Steyn on Mann: A Disgrace to the Profession [W:455]

"Anyway, when I asked Simon Tett about this, he told me that he does not recall the quote, though perhaps it was from a private email (like this) and has all the context removed. Note that the quote is supposed to have come from 2001, so Tett assumes it would have been, had he actually said it, a criticism of the hockey stick paper. He told me, “I think my criticism was that it was likely missing some variances. My view then and still is that recent warming is very likely outside the range of natural variability.”

I have not seen Tett’s quote in its original exact context, but I think it is part of a larger bit of text that makes up part of the so-called Climategate 2.0 emails. If so, Tett said,

I think there are issues in Mann et al’s approach −− recall the Esper et al paper which produced a reconstruction with lots more low frequency variability than others. From the comment on the paper by Keith Briffa and Tim Osborn (attached) you can see that Mann’s reconstruction had the least variability of any of the reconstructions. Did Mann et al get it wrong? Yes Mann et al got it wrong. How wrong is still under debate and the ECHO−G/HadCM3 results may be over-exaggerating the variance loss for some model-specific reasons.

This provides more context to Tett’s quote, indicating that this is an argument over variability in Mann et al’s reconstruction of Northern Hemisphere temperatures over the last thousand years. But there is even more to it than that. There was vigorous argument over which models should ultimately be used in the IPCC report that included the Hockey Stick, including one (or two) by Tett that show a similar pattern to Mann et al’s original findings. In asking around about what was happening in those days I learned a lot more than needed for this humble blog post. Suffice it to say, there was arguing about important details, but not about the basic reality of climate change and recent warming. All of the discussion had to do with how much variation there was in the older record, and most of that uncertainty has been addressed over the subsequent decade.

Tett’s contribution to climate science has been to address that variability. He has recently co-authored articles with Mike Mann that confirm the Hockey Stick pattern of temperature changes and seek to understand that pattern in terms of natural and human drives of climate. Clearly, he is one of the nearly 100% of scientists who view global warming as real and caused by human greenhouse gas pollution.

So. That’s settled. Steyn got it wrong.

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I think there are issues in Mann et al’s approach −− recall the Esper et al paper which produced a reconstruction with lots more low frequency variability than others. From the comment on the paper by Keith Briffa and Tim Osborn (attached) you can see that Mann’s reconstruction had the least variability of any of the reconstructions. Did Mann et al get it wrong? Yes Mann et al got it wrong. How wrong is still under debate and the ECHO−G/HadCM3 results may be over-exaggerating the variance loss for some model-specific reasons.

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b) Are M&M right? M&M maybe right. However I think it is unlikely that the Medieval warm period is as warm as today... Their criticism seems to be extremely technical.

c) How unusual is the last 50 years? I think it still to be likely to be the warmest period (see b) BUT the rate of warming may not be highly unusual.

I agree that one of the important claims in the TAR looks like not being correct. The result could be spun to cast doubt on worries about anthropogenic climate change as the evidence that the 20th century is unusual becomes less clear cut....

Simon

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Threegoofs said:

And as Greg Laden showed, those quotes (at least the headline ones) are not exactly in context.

Dishonestly portrayed, to no ones surprise.

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