Comments on: MBH98 Confidence Intervals http://climateaudit.org/2005/05/07/mbh98-confidence-intervals/ by Steve McIntyre Thu, 20 Jun 2013 02:13:38 +0000 hourly 1 http://wordpress.com/ By: Steve McIntyre http://climateaudit.org/2005/05/07/mbh98-confidence-intervals/#comment-33542 Sun, 08 May 2005 02:54:41 +0000 /?p=200#comment-33542 Hi, Lubos. If the error bars are decreasing with fewer proxies, it would indicate that the proxies being added are worse than noise, I guess. EVen so, it’s hard to figure out theoretically.

If you look at my next post, the standard error of the residuals is higher than the standard deviation of the temperature series being modeled. So one would conclude that there is no skill in the model.

But the statistics of MBH98 is really simplistic. These series have a lot of serial correlation. They also have low frequency red noise (at all scales up to ice ages) so the variance/standard deviation in a relatively short period like a 79 year calibration period would be an under-estimate. There’s a lot of research in econometrics on this.

Even on the data shown here, I don’t see how their reconstruction achieves a confidence interval below natural variation.

Regards, Steve

]]> By: Luboš Motl http://climateaudit.org/2005/05/07/mbh98-confidence-intervals/#comment-33541 Sun, 08 May 2005 00:51:57 +0000 /?p=200#comment-33541 Dear Steve, I simply think that these numbers were invented in such a way that they “would look plausible” to a fast reader. The fact that MBH98 was certainly not a perfect manipulation with the numbers where every detail can be measured has already been demonstrated in MM2003.

Generally, it looks puzzling why an older period should be more accurate than a newer one, but on the other hand, it can probably happen, can’t it? More generally, I think that the error margin for the 15th century is many, many times higher than what they say – it’s enough to look at different papers that try to answer the same question.

]]> By: Steve McIntyre http://climateaudit.org/2005/05/07/mbh98-confidence-intervals/#comment-33540 Sun, 08 May 2005 00:51:31 +0000 /?p=200#comment-33540 Jeff, the error bars are +- 2 sigma. There’s a curious difference between MBH98 and MBH99 error bars which I just noticed and will post. There is a lot of work in econometrics on variance if there’s autocorrelation, bu obviously MBH98 doesn’t consider this. It looks like they just calculated the standard error of the residuals in the calibration period (not even the verification period(!?!) as an estimate. Steve

]]> By: Jeff Norman http://climateaudit.org/2005/05/07/mbh98-confidence-intervals/#comment-33539 Sun, 08 May 2005 00:12:07 +0000 /?p=200#comment-33539 Steve,

How did they report the error bars? Was it just the à?Æ’ or some function of the à?Æ’ (along the lines of 2 X à?Æ’)?

What were the error bars for the period 1900 to 1980? How do these compare to the error bars reported with the syrface insrument record?

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