Sci-AM: Confirming the importance of MBH 99

A new profile of Michael Mann appears in the March edition of Scientific American (on the grounds that you can never have too many profiles) Update: the author of the profile is David Appell. Isn’t it a small world? You’ll have to pay real money to see all of it, but here’s a rather revealing extract (my emphasis added):

To construct the hockey-stick plot, Mann, Raymond S. Bradley of the University of Massachusetts Amherst and Malcolm K. Hughes of the University of Arizona analyzed paleoclimatic data sets such as those from tree rings, ice cores and coral, joining historical data with thermometer readings from the recent past. In 1998 they obtained a "reconstruction" of Northern Hemisphere temperatures going back 600 years; by the next year they had extended their analysis to the past 1,000 years. In 2003 Mann and Philip D. Jones of the University of East Anglia in England used a different method to extend results back 2,000 years.

In each case, the outcome was clear: global mean temperature began to rise dramatically in the early 20th century. That rise coincided with the unprecedented release of carbon dioxide and other heat-trapping gases into the earth’s atmosphere, leading to the conclusion that industrial activity was boosting the world’s mean temperature. Other researchers subsequently confirmed the plot.

So yet again, Sci-Am have confirmed what many skeptics have claimed: that the Mann Hockey Stick is indeed the key reconstruction used to "prove" the Greenhouse Warming hypothesis, that the 20th Century warming period is caused by human industrial activity since the dramatic rise in global mean temperature began in the early 20th Century.

In contradiction to the recent statements on and elsewhere, MBH99 is the one reconstruction that everybody reaches for when discussions of "greenhouse warming" and "anthropogenic climate change" are given. That’s why MBH99 is so important.

And yet, no other reconstruction has the warming begin in the mid 19th Century. The latest one by Moburg et al (2005) has the lowest temperature in the mid 17th Century, co-inciding with the depths of the "Little Ice Age" and (obviously by coincidence) the "Maunder Minimum", a period of 70 years when the solar cycle disappeared and the Sun produced about 0.15% less energy than it does today.

Sunspots and the Maunder Minimum

Just in case you don’t believe how pivotal the MBH99 paper was in the eyes of the IPCC, here is how the IPCC reconstructed the past 1000 years of climate back in 1990:

MWP and LIA - IPCC 1990

As far as I am aware, the IPCC has never bothered to explain why it threw away its previously stated view on climate history and embraced the Hockey Stick so enthusiastically and completely.

But I think I can guess…


  1. Michael Ballantine
    Posted Feb 20, 2005 at 9:47 AM | Permalink

    The statement “That rise coincided with the unprecedented release of carbon dioxide and other heat-trapping gases into the earth’s atmosphere, leading to the conclusion that industrial activity was boosting the world’s mean temperature.” reminds me of an old joke.

    A scientist teaches a flea to jump whenever he says “jump”. It is very repeatable. He removes one of the legs and whenever he says “jump” the flea still jumps. He continues the experiment until there are no more legs. Now, whenever he says “jump” the the flea just lays there. His conclusion: Removing all the legs from a flea renders the flea deaf.

    That would seem to be a logical conclusion, if the scientist is narrowly focused in the extreme. It just happens to be wrong.

    If we have increased tree ring growth associated with increased CO2, why would any rational person assume that this indicates increased temperature instead of the obvious direct correlation. Give the tree more nutrition and it grows faster.

    Does anyone know of a study that correlates tree ring growth with CO2 concentrations? I know there is a study on here that says tree ring growth does not correlate well with temperature.

    The infamous Bristle Cone Pines. Are they perhaps “downwind” or otherwise in the area of higher levels of CO2?

  2. Chas
    Posted Feb 20, 2005 at 3:07 PM | Permalink

    Yes, there is at least one study of CO2 on ring-width precied at ; Telewski et al. (1999)-look in the subject index under ‘D’ (Density)then ‘Wood’. This particular four-year in-field air-enrichment to 650 ppm C02, increased the pine’s ring-widths by 93,29,15 and 37% in the consecutive years. There are several other reviews of CO2/wood papers at the site.
    [The site run by the Idso’s]

  3. Peter Hearnden
    Posted Feb 26, 2005 at 6:20 AM | Permalink

    John, To what part(s) of the world did the IPCC chart you reproduce apply to? Why do you seem to me to think it was the last word in climate reconstruction? Is the implication that climate reconstructions get worse with time? If so what did we think (know?) about past climate in the 50’s and the 1700’s? Peter

    John writes: As far as I recall the IPCC reconstruction of 1990 refers to global climate. I don’t think that climate reconstructions get worse over time. They were fairly good over a long period, then declined suddenly in a period we observers call "The Little IPCC Age" before recovering more recently to almost the quality that they were before. In all periods of climate history we thought that the modern version was better than the old, and that the sins of Mankind were causing the climate system to turn against us, and that we must repent of our sinful ways, lest we be stricken from the earth.

  4. Posted Feb 26, 2005 at 2:57 PM | Permalink

    I sure had the opinion that the IPCC was opining on global climate.

  5. TCO
    Posted Sep 10, 2005 at 8:06 PM | Permalink

    What was the science behind the 1990 IPCC claim? did they cite a study or do a new reocnsutruciton to get that 1990 result.

    And if we accept the 2000 year hockey stick, is it reasonable? What it’s telling us about climate that is? Seems to be saying in the absence of man, that climate will not change much (at least nowadays). That seems like a checkable hypothesis. for instance do models show a chaotic or stable system?

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