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« New Newsnight editor eulogises 10:10 campaign | Main | All-party group on unconventional oil and gas »
Thursday
May162013

Lewis responds to Nuccitelli

Nic Lewis has left a comment under Dana Nuccitelli's astonishing article in the Guardian.

In his piece, Dana Nuticelli links to his earlier article "Climate Sensitivity Single Study Syndrome, Nic Lewis Edition" at a climate change/global warming blog he is associated with. As the author of the paper "An objective Bayesian, improved approach for applying optimal fingerprint techniques to estimate climate sensitivity" (Journal of Climate, in press) that Dana Nuticelli's earlier article is about, I would like to take this opportunity to put on record my rebuttals of a number of misrepresentations he made of my paper, to avoid any Guardian readers who follow the link being misled. I apologise in advance for the length of this comment.

1. Nuticelli stated that my paper was an outlier. If it were, as his title suggested, the only study showing a low climate sensitivity – one below the bottom of the IPCC 4th assessment report (AR4) 2–4.5°C 'likely' (2/3rds probability) range – then that would be a fair point. But it seems increasingly clear that warming over the instrumental period (from the mid/late nineteenth century to date) indicates a lower 'likely' range for climate sensitivity than 2–4.5°C. As well as the Skeie et al. Norwegian study to which he referred, three recent peer-reviewed studies (Ring et al, 2012, Atmospheric and Climate Sciences; Aldrin et al., 2012, Environmetrics; and Masters, 2013, Climate Dynamics) all point to a considerably lower 'likely' range for climate sensitivity than 2–4.5°C.

2. Nuticelli stated that the Bayesian approach I employed involves "making use of prior knowledge of climate changes to establish a probability distribution function for climate sensitivity". In fact, the purpose of my using an objective Bayesian approach was precisely to avoid making use of prior knowledge or assumptions about the likely values of the climate system parameters being estimated. Typically, Bayesian climate sensitivity studies have inappropriately used a uniform prior distribution for climate sensitivity (and sometimes for another key parameter), and thereby greatly exaggerated the risk of climate sensitivity being high.

3. Nuticelli floated "The Climate Variability Question Mark in Lewis' Approach". Referring to the 2013 study by Olson et al., he stated that they investigate "three main sources of what they call "unresolved climate noise": (i) climate model error; (ii) unresolved internal climate variability; and (iii) observational error". In fact, they focus only on item (ii). Their findings have limited relevance to my study, which (a) makes due allowance for internal climate variability and the uncertainty arising therefrom; (b) does not attempt (as Olson et al. did) to estimate aerosol forcing from purely global temperature measurements; and (c) avoids the uniform priors they use.

4. Nuticelli suggested that my study, while stating that it estimates "equilibrium climate sensitivity", in fact estimates "effective climate sensitivity, which is a somewhat different parameter". It does in fact estimate equilibrium climate sensitivity. I would anyway question whether there is any significant difference between the two parameters. The IPCC AR4 report uses the two terms virtually synonymously. The x-axis of its figure showing estimated probability density functions (PDFs) from studies based on 20th-century warming, including the study whose data I reanalysed, is labelled "Equilibrium Climate Sensitivity", notwithstanding that, strictly speaking, a good proportion of the featured studies estimated effective climate sensitivity.

5. Perhaps most seriously, Nuticelli claimed that my study misrepresents Aldrin et al. (2012). In it, I stated that the 1.6°C mode I obtained for climate sensitivity was identical to that per the main results in Aldrin et al. (2012). The truth of my statement is easily verified by inspecting Figure 6.a) of that paper. The mode of a climate sensitivity PDF is the location of its peak value, and was referred to in the IPCC AR4 report as being the best estimate. An alternative measure is the median – the value with equal probability (area under the PDF) above and below it. However, it would have been difficult to be certain of the accuracy of a median estimate measured from Figure 6.a), and the mode has the advantage of being less affected than the median by the choice of prior distribution. I do not consider the mean, quoted by Aldrin et al., to be a suitable central measure for climate sensitivity PDFs, because the PDFs are skewed. Consistent with my view, the relevant chapter of IPCC AR4 quotes modes and medians for climate sensitivity estimates, but not means. For completeness, I also gave the 5–95% climate sensitivity range for the main Aldrin et al. (2012) results, of 1.2–3.5°C.

A commenter has raised the hope that Nuccitelli will respond.

A forlorn hope in my opinion.

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Reader Comments (20)

If he does respond it will be with waving hands and raised voices and claim that there is nothing here to see while calling Nick a denier.

Regards

Mailman

May 16, 2013 at 8:56 AM | Unregistered Commentermailman

I am on the verge of dismissing the blog hosted by Abrahams and Nuccitelli in its entirety. Their production so far has been of breathtakingly low quality. As half of my comments get deleted in any event I am mostly wasting my time reading it and having a say.. The blog only needs to add Stephen Lewandowsky as a contributor and it will have the complete trifecta.
It must be difficult for Nic Lewis. When a national newspaper provides a platform for these bozos to write whatever they wish, he has to reply...but he is wasting his time.

May 16, 2013 at 9:00 AM | Unregistered CommenterJack Savage

I am amused that they let him write Nuticelli. Is celli another form of plural for cellos? What about a second t?

May 16, 2013 at 9:18 AM | Unregistered CommenterAlexej Buergin

I have noticed that the moderation on the Nuccitelli blogs for the Guardian resemble those seen on SS. The only step left for them to take for complete assimilation is to actually modify some of the posts to create straw men for them to burn down.

I`m with Jack. The 97% blah blah series of posts by Nuccitelli are only worthy of being ignored. Let the most shrill of the Guardian alarmists use it as there stomping ground. Those poor, beleaguered souls need some respite from empirical data.

May 16, 2013 at 9:31 AM | Unregistered CommenterGalvanize

"Nuticelli"

Or Nutty Jelly, as we call him round here. :-)

May 16, 2013 at 9:33 AM | Registered Commenterjamesp

Sorry, did someone say something? :)

Regards

Mailman

May 16, 2013 at 10:28 AM | Unregistered CommenterMailman

Sorry, did someone say something? :)

I think a passing sloth broke wind, mailman. Nothing to get excited about.

May 16, 2013 at 11:06 AM | Registered CommenterMike Jackson

Whole lot of moderated posts in those Guardian comments, in among the Chicken Littles. It's almost as if there is a POV they don't want to see expressed.

May 16, 2013 at 1:53 PM | Unregistered CommenterNW

Can't wait for the dissection of this: http://www.guardian.co.uk/environment/climate-consensus-97-per-cent/2013/may/16/climate-change-scienceofclimatechange

May 16, 2013 at 3:23 PM | Unregistered CommenterMikeC

Love the way he refers to him as Nutty-celli throughout.

May 16, 2013 at 4:00 PM | Unregistered Commenterharpo

Guys,

Don't you think it a bit juvenile to make fun of Scooter's last name?

The kid has his own sandbox now. If he throws sand at others, an adult (such as Nic) will give him a good spanking. Otherwise we can ignore him.

May 16, 2013 at 4:51 PM | Unregistered Commentertimg56

Guys,

Don't you think it a bit juvenile to make fun of Scooter's last name?

The kid has his own sandbox now. If he throws sand at others, an adult (such as Nic) will give him a good spanking. Otherwise we can ignore him.

May 16, 2013 at 4:52 PM | Unregistered Commentertimg56

Even if writing about, or responding to a wazzock, it's best to remain professional and spell their name correctly.

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

I don't see any comments at that article. They make a basic mathematical mistake: "So far we're about 40% of the way to doubling atmospheric carbon dioxide compared to levels before the Industrial Revolution, and rising fast."

A half-doubling is sqrt(2), and we have just reached that point. Depending when you start (1950, not 1800), there is about 1C rise. That should rule out climate sensitivity above 2C.

May 16, 2013 at 7:21 PM | Unregistered CommenterEric Gisin

[self-deleted...figures were not quite right]

May 16, 2013 at 8:06 PM | Registered CommenterHaroldW

It didn't convince the acolytes, unfortunately. That was always a false hope, I know.
One commenter (without irony) suggested we all paint our roofs white!

What hope is there?

May 16, 2013 at 10:18 PM | Registered CommenterGrumpyDenier

The cartoonists; lapdog regular slot on the Guardian is likely to provide much amusement if little fact and the moderation is heavy . Almost has if they know that its dog with little bark and no bite that needs lots of protection from those nasty 'deniers' and there bog hard facts .

May 16, 2013 at 11:22 PM | Unregistered CommenterKNR

Eric Gison.

Lag.

May 16, 2013 at 11:26 PM | Unregistered CommenterEntropic Man

"Lag"

Give us a number.

May 17, 2013 at 12:22 AM | Unregistered CommenterJohn M

It is interesting to see who are the most strident commentators on thosearticulsr cif posts, mainly Sks'rs. Any reasoned debate then leaves the building as the usual insult fest rears up baboon poop is flung willynilly. Which is a shame, because Guardian loses even more credibility and readers. I used to really appreciate that newspaper.

May 17, 2013 at 8:45 AM | Unregistered CommenterIsabelle

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