Bishop Hill Sans science, sans maths, sans everything
Jan 12, 2015 Climate: sensitivity Over at Lucia's place, there has been some interesting conversation in the comments about the technical abilities of some of those on the other side of the climate debate. This originally arose in connection the host of And Then There's Physics, who had apparently reduced Blackboard regular Paul K to laughter in a post about a paper on climate sensitivity by Craig Loehle and a response to it, Cawley et al, which was written by five of the denizens of Skeptical Science. This amusement was followed by others chipping in with their own surprise at ATTP's comments. It's all good family fun. However, it turns out that it's not only ATTP who is struggling. Nic Lewis has added a comment to the thread about the Cawley paper itself which is astonishing.
First a bit of background. Loehle's paper described a model developed in an earlier paper (Loehle and Scafetta 2011) and used it to derive an anthropogenic warming trend from the mid-20th century onwards. The paper then derived an estimate of transient climate response (TCR) of 1.1°C by relating the anthropogenic trend rise in temperature to the increase in anthropogenic radiative forcing, and went on to derive an estimate of equilibrium climate sensitivity (ECS) of 2.0°C. The Skeptical Science response appeared about six months later and was written by Gavin Cawley, Kevin Cowtan, Robert Way, Peter Jacobs and Ari Jokimäki. This is the key part of the abstract.
We demonstrate that the Loehle and Scafetta model systematically underestimates the transient climate response, due to a number of unsupportable assumptions regarding the climate system. Once the flaws in Loehle and Scafetta’s model are addressed, the estimates of transient climate response and equilibrium climate sensitivity derived from the model are entirely consistent with those obtained from general circulation models, and indeed exclude the possibility of low climate sensitivity, directly contradicting the principal conclusion drawn by Loehle. Further, we present an even more parsimonious model for estimating climate sensitivity. Our model is based on observed changes in radiative forcings, and is therefore constrained by physics, unlike the Loehle model, which is little more than a curve-fitting exercise.
Nic notes that one of the key issues that Cawley et al raise concerns Loehle's estimate of the forcing that has produced the recent warming:
The paper notes...that Loehle assumed aerosol and non-CO2 greenhouse gases and other forcings approximately cancel each other out, and accordingly used only CO2 forcing. The Cawley et al. authors dispute the validity of this assumption, saying about the IPCC AR4 chart of 1750–2005 forcings that Loehle cited in support of it:
This does not however imply that these forcings have approximately cancelled over the period from 1951 to 2010, used to estimate the anthropogenic warming after 1950. The RCP8.5 forcings (Meinshausen et al., 2011), shown in Fig. 3(a) suggest that total anthropogenic forcing since 1950 has risen appreciably faster than the forcing from CO2 alone by a ratio of approximately 1.145:1.
Nic agrees with this this point, and in fact goes on to note that even Cawley et al's figure is too low.
Cawley et al. are correct in their assertion that total anthropogenic forcing since 1950 has exceeded that from CO2 alone. However, they understate the difference over the stated period, for two reasons. First, 1.145 is the ratio of the RCP8.5 increase between 1950 and 2010 in total forcing (including solar and volcanic), not anthropogenic forcing, to that in CO2 forcing. The correct ratio is 1.245. Secondly, the RCP forcings dataset does not represent current best estimates. Based on the IPCC AR5 forcing dataset, the ratio of the increase in total anthropogenic forcing over 1950–2010 to that from CO2 alone is 1.361 times.
But this is where it gets rather hilarious. In simple terms, transient climate response is calculated as follows:
TCR = Temperature change/change in forcing
So if, as everyone agrees, Loehle got his forcing too small then his TCR figure is actually too large not, as the crack team at Skeptical Science seem to think, too small as well.
I was rather nonplussed at this point in my reading of the Cawley paper. Its main thesis was that Loehle had underestimated transient climate response (TCR) and hence equilibrium climate sensitivity (ECS). But Loehle derived TCR by dividing the estimated anthropogenic warming by the estimated change in anthropogenic forcing (relative to that from a doubling of CO2 concentration) over 1959–2013, which is broadly consistent with the generic definition of TCR given in AR5 (10.8.1). Obviously, if the change in forcing were greater than Loehle had assumed, that would imply an overestimate of TCR and thereby of ECS, not an underestimate. Very odd. But then I read on:
As a result of this assumption, the method of LS14 underestimates climate sensitivity by about 13%...
Unbelievable! Instead of adjusting the Loehle TCR estimate by dividing it by 1.145, to reflect Loehle's underestimate of forcing by that ratio, Cawley et al. have multiplied the sensitivity estimate (which is for TCR here, not ECS) by 1.145. On that incorrect arithmetical basis, Loehle's method of working from just the increase in CO2 forcing would indeed have underestimated TCR by 13%. But the correct conclusion should be that Loehle's method overestimates TCR by 24.5% (rather than 14.5%) based on the RCP8.5 forcing data – or by 36.1% based on the more up to date AR5 forcing estimates.
Interestingly, Craig Loehle has noted in the subsequent comments that he was not given the opportunity to respond to Cawley et al before the paper was published.
Bishop Hill
In the comments, WB notes that Robert Way posted a series of tweets about Loehle's paper last year. Concatenated, they read:
Last year, this rubbish [i.e. the Loehle paper] was published in an out-of-topic journal that contained the author on its advisory board. Beyond the 4-month timeline from receipt to published, clear statistical errors showed it had not been scrutinized enough during review. Reimplementing their analysis showed a number of methodological flaws and assumptions to the point where a response was necessary. Enter Cawley et al (2015) who show how fundamentally flawed Loehle (2013) was in reality.
Too funny.
Bishop Hill
ATTP is doing some hilarious handwaving:
I think that is a genuine error in the Cawley et al. paper, in that they got that Loehle’s method under-estimates TCR, rather than overestimates it (by mutiplying rather than dividing). A silly mistake I imagine since it is trivial, and I don’t doubt all those involved in the paper could easily do this. Of course, what Nic Lewis fails to point out is that the Loehle paper is rubbish and full of completely unjustified assumptions. That it’s already low TCR estimate should actually be lower if he’d done it with more reasonable numbers, just highlights this even more. Would be nice if he focused on the interesting part of the Cawley paper, which I discuss here, rather than nit picking something minor and rather trivial (however, this does seem to be his normal style, so not surprised).
Reader Comments (71)
Upside down Tijander, Maine rain in the Seine....like leader, like followers.
They are not particularly interested in Cawley et al being correct, only in there being a "peer reviewed paper" out there that they can claim rebuts Loehle.
As a physicist, I do not accept this radiative forcing nonsense. But I do find the non-scientific antics of these alarmists highly amusing. You have to wonder about their intelligence (or lack thereof).
As a physicist, I do not accept this radiative forcing nonsense. But I do find the non-scientific antics of these alarmists highly amusing. You have to wonder about their intelligence (or lack thereof).
Phillip Bratby
And me. Just a pile of jargon ridden crap. But hey ho, it's still funny when a team of crack scientologists manage to get there basic maths wrong.
SR BSc Msc physics
I expect anders will be here shortly to vigorously defend himself by answering a completely unrelated question he was never asked!!! :)
Regards
Mailman
Well I expect they'll retract or correct their paper now -> not.
In other words the SkS crew's paper (when corrected for mathematical errors) is another paper that demonstrates low climate sensitivity.
Alarmists get lost in walking round the corner into statistical analysis, in the labyrinthine realm of ................ physics and where some actual 'grey matter' is required, it's likely we'll never hear of them again.
The whole idea is bogus.
Real coefficients and constants in real physics rely on underlying laws. Resistivity relies on Ohm's Law. Big G relies on Newton's gravitational law. Young's Modulus relies on Hooke's Law.
Without an underlying physical law you are just doing bogus arithmetic - like calculating an average telephone number or like adding a social security number to a postcode.
so those who clàim to be always on the right side of doing science prooerly fail at doing and understanding basic arithmetic?
Not just a typo but paid warmish team publishing papers and trying to engage with amateur sceptics.
Really a bunch of establishment DUNCES
iit's a good thing they have sell out shills in taxoverpaid public media to cover their backs isnt it
Lucky this error got caught in peer review...
I don't get how people in climate science working in universities can keep making basic maths mistakes.
All they need to do is nip across to the maths department and ask a nice Professor to sense check the paper before publication.
When that blog (the blog ... and elsewhere there's real physics) covered Salby's paper, all the numpty could find to critique was the fact Salby had produced a graph with CO2 and temperature ... labelled each one carefully and given appropriate axes and described the graph as showing the lack of correlation between the two.
The only other interesting comment was someone who said "CO2 globally is not affected by temperature ... because CO2 in South America is affected by El Nino". Fortunately - and unlike all the other idiots who comment on his blog - that commenter had the good grace to shut up when I pointed out the absurdity of their comment which was in effect the absurd statement that global CO2 changes were not the sum of local CO2 changes.
I was going to critique Salby's paper myself - but I realised the crowd at There's physics elsewhere wouldn't understand a word I was saying - would only latch onto the fact I had "not agreed" - and I had wasted enough time feeding peanuts to those monkeys only to have my hand bitten off.
Classic case of 'abstract proof' that is they hope all that will l be read this the abstract, so people never check to see if the abstract is supported by the contents ,such has the maths, of the actually article .
While once again 'peer review ' work as normal within climate 'science', and by normal we mean any shi* can get through as long as it supports 'the cause ' and offers more justification to models.
If this is correct then it is very embarrassing for the authors of the paper, of course.
But also for the journal. It claims to have arranged for peer review prior to publication - but clearly hasn't.
If this is correct.
The most perceptive comment on that thread (before everyone started speculating on Anders' gender and marital status) was from TimtheToolMan, and I take the liberty of re-posting it here because in my view it encapsulates virtually the entire global warming "problem":
It's yet one more variation on a favourite theme of mine, namely that our grandchildren will not thank us for trying to second-guess the problems that they will face (still less our great-great grand children). Whatever is in store is not going to happen overnight, whatever the scaremongers might want us to believe, and we will adapt as and when and to the extent that adaptation becomes necessary —like we always have.Reminds me of undergrads managing to get the right answer with a wrong calculation. Their card is usually marked once that happens.
If you throw a boomerang, and miss your target, you should expect to get hit on the back of your head.
I'm afraid Cowton and Wray have now damaged their careers beyond repair after this second fiasco following on from their hockey stick paper temperature grafting which they had to admit was fatally flawed.
Were the computations checked in Excel by a certain P Jones?
"I'm afraid Cowton and Wray have now damaged their careers beyond repair after this second fiasco following on from their hockey stick paper temperature grafting which they had to admit was fatally flawed." Did they do a hockey stick paper? I thought they'd look at the HadCRUt data and interpolated (that's a scientific word for "made up") temperatures in the Arctic that showed there has been no pause.
Did you mean Marcott et al 2013?
No matter, the C & W paper was welcomed as gospel truth by the whole of the consensus science practitioners of our mutual acquaintance and was hailed as proof positive that the pause wasn't occurring. I don't know if they voted on it so it may not be legitimate climate science if there's no vote.
Jan 12, 2015 at 12:03 PM | Unregistered CommenterJohn B
Unfortunately, evidence to date suggests that Cli Sci occupies a parallel universe, in which it is OK to publish anything, however flawed, if it supports the CAGW hysteria. The journals don't care, the universities don't care (indeed, both are complicit).
SKS
Swiftly Killing Science?
Are Environmentalists aware of the true toxicity of SKS discharges and emissions?
I believe that the most important finding is...once again...that 'peer review' in climate science amounts to 'pal review'.
We see time and time again that for the climate obsessed it is not accurate facts or figures that drives them or that they look to. It is rather a veneer of fact-like and figure-like things they can dress up their beliefs in that they are seeking.
I presume that when "total anthropogenic forcing" is mentioned, what in fact is meant is 'net anthropogenic forcing' = CO2 + other GHGs - man-made aerosols. Whereas the Loehle paper assumed aerosols and other GHGs cancelled each other out, the actual situation I presume is that the positive forcings from other GHGs have exceeded the negative forcings from aerosols over the period 1951-2010. So I presume that the current best estimate for the ratio between anthro CO2 forcing and total (net) anthro forcings is 1:1.361.
A minor point but it makes it clearer in that the actual reason for the increase in total anthropogenic forcing over CO2 alone basically comes from the relative diminishing cooling effect of aerosols in comparison to the warming effect of other GHGs. At least, that's how i read it!
Jaime Jessop
Yes, that is broadly correct. Per the IPCC AR5 forcing best estimates, between 1950 and 2010 CO2 forcing increased by 1.2 W/m2, Other GHGs by 0.9 W/m2 (of which 0.2 was from short-lived Ozone), whilst cooling Aerosol forcing strengthened by -0.5 W/m2.
Over 1980-2010 CO2 forcing rose by 0.75 W/m2 and Other GHG forcing (including Ozone) by 0.4 W/m2, but Aerosol forcing strengthened by only -0.15 W/m2. So, relative to the rise in CO2 forcing, that from Other GHG has become less important, and the partially-offsetting strengthening of Aerosol forcing has become of only marginal significance.
I want to thank Nic Lewis for finding the errors in these two papers--he is incredibly sharp-eyed. I always welcome close reading and correcting of work. I plan to submit a comment on Cawley et al very soon.
So much for peer review in climate 'science'. The reviewers are so blinded by confirmation bias that they can't see even glaring logical errors, never mind the sometimes less obvious bias in most everything that is published in the field (eg Steig's smearing of peninsula warming over the whole of Antarctica, Foster & Rahmstorf's silly curve-fit 'proof' the pause never happened, any of Rahmstorf's multiple meter+ sea level rise projections for 2100, etc, etc, etc).
Will the SKS team of five issue a correction or a retraction? I doubt it. They obviously like the 'peer reviewed' results they got, no matter how comically wrong those results are. Besides, how could they face their 'peers' at the next climate 'science' conference if they actually admitted in print that climate sensitivity to GHG forcing is probably 'even lower than Craig Loehle calculated' and far below the CGCM model ensemble estimate? Such admissions are verboten in climate 'science'.
Let's compromise and just declare that Skeptical Science thinks warming is below 2C.
Interesting that Craig Loehle's error made his argument weaker in his published paper.
Why is it that the "consensus" always is "strengthened" when the usual crowd makes its errors? (Gergis' wrong technique, upside down Tiljander, Steig's peninsular smearing, Hansen's Y2K, Loo's paleo- respondent, etc.)
Craig Loehle,
I am impressed that at both websites I've seen you comment on so far, that you are willing to accept and admit your own calculation errors and that you plan to issue a correction. I don't see that a lot these days in the science world-humility, honesty, and what I take to be a sincere interest in getting the science right, rather than proving some agenda to be right.
I just wanted to thank you for your refreshing example today.
Steve Fitzpatrick - and therein lies the rub.
They cannot correct the paper without eliminating its whole reason for being.
The best they could do is throw it on the shelf next to Gergis et al.
I do not hold the Msc or PhD qualification.
I do know multiplying or dividing a number will normally produce a different result if the number is not 1 or 0. :)
My query is with this quote based on the IPCC AR4 chart of 1750–2005 forcings
Nic Lewis has recalculated this ratio to 1.361:1
In AR4 CO2 forcings were 1.66 Wm-2 or 97% of net forcings of 1.72 Wm-2. It was therefore quite valid for the period 1750-2005 to deal look at CO2 alone in place of all the forcings.
In AR5 CO2 forcings for 1750 to 2011 were 1.68 Wm-2 or 76% of net forcings of 2.21 Wm-2. A major change was in the doubling of the “potency” of Methane.
Given that the majority of the rise in CO2 was post 1950, whilst the majority of the rise in methane levels was pre-1950, the more recent figures may have a bearing on the ratio. Anyone able to estimate the impact?
The relevant comparative figures between AR4 and AR5 I documented here here, but I do not have the radiative forcing changes from 1950-2010.
Kevin Marshall
Not according to AR5 (Section 8.3.2.2 Methane), where it explains the 2005-2011 rise in methane forcing:
Per the best estimate forcing data in Table AII.1.2 in Annex II of AR5 WG1 (easily downloaded and copied into Excel), between 1950 and 2010 CO2 forcing increased by 1.185 W/m2 but Total anthropogenic forcing (the sum of all columns except solar and volcanic) increased by 1.613 W/m2, or 1.361 times as much.
Some tips for scientists*:
1. If you check your units, you will be more likely to get your sums to be error free.
2. If your physics are correct, your simulations might produce testable predictions, if your model is correct.
3. If you collect raw data, do not change/homogenize/modify/improve these data and attempt to hide raw data.
4. If you publish the results of a model, provide sufficient information so that others can reproduce that model.
*Not relevant for climatologists
"As a physicist, I do not accept this radiative forcing nonsense." - Phillip Bratby
Don't get you, old son. Do you mean their radiative forcing nonsense, or radiative forcing in general? Do explain. I'm all agog.
Nic Lewis,
Thanks for the response and basically confirming my thoughts whilst also expanding further with more detail.
It's remarkable that Cawley et al at SkS would think that an increase in anthro radiative forcing for a given rise in temp would imply an increase in putative sensitivity to a doubling of CO2 but I think it illustrates alarmists' fixation with anything which points in the general direction of enhanced warming, i.e. more anthro GHGs = greater AGW which MUST imply a higher TCR . . . . mustn't it? Blinded to the rules of basic arithmetic it would seem by their eagerness to follow the trail of a promising scent.
"Loehle ... was not given the opportunity to respond to Cawley et al before the paper was published."
This was published? Oh my lord:
http://www.sciencedirect.com/science/article/pii/S0304380014004876
We need another climate-gate leak so we can see the backdoor communications between the "reviewers."
TerryS is right: They are not particularly interested in Cawley et al being correct, only in there being a "peer reviewed paper" out there that they can claim rebuts Loehle.
That's all they need : something that the faithful can cite, so that they can deflect any criticism of their high priests.
Aren't we talking of a TCR calculated on the ASSUMPTION that a certain climate forcing is ENTIRELY RESPONSIBLE for the change in temperature? Take away that assumption and the game changes because the sensivity of temperature to the forcing in question diminishes even further.
Even the latest IPCC report says that greenhouse gases caused the majority of warming since 1950, a foolish and unsupportable statement given the climate model flawed that it admits to but even so it means that the TCR for greenhouse gases should be even lower than Loehle and his critics claim.
If you take my recent paper, that argued that first a ENSO shift and then a reduction in total cloud cover can account for virtually all the warming since 1950 then there's very little (if any) left for greenhouse gases to drive, hence the GHG TCR is very small.
Seems like a well written paper, way above the normal clap trap from others in the trade. Bravo
;)
/sarc
Lol
Nic Lewis at 6.21pm
Thank you for the quick response to my query. The reason for my believing that the "potency" of Methane has doubled between AR4 and AR5 is by comparing the RF values in the two reports.
From Figure 2.9 AR4 WG1 SPM, CH4 is 0.48{.43 to .53}
From Figure SPM.5 (Page14) AR5 WG1 SPM, CH4 is 0.97{.74 to 1.20}
The switch is, I believe, is from using Radiative Forcing to Effective Radiative Forcing, as explained in Box 8.1 on page 665 of AR5 WG1 chapter 8. However, there is no bridging analysis to show the impact of those methodological changes. Section 8.1.1.3 (Limitations of Radiative Forcing) has a rambling discussion, but nothing that ties in with the changes, nor even an attempt to evaluate the latest data with the old method. (One possible reason – the AR4 RF method shows signs of ad hoc adjustments to arrive at a desired conclusion).
The comment in section 8.2.3.3 Methane for 2005-2011 is just the change in forcing using the AR5 methodology, not the change in the calculated impact of methane between AR4 and AR5 using the different methodologies.
Talk about obvious physics. Radiative forcings don't exist in the real world. They're just useful to allow computations. Nobody will ever invent a forcing-o-meter.
Climate scientist Robert Way, one of the 6 Cawley et al authors, is on Twitter as @LabradorIce. He posted 4 tweets about this on 15 Nov 2014 that read:
Last year, this rubbish (WB - he's referring here to the Loehle paper) was published in an out-of-topic journal that contained the author on its advisory board 1/4
Beyond the 4-month timeline from receipt to published, clear statistical errors showed it had not been scrutinized enough during review 2/4
Reimplementing their analysis showed a number of methodological flaws and assumptions to the point where a response was necessary 3/4
Enter Cawley et al (2015) who show how fundamentally flawed Loehle (2013) was in reality #climate (4/4)
"Fundamentally flawed".
From a man who doesn't know his times by from his divides by.
LOL
Gus: omnologos has answered for me.
I'll add to omnologos' comment
Nobody will ever invent a feedback-o-meter either. And that [water feedback, primarily] is the dog which is modelled as being wagged by both the CO2 and the aerosol forcing. Will they both affect feedbacks? Yes. Will they affect feedbacks in the same way, place, and time, independently of each other? I think not.
If I had an Angel for every head-of-pin that climate models had danced on, then I wouldn't need to call myself Michael.
WB, yesterday I wrote a tweet
Basic divide-multiply error in TCR paper by @gavin_cawley Cowtan @agwobserver @LabradorIce Jacobs.
with a link to NIc's comment at Lucia's.
So far 6 retweets but no response from any of the authors.
Heh, 'Enter Cawley et al (2015)' wearing seven league boots on the wrong feet.
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