigator's "judgement" is involved perhaps?'

Yes, indeed.

'For me, complicated unvalidated computer climate models are, at best, an expensive form of guessing, at worst, an expensive form of self-delusion.'

I have much sympathy with that view in relation to the way AOGCMs are normally used to simulate future climate changes. But the MIT 2D computer climate model used here has adjustable parameters controlling key climate properties (such as climate sensitivity), which are meant to have been calibrated in terms of those properties, and which are varied systematically. By contrast, AOGCMs are normally left to run free with their standard parameters and do not have calibrated parameters.
The standard settings of the MIT 2D climate model's parameters have no influence on the results of Forest 2006 or this study. I have carried out some tests of the MIT 2D model's calibration against a simple global energy balance model.

Apr 16, 2013 at 2:43 PM | Unregistered CommenterNic Lewis

Nic - Thank you. Makes sense. Glad I was on the right track.

Apr 16, 2013 at 2:45 PM | Registered CommenterMartin A

.Apr 16, 2013 at 2:34 PM TerryS

Terry, Do you have a reference for the log formula? It seems to be climate science folklore - everybody knows it but nobody can say where it came from.

Apr 16, 2013 at 2:46 PM | Registered CommenterMartin A

Nic:

I think that the paper probably will be cited in AR5 WG1.

Congratulations, once again. The consensus is shifting, for the best of reasons: better science.

The standard settings of the MIT 2D climate model's parameters have no influence on the results of Forest 2006 or this study. I have carried out some tests of the MIT 2D model's calibration against a simple global energy balance model.

I understand the first statement. Sort of :) What was the purpose of the calibration?

Apr 16, 2013 at 2:58 PM | Registered CommenterRichard Drake

TerryS:

Your way is rather more elegant than mine.

Apr 16, 2013 at 3:02 PM | Unregistered CommenterJit

I got to it from the formula for climate sensitivity

T∆ = 5.35 x λ ln CO2P/CO20

T∆ = change in temperature
λ = 0.8
CO2P = Present level of CO2
CO20 = 280 ppm

I then substituted the current T∆ of 0.8C and calculated the value of λ as observed for 400ppm and it popped out as 0.42.

I substituted λ = 0.42 instead of 0.8 for the doubling of CO2 and lo and behold - T∆ came out as 1.55C.

It's got to be a coincidence of course, because I don't know how lambda was derived to be 0.8, but using actual data it came our as 0.42.

Apr 16, 2013 at 3:04 PM | Unregistered Commentergeronimo

Apr 16, 2013 at 11:08 AM | ivan
Apr 16, 2013 at 11:25 AM | John Shade
//////////////////////////////////////////////
Apologies count for very little.

What is needed is compensation. All NGOs pushing the cAGW meme, scientists, politicians etc. should be held to account and be forced to give redress to those that have suffered as a consequence of their misguided mantra and policies.

Apr 16, 2013 at 3:08 PM | Unregistered Commenterrichard verney

Nic, where did you get the £20M computer from to run these numbers? The MO say it can't be done on a smaller machine.

Apr 16, 2013 at 3:09 PM | Unregistered Commentersteveta_uk

Re: Martin A

The formula is based purely on the claim that climate sensitivity is 1.5C per doubling of CO2 and that the effect of CO2 is logarithmic.

It is consistent no matter how you express sensitivity so, for example, if you claimed that the climate sensitivity per CO2 tripling was 2.38C (see note below) you would calculate the impact of a sevenfold increase of CO2 with the following:

2.38 x log3(7) = 4.2 (log3 because it is sensitivity to tripling)
1.5 x log2(7) = 4.2 (log2 because it is sensitivity to doubling)

NOTE: In the previous comment I rounded the 2.38 to 2.4 but if I do that here then rounding errors will result in different values).

Apr 16, 2013 at 3:16 PM | Unregistered CommenterTerryS

Apologies;

λ = 0.8C/W/m^2

Apr 16, 2013 at 3:22 PM | Unregistered Commentergeronimo

Re: geronimo

log2(x) = ln(x)/ln(2)

Apr 16, 2013 at 3:23 PM | Unregistered CommenterTerryS

I fail to see how climate sensitivity can be assessed until one knows the bounds of natural variation.

It is necessary to know all natural forcings and their upper bounds before one is able to decide what changes in observed temperature may be due to natural variation.

One cannot seperate the signal of climate sensitivity from the noise of natural variation until absolutely everything is known about natural variation. It is only then that natural variation can be removed from/filtered out of the observational temperature record so that what we are then left with, is changes in temperature due to some manmade activity.

Even once you have got to that stage, difficulties still exist in that one then has to seperate the effects of say CO2 emissions from black carbon, from manmade aerosol emissions, from land use changes etc, before one can hone into climate sensitivity to CO2. To be accurate, one would also need to eliminate the effects of UHI from the temperature data sets (probably UHI is at its strongest between 1950 to 1990).

In my opinion, all these assessments are simply guess work. The only quantative stab we can make on climate sensitivity is that it is not as strong as natural variation (hence why there was cooling between say 1940 to late 1970s despite rising CO2, and why there has been no warming these past 16 to 22 years - dependent on data set- despite rising CO2).

Finally, if one looks at the satellite data since 1979 there is no first order correlation with CO2. The temperature was essentially flat between 1979 through to 1978 and flat beteeen 1999 to date. All there is is a step change in and around the super El Nino of 1998 and unless that El Nino was caused by CO2 (which no one is yet suggesting), the only conclusiion that one can sensibly draw is that climate sensitivity to CO2 is so small that its signal can not be found in the satellite temperature record.

Apr 16, 2013 at 3:23 PM | Unregistered Commenterrichard verney

steveta_uk: I think the clue may be in the term 2D :)

Apr 16, 2013 at 3:41 PM | Registered CommenterRichard Drake

steveta_uk
'Nic, where did you get the £20M computer from to run these numbers?'

The numbers had already been run, on the MIT computer. But as Richard Drake says, running a 2D model uses a lot less computing power than running a 3D model.

Nic

Apr 16, 2013 at 4:16 PM | Unregistered CommenterNic Lewis

richard verney - I totally support your comments which are a good summary of the empirical evidence IMHO.

I notice you say "probably UHI is at its strongest between 1950 to 1990". Well certainly its effect was ramping up during that period. AND also according to the paper covered at this link another suspect was at a maximum in this period as well -

http://hockeyschtick.blogspot.co.uk/2013/01/paper-finds-solar-activity-at-end-of.html

Apr 16, 2013 at 4:23 PM | Registered Commenterretireddave

Ricahrd Drake
'What was the purpose of the calibration?

The model parameters used to control climate sensitivity and other climate system properties such as aerosol forcing actually determine how different things, such as a cloud property in the case of climate sensitivity, are modelled. So the model parameters had to be calibrated in terms of what values of the climate system property of interest were produced by each setting of the relevant model parameter.

Apr 16, 2013 at 4:32 PM | Unregistered CommenterNic Lewis

Martin

As with most things in climate science, you can get the official version at Wikipedia:

http://en.wikipedia.org/wiki/Radiative_forcing

Apr 16, 2013 at 4:35 PM | Unregistered CommenterRon C.

Martin A (2:46 PM)
"Do you have a reference for the log formula?"

Try Myhre et al. (1998), "New estimates of radiative forcing due to well mixed greenhouse gases", in particular their figure 1.

Apr 16, 2013 at 4:58 PM | Registered CommenterHaroldW

@ Apr 16, 2013 at 12:57 PM | Colonel Shotover

"... But we still need to do all the daft things we are doing at the moment..."

No, "we" do not need to do the daft things that are being done now. There is now more time, before "Armageddon"- if it comes. We can stop wasting money on windmills and solar plants, which we know do not work. We can invest that money in a well thought out energy system, probably a nuclear roadmap.

Apr 16, 2013 at 6:01 PM | Registered CommenterAlbert Stienstra

Martin A (2:46 PM)
"Do you have a reference for the log formula?"

Try Myhre et al. (1998), "New estimates of radiative forcing due to well mixed greenhouse gases", in particular their figure 1.
Apr 16, 2013 at 4:58 PM HaroldW

Harold thank you. That paper has been referred to before as the source of the climate sensitivity logarithm rule. Yet it involves nothing more fundamental than fitting a log formula to numerical results over a limited range from a "radiative forcing" model, not something derived from first principles. From there, it seems to have acquired the status of a physical law without, so far as I know, any further investigation.

I have problems anyway with the non-physical nature of "radiative forcing" - something that can only exist in models (not in reality) and which involves gross simplifications and approximations.

Even Science of Doom seemed unimpressed with the concept. He said:
"The good news is, when we get the results from a GCM, we can be sure the value of radiative forcing wasn’t actually used. Radiative forcing is more to inform the public and penniless climate scientists who don’t have access to a GCM."
(the text on the page has since changed).

For a sceptical view of "radiative forcing" see Willis Eschenbach

Apr 16, 2013 at 6:27 PM | Registered CommenterMartin A


Martin

As with most things in climate science, you can get the official version at Wikipedia:

http://en.wikipedia.org/wiki/Radiative_forcing
Apr 16, 2013 at 4:35 PM Ron C.

Thanks Ron. I have steered clear of Wikipedia for anything to do with climate ever since Connelly's antics there became apparent.

I had a "Personal Message" from Jimmy Wales asking me for money. I sent a personal message back to Jimmy Wales about Connelly, Wikipedia and climate and the harm this caused.

I got a message back from a Wikipaedia employee saying:
- Mr Wales is not involved in such matters
- Connelly's activities are not a problem.

Apr 16, 2013 at 6:34 PM | Registered CommenterMartin A

Martin A: Well done for trying!

Apr 16, 2013 at 7:04 PM | Registered CommenterRichard Drake

Climate sensitivity is an abstraction from the models and cannot be measured.

If I was feeling particularly cruel I would ask "When does the model reach equilibrium?"

Apr 16, 2013 at 8:11 PM | Unregistered Commentermichael hart

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