Wednesday, August 20, 2008

answering David Duff's "simple question"


Duff has revealed himself to be a rather unpleasant character over the last few weeks through ad hominem attacks on me on his own blog and trolling here. Lately I decided to delete any further comments of his from this blog and I just wanted to justify why, as well as take the opportunity to hold his hand and walk him through my answer to his persistent, rhetorical question of "do wind turbines need back-up supply from conventional power stations?".

So, he will not be tolerated here any more for two reasons: Firstly his racism, as I established in the comments thread of this post. Secondly, his climate change denial, which he explicitly advocated in a comment that I deleted from the comments in this post and I will reproduce here:
"Yes, but unlike Lomborg I'm not using it to try and sell a dangerous and unscientific conclusion to the public"

Well, that, of course, is your *opinion*, to which you are fully entitled, believing, as you do, that:

1. Global temperatures are increasing, and,
2. That the cause of it is man-made.

On the other hand, it is my *opinion* that you may, or may not, be right on the first, but that you are probably wrong on the second.

However, let us agree (go on, give it a try!) that in this debate we must be strictly scientific and maintain ethical standards. Thus, we can both join hands and condemn loudly the disgraceful behaviour that went on in the publication of Amman & Wahl's papers which claimed to have replicated the Mann 'et al' results and thus confirmed the 'hockey stick' graph upon which much of the global warming hypothesis depends. The whole thing appears to be as reliable as a nine bob note! You can read a layman's summary here:

Now, I'm going to actually take on the task of debunking this rubbish, at the expense of my own research, just so I can put Duff in his place for being so pig-ignorant of the real world.

Duff states that I am "probably wrong" that the cause of climate change is anthropogenic activity and even abstains from endorsing the fact that global mean temperatures are increasing. He goes on to condemn the work of two research groups who have authored papers on the "hockey stick" as "disgraceful" and "as reliable as a nine-bob note" before linking to a page containing what is alleged to be a critique, in laymen's terms, of the bad science behind these researcher's publications. I'll leave the anthropogenic causes of climate change to the end because that's clearly the easiest and juiciest bit.

What I don't understand is why Duff confesses to be unconvinced that climate change is happening before going on to rubbish peer-reviewed publications that present data suggesting it is. But then, he is clearly an idiot so I won't pretend to understand. I'll just carry on with my criticism of his bullshit position.

Everyone is probably familiar with the "hockey stick" graph. It makes a major cameo in An Inconvenient Truth. The graph came from a paper (pdf)- referred to as 'MBH'- by Mann, Bradley and Hughes in which the authors had reconstructed estimates of Northern Hemisphere mean temperature changes over the past millennium. A summary of their findings, and more, can be found in the Wikipedia article on the controversy surrounding the hockey stick, so I won't explain that any further. The second paper attacked in the critique is this one, by Wahl and Ammann. The criticisms levelled against these authors is that they have used inappropriate statistical analysis and simple 'cherry picking' to produce results that validate their conclusions as well as manipulating peer review to allow their data to become part of the IPCC's Fourth Assessment Report. The author of the critique doesn't begin to address the nature of the data used in the papers, which is derived from dendrochronological analysis and the isotopic composition of snow, corals, and stalactites.

Now, I do not pretend for one second that peer-review is flawless. It isn't. Simple as that. But I do condemn out of hand, the implication that, because criticisms of these author's work exist and have been published (and also refuted), it is 'bad science'. The nature of science at the cutting edge is incredibly subjective. That's just the way it works. When something controversial appears in the scientific community it inevitably shoots down someone's pet project and offends others' philosophies and convictions and so people set out to knock the new kid off his block. What happens next is what makes science so awesome. Independent replication of the original work- as happened with MBH- reveals the robustness of the theory and allows it to be developed. What 'Bishop Hill' and Duff are criticising is that the original theory wasn't perfect. But few papers are! Certainly neither of the ones that have my name on are. What matters is that subsequent work validates or contradicts the original work and the ultimate synthesis of climate science- although admittedly politicised, years behind the cutting edge and heavily conservative- is the IPCC annual reports. MBH is referenced prominently in the IPCC AR4:

With the development of multi-proxy reconstructions, the climate data were extended not only from local to global, but also from instrumental data to patterns of climate variability (Wanner et al., 1995; Mann et al., 1998; Luterbacher et al., 1999). Most of these reconstructions were at single sites and only loose efforts had been made to consolidate records. Mann et al. (1998) made a notable advance in the use of proxy data by ensuring that the dating of different records lined up. Thus, the true spatial patterns of temperature variability and change could be derived, and estimates of NH average surface temperatures were obtained. (IPCC AR4 - WG1, Chapter 1, pp107) - emphasis is mine

So criticising their- and follow up worker's- choice of statistical analysis is somewhat pointless because a load more groups have picked up their work, critically assessed its merit and replicated or expanded upon it to get the same results!

Eg (its a link):

This rather pretty graph is a plot of the various results from these papers:

  • Jones, P.D., K.R. Briffa, T.P. Barnett, and S.F.B. Tett (1998). "High-resolution Palaeoclimatic Records for the last Millennium: Interpretation, Integration and Comparison with General Circulation Model Control-run Temperatures". The Holocene 8: 455-471.
  • Mann, M.E., R.S. Bradley, and M.K. Hughes (1999). "Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations". Geophysical Research Letters 26 (6): 759-762. (light blue 1000-1965): [abstract]
  • Crowley, Thomas J. and Thomas S. Lowery (2000). "Northern Hemisphere Temperature Reconstruction". Ambio 29: 51-54. ; Modified as published in [abstract] [DOI]
  • Crowley (2000). "Causes of Climate Change Over the Past 1000 Years". Science 289: 270-277.
  • Briffa, K.R., T.J. Osborn, F.H. Schweingruber, I.C. Harris, P.D. Jones, S.G. Shiyatov, and E.A. Vaganov (2001). "Low-frequency temperature variations from a northern tree-ring density network". J. Geophys. Res. 106: 2929-2941.
  • Esper, J., E.R. Cook, and F.H. Schweingruber (2002). "Low-Frequency Signals in Long Tree-Ring Chronologies for Reconstructing Past Temperature Variability". Science 295 (5563): 2250-2253.
  • Mann, M.E. and P.D. Jones (2003). "Global Surface Temperatures over the Past Two Millennia". Geophysical Research Letters 30 (15): 1820.
  • Jones, P.D. and M.E. Mann (2004). "Climate Over Past Millennia". Reviews of Geophysics 42: RG2002. (red-orange 1500-1980):
  • Huang, S. (2004). "Merging Information from Different Resources for New Insights into Climate Change in the Past and Future". Geophys. Res Lett. 31: L13205.
  • Moberg, A., D.M. Sonechkin, K. Holmgren, N.M. Datsenko and W. KarlĂ©n (2005). "Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data". Nature 443: 613-617.
  • Oerlemans, J.H. (2005). "Extracting a Climate Signal from 169 Glacier Records". Science 308: 675-677.

The black line represents instrumental data jointly compiled by the Climatic Research Unit and the UK Meteorological Office Hadley Centre. Global Annual Average data set TaveGL2v was used. Documentation for the most recent update of the CRU/Hadley instrumental data set appears in: [abstract] Jones, P.D. and A. Moberg (2003). "Hemispheric and large-scale surface air temperature variations: An extensive revision and an update to 2001". Journal of Climate 16: 206-223.

So, we have extensive evidence, from a variety of sources, confirming that mean global temperatures (or Northern Hemisphere temperatures specifically- as for many of those models) are rising. Got it, Duff? End of story.

Phew! (wipes sweat from forehead)

As for the statistical basis of the Bishop Hill's criticism, he states that, in constructing his criticism he has met with "a heavy mathematics burden for the casual reader, which, with a bit of research I think I can now just about follow". Well, no Bishop. You can't.

Most of Bishop Hill's criticism revolves around the failure of Mann et al or Ammann & Wahl to present associated R^2 values for their models, despite the fact that they both do include those values, Mann in figure 3 and Wahl et al in appendix 1. I spent about a minute scanning through each paper before I found them so the people doing the criticism here are a little bit stupid.

Now! Onwards to Duff's insane rejection of anthropogenic responsibility for climate change! I'm running out of steam after all this so I'm going to make it brief:

"With the July 2007 release of the revised statement by the American Association of Petroleum Geologists, no remaining scientific body of national or international standing is known to reject the basic findings of human influence on recent climate."

There. That was it. That one sentence. I really don't think I need to elaborate further. Got that, Duff? You are wrong.

Finally, I bring myself to Duff's pathetic inability to follow a link and answer his own question. I was posting about renewables, being the renewable evangelist that I am. In a comment where I condemned nuclear and hydrogen technologies for their sustainability- my words were:

"once again, in case anyone missed it, both 'safe nuclear generation' and 'the hydrogen economy' suck goat cock"

The post links to a couple of pages detailing why this would be the case. Duff then asked, perfectly reasonably:

"So what do you suggest?"
To which I replied:

Supegrids [sic]

and massive investment in renewable generation

So, we have a question and we have an answer. Duff, however, wasn't content to keep my meagre hit rate climbing by following the links. Instead he responded with some classical REN bullshit (I'm not going to keep copying his crap in here- you can follow the link). Basically, Duff thought he'd posed a nasty little reality-slap of a question by postulating that wind turbines required conventional base-load supply as a back-up to keep the electricity flowing when the wind wasn't blowing. Typically, I refused to answer this question, having just linked to two of my posts that contain plenty of links to information explaining why this wasn't the case. I also chastised him for concentrating on wind generation when I was referring to 'renewables' generally. Duff didn't get it. He really didn't even bother. He just kept asking for a 'yes' or 'no' answer. So, Duff, you lazy bastard. Here's your answer, framed within the context of my original answer to you re. supergrids and renewables:


Capisce, cockweasel?

1 comment:

  1. You are being a bit misleading here. The verification R^2 for the critical AD1400 step was withheld by MBH. The figure 3 you refer to was for the 1820 step. Withholding results that are adverse to your case is not good science, is it? Or do you think it's OK if it's in a good cause?

    You are also being misleading about the alleged replication of the stick by other groups. If we examine your list from the top and look at the data sets they use, we see that they tend to use the same dodgy data sets as MBH. How many of those studies use bristlecones and foxtails? Nearly all, I think. How many have archived their data and code? And let's not forget Briffa et al, where the graph goes down sharply in the second half of the twentieth century, so the IPCC cut it off in the 60s. Makes the spaghetti graph look so much more threatening don't you think?

    Speaking as a scientist, do you support truncation of adverse datasets? What about withholding data? Do you do this kind of thing yourself?


Feel free to share your opinions of my opinions. Oh- and cocking fuckmouse.