BishopHill reported yesterday on the withdrawn Gergis paper that
The authors are currently reviewing the data and methods. The revised paper will be re-submitted to the Journal of Climate by the end of July and it will be sent out for peer review again.
It is worth listing the long list of criticisms that have been made of the paper. There are a lot of hurdles to overcome before Gergis et al 2012 should qualify for the status of a scientific paper.
My own, quite basic, points are:-
- Too few proxies for such a large area. Just 27 for > 5% of the globe.
- Even then, 6 are well outside the area.
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Of these six, Gergis’s table makes it appear 3 are inside the area. My analysis is below.
- Despite huge area, there are significant clusters – with massive differences between proxies at the same or nearby sites.
- There are no proxies from the sub-continental land mass of Australia.
- Need to remove the Palmyra Proxy because (a) it has errant readings (b) fails the ‘t’ test (c) > 2000km outside of the area, in the Northern Hemisphere.
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Without Palmyra the medieval period becomes the warmest of the millennium. But with just two tree ring proxies, one at 42 O South and the other at 43 O S representing an range from 0 to 50O S, this is hardly reliable. See the sum of proxies by year. Palmyra is the coral proxy in the 12th, 14th and 15th centuries.
On top of this are Steve McIntyre’s (with assistance from JeanS and RomanM) more fundamental criticisms:-
- The filtering method of Gergis excluded the high quality Law Dome series, but included the lower quality Vostok data, and the Oroko tree ring proxy. McIntyre notes that Jones and Mann 2003 rejected Oroko, but included Law Dome on different criteria.
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Gergis screening correlations were incorrectly calculated. JeanS calculated properly. Only 6 out of 27 proxies passed. (NB none of the six proxies outside the area passed)
- The Gergis initially screened 62 proxies. Given that the screening included proxies that should not have included 21 proxies, but should it have included some of the 35 excluded proxies. We do not know, as Gergis has refused to reveal these excluded proxies.
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Screening creates a bias in the results in favour of the desired result if that correlation is with a short period of the data. RomanM states the issues succinctly here. My, more colloquial take, is that if the proxies (to some extent) randomly show C20th warming or not, then you will accept proxies with a C20th uptick. If proxies show previous fluctuations (to some extent) randomly and (to some extent) independently of the C20th uptick, then those previous fluctuations will be understated. There only has to be a minor amount of randomness to show bias given that a major conclusion was
The average reconstructed temperature anomaly in Australasia during A.D. 1238-1267, the warmest 30-year pre-instrumental period, is 0.09°C (±0.19°C) below 1961-1990 levels.
UPDATE 03/08/12
The end of July submissions date seems to have slipped to the end of September.
ManicBeancounter 
Paul M
/ 28/06/2012Another issue is that one of the tree ring datasets, Urewera, was used ‘upside down’. It has negative correlation with temperature. That’s the green bar that goes down in the graph you’ve posted. See CA post Gergis “significance” and search thread for Urewera.
Mohamed
/ 21/08/2012The climate deabte is, at its heart, all about violence. The climate deabte is a proxy war in the age old struggle between the power of Government and the natural rights of the individual. Benjamin Franklin commented on this.“Those who exchange security for freedom deserve neither” We are being asked to give up some of our freedom, thus increasing the proportion of decisions we make under a threat of violence. In exchange we are promised an amount of”climate security”, the value of which is claimed to exceed the value of the freedom we are to give up for it. Skeptics want to know if the exchange is worth it. History tells us that we will not receive a refund of our freedom if it turns out that AGW is a myth, or that the programs to alleviate it fail to deliver as promised. Chris Riley sums this up accurately in my opinion. This talkfest is a waste of time. The horse has long bolted. Already the governments of the world are taxing their citizens to death (because they will not be able to pay for the energy they need to keep warm) to replace cheap energy sources with expensive and inefficient alternatives – all on the basis of an unproven belief that co2 is going to cause catastrophic global warming unless it is reduced. Taxing people to death That is violence.And President Obama intones in his State of the Union address ‘We’ll invest in biomedical research, information technology, and especially clean energy technology – an investment that will strengthen our security, protect our planet, and create countless new jobs for our people’Business as usual ‘clean energy technology’ = Windmills. Countless new jobs = building windmills. Protect our planet. Utter hubris. I know he is the president of the US – but – those words are the words of God! The horse has truly bolted. And Obama is a babe compared to the Euro demigods.If he is going to protect the planet we have to acquiesce – game set and match.And these people are indulging themselves in a talkfest about violent argument?Douglas
Skiphil
/ 04/08/2012MBC, great work here now and before! btw, have you seen the Climategate email I just discussed at CA, in which Neukom explicitly tells Phil Jones of how he juggles different “ensembles” of proxies looking for just the right recipe:
http://climateaudit.org/2012/08/02/gergis-and-watts-delayed/#comment-345999
this was pertaining to his prior SH recon for South America, but it is indicative of a very dubious method (at best) of ad hoc parsing of proxies until one gets just the right result. Statistical “skill” or cooking the books for a desired outcome???
manicbeancounter
/ 04/08/2012I do not usually follow who said what, or what people’s opinions are – it matters little to me at all. What is more important is having a robust analysis. Your quote from Neukom confirms what I have found with Gergis and what Steve McIntyre has found with numerous other studies – To get the results presented requires a series of “dubious” choices to be made in data selection, statistical techniques, presentation and conclusions drawn. That is why so much effort is put into blocking questions and denigrating anyone who tries to investigate.
lista de emails
/ 08/08/2012with this i disagree. lista de emails lista de emails lista de emails lista de emails lista de emails
manicbeancounter
/ 11/08/2012It is OK to disagree with what I say. However, it would be interesting to know why you disagree.
É OK para concordar com o que eu digo. No entanto, seria interessante saber por que você discorda.