You Dirty Errata

Mann, Bradley and Hughes have published some corrections to the supplementary information for the famous hockey stick graph showing the temperature record of the last 1000 years. They say that the errors do not affect their published results. This could explain why McKitrick and McIntyre could not reproduce their results, but McKitrick is continuing to insist that Mann’s graph is wrong.

McKitrick has also published some errata. Unlike Mann’s error McKitrick’s error affects his results:

Figure 3 in the Cooler Heads Briefing on TBS contains an error. Tim Lambert of Australia has pointed out that missing data were handled differently between Figures 2 and 3, and when this is fixed the example no longer illustrates the intended point. The point (that the trend can change if the averaging rule is changed) is shown in this Revised Spreadsheet. Our thanks to Tim Lambert for pointing out the error.

(The post where I pointed out the error is here.)

I looked at his revised spreadsheet. This time he has dealt with missing values consistently and it does indeed show a warming trend when the usual arithmetic mean is used and a cooling trend when their unusual root-mean square is used. So how did he manage this? After all, as I showed in my earlier post, the root-mean square in Kelvins gives almost he same answer as the regular average. Well, McKitrick invented his own temperature scale. McKitrick modestly did not give it a name, but I am dubbing it the McKitrick scale in honour of its creator. To help you gain familiarity with this new scale, the form below lets you convert between degrees McKitrick and the old-fashioned degrees Celsius and degrees Fahrenheit. Just type a number into any of the boxes and press “Enter”.

°M     °F     °C

Anyway, in his revised spreadsheet McKitrick takes the root-mean-square average of temperatures measured in degrees McKitrick. This way of averaging temperatures gives some rather odd results. For example, the RMS average of -10°M and -10°M is not -10°M as you might expect, but +10°M. Needless to say no-one actually uses RMS averages of temperatures in the McKitrick or any other scale, and no-one in their right mind would use them.

So revising their original example to use degrees McKitrick means the trend is different for different averaging methods? Well, no. If you take their original example and use the root-mean-square-in-degrees-McKitrick average, you still get the same trend. In the revised spreadsheet McKitrick has also changed the set of weather stations used. Even then it makes little difference to the size of trend—it changes an insignificant warming trend to an insignificant cooling trend.

To summarize: even if you use a weird root-mean-square-in-degrees-McKitrick average it makes little difference to the size of any warming or cooling trend you might see.


  1. #1 Louis Hissink
    July 9, 2004


    The Mann et al graph is not a representation of a functional relationship of temperature with time, but one of historical record.

    As such, it cannot be used as a means to predict anything.

    Furthermore it is a compilation of proxy data, measured data and predicted data – a contatenation of stupidity only equalled by the Spanish Inquisition.

  2. #2 Tim Lambert
    July 9, 2004

    Louis, nobody expects the Spanish inquisition.

  3. #3 Ken Miles
    July 10, 2004

    Tim, nice work.

    Louis, do you have even the faintest idea about how the MGH graph was constructed? Judging by that post, I think not.

  4. #4 Dano
    July 13, 2004

    Louis, do you have even the faintest idea about how the MGH graph was constructed? Judging by that post, I think not.

    What was it that tipped you off, Ken? The ridiculous incantation of a religious analogy, or the ignorant/ideological position maintenance that different datasets cannot/should not be merged?


  5. #5 Ken Miles
    July 13, 2004

    Dano, combination of all of them really. Plus prior experience tells me that Louis very rarely (ever?) knows what he’s talking about.

  6. #6 Dano
    July 14, 2004

    Judging from the one time I went to the aptly-named BS website, Ken, I’d say your parenthetical is correct.


  7. I don’t know how you can take it. I forced myself to read the Essex & McKitrick “Taken By Storm’ tome after getting it on the cheap. What will stick with me for ages, is that not one graph Y-axis was labelled out the several charts printed!
    My complete review here ..

    Bastardizing what King Louis said I would call McKitrick’s stuff “a functional relationship of imagination with time”.

  8. #8 Skeptic
    August 8, 2004

    Well, at least McKitrick is accomodating in that his data is available for peering. Far more than Mann has been able to make publicly available.

    Debate is at the heart of science. An environment of intellectual intolerance isn’t good for anybody let alone the science.

  9. #9 Tim Lambert
    August 8, 2004

    Mann’s data is publically available. If you had bothered to follow the very first link in my post you would have found that out.

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