McIntyre on Kaufman et al 2020

Andrew Revkin was fawning over the paper on Twitter when McIntyre showed up.

Here is the complete response by Steve McIntyre.

I was curious as to why their new Antarctic reconstruction was so dramatically different from PAGES2K only seven years ago – a question that both they and reviewers ought to have thought about. Difference arises mainly from one catastrophic error and 2 implausible new series.

the largest difference from PAGES2K -and main contributor to “new” blade – came from Kaufman’s version of Dahl-Jensen borehole inversion series. Kaufman has HS (worse with binning). Opposite to original.

3/ so how did they get such a different appearance? Total cock-up. They dropped the earliest Dahl value, then reversed the years. So the Dahl value from 5502 BC was used in 1995 AD, from 4438 BC in 1987 and so on. A goof of Mannian proportions.

4/ it was easy to notice. I tweeted on this within a day or so after publication. There are two other very questionable “new” series. Instead of using the new WAIS isotope series – the highest resolution Antarctic series over the Holocene – they use a WAIS borehole inversion

5/ in which isotopes are a sort of fringe. The inversion matrices used in borehole inversion are hugely multicollinear, so the inversion math is very unstable. This whole discipline should be thrown out on those grounds. But there is a special problem with ice core inversions.

6/ there is very very strong seasonal swing in temperatures of top 15 meters or so of Antarctic ice core boreholes. In the published article on WAIS inversion, they excluded the top portion – which are the layers laid down after 1960 or so. So supposed recent uptick in WAIS

7/ temperature reconstruction arises from ice layers laid down prior to 1960. It is a really stupid series. And yet, the WAIS isotope series is fantastically high resolution over long series. d18O series are backbone of paleoclimate – so why didn’t they just use d18O?

8/ you know the answer. The WAIS d18O series didn’t yield a HS, so they used the stupid borehole inversion series which did.

9/ the only other series contributing to “new” HS is a melt layer frequency series from Siple Dome – where there is an isotope series available. Siple Dome is near Ross Sea, where icesheet has been gradually eroding during Holocene as it is maritime grounded. As a result,

10/ even though isotope data shows slight decline in temperature over Holocene, there has been a slight increase in melt frequency in Siple Dome. They calculated this series as a running total of melt layers in prior 1000 years, which Kaufman incorrectly used as annual resolution

11/ Kaufman then binned this series. If one were to use this crappy data at all, you’d be required to bin the original data, not the running 1000 year total. If you did that, it has max 500 years ago, not in 20th century.

12/ also, unlike isotope series which have been taken at many sites and properties and vagaries thus known, use of a singleton series where there are no comparanda in region lends itself to abusive cherrypicking, such as here.

13/ I haven’t looked at other regions, but Kaufman’s Antarctic reconstruction is a mess and needs to be retracted. You may recall that Kaufman’s Arctic PAGES2K series was similarly screwed by upside-down series in Iceland and series in Greenland which had similar contamination

14/ to the contaminated Finnish lake sediment series (also used upside down) relied upon in Mann’s supposed no-dendro reconstruction in 2008.

Originally tweeted by Stephen McIntyre (@ClimateAudit) on August 7, 2020.

HT/Tim P

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August 13, 2020 at 01:01AM

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