OK this is a fascinating email showing dissension among the ranks of the CRU-IPCC club. Apparently a tree-ring study was produced in 2001 (Esper, et al – sometimes referred to as “ECS”) which challenged Mann’s Hockey stick. This study showed a much higher MWP, which sent Dr Mann and his touchy ego into full meltdown.  As usual you have to read this email from bottom up. Here is Dr Cook slamming Mann for his irritation with having his hockey stick wilted:

I must admit to being really irritated over the criticism of the ECS tree-ring data standardized using the RCS method. First of all, ECS acknowledged up front the declining available data prior to 1200 and its possible effect on interpreting an MWP in the mean record.

Basically, when the number of samples (data points) drop the ability to set a relative (mean) MWP temperature becomes impossible due to the higher ‘noise’ (uncertainties or errors). More:

ECS also showed bootstrap confidence intervals for the mean of the RCS chronologies and showed where the chronologies drop out. Even allowing for the reduction in the number of represented sites before 1400 (ECS Fig. 2d), and the reduction in overall sample size (ECS Fig. 2b), there is still some evidence for significantly above average growth during two intervals that can be plausibly assigned to the MWP.

Even these small samples, using the ECS method vs Mann’s showed a MWP.

Of course we would like to have had all 14 series cover the past 1000-1200 years. This doesn’t mean that we can’t usefully examine the data in the more weakly replicated intervals. In any case, the replication in the MWP of the ECS chronology is at least as good as in other published tree-ring estimates of large-scale temperatures (e.g., NH extra-tropical) covering the past 1000+ years.

I.e., our methods are just as valid as yours, therefore our results are just as possible as yours.

It also includes more long tree-ring records from the NH temperate latitudes than ever before.

And, oh BTW, we had more data than you did.

So to state that “this is a perilous basis for an estimate of temperature on such a large geographic scale” is disingenuous, especially when it is unclear how many millennia-long series are contributing the majority of the temperature information in the Mann/Bradley/Hughes (MBH) reconstruction prior to AD 1400. Let’s be balanced here.

Mann did not share his data with his colleagues either. I would guess Briffa and others are more than ready to rid themselves of the egotistical Mike Mann. Especially in light what initiated this exchange:

Keith and Tim,
Sadly, your piece on the Esper et al paper is more flawed than even the paper itself. Ed, the AP release that appeared in the papers was even worse. Apparently you allowed yourself to be quoted saying things that are inconsistent with what you told me you had said.

You three all should have known better. Keith and Tim: Arguing you can scale the relationship between full Northern Hemisphere and extratropical Northern Hemisphere is *much* more problematic than even any of the seasonal issues you discuss, and this isn’t even touched on in your piece.

Mann is one of those pushy control freaks. Briffa and Cook pretty much blow him out of the water and tell him to bugger off in this email:

Finally, we have to say that we do not feel constrained in what we say to the media or write in the scientific or popular press, by what the sceptics will say or do with our results. We can only strive to do our best and address the issues honestly. Some “sceptics” have their own dishonest agenda – we have no doubt of that. If you believe that I, or Tim, have any other objective but to be open and honest about the uncertainties in the climate change debate, then I am disappointed in you also.
Best regards
Keith (and Tim)

The chronology here is 1st email, latest, 2nd email 1st, 3rd email in between (sorry for them being out of time sequence).

Mann is in deep trouble if I am reading this right. No wonder he tried to throw Phil Jones under the bus. Briffa is EAU CRU, as are others. My guess is someone will need to be the fall guy, and Mann may not have enough friends to keep him safe.

But it is clear Steve McIntyre was not the only one challenging Mann’s computational methods and conclusions.